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Abstract: Recent years have seen an increasing interest in the use of intense, short pulse electron beams for pulsed radiolysis research. Laser driven photo-cathodes inserted in radio frequency (RF) guns are ideal candidates to provide electron beams for time-resolved spectroscopic observation of very fast chemical reactions. These guns have been developed through accelerator R&D programmes in the field of high brightness sources for other applications (linear colliders, free electron lasers). The Physical Chemistry Laboratory at the University of Paris-Sud has created a Fast Kinetics Centre for experimental pulse radiolysis with picosecond time resolution. At the heart of this new facility is a compact 4–9MeV electron accelerator, ELYSE, using RF gun technology. It has been designed and built by the Linear Acclerator Laboratory at the University of Paris-Sud. We will describe the construction and commissioning of ELYSE, the first machine of this type in Europe. [Copyright &y& Elsevier]

Abstract: ELYSE is a fast kinetics center created for pulse radiolysis with picosecond time-resolution. The facility is a 4–9MeV electron accelerator using a subpicosecond laser pulse to produce an electron pulse from a Cs2Te semiconductor photocathode and RF gun technology for the electron acceleration. The pulse duration is around 5ps at low charge (<2nC) and high energy (9MeV), and is under routine conditions 10ps at higher charge (5nC) and >8MeV. The dark current at the target is less than 1% of the pulse photocurrent. Time-resolved absorbance measurements in cells placed in front of the electron beam are achieved using pulsed laser diodes, or a xenon flash lamp as light sources, and photodiodes connected to a 3GHz transient digitizer or a streak camera (250–800nm range and 3.7ps time resolution) as detection instruments. In addition, the synchronization between the laser beam and the electron beam is exploited to measure the absorbance by a pump-probe set-up, the pump being the electron pulse produced by the laser pulse, and the probe being part of the laser beam (120fs–3ps) delayed by a variable optical line. [Copyright &y& Elsevier]

Abstract: The present work reports the first pulse-probe absorbance measurements of the hydrated electron at picosecond range and at elevated temperature. The decay of the hydrated electron, from room temperature up to 350°C, is observed at 790nm using a laser triggered picosecond electron accelerator. With increasing temperature, the decay of the hydrated electron becomes less and less pronounced. At 350°C, almost a flat signal from 100ps to 2.75ns is observed, suggesting an efficient escape of hydrated electrons from spur reactions. [Copyright &y& Elsevier]

A new versatile facility LEETECH for detector R&D, tests and calibration is designed and constructed. It uses electrons produced by the photoinjector PHIL at LAL, Orsay and provides a powerful tool for wide range R&D studies of different detector concepts delivering “mono-chromatic” samples of low energy electrons with adjustable energy and intensity. Among other innovative instrumentation techniques, LEETECH will be used for testing various gaseous tracking detectors and studying new Micromegas/InGrid concept which has very promising characteristics of spatial resolution and can be a good candidate for particle tracking and identification. In this paper the importance and expected characteristics of such facility based on detailed simulation studies are addressed. [ABSTRACT FROM AUTHOR]

The Alpha-X RF-gun was designed to produce an ultra-short (<100 fs rms), 100 pC and 6.3 MeV electron beam with a normalized rms transverse emittance of 1π mm mrad for a gun peak accelerating field of 100 MV/m. Such beams will be required by the Alpha-X project, which aims to study a laser-driven plasma accelerator with a short wavelength accelerating medium. It has been demonstrated on PHIL (Photo-Injector at LAL) that the coaxial RF coupling, chosen to preserve the gun field cylindrical symmetry, is perfectly understood and allows reaching the required peak accelerating field of 100 MV/m giving beam energy of 6.3 MeV. Moreover, a quite low beam rms relative energy spread of 0.15% at 3.8 MeV has been measured, completely agreeing with simulations. Dark current, quantum efficiencies and dephasing curves measurements have also been performed. They all show high values of the field enhancement factor β , which can be explained by the preparation of the photocathodes. Finally, measurements on the transverse phase-space have been carried out, with some limitations given by the difficult modelization of one of the PHIL solenoid magnets and by the enlargement of the beam transverse dimensions due to the use of YAG screens. These measurements give a normalized rms transverse emittance around 5π mm mrad, which does not fulfill the requirement for the Alpha-X project. [ABSTRACT FROM AUTHOR]

This article gives a detailed description of a single shot electron spectrometer which was used to characterize electron beams produced by laser-plasma interaction. Contrary to conventional electron sources, electron beams from laser-plasma accelerators can produce a broad range of energies. Therefore, diagnosing these electron spectra requires specific attention and experimental development. Here, we provide an absolute calibration of the Lanex Kodak Fine screen on a laser-triggered radio frequency picosecond electron accelerator. The efficiency of scintillating screens irradiated by electron beams has never been investigated so far. This absolute calibration is then compared to charge measurements from an integrating current transformer for quasimonoenergetic electron spectra from laser-plasma interaction. [ABSTRACT FROM AUTHOR]

This article deals with the design of an impedance model (including geometric, resistive wall and coherent synchrotron radiation (CSR) wakefields) for ThomX, a 50 MeV electron storage ring designed to work in pulsed mode. The beam dynamics is very different from usual damped storage rings and is strongly dominated by collective effects. The geometric and resistive wall impedance model is obtained using simulation or analytical modelling of the individual elements and is checked using wire measurements on prototypes. The CSR is simulated in a rectangular vacuum chamber to take into account transient effects and resonances. From these models, two distinct regimes of beam dynamics stand out, driven respectively by the CSR and by the geometric impedance. [ABSTRACT FROM AUTHOR]