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New transition radiation detection technique based on DEPFET silicon pixel matrices
Abstract
Transition Radiation Detectors (TRD) have the attractive feature of being able to separate particles by their gamma factor. Replacing the xenon based gaseous detectors by modern silicon detectors is complicated by the large energy losses of charged particles in 300–700μm of silicon. A silicon active pixel detector—DEPFET—has features which allows another detection technique to be used, in order to overcome the existing limitation on separating transition radiation photons with an energy loss from a charged particle in the same pixel. The tests of DEPFET with fiber radiator have been carried out at CERN SPS and DESY beams. The first results of test-beam measurements and Monte Carlo simulation are presented.
... The latter considerations and moreover the high costs of large detector areas, are two very important reasons, why by far most of today's TRDs are based on gaseous multi-wire proportional chambers (MWPC). But for example also straw tubes are sometimes used, and moreover completely new concepts such as for instance TRDs based on DEPFET sensors were proposed [37]. ...
The intention of this dissertation was the development of a multi-channel mixedsignal
detector readout ASIC. This paper describes the whole design process that starts
with the vague requirement for a readout chip for some CBM/FAIR sub-detector and that
ends with the latest and actually realized system on a chip solution called SPADIC, which
is mainly intended to read out the future CBM-TRD. This work comprises the design from
scratch of 6 ASIC prototypes and 10 PCB readout setups as well as the development of
various software and firmware components, the characterization of the designed ASICs, the
development of the SPADIC concept, the design of the SPADIC website, and not at least the
collaboration with the TRD physicists with the achieved goal to read out signals of chamber
prototypes using different SPADICs during CERN beam-times or in the laboratory. Besides
the descriptions of the most important chip details and the corresponding theoretical
analyses, an overall introduction into detectors and detector physics – written on a level
for engineers – is given in this paper in order to embed this technical work into its physical
context. The effective output of this dissertation is the self-triggered 32-channel charge
pulse amplification and digitization chip SPADIC 1.0.
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.
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.
Algorithm for the angular distribution of X-ray transition radiation generated by a relativistic charged particle in regular radiators is discussed in the framework of the Geant4 simulation toolkit. The model predictions are compared with experimental data sensitive to the angular distribution of X-ray transition radiation.
This paper presents new developments in Monte Carlo simulation for test beam measurements of a silicon transition radiation detector based on DEPFET—a silicon active pixel detector. The test of DEPFET with fiber radiator has been carried out at the DESY 5 GeV electron beam. Monte Carlo simulation of the test beam setup is based on Geant4. A comparison of Geant4 simulation with test beam data is presented.
A new generation of MOS-type DEPFET active pixel sensors in double metal/double poly technology with ∼25 μm pixel size has been developed to meet the requirements of the vertex detector at the ILC (International Linear Collider). The paper presents the design and technology of the new linear MOS-type DEPFET sensors including a module concept and results of a feasibility study on how to build ultra-thin fully depleted sensors. One of the major challenges at the ILC is the dominant e<sup>+</sup>e<sup>-</sup> pair background from beam-beam interactions. The resulting high occupancy in the first layer of the vertex detector can be reduced by an extremely fast read out of the pixel arrays but the pair-produced electrons will also damage the sensor by ionization. Like all MOS devices, the DEPFET is inherently susceptible to ionizing radiation. The predominant effect of this kind of irradiation is the shift of the threshold voltage to more negative values due to the build up of positive oxide charges. The paper presents the first results of the irradiation of such devices with hard X-rays and gamma rays from a <sup>60</sup>Co source up to 1 Mrad(Si) under various biasing conditions.
DePMOS structure provides detection and amplification jointly and it is free of interconnection stray capacitance. An electrical model of the device has been provided. The most relevant parameters have been measured in order to choose an adequate readout electronics, to fully exploit the intrinsic low noise of the device. DePMOS can operate in continuous mode, i.e. without applying any clear pulse during the signal processing, and can be read out by a time continuous shaper amplifier. An unequalled noise of 2.2 electrons r.m.s. at room temperature has been measured. In this mode DePMOS can be used e.g. as the readout device for silicon drift detectors. DePMOS was developed to be the basic element of an active pixel sensor suitable to cope with the requirements of XEUS wide field imager. In a matrix arrangement, each pixel must be read out by a time variant filter. A multichannel integrated shaping amplifier, based on multi correlated double sampling, has been designed. Spectroscopic resolution obtained filtering the pixel matrix with this readout chip is in agreement with measurements in continuous mode and matches the predictions of the model presented. It has also been experimentally proved that the clear procedure doesn't introduce additional noise contribution, even in the very low noise range achieved. This qualifies DePMOS as a "reset-noise-free" device.
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.
The DEPFET pixel detector offers first stage in-pixel amplification by incorporating a field effect transistor in the high resistivity silicon substrate. In this concept, a very small input capacitance can be realized thus allowing for low noise measurements. This makes DEPFET sensors a favorable technology for tracking in particle physics. Therefore a system with a DEPFET pixel matrix was developed to test DEPFET performance for an application as a vertex detector for the Belle II experiment. The system features a current based, row-wise readout of a DEPFET pixel matrix with a designated readout chip, steering chips for matrix control, a FPGA based data acquisition board, and a dedicated software package. The system was successfully operated in both test beam and lab environment. In 2009 new DEPFET matrices have been characterized in a 120GeV pion beam at the CERN SPS. The current status of the DEPFET system and test beam results are presented.
The Alpha Magnetic Spectrometer (AMS-02) experiment will be mounted on the International Space Station (ISS) for 3 years to perform precision cosmic particle spectroscopy in space. The search for dark matter candidates requires precise e+-spectroscopy in the energy range from 10GeV up to 300GeV. Therefore, the dominating p-background has to be reduced by a factor of 106. This will be achieved with the AMS-02 electromagnetic calorimeter delivering 3–4 orders of magnitude and the transition radiation detector with proton rejection between 100 and 1000.The AMS-02 TRD consists of 20 layers of 6mm diameter straw modules alternating with 20mm layers of polyethylene/polypropylene fleece radiator. The straws are filled with a 80%:20%Xe/CO2 gas mixture at 1.0bar absolute from a recirculating gas system designed to operate >3 years. The straw modules will be operated in proportional mode at a gas gain of 3000. For the readout a dedicated low-power data-acquisition system based on VA analog multiplexers has been developed.The completed construction and assembly of the detector is presented with special emphasis on space qualification, long flight duration aspects and calibration of the AMS-02 TRD. This project is funded by the German Space Agency DLR (contract 50OO0501), the US Department of Energy DOE and NASA.
On the basis of the semiconductor drift chamber many new detectors are proposed, which enable the determination of energy, energy loss, position and penetration depth of radiation. A novel integrated transistor-detector configuration allows nondestructive repeated readout and amplification of the signal. The concept may be used for the construction of one-or-two-dimensional pixel arrays.
Pixel detectors, as the current technology of choice for the innermost vertex detection, have reached a stage at which large detectors have been built for the LHC experiments and a new era of developments, both for hybrid and for monolithic or semi-monolithic pixel detectors is in full swing. This is largely driven by the requirements of the upgrade programme for the superLHC and by other collider experiments which plan to use monolithic pixel detectors for the first time. A review on current pixel detector developments for particle tracking and vertexing is given, comprising hybrid pixel detectors for superLHC with its own challenges in radiation and rate, as well as on monolithic, so-called active pixel detectors, including monolithic active pixels (MAPS) and DEPFET pixels for RHIC and superBelle.
A new generation of MOS-type DEPFET active pixel sensors in double metal/double poly technology with ∼25 μm pixel size has been developed to meet the requirements of the vertex detector at the International Linear Collider (ILC). The paper presents the design and technology of the new linear MOS-type DEPFET sensors including a module concept and results of a feasibility study on how to build ultra-thin fully depleted sensors. One of the major challenges at the ILC is the dominant e+e− pair background from beam–beam interactions. The resulting high occupancy in the first layer of the vertex detector can be reduced by an extremely fast read out of the pixel arrays but the pair-produced electrons will also damage the sensor by ionization. Like all MOS devices, the DEPFET is inherently susceptible to ionizing radiation. The predominant effect of this kind of irradiation is the shift of the threshold voltage to more negative values due to the build up of positive oxide charges. The paper presents the first results of the irradiation of such devices with hard X-rays and gamma rays from a 60Co source up to 1 Mrad(Si) under various biasing conditions.
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.