[Show abstract][Hide abstract] ABSTRACT: High conversion efficiency between electrical and optical power is highly
desirable both for high peak and high average power radiation sources. In this
paper we discuss a new mechanism based on stimulated superradiant emission in a
strongly tapered undulator whereby an optimal undulator tapering is calculated
by dynamically matching the resonant energy variation to the ponderomotive
decelerating gradient. The method has the potential to allow the extraction of
a large fraction (~50%) of power from a relativistic electron beam and convert
it into coherent narrow-band tunable radiation, and shows a clear path to very
high average power radiation sources.
[Show abstract][Hide abstract] ABSTRACT: In this paper we review the present status of MeV electron sources for ultrafast diffraction and microscopy applications
and trace the path forward to improve the spatio-temporal resolution of electron scattering probes.
[Show abstract][Hide abstract] ABSTRACT: We report observations of strong-field effects in inverse Compton scattering via its X-ray characteristics using K-, L-edge, and attenuation filters. A CO2 laser of a0 ≈ 0.6 is collided by a 65-MeV electron beam.
[Show abstract][Hide abstract] ABSTRACT: We present the first experimental demonstration of MEMS-based magnetic optics for control of charged particle beams. Combined function (steering and focusing) 4-pole electromagnets with a 600-µm bore and 55-µm yoke thickness (686-µm magnetic length) have been fabricated with a novel MEMS process. These 3D solenoidal multi-pole electromagnets have demonstrated hysteresis-free adjustable 2D steering and focusing of a pC-charge 34-keV electron beam with 24-mT field intensity, 220-T/m field gradient, and potential for pulsed operation beyond 100 kHz. Simple geometric optimizations promise a 4-fold improvement in both field intensity and gradient without further scaling.
Solid-state Sensors, Actuators and Microsystems Workshop (Hilton Head 2014), Hilton Head Isl., SC; 06/2014
[Show abstract][Hide abstract] ABSTRACT: Pushing the limits in temporal resolution for transmission electron
microscopy (TEM) requires a revolutionary change in the electron source
technology. In this paper we study the possibility of employing a
radiofrequency photoinjector as the electron source for a time-resolved TEM. By
raising the beam energy to the relativistic regime we minimize the space charge
effects which otherwise limit the spatio-temporal resolution of the instrument.
Analysis and optimization of the system taking into account the achievable beam
brightness, electron flux on the sample, chromatic and spherical aberration of
the electron optic system, and space charge effects in image formation are
presented and supported by detailed numerical modeling. The results demonstrate
the feasibility of 10 nanometer - 10 picosecond spatio-temporal resolution
single-shot MeV TEM.
[Show abstract][Hide abstract] ABSTRACT: This letter introduces a fabrication process for thick (>50 μm) multipole electromagnets that produce fields exceeding 20 mT across 0.2-mm3 free-space volumes. The novelty of the process involves the multistep thick-film electroplating of a magnetic alloy inside a high-density high-aspect-ratio solenoidal coil, producing high intensity fields across a larger volume than previous microelectromechanical systems electromagnets. To demonstrate an application enabled by this process, a 600-μm-gap four-pole electromagnet is fabricated, packaged, and used to steer a 34-keV electron beam.
Journal of Microelectromechanical Systems 04/2014; 23(3):505-507. · 2.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We discuss a two-color SASE free-electron laser (FEL) amplifier where the time and energy separation of two separated radiation pulses are controlled by manipulation of the electron beam phase space. Two electron beamlets with adjustable time and energy spacing are generated in an RF photo-injector illuminating the cathode with a comb-like laser pulse followed by RF compression in the linear accelerator. We review the electron beam manipulation technique to generate bunches with time and energy properties suitable for driving two-color FEL radiation. Experimental measurements at the SPARC-LAB facility illustrate the flexibility of the scheme for the generation of two-color FEL spectra.
New Journal of Physics 03/2014; 16(3):033018. · 4.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper describes the scientific aims and potentials as well as the preliminary technical design of IRIDE, an innovative tool for multi-disciplinary investigations in a wide field of scientific, technological and industrial applications. IRIDE will be a high intensity “particles factory”, based on a combination of high duty cycle radio-frequency superconducting electron linacs and of high energy lasers. Conceived to provid eunique research possibilities for particle physics, for condensed matter physics,chemistry and material science, for structural biology and industrial applications, IRIDE will open completely new research possibilities and advance our knowledge in many branches of science and technology. IRIDE is also supposed to be realized in subsequent stages of development depending on the assigned priorities.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 03/2014; 740:138-146. · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In Plasma Wakefield Acceleration (PWFA) plasma oscillations are driven by ultra relativistic electron beams. The ratio of the maximum accelerating field behind the driving beam (bunch) and the maximum decelerating field inside the driving beam (bunch) is defined as Transformer Ratio, a key parameter that determines the energy gain in particle acceleration. We investigate the transformer ratio for different shapes of a single driving bunch. One dimensional, fluid, relativistic, cold plasma equations have been numerically solved. A complete map of the transformer ratio is obtained by varying: bunch shape, bunch length and density ratio. It is found that the transformer ratio critically depends on the bunch shape and on the density ratio. Moreover both in the linear as well as in the non-linear regime the theoretical limit of 2 for the transformer ratio of a single symmetric bunch can be exceeded using asymmetric bunches in the linear regime as well as symmetric bunches in nonlinear regime.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 02/2014; · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper discusses the extension to different electron beam aspect ratio of the Child-Langmuir law for the maximum achievable current density in electron guns. Using a simple model, we derive quantitative formulas in good agreement with simulation codes. The new scaling laws for the peak current density of temporally long and transversely narrow initial beam distributions can be used to estimate the maximum beam brightness and suggest new paths for injector optimization.
[Show abstract][Hide abstract] ABSTRACT: Recent advances in ultrafast technology enable both the study and the control of materials properties thanks to the ability to record high temporal resolution movies of their transformations, or the ability to generate new states of matter by selecting ad hoc an excitation to drive the system out of equilibrium. The holy grail of this type of experiments is to combine a high tuneability of the excitation with a wide observation window. For example, this is achieved in multidimensional optical spectroscopy where the response to several excitation energies is monitored in a broad energy range by a large bandwidth optical pulse. In this article, the possibility to combine the chemical sensitivity of intense tuneable X-rays pulses from a free electron laser, with the wide range of observables available in an ultrafast transmission electron microscope is discussed. The requirements for such experiments are quantified via estimates based on state of the art experiments and simulations, and it is proposed that ultrafast electron imaging, diffraction and spectroscopy experiments can be performed in combination with a chemically selective X-ray excitation of materials.
[Show abstract][Hide abstract] ABSTRACT: Plasma acceleration is the new frontier in particle beam accelerators. Using the strong electric fields inside a plasma it is possible to achieve accelerating gradients orders of magnitude larger with respect to current technologies. Different schemes, using completely different approaches, have been proposed and several already tested, producing beams of energy up to several GeV. Regardless of the technique used for acceleration a precise determination of the output beam parameters is mandatory for the fine tuning of the process. The measurement of these parameters, in particular the beam distribution in transverse and longitudinal phase space, is not trivial, mainly due to the large energy spread and to the tight focusing of these beams or to the background noise produced in the plasma channel. We illustrate the main problems related to the diagnostic of this kind of beams and some of the proposed or already realized solutions
[Show abstract][Hide abstract] ABSTRACT: We discuss a new method for the production of trains of FEL radiation pulses based on the FEL emission driven by a comb-like electron beam. In addition, we present recent experimental results on the two color FEL emission as generated at the SPARC_LAB facility: a train of two short (<200 fs) electron bunches, almost overlapped in time, with a comb-like energy distribution, has been injected in the undulator, giving rise to FEL pulses at two characteristic frequencies with multi-peaked time structure. This scheme shows also the versatility of the SPARC photo-injector to generate and manipulate such energy and time distributions.
[Show abstract][Hide abstract] ABSTRACT: Compact, table-top sized accelerators are key to improving access to high-quality beams for use in industry, medicine and academic research. Among laser-based accelerating schemes, the inverse free-electron laser (IFEL) enjoys unique advantages. By using an undulator magnetic field in combination with a laser, GeV m(-1) gradients may be sustained over metre-scale distances using laser intensities several orders of magnitude less than those used in laser wake-field accelerators. Here we show for the first time the capture and high-gradient acceleration of monoenergetic electron beams from a helical IFEL. Using a modest intensity (~10(13) W cm(-2)) laser pulse and strongly tapered 0.5 m long undulator, we demonstrate >100 MV m(-1) accelerating gradient, >50 MeV energy gain and excellent output beam quality. Our results pave the way towards compact, tunable GeV IFEL accelerators for applications such as driving soft X-ray free-electron lasers and producing γ-rays by inverse Compton scattering.
[Show abstract][Hide abstract] ABSTRACT: a b s t r a c t Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (10–100 GV m À 1), enabling acceleration of electrons to GeV energy in few centimetres. However, the quality of the electron bunches accelerated with this technique is still not comparable with that of conventional accelerators; radiofrequency-based accelerators, in fact, are limited in the accelerating field (10–100 MV m À 1) requiring therefore kilometric distances to reach the GeV energies, but can provide very bright electron bunches. Combining high brightness electron bunches from conventional accelerators and high accelerating fields reachable with plasmas could be a good compromise allowing to further accelerate high brightness electron bunches coming from LINAC while preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train of short bunches, we have started to study the requirements in terms of plasma for SPARC-LAB [1,2]. In particular, here we focus on the ionization process; we show a simplified model to study the evolution of plasma induced by discharge, very useful to design the discharge circuit able to fully ionize the gas and bring the plasma at the needed temperature and density. & 2013 Published by Elsevier B.V.
[Show abstract][Hide abstract] ABSTRACT: The evolution of picosecond modulations of the longitudinal profile of an electron beam generated in an rf photoinjector is analyzed and optimized with the goal of obtaining high peak current electron bunch trains at very high frequencies (≥THz). Taking advantage of nonlinear longitudinal space charge forces, it is found that more than 500 A peak current 1 THz bunch trains can be generated using a standard 1.6 cell SLAC/UCLA/BNL rf gun. Postacceleration is used to freeze the longitudinal phase space dynamics after one half plasma oscillation. Applications range from tunable narrow bandwidth THz radiation generation to drivers for high frequency high gradient accelerators.
Physical Review Special Topics - Accelerators and Beams 10/2013; 16(10). · 1.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present the experimental demonstration of a new scheme for the generation of ultrashort pulse trains based on free-electron-laser (FEL) emission from a multipeaked electron energy distribution. Two electron beamlets with energy difference larger than the FEL parameter ρ have been generated by illuminating the cathode with two ps-spaced laser pulses, followed by a rotation of the longitudinal phase space by velocity bunching in the linac. The resulting self-amplified spontaneous emission FEL radiation, measured through frequency-resolved optical gating diagnostics, reveals a double-peaked spectrum and a temporally modulated pulse structure.
[Show abstract][Hide abstract] ABSTRACT: Resonant Cherenkov radiation in capillary slow-wave structures driven by relativistic beams from a low-energy S-band photoelectron gun is considered. The generation of few megaelectron volt, sub-millimeter-sized, sub-ps microbunches is analyzed numerically. Different modes of operation of such an overfocused, high-current-density system with corresponding adaptation of RF photoinjector is discussed including some experimental measurements with beam on-cathode microbunching. Feasibility of generation of high peak power generation at terahertz frequencies is demonstrated with laser pulse multiplexing and photomixing.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 09/2013; 721:1–9. · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present the experimental demonstration of a novel scheme for the generation of ultrashort pulse trains based on the FEL lasing from a multi-peaked eletron energy distribution. At SPARC we generated two electron beamlets with relative energy difference larger than the FEL parameter ρ by illuminating the cathode with a combed laser, followed by a manipulation of the longitudinal phase space by velocity bunching in the linac. The SASE FEL radiation obtained by sending such beam in the undulator is analyzed by a FROG diagnostic revealing the double-peaked spectrum and temporally modulated pulse structure.
35th Intern. Free-Electron Laser Conference, Yew York (Manhattan), USA; 08/2013
[Show abstract][Hide abstract] ABSTRACT: This report describes the scientific aims and potentials as well as the
preliminary technical design of IRIDE, an innovative tool for
multi-disciplinary investigations in a wide field of scientific, technological
and industrial applications. IRIDE will be a high intensity 'particle factory',
based on a combination of a high duty cycle radio-frequency superconducting
electron linac and of high energy lasers. Conceived to provide unique research
possibilities for particle physics, for condensed matter physics, chemistry and
material science, for structural biology and industrial applications, IRIDE
will open completely new research possibilities and advance our knowledge in
many branches of science and technology. IRIDE will contribute to open new
avenues of discoveries and to address most important riddles: What does matter
consist of? What is the structure of proteins that have a fundamental role in
life processes? What can we learn from protein structure to improve the
treatment of diseases and to design more efficient drugs? But also how does an
electronic chip behave under the effect of radiations? How can the heat flow in
a large heat exchanger be optimized? The scientific potential of IRIDE is far
reaching and justifies the construction of such a large facility in Italy in
synergy with the national research institutes and companies and in the
framework of the European and international research. It will impact also on
R&D work for ILC, FEL, and will be complementarity to other large scale
accelerator projects. IRIDE is also intended to be realized in subsequent
stages of development depending on the assigned priorities.