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Transition radiation detectors
Abstract
The use of transition radiation (TR) as a means of identifying high energy particles has now become a subject of intensive experimental investigations and applications. Our intention is first to study the physics of these phenomena and to describe ways of building detectors which can efficiently identify particles.
... On the other hand, for highly relativistic charged particles, the total energy of photons emitted in transition radiation per interface is proportional to [15], where = 1 √1− 2 2 ⁄ is the Lorentz factor and is the speed of light in free space. Such a unique feature makes transition radiation attractive as an underlying mechanism for high-energy particle detectors, namely the transition radiation detector [16][17][18]. The transition radiation detector is useful for the identification of particles at extremely high energies where other existing technologies such as Cherenkov detectors [19,20] are not accessible. ...
... The fact of ̅ z R = 0 from equation (14) is used in equation (16). As shown in Fig. 1, we have the permittivity ,⊥ ( ) = 1 ( < 0) + gra, ,⊥ ( = 0) + 2 ( > 0) in equation (16). ...
... The fact of ̅ z R = 0 from equation (14) is used in equation (16). As shown in Fig. 1, we have the permittivity ,⊥ ( ) = 1 ( < 0) + gra, ,⊥ ( = 0) + 2 ( > 0) in equation (16). If ′ → , ...
In the framework of full Maxwell equations, we systematically study the electromagnetic radiation, namely the transition radiation, when a swift electron perpendicularly crosses a monolayer graphene. Based on the plane wave expansion and the Sommerfeld integration, we demonstrate the spatial distribution of this free-electron radiation process in the frequency domain, which clearly shows the broadband excitation of both the photons and graphene plasmons. Moreover, the radiation spectra for the excited photons and graphene plasmons are analytically derived. We find that the excitation of photons and graphene plasmons favours different velocities of the swift electron. To be specific, a higher electron velocity can give rise to the excitation of photons with better directivity and higher intensity, while a lower electron velocity can enable the efficient excitation of graphene plasmons in a broader frequency range. Our work indicates that the interaction between swift charged particles and ultrathin 2D materials or metasurfaces is promising for the design of terahertz on-chip radiation sources.
... Then the total radiated power is approximately constant. [90] It can be shown that the mean radiated energy in this single surface configuration can be written as: ...
... The basic mathematics can be found in [85,90,98]. Computational models can be found in [100]. ...
... For a practical transition radiation radiator and following [90], the expression of the total flux, is then represented by an integration over the emission angle and a function which represents the incoherent addition of the single foil intensities and includes the photon absorption in the radiator. The effective number of foils in the radiator can then be expressed as: ...
Particle identification, PID, is of crucial importance in most experiments. The requirement can range from positive π/K identification in B-physics channels like B\(^0_{\mathrm {s}}\rightarrow \)D\(^\mp _{\mathrm {s}}\)K± against a background from B\(^0_{\mathrm {s}}\rightarrow \)D\(^-_{\mathrm {s}}\pi ^+\) which is ∼15 times more abundant, to e/π separation at the level of ∼ 10⁻² for momenta > 1 GeV/c in order to effectively suppress a combinatorial background in channels like leptonic decays of heavy vector resonances.
... As the TR photon yield per boundary crossing is of the order of the fine structure constant 1 See Appendix for the list of collaboration members. ( = 1∕137), many boundaries are needed in detectors to increase the radiation yield [10]. The absorption of the emitted X-ray photons in high-gas detectors leads to a large energy deposition compared to the specific energy loss by ionisation of the traversing particle. ...
... Since their development in the 1970s, transition radiation detectors have proven to be powerful devices in cosmic-ray, astroparticle and accelerator experiments [10][11][12][13][14][15][16][17][18][19][20]. The main purpose of the transition radiation detectors in these experiments was the discrimination of electrons from hadrons via, e.g. ...
... The transition radiation photons are in most cases detected either by straw tubes or by multiwire proportional chambers (MWPC). In some experiments [10,13,16,21] and in test setups [22][23][24][25], short drift chambers (usually about 1 cm) were employed for the detection. Detailed reviews on the transition radiation phenomenon, detectors, and their application to particle identification can be found in [10,[26][27][28]. ...
... The radiation is extremely forward peaked relative to the particle direction [7]. As the TR photon yield per boundary crossing is of the order of the fine structure constant (α = 1/137), many boundaries are needed in detectors to increase the radiation yield [10]. The absorption of the emitted X-ray photons in high-Z gas detectors leads to a large energy deposition compared to the specific energy loss by ionisation of the traversing particle. ...
... Since their development in the 1970s, transition radiation detectors have proven to be powerful devices in cosmic-ray, astroparticle and accelerator experiments [10][11][12][13][14][15][16][17][18][19][20]. The main purpose of the transition radiation detectors in these experiments was the discrimination of electrons from hadrons via, e.g. ...
... The transition radiation photons are in most cases detected either by straw tubes or by multiwire proportional chambers (MWPC). In some experiments [10,13,16,21] and in test setups [22][23][24][25], short drift chambers (usually about 1 cm) were employed for the detection. Detailed reviews on the transition radiation phenomenon, detectors, and their application to particle identification can be found in [10,[26][27][28]. ...
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/$c$ in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
... yield spec- The number of transition radiation photons for each interface is very low due to its electromagnetic nature. For photons with frequencies greater than a lower limit W, it is given by [78]: Structure The configuration of TRD is shown in Figure 3 To perform particle identification using 20 layers of TRD measurement, a likelihood approach is used. For each event, the likelihood can be calculated from the PDFs for electron/positron and protons at each layer, and after combining all the TRD layers [76]: ...
... As can be seen in Figure 6-6, the TRD estimator varies slightly in energy range below 10 GeV~yfactor< 1O4). Due to the saturation of transition radiation at even higher energies [78], the electron TRD estimator distribution is not changing (Figure 6-7). ...
... 312.0 GeV in the ECAL is shownAt the interface of material with dielectric constant e and vacuum, the trum of transition radiation is[78]: ...
The cosmic ray electron and positron flux measurement can address a series of astrophysics and particle physics questions. This thesis presents an analysis of electron and positron flux from 0.5 GeV to 1 TeV using the first 30 months of data taking( over 41 billion events), with the AMS-02 detector on the International Space Station(ISS) 330-410 km above earth. A precise calibration of the Electromagnetic Calorimeter(ECAL) signals is performed to obtain stable energy measurement. A reconstruction algorithm for electromagnetic showers is implemented to measure energy and achieve high particle identification accuracy of electron and positron separating them from the proton background. The result of combined electron and positron flux measurement shows a smooth spectrum with no sharp structure. The spectral index ... above 30 GeV is observed to be ... (energy scale). This provides precise measurement for cosmic ray electrons and positrons and can contribute to probing the origin of cosmic rays, informing the studies of new physics..
... A famous example is Cherenkov radiation [1][2][3][4][5][6], in which photons are emitted from the bulk of a medium when the electron's speed exceeds the speed of light in the medium. Another type of free-electron radiation, known as transition radiation [7][8][9][10][11][12], refers to photon emission from an interface-when an electron crosses an interface between different media, the electron will always emit photons, at any speed. As an alternative photon emission mechanism apart from atomic spontaneous emission and stimulated emission, free-electron radiation plays a significant role in many practical applications, ranging from high-energy particle detectors, free-electron lasers, electron microscopies, medical imaging, security scanning, to astronomy and cosmology [13][14][15][16][17][18][19]. ...
... This concept has already provided valuable guidance for practical applications. For example, the influence of formation time should be avoided in the design of transition radiation detectors [10], which are widely used in the identification of high-energy particles. ...
Free-electron radiation is a fundamental photon emission process that is induced by fast-moving electrons interacting with optical media. Historically, it has been understood that, just like any other photon emission process, free-electron radiation must be constrained within a finite time interval known as the "formation time", whose concept is applicable to both Cherenkov radiation and transition radiation, the two basic mechanisms describing radiation from a bulk medium and from an interface, respectively. Here we reveal an alternative mechanism of free-electron radiation far beyond the previously defined formation time. It occurs when a fast electron crosses the interface between vacuum and a plasmonic medium supporting bulk plasmons. While emitted continuously from the crossing point on the interface - thus consistent with the features of transition radiation - the anomalous radiation beyond the conventional formation time is supported by a long tail of bulk plasmons following the electron's trajectory deep into the plasmonic medium. Such a plasmonic tail mixes surface and bulk effects, and provides a sustained channel for electron-interface interaction. These results also settle the historical debate in Ferrell radiation, regarding whether it is a surface or bulk effect, from transition radiation or plasmonic oscillation.
... A classical detector is composed of several similar modules which respond nearly independently. Such detectors were used in the UA2, NA34 and other experiments [178], are being used in the ALICE experiment [179,180] and are built for the CBM experiment [181]. In another TRD concept a fine granular radiator/detector structure exploits the soft part of the TR spectrum more efficiently. ...
... Apart from the beam energy variations, the observed scattering of the points in the plot reflects how effectively the detector space is used and how well the exact response to different particles is taken into account in the analysis. For instance, the ATLAS TRT was built as a compromise between TR and tracking requirements; that is why the test-beam prototype result (lower point) is better than the real End-Cap TRT performance at the LHC shown in The plot is based on the table given in [178]. ...
Prog. Theor. Exp. Phys. 2020, 083C01 (2020) and 2021 update.
... To build up a detectable signal, one typically allows the particle to pass through a periodic stack of several hundred or thousand foils of fixed thickness each separated by a fixed spacing of gas or vacuum [13,14]. If the field amplitudes at each interface are added in phase, it can be shown that the result is an interference pattern, with peaks appearing at frequencies governed by a resonance condition determined by the foil thickness l 1 and spacing l 2 [15,16,17,18]. As γ increases, the spectrum extends to successively higher frequencies, with the largest contribution to the emitted energy appearing at the highest frequency maximum near ω max ∼ ω 2 1 l 1 /2πc. ...
... In a regular radiator consisting of N identical foils of thickness l 1 separated by equal distances l 2 , the field amplitudes at each interface must be added in phase. The resulting intensity per unit frequency ω per unit solid angle Ω is given by the expression [13,14,15,16,17,18] ...
Transition radiation detectors (TRDs) have been used to identify high-energy particles (in particular, to separate electrons from heavier particles) in accelerator experiments. In space, they have been used to identify cosmic-ray electrons and measure the energies of cosmic-ray nuclei. To date, radiators have consisted of regular configurations of foils with fixed values of foil thickness and spacing (or foam or fiber radiators with comparable average dimensions) that have operated over a relatively restricted range of Lorentz factors. In order to extend the applicability of future TRDs (for example, to identify 0.5 - 3 TeV pions, kaons, and protons in the far forward region in a future accelerator experiment or to measure the energy spectrum of cosmic-ray nuclei up to 20 TeV/nucleon or higher), there is a need to increase the signal strength and extend the range of Lorentz factors that can be measured in a single detector. A possible approach is to utilize compound radiators consisting of varying radiator parameters. We discuss the case of a compound radiator and derive the yield produced in a TRD with an arbitrary configuration of foil thicknesses and spacings.
... Transition radiation, first predicted by Ginzberg and Frank [1], and later analysed in more details by others [2,3], is produced when a charged particle, moving with a certain speed, crosses a boundary between two mediums with different dielectric constants. The spectrum of the radiation depends on the dielectric constants of the two media. ...
... This is the traditional equation that is being used in analysing the transition radiation [1,2,3]. However, confining our analysis to the time domain, the total energy lost by the charged particle as transition radiation is given by ...
The energy, momentum and the action associated with the time domain transition radiation fields are investigated. The results show that for a charged particle moving with speed v, the longitudinal momentum associated with the transition radiation is approximately equal to E/c for values of 1−v/c smaller than about 10-3 where E is the total radiated energy and c is the speed of light in free space. The action of the transition radiation, defined as the product of the energy dissipated and the duration of the emission, increases as 1−v/c decreases and, for an electron, it becomes equal to h/4π when v=c− v m where v m is the speed associated with the lowest energy state of a particle confined inside the universe and h is the Plank constant. Combining these results with Heisenberg’s uncertainty principle, an expression for the electronic charge based on other fundamental physical constants is derived. The best agreement between the experimentally observed electronic charge and the theoretical prediction is obtained when one assumes that the actual size of the universe is about 250 times larger than the visible universe.
... The radiation fields generated by such events are known in the literature as transition radiation. The existence of transition radiation was first predicted by Ginzberg and Frank [6], and later analysed in more details by others [7,8]. In general, transition radiation is produced when a charged particle, moving with a certain speed, crosses a boundary between two mediums with different dielectric constants. ...
... . This is the traditional equation that is being used in analysing the transition radiation [6,7,8]. In the limit when the current is represented by a Delta function ( ) A q ω = and the spectrum becomes flat and independent of frequency. ...
The energy, momentum and the action associated with the time domain transition radiation fields are investigated. The results show that for a charged particle moving with speed v, the longitudinal momentum associated with the transition radiation is approximately equal to E/c for values of 1−v/c smaller than about 10-3 where E is the total radiated energy and c is the speed of light in free space. The action of the transition radiation, defined as the product of the energy dissipated and the duration of the emission, increases as 1−v/c decreases and, for an electron, it becomes equal to h/4π when v=c− v m where v m is the speed associated with the lowest energy state of a particle confined inside the universe and h is the Plank constant. Combining these results with Heisenberg’s uncertainty principle, an expression for the electronic charge based on other fundamental physical constants is derived. The best agreement between the experimentally observed electronic charge and the theoretical prediction is obtained when one assumes that the actual size of the universe is about 250 times larger than the visible universe.
... This is specially relevant in detectors that include charge multiplication as a large number of ions is formed, and which can affect their performance. Examples include the Multi-Wire Proportional Chambers (MWPCs) [4], also of Transition Radiation Detectors (TRDs) [5,6], where the electron and ion velocity influences their rate capability [5,6] and of Time Projection Chambers (TPC) that have to deal with the space charge build-up from ion backflow at the endcaps [7]. For these cases the choice of the gas mixture, namely of the additives to the main gas (usually noble gases) implies the knowledge of several parameters of the gas mixture, among which the ions' mobility [3]. ...
... This is specially relevant in detectors that include charge multiplication as a large number of ions is formed, and which can affect their performance. Examples include the Multi-Wire Proportional Chambers (MWPCs) [4], also of Transition Radiation Detectors (TRDs) [5,6], where the electron and ion velocity influences their rate capability [5,6] and of Time Projection Chambers (TPC) that have to deal with the space charge build-up from ion backflow at the endcaps [7]. For these cases the choice of the gas mixture, namely of the additives to the main gas (usually noble gases) implies the knowledge of several parameters of the gas mixture, among which the ions' mobility [3]. ...
In this paper we present the results of the ion mobility measurements made in pure isobutane (iC 4 H 10) and in mixtures with argon (Ar-iC4H10) for a total pressure of 8 Torr (10.6 mbar) and for low reduced electric fields in the 10 Td to 45 Td range (2.4-10.8 kV·cm −1 ·bar −1), at room temperature. The reduced mobilities, obtained from the peak centroid of the time-of-arrival spectra, are presented for Ar concentrations in the 5%-95% range.
... Transition radiation is the emission of a photon that can occur when an energetic charged particle crosses the boundary between two media with different dielectric constants [1,2]. The TRD employs multi-wire proportional chambers (MWPC) with a drift region preceded by a Figure 1. ...
Particle collider experiments generate huge volumes of complex data, and event displays provide a useful visual representation to accelerate the learning process towards physics results. Event displays are also used to verify expected behaviour, identify anomalous data, or explain important results. They often have a steep learning curve, a high barrier to entry, or are tightly bound to a specific environment. The upgrade of ALICE in preparation for Run 3 of the LHC requires modifications to existing event displays. We present here a cross-platform, browser-based event display, focused on interactive 2-dimensional projections of collision data from ALICE, specifically focused on the operation of the Transition Radiation Detector (TRD). It is driven by a flexible intermediate JSON data format suitable for web-based displays, and a generic task to convert existing data acquired in previous runs to this format. The relationship between raw and reconstructed data in the TRD is illustrated through a novel pairing of raw and reconstructed data in a unified interactive view. A formal design study methodology was used to guide these choices, and the display was evaluated by both scientists and the public, through a series of case studies.
... Its operation is based on taking advantage of transition radiation. Transition radiation is emitted when a charged particle traverses the interface between two media of different dielectric constants [95]. The TRT can provide continuous tracking as its basic components are highly modular, thin walled, proportional drift tubes termed straws. ...
The formulation of the Standard Model of particle physics (SM) is one of the greatest scientific achievements of the 20th century. It is, however, incomplete (for example, it lacks a dark matter candidate) as well as the fact that the hierarchy problem violates naturalness arguments. This has motivated the construction of particle accelerators to probe fundamental particles at increasingly high center-of-mass energies and luminosities, the LHC at CERN being the latest to continue this legacy. This thesis covers both the enhancement of luminosity measurements of pp collisions at ATLAS, underpinning the accuracy of all measurements made by the detector, and a search for one of the most theoretically viable extensions to the SM: supersymmetry. ATLAS uses mainly event-counting algorithms to measure luminosity, which break down at higher luminosities. If the ATLAS SemiConductor Tracker (SCT) can be employed as a luminometer using hit-counting algorithms, this issue may be mitigated. It is established here that the SCT can feasibly operate as a luminometer when recording two-or-more strip clusters with the standard binary readout mode (01X). Thus, the SCT can measure the luminosity with an accuracy within 10% of two of ATLAS’s existing luminometers: LUCID and TileCal. The discovery of the supersymmetric top (stop) would be fundamental for solving the hierarchy problem. An analysis of an experimentally challenging region of phase space, where stop decays have a compressed mass spectrum, complements the ATLAS one-lepton stop search using 13 TeV pp collisions at 139 fb−1 is presented. The aMT2 kinematic variable, designed to give a lower limit on pair-produced particle masses, is found to be effective at differentiating SUSY decays from the SM background, when used as an upper bound. No significant excess was observed above the Standard Model background and limits at 95% confidence level are set. Stop quarks are found to be excluded up to 500 GeV and mass splittings between the stop and the neutralino are found to be excluded up to 130 GeV, complimenting the exclusion limits found by other ATLAS searches for stop decays with one-lepton final states.
... The probability to emit one photon per boundary crossing is of order α ∼ 1/137. To increase the transition radiation yield, multi-layer dielectric radiators are used, typically several hundred mylar foils, polyethylene foam, or fibers (fleece) [77]. The energies of transition radiation photons emitted by relativistic particles are in the X-ray region with a detectable energy range of 3-50 keV [78]. ...
Many current and future nuclear physics (NP) experiments across the United States have and are implementing micro-pattern gas detectors (MPGDs) to be used for tracking and PID purposes. MPGDs are capable of operating in high rate environments and providing excellent spatial resolution over a large-area with a low material budget. Summarized in this white paper is the role that MPGDs are playing in NP experiments and the R&D which is needed to meet the requirements of future NP experiments.
... At the same time, electron-photon interactions comprise many intriguing effects including the Kapitza-Dirac effect [65][66][67][68], Smith-Purcell radiation [69][70][71], Cerenkov radiation [72][73][74][75], transition radiation [76,77], Bremmstrahlung [78][79][80], and Compton scattering [81,82]. These effects have fueled the development of light sources [83][84][85][86][87][88], particle accelerators [89][90][91][92][93] and detectors [94][95][96][97][98][99], and medical devices. Electron-photon interactions form the basis of innovative diagnostic tools including electron energy-loss spectroscopy (EELS) [100][101][102][103][104][105][106][107][108][109] and its variants [101,109,110], cathodoluminescence (CL) [101,108,109,111] and photon-induced near-field electron microscopy (PINEM) [107][108][109][112][113][114][115][116][117][118][119][120]. ...
Photon emission from atoms and free electrons underlie a wealth of fundamental science and technological innovations. We present a regime where atom-photon and electron-photon interactions interfere with each other, resulting in substantial changes in the spontaneous emission rate compared to the sum of each interaction considered in isolation. We highlight the critical role played by quantum electron wavepackets, and how the emission can be tailored via the electron waveshape, as well as the atomic population and coherence. Our findings reveal that atom-photon and electron-photon interactions cannot be considered in isolation even when higher-order contributions involving all three bodies (atom, photon and free electron) are negligible. Our findings pave the way to more precise control over photon emission processes and related diagnostics.
... Transition Radiation Detectors (TRDs) are widely used for electron-hadron separation in both accelerator and cosmic-ray experiments (see reviews [1][2][3]). With growing energies of modern and planned accelerators there is also a need to separate hadrons in the TeV energy range [4]. ...
New developments of pixel detectors based on GaAs sensors offer effective registration of the transition radiation (TR) X-rays and perform simultaneous measurements of their energies and emission angles. This unique feature opens new possibilities for particle identification on the basis of maximum available information about generated TR photons. Results of studies of TR energy-angular distributions using a 500 |j.m thick GaAs sensor attached to a Timepix3 chip are presented. Measurements, analysis techniques and a comparison with Monte Carlo (MC) simulations are described and discussed.
... The experimental results were compared with the theoretical calculation of TR, and a very good convergence was found ( Figure 3E). TR radiation has been studied both theoretically and experimentally [17,[59][60][61]. Ginzburg [62], who was the first to predict the TR phenomenon, carried out a theoretical approach in several ways. ...
Electron beams in electron microscopes are efficient probes of optical near-fields, thanks to spectroscopy tools like electron energy-loss spectroscopy and cathodoluminescence spectroscopy. Nowadays, we can acquire multitudes of information about nanophotonic systems by applying space-resolved diffraction and time-resolved spectroscopy techniques. In addition, moving electrons interacting with metallic materials and optical gratings appear as coherent sources of radiation. A swift electron traversing metallic nanostructures induces polarization density waves in the form of electronic collective excitations, i.e., the so-called plasmon polariton. Propagating plasmon polariton waves normally do not contribute to the radiation; nevertheless, they diffract from natural and engineered defects and cause radiation. Additionally, electrons can emit coherent light waves due to transition radiation, diffraction radiation, and Smith-Purcell radiation. Some of the mechanisms of radiation from electron beams have so far been employed for designing tunable radiation sources, particularly in those energy ranges not easily accessible by the state-of-the-art laser technology, such as the THz regime. Here, we review various approaches for the design of coherent electron-driven photon sources. In particular, we introduce the theory and nanofabrication techniques and discuss the possibilities for designing and realizing electron-driven photon sources for on-demand radiation beam shaping in an ultrabroadband spectral range to be able to realize ultrafast few-photon sources. We also discuss our recent attempts for generating structured light from precisely fabricated nanostructures. Our outlook for the realization of a correlative electron-photon microscope/spectroscope, which utilizes the above-mentioned radiation sources, is also described.
... More information on these issues can be found in the reviews by Bass & Yakovenko [1965]; Ter-Mikaelian [1972]. From the application point of view, TR has been widely used as a diagnostic in the particle accelerator community, where it is commonly referred to as optical transition radiation (OTR), since its intensity is proportional to the γ factor of the charged particles [Dolgoshein 1993]. ...
Les impulsions laser femtosecondes produisent des phénomènes non linéaires extrêmes dans la matière, conduisant à une forte émission de rayonnement secondaire qui couvre un domaine en fréquence allant du terahertz (THz) aux rayons X et gamma. De nombreuses applications utilisent la bande de fréquences terahertz (0.1-100 THz) afin de sonder la matière (spectroscopie, médecine, science des matériaux). Ce travail est dédié à l'étude théorique et numérique du rayonnement THz généré par interaction laser-plasma. Comparé aux techniques conventionnelles, ces impulsions laser permettent de créer des sources THz particulièrement énergétiques et à large bande. Notre objectif a donc été d'étudier ces régimes d'interaction relativiste, encore peu explorés, afin d'optimiser l'efficacité de conversion du laser vers les fréquences THz. L'étude de l'interaction laser-gaz en régime classique nous permet, d'abord, de valider un modèle de propagation unidirectionnelle prenant en compte la génération d'impulsion THz et de le comparer à la solution exacte des équations de Maxwell. Ensuite, en augmentant l'intensité laser au-delà du seuil relativiste, nous simulons à l'aide d'un code PIC une onde plasma non linéaire dans le sillage du laser, accélérant ainsi des électrons à plusieurs centaines de MeV. Nous montrons que le mécanisme standard des photocourrants est dominé par le rayonnement de transition cohérent induit par les électrons accélérés dans l'onde de sillage. La robustesse de ce rayonnement est ensuite observée grâce à une étude paramétrique faisant varier la densité du plasma sur plusieurs ordres de grandeur. Nous démontrons également la pertinence des grandes longueurs d'ondes laser qui sont à même de déclencher une forte pression d'ionisation, ce qui augmente la force pondéromotrice du laser. Enfin, les rayonnements THz émis à partir d'interactions laser-solide sont examinés dans le contexte de cibles ultra fine, mettant en lumière les différents processus impliqués.
... In these cases, the knowledge of the ion mobility can help to infer the rate detection limit [1]. Examples of this kind of detectors are micropattern gas detectors (MPGD), Transition Radiation Detectors (TRD) and Time Projection Chambers (TPC) [1][2][3][4][5]. Noble gases, like Xe, Ar and Ne are usually the preferred filling gases of detectors, but it is often necessary to add a molecular gas in low percentages to avoid some undesired effects, like the large electron diffusion, spurious pulses due to scintillation, among others [1,6,7]. ...
In this paper we present the results of the ion mobility measurements made in gaseous mixtures of neon with carbon tetrafluoride (Ne-CF4) at a total pressure 8 Torr (10.6 mbar) and for low reduced electric fields in the 10 to 25 Td range (2.4–6.1 kV⋅cm⁻¹⋅bar⁻¹), at room temperature. The time-of-arrival spectra revealed only one peak, which was attributed to CF3⁺. The reduced mobilities obtained from the peak centroid of the time-of-arrival spectra are presented for Ne concentrations in the 5%–95% range.
... . By changing the parameters of the radiator, the sensitivity of a TRD (Transition Radiation Detector) can be tuned to a certain -factor range (see for instance reviews [2,3]). This in turn makes TR attractive for particle identification at very high where other effects, such as Cherenkov radiation, reach saturation. ...
Growing energies of particles at modern or planned particle accelerator experiments as well as cosmic ray experiments require particle identification at gamma-factors (γ) of up to ∼10 ⁵ . At present there are no detectors capable of identifying charged particles with reliable efficiency in this range of γ. New developments in high granular pixel detectors allow one to perform simultaneous measurements of the energies and the emission angles of generated transition radiation (TR) X-rays and use the maximum available information to identify particles. First results of studies of TR energy-angular distributions using gallium arsenide (GaAs) sensors bonded to Timepix3 chips are presented. The results are compared with those obtained using a silicon (Si) sensor of the same thickness of 500 μm. The analysis techniques used for these experiments are discussed.
... These detectors are used for particle identification at high momenta [128,129]. The choice of the gas mixture for such detectors is determined by several parameters such as high electron/ion velocity and low electron diffusion, which are of key importance [5] as they influence the rate capability and signal formation of TRDs' of the Multi-Wire Proportional Chamber type (MWPCs) [8]. ...
This thesis presents the studies conducted with the objective of developing a new and ruggedized Gas Proportional Scintillation Counter (GPSC) based on high-pressure Xe (5- 20 bar) with a cylindrical geometry for the detection of hard X- and gamma-rays (100
keV to 662 keV). It is to be used in �eld applications, where robustness is a requirement,
for example in homeland security (detection of illegal transport of radioactive material)
or for geological prospection (instrumentation for boreholes). A study of the mobility of
ions in gases used in large volume detectors is also presented.
In GPSCs, the detection of ionizing radiation is based on the production of scintillation
photons as the ampli�cation stage, followed by their detection with the help of a photosensor, typically a photomultiplier. GPSCs have an absorption/drift region where
the ionizing radiation is absorbed, producing a cloud of primary electrons which is guided
by a low electric �eld (kept below the excitation threshold of the gas) to the scintillation
region, where the electric �eld is above the scintillation threshold but below the ionization
threshold of the gas. In the scintillation region, they produce a large number of scintillation photons (vacuum ultra-violet photons), emitted during the deexcitation process of the gas atoms. These will eventually reach the photosensor, producing a signal proportional to the energy of the incident radiation.
Conventionally, the adopted geometry is planar, since it displays the best energy resolution, but because of the photosensors usually adopted, its use in �eld applications is
limited. In a recent work, a prototype was developed with a planar geometry with the
objective of being more ruggedized for �eld applications. The main di�erence consisted
of the use of a deposited caesium iodide as the photosensor, with the photoelectrons produced by the VUV photons being collected at a grid close to the photocathode. However, this new detector displayed several limitations: low detection e�ciency for high energy radiation (above 50 keV); small solid angle subtended by the photosensor; and the high bias voltage needed, which reduced its performance and its application scope.
So, to solve these limitations a new detector for higher energies (100-662 keV) was
developed using a cylindrical geometry, which is expected to display several advantages.
On one hand, the cylindrical con�guration allows the number of metallic grids used to be
decreased, thus reducing the impact of the internal optical transmission in the detector
gain. In addition, the fact that the photocathode is deposited on the inner surface of
the detector walls signi�cantly increases the solid angle subtended by the photosensor,
improving the gain. Also because the radiation is absorbed along the cylinder axis, the
detecting e�ciency is improved. Moreover, this con�guration will, in principle, allow the
bias voltage to be minimized for the same gain when compared with the planar geometry.
In this work, this new prototype was designed according to the initial performance
requirements, constructed and assembled, followed by its characterization with the assessment of the prototype performance using an alpha particle source of 241Am, varying the pressure from 1 up to 3 bar. In the initial stage, the characterization of the 241Am source was performed, followed by the study of the charge collection at the anode and the characterization of the scintillation signal.
In this study, it was possible to verify that increasing the E=p above the ionization threshold at the anode surface and slightly above the scintillation one in the collecting
region, the energy resolution was improved. In addition, the gain and the signal-to-noise
ratio (SNR) of the detector were also determined. Regarding the gain, the experimental
values determined were in agreement with the theoretical ones, and at the best possible
conditions we were able to reach a gain of 1.9 at 1.05 bar, which gives a good outlook for
achieving gains of about 30 at 15 bar. As for the SNR, in the best possible conditions
studied, the signal was 10 times greater than the noise, which allowed the minimum
detectable energy to be estimated with the detector in the present operating conditions.
In parallel with the development of this new detector, the transport properties of ions
were also studied to provide information on ion mobility for di�erent gas mixtures used or
considered for several major experiments (ALICE TPC and TRD, CBM TRD, NEXT and
the future LCTPC), as the information of the mobility of ions in gases is relevant not only
for the design and modelling of gaseous radiation detectors, but also in the understanding of the signal formation. This work was developed in the scope of our participation in the NEXT Collaboration and RD51 Collaboration from CERN. The ion drift chamber used in these studies, already available in our laboratory, allows the drift time of this group of ions to be determined with precision and consequently their drift velocity and mobility.
Finally, knowing the mobility of these ions and using Blanc's law with the polarization
limit of the Langevin's formula, it is possible to identify most of the collected ions. In the
scope of this thesis, 5 gas mixtures of interest for the above-mentioned experiments were
studied: Xe-N2, Xe-CO2, Xe-CF4, Ar-C2H6 and Ar-CH4.
Another interesting result coming from this work is related to the validity of the Langevin polarization formula used to predict the mobility of ions and whose limitations are related to the weak polarizability of some neutrals such as Ne, or by the numerous internal degrees of freedom, responsible for reducing the mobility in gases such as CO2 by about 10%. An alternative method to the use of the Langevin polarization limit, when it fails, is proposed, which will allow a better estimate of the mobility to be obtained.
... In most of the TRDs used in particle physics, the radiator parameters are chosen to enhance the separation between electrons and pions up to -factors of ∼500 for pions. These detectors normally work as threshold devices, ensuring the best electron/pion separation in the momentum range 1 GeV∕ < < 50 GeV∕ (see reviews [1][2][3] and references there). However, many experiments require particle identification up to ∼ 10 5 . ...
X-ray Transition radiation detectors (TRDs) are used for particle identification in both high energy physics and astroparticle physics. Particle identification is often achieved based on a threshold effect of the X-ray transition radiation (TR). In most of the detectors, TR emission starts at γ factors above ∼500 and reaches saturation at γ∼2−3⋅10³. However, many experiments require particle identification up to γ∼10⁵, which is difficult to achieve with current detectors, based only on the measurement of the photon energy together with the particle ionization losses. Additional information on the Lorentz factor can be extracted from the angular distribution of TR photons. TRDs based on pixel detectors give a unique opportunity for precise measurements of spectral and angular distributions of TR at the same time. A 500 μm thick silicon sensor bump bonded to a Timepix3 chip was used in a test beam measurement at the CERN SPS. A beam telescope was employed to separate clusters produced by the primary beam particles from the potential TR clusters. Spectral and angular distributions of TR were studied with high precision for the first time using beams of pions, electrons and muons at different momenta. In this paper, the measurement and analysis techniques are described, and first results are presented.
... It should be noted that transition radiation (Ginzburg and Frank 1946) also gives rise to optical photons in the fibre due to differing optical properties (Jelley 1958). However, as the intensity of transition radiation is proportional to γ = 1/ 1 − β 2 , the transition radiation in an optical fibre is negligible relative to fluorescence for proton beams at clinical energies, and generally not emitted within the acceptance angle of the fibre (when placed perpendicular to the beam), as the radiation peaks at an angle γ −1 relative to the particle's path (Dolgoshein 1993). ...
Photons emitted in optical fibres under proton irradiations have been attributed to be both entirely Čerenkov radiation or to be light consisting of fluorescence with a substantial amount of Čerenkov radiation. The source of the light emission is assessed in order to understand why the signal from optical fibres irradiated with protons reportedly is quenching-free.
The present study uses the directional emittance of Čerenkov photons in 12 MeV and 20 MeV electron beams to validate a Monte Carlo model for simulating the emittance and transmission of Čerenkov radiation in optical fibres.
We show, that less than 0.01 Čerenkov photons are emitted and guided per 225 MeV proton penetrating the optical fibre, and that the Čerenkov signal in the optical fibre is completely negligible at the Bragg peak. Furthermore, by taking the emittance and guidance of both fluorescence and Čerenkov photons into account, it becomes evident that the reported quenching-free signal in PMMA-based optical fibres under proton irradiations is fluorescence.
... The only particle identification technique able to effectively separate hadrons with these γ-factors is based on the properties of the X-ray transition radiation (TR) production. Transition radiation detectors (TRD) have been used for accelerator experiments and cosmic ray experiments on the ground, at balloon altitudes, and in space (see reviews, [2,3,4]). Most of the transition radiation detectors are designed to separate electrons and pions and they use the threshold effect of the TR production. ...
Measurements of hadron production in the TeV energy range are one of the tasks of the future studies at the Large Hadron Collider (LHC). The main goal of these experiments is a study of the fundamental QCD processes at this energy range, which is very important not only for probing of the Standard Model but also for ultrahigh-energy cosmic particle physics. One of the key elements of these experiments measurements are hadron identification. The only detector technology which has a potential ability to separate hadrons in this energy range is Transition Radiation Detector (TRD) technology. TRD prototype based on straw proportional chambers combined with a specially assembled radiator has been tested at the CERN SPS accelerator beam. The test beam results and comparison with detailed Monte Carlo simulations are presented here.
... Measuring the mobility of ions in gases is relevant in several areas, from physics to chemistry, e.g. in gaseous radiation detectors modelling and in the understanding of the pulse shape formation [1][2][3], and also in IMS (Ion Mobility Spectrometry) a technique used for the detection of narcotics and explosives [4]. One of these examples are the so-called Transition Radiation Detectors (TRDs), used for particle identification at high momenta [5,6]. Xenon (Xe) is considered to be the best choice for the main gas, while the choice of the quencher is determined by different parameters [3]. ...
In this paper we present the results of the ion mobility measurements made in gaseous mixtures of xenon (Xe) with ethane (C2H6) for pressures ranging from 6 to 10 Torr (8–10.6 mbar) and for low reduced electric fields in the 10 Td to 25 Td range (2.4–6.1 kV⋅cm⁻¹⋅ bar⁻¹), at room temperature. The time of arrival spectra revealed two peaks throughout the entire range studied which were attributed to ion species with 3-carbons (C3H5⁺, C3H6⁺ C3H8⁺ and C3H9⁺) and with 4-carbons (C4H7⁺, C4H9⁺ and C4H10⁺). Besides these, and for Xe concentrations above 70%, a bump starts to appear at the right side of the main peak for reduced electric fields higher than 20 Td, which was attributed to the resonant charge transfer of C2H6⁺ to C2H6 that affects the mobility of its ion products (C3H8⁺ and C3H9⁺). The time of arrival spectra for Xe concentrations of 20%, 50%, 70% and 90% are presented, together with the reduced mobilities as a function of the Xe concentration calculated from the peaks observed for the low reduced electric fields and pressures studied.
... Measuring the mobility of ions in gases is relevant in several areas from physics to chemistry, e.g. in gaseous radiation detectors modelling and in the understanding of the pulse shape formation [1][2][3], and also in IMS (Ion Mobility Spectrometry) a technique used for the detection of narcotics and explosives [4]. One of these examples are the so-called Transition Radiation Detectors (TRDs), used for particle identification at high momenta [5,6]. The choice of the gas mixture for such detectors is determined by several parameters such as high electron/ion velocity and low electron diffusion, which are of key importance [3] as they influence the rate capability and signal formation of TRDs' of the Multi-Wire Proportional Chambers type (MWPCs) [7]. ...
Data on ion mobility is important to improve the performance of large volume gaseous detectors. In the present work, the method, experimental setup and results for the ion mobility measurements in Xe-CH4 mixtures are presented. The results for this mixture show the presence of two distinct groups of ions. The nature of the ions depend on the mixture ratio since they are originated by both Xe and CH4. The results here presented were obtained for low reduced electric fields, E/N, 10–25 Td (2.4–6.1 kV ⋅ cm⁻¹ ⋅ bar⁻¹), at low pressure (8 Torr) (10.6 mbar), and at room temperature.
... One of these examples are the so-called Transition Radiation Detectors (TRDs), used for particle identification at high momenta [5,6]. The choice of the gas mixture for such detectors is determined by several parameters such as high electron/ion velocity and low electron diffusion, which are of key importance [3] as they influence the rate capability and signal formation of detectors such as the Multi-Wire Proportional Chambers (MWPCs) [7]. ...
Data on ion mobility is important to improve the performance of large volume gaseous detectors. In the present work the method, experimental setup and results for the ion mobility measurements in Xe-CO2 mixtures are presented. The results for this mixture show the presence of only one peak for all gas ratios of Xe-CO2, low reduced electric fields, E/N, 10-25 Td (2.4-6.1 kVcm⁻¹bar⁻¹), low pressures 6-8 Torr (8-10.6 mbar), at room temperature.
... A key feature of the TRT is its strength in particle identification, due to the use of transition radiation (TR) detection [48]. TR is produced when a charged particle moves between two homogenous media having different dielectric constants. ...
This dissertation summarizes two searches for new physics in LHC proton collision data collected by the ATLAS detector at CERN. In particular, these searches were designed to optimize the chances of discovery of supersymmetric particles, assuming a supersymmetry breaking scheme known as General Gauge Mediation (GGM). The final state considered in these analyses consists of a Z boson, where the Z decays to an electron or muon pair, in association with large missing transverse momentum and jets. The first of the two analyses is based on data collected in 2011, when the LHC delivered collisions at a center of mass energy 7 TeV. Using 1.04 fb???1 of good quality ATLAS data, signal region optimization and quantification of backgrounds using data-driven methods were carried out. No excess above the Standard Model expectation was observed, and these results were interpreted in a GGM context in which the lightest neutralino (the NLSP) is higgsino-like. A follow-up to this search was also performed using 5.84 fb???1 of 8 TeV ATLAS data recorded in 2012. Overall, this analysis is similar to the 2011 work, with some changes in the data-driven background methods and signal models used for interpretation. Again, no excess was observed in relation to the expectation from the Standard Model processes. In addition to the GGM models used in 2011, which are characterized with a low value of tan(beta), a high tan(beta) interpretation was considered for the 2012 analysis. 95% CL limits on the gluino and higgsino mass have been set. For the low tan(beta) scenario, gluino masses in the range 680 < m(gluino) < 880 GeV have been excluded for higgsino masses between 180 and 800 GeV. Assuming high tan(beta), gluino masses between 680 and 820 GeV were excluded for 180 < m(higgsino) < 740 GeV.
Free‐electron radiation is a fundamental photon emission process that is induced by fast‐moving electrons interacting with optical media. Historically, it has been understood that, just like any other photon emission process, free‐electron radiation must be constrained within a finite time interval known as the “formation time,” whose concept is applicable to both Cherenkov radiation and transition radiation, the two basic mechanisms describing radiation from a bulk medium and from an interface, respectively. Here, this work reveals an alternative mechanism of free‐electron radiation far beyond the previously defined formation time. It occurs when a fast electron crosses the interface between vacuum and a plasmonic medium supporting bulk plasmons. While emitted continuously from the crossing point on the interface—thus consistent with the features of transition radiation—the extra radiation beyond the conventional formation time is supported by a long tail of bulk plasmons following the electron's trajectory deep into the plasmonic medium. Such a plasmonic tail mixes surface and bulk effects, and provides a sustained channel for electron–interface interaction. These results also settle the historical debate in Ferrell radiation, regarding whether it is a surface or bulk effect, from transition radiation or plasmonic oscillation.
PurposeThis study aims to create a new tool for fast computer simulations allowing one to design advanced electromagnetic calorimeters with the required properties. The application must calculate the calorimeter efficiency and measure the particles' energies, momenta and interaction time to detect the particles. This application should become the basis for a new technology of positron emission tomography.Methods
To solve the problem, a new C++ application based on Geant4 simulation toolkit has been developed. To monitor the response of calorimeters to different types of primary particles, we used different auxiliary Geant4 classes. In addition, we compare the simulation results for the detectors of three different setups, taking into account the detection of both electrons and gamma-quanta, and analyze their efficiency. To evaluate the capability of calorimeters to work under radiation load, we use an experimentally measured transmission function of radiation-damaged PbF2.ResultsThree calorimeter setups exploiting PbF2 were simulated with a new C++ application based on Geant4. We showed that such type of calorimeter has an energy resolution of \({{4.1\% } \mathord{\left/ {\vphantom {{4.1\% } {\sqrt {E_{{e^{ + } }} [{\text{GeV}}]} }}} \right. \kern-0pt} {\sqrt {E_{{e^{ + } }} [{\text{GeV}}]} }}\) and good linearity of response for GeV positrons measurements. The efficiency of such structures is found to be approximately 20% for gamma photons’ detection. The multilayered structure based on gamma-quanta detection has been proven to be more efficient. It was shown that for the total ionizing dose of 30 krad the Cherenkov light yield decreases by up to two times for 14 cm long PbF2 crystals, while for the shorter ones (2.5 and 1.5 cm) this effect is almost negligible.Conclusions
We present a new user application in Geant4 for fast simulation of complex structures designed for detection of different high-energy neutral and charged particles. Simulation of calorimeter interaction with 103 of 3 GeV positrons takes 20 min on usual laptop, while for 105 511 keV gamma photons it takes 1 min on average. This application allows one to evaluate the efficiency of electromagnetic calorimeters exploiting lead fluoride crystals. Our results pave the way for advanced particle energy measurements, including those used in rapidly developing medical applications such as positron emission tomography, single-photon emission computed tomography etc.
The High Energy cosmic-Radiation Detection facility (HERD) is a calorimetry-based cosmic-ray detection mission on board China space station. A side-on transition radiation detector (TRD) focuses on the TeV energy range calibration of the HERD calorimeter with an error of less than 10% by measuring the Lorentz factor γ of high-energy cosmic-ray protons. A side-on TRD prototype was developed for the performance study and tested by Deutsches Elektronen-Synchrotron electron beams. In this paper, the Monte Carlo simulation based on GEANT4 was compared with the experiment results. All simulations were in good agreement with the test beam results.
We study how transition radiation is modified by the presence of a generic magnetoelectric medium with a special focus on topological insulators. To this end, we use the Green's function for the electromagnetic field in presence of a plane interface between two topological insulators with different topological parameters, permittivities, and permeabilities. We employ the far-field approximation together with the steepest descent method to obtain approximate analytical expressions for the electromagnetic field. Through this method, we find that the electric field is a superposition of spherical waves and lateral waves. Contributions of both kinds can be attributed to a purely topological origin. After computing the angular distribution of the radiation, we find that in a region far from the interface the main contribution to the radiation comes from the spherical waves. We present typical radiation patterns for the topological insulator TlBiSe2
and the magnetoelectric TbPO4. In the ultrarelativistic case, the additional contributions from the magnetoelectric coupling appreciably enhance the global maximum of the angular distribution. We also present an analytic expression for the frequency distribution of the radiation for this case. We find that in the limit where the permittivities are equal, there still exists transition radiation of the order of the square of the topological parameter with a pure topological origin.
Transition radiation detectors (TRDs) have been used to identify high-energy particles (in particular, to separate electrons from heavier particles) in accelerator experiments. In space, they have been used to identify cosmic-ray electrons and measure the energies of cosmic-ray nuclei. To date, radiators have consisted of regular configurations of foils with fixed values of foil thickness and spacing (or foam or fiber radiators with comparable average dimensions) that have operated over a relatively restricted range of Lorentz factors. In order to extend the applicability of future TRDs (for example, to identify 0.5–3 TeV pions, kaons, and protons in the far forward region in a future accelerator experiment or to measure the energy spectrum of cosmic-ray nuclei up to 20 TeV/nucleon or higher), there is a need to increase the signal strength and extend the range of Lorentz factors that can be measured in a single detector. A possible approach is to utilize compound radiators consisting of varying radiator parameters. We discuss the case of a compound radiator and derive the yield produced in a TRD with an arbitrary configuration of foil thicknesses and spacings.
An algorithm for the angular distribution of X-ray transition radiation generated by a relativistic charged particle in regular radiators at small angles (less than 1 mrad) is discussed in the framework of the Geant4 simulation toolkit. The model predictions are compared with experimental data recently obtained at the ATLAS TRT test beam.
Free‐electron radiation phenomena facilitate enticing potential to create light emission with highly tunable spectra, covering hard‐to‐reach frequencies ranging from microwave to X‐ray. Consequently, they take part in many applications such as on‐chip light sources, particle accelerators, and medical imaging. While their spectral tunability is extremely high, their polarizability is usually much harder to control. Such limitations are especially apparent in all free electron based spontaneous radiation sources, such as the Smith−Purcell (SP) radiation. Here, anomalous free‐electron radiation phenomenon is demonstrated at the microwave regime from gradient bianisotropic metasurfaces, by using a phased dipole array to mimics moving charged particles. The phase gradient and the bianisotropy in metasurfaces provide new degrees of freedom for the polarization shaping of free‐electron radiation, going beyond the common spectral and angular shaping. Remarkably, the observed anomalous free‐electron radiation obeys a generalized SP formula derived from Fermat's principle. Polarization shaping of Smith−Purcell (SP) radiation is experimentally demonstrated through the use of gradient bianisotropic metasurfaces. If the phase gradient is nonzero, the anomalous SP radiation obeys the generalized SP formula derived from Fermat's principle, instead of the regular SP formula. The phase gradient and bianisotropy in metasurfaces can provide extra degrees of freedom for the simultaneous polarization, spectral, and angular shaping of anomalous free‐electron radiation.
We theoretically study the transition radiation in the framework of full Maxwell equations, when a swift electron crosses a monolayer graphene. Based on the Sommerfeld integration, we demonstrate in the frequency domain the spatial distribution of this free-electron radiation, which clearly shows the broadband excitation of both photons and graphene plasmons. Moreover, the radiation spectra for photons and graphene plasmons are analytically derived. We find that the excitation of photons and graphene plasmons favors different particle velocities. To be specific, a higher particle velocity gives rise to the excitation of photons with better directivity and higher intensity, while a lower particle velocity enables the efficient excitation of graphene plasmons in a broader frequency range. Our work indicates that the interaction between swift charged particles and various 2D materials or van der Waals heterostructures is promising for the design of terahertz on-chip radiation sources.
The formation region effects in x-ray transition radiation have been experimentally investigated. The radiation was generated using 1-6 GeV electrons impinging on two multilayer targets with considerably different periods. The absolute yield of transition radiation was measured and the wide spectral peak in the range from 10 to 30 keV was observed. In the most part of the electron energy range the emission from the short-period radiator was expectedly suppressed, compared to the case of the long-period one. But for the electron energy of 1 GeV an opposite effect, though rather small, of the emission enhancement in the short-period radiator was observed. The conditions, under which this effect is much stronger, are derived and its possible practical value is outlined. The theory accounting for an arbitrary transversal shape of the electron beam and the finite size of the detector is developed. This theory describes rather well the experimental results.
X-ray transition radiation detectors (TRDs) are used for particle identification in both high energy physics and astroparticle physics. In most of the detectors, emission of the X-ray transition radiation (TR) starts at Lorentz factors above γ∼500 and reaches saturation at γ∼2÷3⋅103. However, many experiments require particle identification up to γ∼105, which is very difficult to achieve with conventional detectors. Semiconductor pixel detectors offer a unique opportunity for precise simultaneous measurements of spectral and angular parameters of TR photons. Test beam studies of the energy and the angular distributions of TR photons emitted by electrons and muons of different momenta crossing several types of radiators were performed at the CERN SPS with a 480 μm thick silicon detector bonded to a Timepix3 chip. High resolution images of the energy−angle phase space of the TR produced by different radiators were obtained and compared with MC simulations. The characteristic interference patterns are in agreement with the theoretical models with an unprecedented level of details. The studies presented in this paper also show that simultaneous measurements of both the energy and the emission angles of the TR X-rays could be used to enhance the particle identification performances of TRDs.
Transition Radiation Detectors (TRD) have the attractive feature of separating particles by their gamma factor. Classical TRDs are based on Multi-Wire Proportional Chambers (MWPC) or straw tubes, using a Xenon based gas mixture to efficiently absorb transition radiation photons. These detectors operate well in experiments with relatively low particle multiplicity. The performance of MWPC-TRD in experiments with luminosity of order 1034 cm2s−1 and above, is significantly deteriorated due to the high particle multiplicity and channel occupancy. Replacing MWPC or straw tubes with a high granularity Micro Pattern Gas Detectors (MPGD) like Gas Electron Multipliers (GEMs), could improve the performance of the TRD. In addition, GEM technology allows one to combine a tracker with TRD identification (GEM-TRD/T). This report presents a new TRD development based on GEM technology for the future Electron Ion Collider (EIC). The first beam test was performed at Jefferson Lab (Hall-D) using 3–6 GeV electrons. A GEM-TRD/T module has been exposed to electrons with and without a fiber radiator. First results of test beam measurements and comparison with Geant4 Monte Carlo are presented in this article.
In this work, we construct for the first time the theory of small-angle transition radiation from multilayered structures. The theoretically obtained spectral and angular distributions of radiated photons are compared with those predicted by Geant4, a very popular package used today for numerical simulation of different physical processes. We demonstrate that, while spectral distributions ideally coincide, the angular ones differ. We argue that transition radiation from the multilayered structure must contain sharp spikes having the interference nature and caused by the effect of merging two maximum frequencies in dispersive media, and thus Geant4 needs improving in this respect. The transition radiation theory developed here for the small-angle case can play a vital part for the possible future Small Angle Spectrometer at the LHC, other experiments of this kind, and detectors for hadrons of the tera-electron-volt energy range.
Plasma-based accelerators that impart energy gain as high as several GeV to electrons or positrons within a few centimeters have engendered a new class of diagnostic techniques very different from those used in connection with conventional radio-frequency (rf) accelerators. The need for new diagnostics stems from the micrometer scale and transient, dynamic structure of plasma accelerators, which contrasts with the meter scale and static structure of conventional accelerators. Because of this micrometer source size, plasma-accelerated electron bunches can emerge with smaller normalized transverse emittance (εn<0.1 mm mrad) and shorter duration (τb∼1 fs) than bunches from rf linacs. Single-shot diagnostics are reviewed that determine such small εn and τb noninvasively and with high resolution from wide-bandwidth spectral measurement of electromagnetic radiation the electrons emit: εn from x rays emitted as electrons interact with transverse internal fields of the plasma accelerator or with external optical fields or undulators; τb from THz to optical coherent transition radiation emitted upon traversing interfaces. The duration of ∼1 fs bunches can also be measured by sampling individual cycles of a copropagating optical pulse or by measuring the associated magnetic field using a transverse probe pulse. Because of their luminal velocity and micrometer size, the evolving structure of plasma accelerators, the key determinant of accelerator performance, is exceptionally challenging to visualize in the laboratory. Here a new generation of laboratory diagnostics is reviewed that yield snapshots, or even movies, of laser- and particle-beam-generated plasma accelerator structures based on their phase modulation or deflection of femtosecond electromagnetic or electron probe pulses. Spatiotemporal resolution limits of these imaging techniques are discussed, along with insight into plasma-based acceleration physics that has emerged from analyzing the images and comparing them to simulated plasma structures.
Transition radiation appearing when a charged particle crosses the interface between two media with different dielectric constants, e.g., a metal–vacuum interface, has been well studied in a wide spectral range. However, primarily, radiation from smooth interfaces has been studied. Transition radiation from conducting gratings (grating transition radiation) is experimentally studied and theoretically analyzed in this work. In this case, it is possible to obtain monochromatic radiation with a tunable frequency depending on the rotation angle of the grating with respect to the electron momentum. Coherent grating transition radiation can be efficiently used as a source of terahertz radiation based on the use of a compact electron accelerator with an energy below 10 MeV and a bunch duration of ≤1 ps.
We review the basic features of transition radiation and how they are used for the design of modern Transition Radiation Detectors (TRD). The discussion will include the various realizations of radiators as well as a discussion of the detection media and aspects of detector construction. With regard to particle identification we assess the different methods for efficient discrimination of different particles and outline the methods for the quantification of this property. Since a number of comprehensive reviews already exist, we predominantly focus on the detectors currently operated at the LHC. To a lesser extent we also cover some other TRDs, which are planned or are currently being operated in balloon or spaceborne astro-particle physics experiments.
We present results from tests of a prototype of the TRD for the ALICE experiment at LHC. We investigate the performance of different radiator types, composed of foils, fibres and foams. The pion rejection performance for different methods of analysis over a momentum range from 0.7 to 2 GeV/c is presented.
The aging phenomena are very complex physical and chemical processes.
The author attempts to qualitatively discuss various physical processes
contributing to aging. A satisfactory quantitative explanation is not
presently available. In this sense, little progress has been made since
the 1986 LBL Aging Workshop. However, what was accomplished during the
past decade is a heightened awareness from the research and management
sides to pay more attention to this problem, and as a result a number of
aging tests have increased in quantity and quality. These efforts will
undoubtedly yield some new results in the future. Examples in this paper
are mainly from a "pre-LHC and pre-HERA-B era of aging," where the total
charge doses are limited to much less than 1 C/cm.
The ATLAS central level-1 trigger logic consists in the Central Trigger Processor and the interface to the detector-specific muon level-1 trigger electronics. It is responsible for forming a level-1 trigger in the ATLAS experiment. The distribution of the timing, trigger and control information from the central trigger processor to the readout electronics of the ATLAS subdetectors is done with the TTC system. Both systems are presented.
An improved method of particle detection is described, utilizing both the x-ray transition radiation and the ionization of a gas by the particle.
A new method for x-ray transition radiation detection by a streamer spark chamber is suggested. The use of the chamber secures a separate observation of both the radiation and the particle. It is shown that the mean number of the transition quanta linearly increases in the electron energy range 1.2 to 2.46 GeV. When plastic foam was used instead of a layered medium the efficiency of electron detection by transition radiation was 86%.
Transition radiation in the optical region of the spectrum from individual charged pions and protons in the momentum region of 0.8 to 3.5 BeV/c was obtained from a stack of thin metal foils spaced uniformly in vacuum. The radiation was observed simultaneously in the forward and in the backward directions, with a forward-to-backward intensity ratio of the order of 8 to 1. A logarithmic increase in the intensity of the transition radiation with the total energy of the particle is found in the momentum region of the present investigation.
Transition radiation has been revisited to rectify some inconsistencies in the original Ginzburg and Frank formulation. Our calcualtions of radiation intensity exhibit qualitative deviations from the original formula, particularly in the nonrelativistic limit. In highly relativistic cases, differences in the radiation intensity are insignificant.
This paper employs Monte Carlo simulations of the performance of a transition radiation detector (TRD). The program has been written for the TRD in the ZEUS spectrometer, which separates electrons from hadrons in the momentum range between 1 and 30 GeV/c. Both, total charge method and cluster counting method were simulated taking into account various experimental parameters. In particular, it was found that the cluster counting method relies on a quantitative understanding of the background originating from the production of δ-electrons by charged particles. The results of the Monte Carlo calculations are in agreement with experimental data obtained with prototypes within a systematic uncertainty of 20%. We applied our Monte Carlo program to studies in order to find an optimum layout for the TRD within available space in the ZEUS spectrometer. In this context, the performance of TRD layouts with different geometries and materials has been evaluated comprehensively. The geometry found by optimization promises an improvement on hadron suppression by a factor of about two for both methods compared with present results from test measurements. Applying algorithms for a detailed analysis of the energy and space distributions of the clusters in the TRD, hadrons in the momentum range from 1 to 30 GeV/c can be suppressed to a level of less than 2%. This method of cluster analysing improves the suppression of hadrons by a factor of about two compared to the total charge method.
The results of an experiment on the investigation of a XTR-detector are given. On the basis of these results and theoretical calculations the possibilities of using XTR-detectors for identifying particles with various masses in the momentum region P ⩾ 100 GeV/c are analysed.
Transition radiation in the optical region of the spectrum from individual charged pions and protons in the momentum region of 0.8 to 3.5 BeV/c was obtained from a stack of thin metal foils spaced uniformly in vacuum. The radiation was observed simultaneously in the forward and in the backward directions, with a forward-to-backward intensity ratio of the order of 8 to 1. A logarithmic increase in the intensity of the transition radiation with the total energy of the particle is found in the momentum region of the present investigation.
Preliminary measurements of the transition radiation in the x-ray region indicate that an average of 12 x-ray photons are produced by a single positron of 2-BeV energy traversing a stack of 231 thin aluminum foils. This number is large enough to indicate that it is feasible to use the x-ray transition radiation for the determination of the relativistic factor gamma rather than beta of superhigh-energy particles. Such an application may well provide a unique method for distinguishing monoenergetic particles in the superhigh-energy region.
The mechanisms of the reorganization of atoms with inner shell vacancies are reviewed. All available experimental values of K-, L-, and M-shell fluorescence yields, together with L-shell Coster-Kronig yields are summarized and compared with available theoretical calculations. Rather good agreement exists in general between theory and experiment for the K shell, but experimental values of the L2 and L3 subshell fluorescence yields disagree substantially with the semitheoretical results of Listengarten. Related phenomena in mu-mesic atoms are included. Experimental methods of measurement are summarized and discussed, together with suggestions for future studies with high resolution techniques. Results from the literature have been included up to 10 May 1966.
The use of relatively thick foils, large spacings, and high plasma frequencies makes it possible to extend the energy range of transition radiation detectors up to Lorentz factors near 105. The maximum sensitivity to particle energy then comes at frequencies above 100keV, where inorganic scintillators are effective X-ray detectors and Compton scattering can be used to separate the X-ray signal from the particle's ionization. We describe the motivation and use of scintillator-based detectors to measure particle energies.
Transition Radiation is the term adopted to describe a feeble radiation emitted when a charged particle crosses the boundary between two media having different optical properties. The paper describes experiments to establish the existence of this effect, which has previously only been studied theoretically. The results, obtained from studies of the polarization of the radiation, its excitation function and its absolute yield, confirm the predictions of theory.
The improvement in the separation of electrons and pions by using flash ADCs in the readout compared to the methods of total charge integration and cluster counting was investigated. A detector using a Xe-CO2 filled chamber and polyethylene foil radiators was tested in 3 GeV pion and electron beams. We conclude that in a setup of four such radiators and chambers pions are counted with 0.7% efficiency, when the electron detection efficiency is 90%. By measuring individual cluster charges and positions an improvement in particle separation by a factor of 2 with respect to the method of total charge integration is obtained.
Transition radiation detectors (TRDs) have been tested for the separation of electrons from pions in the momentum range between 1 and 6 GeV/c. Foams as well as fibres and foils served as radiator materials while two types of chambers, a longitudinal drift chamber (DC) and a multiwire proportional chamber (MWPC), both of 16 mm depth and dominantly filled with xenon, were used for detecting the transition radiation photons with a setup of four chambers. Analyzing the data we compared the methods of mean, truncated mean and of maximum likelihood of the total charge measurements and several methods of cluster analysis. As a result of the total charge measurements performed at test beams at CERN and DESY we obtained about 1% pion contamination at 90% electron efficiency for the polypropylene materials in the configuration of four modules with a total length of 40 cm. An improvement by a factor of about two for the electron/pion discrimination can be obtained in the case of a detailed analysis of the clusters.
This paper is concerned with the radiation arising in the passage of relativistic particles of constant velocity through an arbitrary periodical heterogeneous medium. The necessary condition of the origin of radiation, the condition of resonance (2,1), is derived on the basis of the laws of conservation of energy and momentum. The total radiation in a periodic medium is composed of radiations of different orders (harmonics). For each order of radiation there is a special frequency interval (2,6) and its own energy threshold (2, 10). The radiation of each order is concentrated around the lower boundary of the respective spectrum intervals. The intensity of resonance radiation and its spectrum are calculated a for a medium changing its properties by the cosinus las (sec. 4/b) for a medium of arbitrary periodicity with a weak change of density (sec. 4) and c) for a stratified medium (sec. 5), probably the most suitable for experimental purposes. Different effects influencing the accuracy of the formulas derived are analyzed in the last section. The properties of resonance radiation enumerated above can be applied in the physics of particles of ultra-high energy (secs. 5 and 6).
The possibility of spatial separation of relativistic particle ionization loss and transition radiation (RTR) γ-quanta from this particle was investigated. For this aim a double electroluminescent drift chamber filled with xenon at 10 atm pressure was built. The detailed characteristics of the chamber have been investigated on the 3.5 GeV electron beam of the Serpukhov accelerator. The results show the possibility of spatial resolution of TR and ionization signals.
A transition radiation detector operating at low gas pressures was built at Yerevan and tested at Fermilab. At low pressure, total dE/dx is decreased without loss of efficiency for transition radiation X-rays. Data with π's and p's at 40, 100 and 200 GeV/c momenta are presented. The data show that 0.5% overlap between π's and p's may be achieved at 40 GeV/c with a 2 m long detector.
The problem of utilising the phenomenon of transition radiation for the detection of ultra-relativistic charged particles is analysed. It is shown that a foam of liquid deuterium is likely to provide the best possible laminar medium for particles in the energy range accessible to the new high energy accelerators. A proposal is made for the deuterium bubble-bath detector which will give useful resolution of the Lorentz factor (γ) in the range 500–10000. Application of this device to particle discrimination in momentum analysed beams is very promising. Rejection factors of greater than 100:1 are predicted for pion-kaon separation in the region of 100 GeV/c.
Starting from an approximation formula for the stopping power of electrons there is derived a semi-empirical range-energy-relation for electrons of the form R = AE[1 + B (1 + CE)−1] which is representing the known experimental data of electron ranges in the region 3 keV … 3 MeV with good accuracy. The constants A, B and C are determined by comparison with known empirical approximation formulae for true and maximal ranges of monoenergetic electrons and β-particles and for extrapolated ranges of monoenergetic electrons in aluminium.
We report a measurement of the frequency spectrum of x-ray transition radiation. X rays were generated by electrons of 5 and 9 GeV in radiators of multiple polypropylene foils, and detected in the range 4 to 30 keV with a calibrated single-crystal Bragg spectrometer. The experimental results closely reproduce the features of the theoretically predicted spectrum. In particular, the pronounced interference pattern of multifoil radiators and the expected hardening of the radiation with increasing foil thickness are clearly observed. The overall intensity of the radiation is somewhat lower than predicted by calculations. (AIP)
We report a new type of counter based on the transition radiation from ultrarelativistic charged particles. The efficiency of the "transition counter" depends almost linearly on the Lorentz factor of the particle in the energy region covered and is over 80% for 2-GeV electrons. Particles heavier than electrons in a 2-GeV unseparated beam are effectively rejected. A possible application of the counter at multihundred-GeV accelerators is discussed.
A general formula for the energy distribution of transition radiation is obtained. Approximations corresponding to small and large average numbers of emitted photons are anlayzed. The theory considered is compared with experimental data.
Measurements have been made of X-ray transition radiation spectra, which
were produced by relativistic electrons traversing periodic stacks of
mylar and lithium foils. The dependence of the spectral yield on the
stack parameters and on the momentum of the electrons establishes the
influence of long-range coherence in the emission of transition
radiation.
Experimental results for two types of detectors, that use resonance radiation of electrons with energies of 2.8 and 3.7 GeV in a laminar medium are presented. The detectors are tested in an experiment in selecting electrons from a pi--meson beam; about 50% efficiency is achieved.
Measurements have been made on the gamma (Lorentz factor) dependence of the transition radiation intensity in the x-ray region caused by positrons with gamma ranging from 1000 to 8000. Our results show that the intensity of the X-ray transition is linearly proportional to gamma as predicted by theory. Because of such a linear dependence as well as a reasonable intensity available the X-ray transition radiation can be feasibly used for the determination of the gamma value of ultrarelativistic particles.
A Monte Carlo program to design a transition radiation detector is shown; this program is able to calculate X-ray yields from multiple modules of such a detector taking into account the absorption inside materials eventually interposed between radiators and chambers. In addition the program computes the delta-ray background produced by incident particles.
A Monte Carlo program to design a transition radiator detector is described. The program provides the possibility to calculate the X-ray yield from radiators of different materials and structures, and analyzes the transition radiation energy release in various gaseous detectors.
Studies of the behaviour of straw proportional tubes, 4 mm in diameter, under sustained irradiation were carried out with a Xe-CO2-CF4 [50-30-20] gas mixture. No observable gain drop has been found to affect the tubes up to reasonable doses (less-than-or-equal-to 1 C/cm of wire). The chemical modification of the gas composition, causing the formation of electronegative, relatively stable species during the avalanche processes in a highly irradiated straw tube, is suggested to be responsible for a decrease of the pulse height in a second proportional counter (12.5 mm drift distance) operated with this (radical-enriched) gas mixture. Finally, we have observed that, for a straw tube operated at gain of a few times 10(4), there is a contribution to the total collected charge coming from few, very large pulses, probably due to occasional transition to a limited streamer regime.
Transition radiation in the optical region from individual protons and pions, as well as from electrons in the relativistic energy region was obtained from aluminum and silver foils. The intensity increases logarithmically with the particle energy in agreement with theory.
The transition radiation detector (TRD) for the D0 experiment is currently under construction at Saclay. The first part of this paper reports on the tests performed with a prototype detector at the CERN PS. Chamber operation was studied with xenon gas and small additions of CO2, CH4, or isobutane as quenchers. X-ray yields from lithium and polypropylene radiators were compared, with different analysis methods. The second part describes the design and construction of the cylindrical TRD, to be built and installed in the D0 Experiment (E740) at FNAL ** See the D0 experiment at the Fermilab antiproton-proton collider, Design Report, FNAL (October 1984). , which should provide a pion rejection factor of 50 for 90% electron efficiency. The first chamber of this 3-unit detector will be ready for test in April 1987, and the full TRD is planned to be assembled at the end of 1987.
A formula is derived for the spectral distribution of the xray
transition radiation quanta produced in an irregular medium consisting of
randomly distributed plates of arbitrary thickness which are parallel to each
other. Absorption of the radiation in the plates is taken into account in the
formulas. The formula is averaged over the thicknesses and distances between the
plates for arbitrary distributions of these quantities. In the limiting case of
zero irregulariiy, the familiar formula for x-ray transition radiation in a
regular stack can be derived from the general formula. In another limiting case,
when the medium is extremely irregular (i.e., when the spread of the plate
thicknesses and of the distances beiween them are much greater than formation
zones in matter and vacuum respectively), the number of radiation quanta produced
in the medium is an additive sum of the number of radiation quanta produced at
the boundaries. A numerical calculation is performed for a model in which the
plate thicknesses and distances can be described by a gamma-distribution. (auth)
In the present paper, we give a simple derivation of the spectrum and angular distribution of the transition radiation emitted by ultrarelativistic particles which pass through dielectric foils. The approximations appropriate for high-frequency radiation in the ultrarelativistic limit are made at the beginning. The calculations are consequently much simpler than standard calculations, and our results, some of which are apparently new, are relatively simple and easy to interpret. The primary emphasis in the development is on conditions likely to be encountered in the application of transition radiation detectors in high-energy physics.
Transition radiation detectors (TRDs) have been used for three decades to study highly relativistic cosmic rays. Their relatively low weight but large sensitive area makes them particularly suitable for measurements above the atmosphere, on balloons or in space. A review is given of the different requirements and experimental solutions for threshold detectors and energy-measuring devices, and the astrophysical significance of the measurements is briefly summarized. Finally, the importance of TRD devices for future works is discussed.
This text explains how drift chambers - the modern detectors for particles - work. It provides a solid foundation for judging the achievable accuracy of co-ordinate and ionization measurements. The book covers topics such as gas ionization by particles and by laser rays; the drift of electrons and ions in gases; electrostatics of wire grids and field cages; amplification of ionization; creation of the signal track parameters and their errors; ion gates; particle identification by measurement of ionization; existing chambers; and drift chamber gas. The topics are treated in a textbook style with many figures. Calculations are presented in some detail. The text is suitable for all students who want to begin to understand particle detection and drift chambers. Information that was previously scattered throughout the research literature is combined with calculations by the authors of the statistics of ionization and the fundamental limits of accuracy, along with the results of the authors' experiments on ionization, drift and diffusion of electrons in gases, and the amplification process.
The AMS02 experiment will be installed on the International Space Station for a data taking period of 3 years. The TRD consists of 20 layers of straw modules and fleece radiator with a total of 328 modules (16 straws each). The housing consists of a conically shaped octagon structure made out of CFC-Al-honeycomb material and is closed by a lower and upper honeycomb plate. The gas is a 80:20 Xe/CO2 mixture. The straw modules will be operated in proportional mode at a gasgain of 3000. The signals are readout by VA chips. The detector is under construction at RWTH Aachen, the gas system will be built at MIT, slow-control at INFN Rome and DAQ at TH Karlsruhe. In the presentation special emphasis will be dedicated to the space qualification aspects and the status of the straw module production.
A transition radiation detector has been built for the CERN hyperon beam experiment WA89. The task of this detector is to reject at an early trigger stage beam pions, which are more than twice as abundant as hyperons. Special requirements were imposed by the high beam flux and the need for an early trigger signal. Setup and performance of the detector are presented.
Electron drift velocities are reported for XeCF4, XeC2H2 and XeCF4C2H2 mixtures. For a number of these mixtures the drift velocities are large (4 to 10 × 106 cm s−1) over a range of values below 3.5 V cm−1 Torr−1. Such mixtures may find application in gas-filled detectors, especially those involving electromagnetic ionizing radiation.
Spectra of X-ray transition radiation (XTR) were measured, which were emitted in the passage of relativistic electrons through different samples of polyethylene foam. Based on the good agreement with absolute theoretical predictions, possible TR detectors are optimized for the Lorentz factor γL rangeγL=200−1000. Such radiations are predicted to offer useful discrimination between pions, kaons, and protons with momenta above 100 GeV/c.
A neural network algorithm has been applied in order to distinguish positrons from protons by a transition radiation detector (TRD). New variables are introduced, that simultaneously take into account spatial and energy TRD information. This method is found to be better than the one based on classical analysis: the results improve the detector performance in particle identification for efficiency higher than 90%. The high accuracy achieved with this method is used to identify positrons versus protons with 3 × 10−3 contamination, as required by TRAMP-SI cosmic ray space experiment on the NASA Balloon-Borne Magnet Facility.
Aging of gaseous detectors is known as the degradation of their performance under the exposure to ionizing radiation. It is a complex phenomenon that depends on many parameters. Among others, aging depends on the gas mixture and may be enhanced by the presence of pollutants in the gas. The origin of the impurities is diverse and includes outgassing from assembly materials, contamination of the detector during the assembly process and the gas system itself. Systematic studies on this topic have been carried out. Methods used to ascertain the outgassing properties of materials are described and compared. Materials that might be used for assembling gaseous detectors and associated gas systems are catalogued according to their outgassing rate. Some factors affecting the aging rate of some fast gases are presented. Finally, a set of recommendations to build and operate gaseous detectors in high luminosity experiments is given.
The microstructures of a variety of low-density (less than 0.1 g cm–3) polymeric foam materials are presented. Structures include the large, but well-defined, closed cells of commercially produced foams and a variety of finer, but often less well-defined, open cells of research foams produced from polymers, carbon, and silica. Other topics covered are the sizes and lowest densities of foams available, optical and X-ray opacity, and ease of handling.
The status of the operation and performance of the H1 Forward Track Detector at the HERA ep storage rings for the detection of electrons (e−) and positrons (e+) is reported. Events with charged particles produced at small angles (7° < θ <25°) relative to the incident proton beam are reconstructed using radial wire and planar wire drift chambers with an accuracy of for momenta p>3 GeV. Transition radiation X-rays, produced in polypropylene foil radiators immediately upstream of each radial wire drift chamber, are detected in the latter as ionisation charge additional to the usual contribution. Progress towards achieving the design discrimination of better than 10% π contamination for 90% e± acceptance, which has been established with single tracks, in the complex multi-track environment of ep events at HERA, is reported.
We describe the design considerations and construction techniques of a large cylindrical transition radiation detector (TRD), 296 cm long and 311.4 cm in diameter, for the VENUS experiment at the e+e+ storage ring, TRISTAN. The design is based on measurements by using test chambers with e/π beams and X-ray sources. The test results will be fully described. The TRD contains four modules of radiators, each followed by an X-ray chamber with 8192 (2688) total (sense) wires. The gain calibration of all sense wires has been completed with an accuracy of 5%. The TRD is expected to provide a pion rejection ratio of 15±3 with an electron efficiency of 90% for isolated tracks with momenta above 1 GeV/c.