Absolute calibration for a broad range single shot electron spectrometer

Abstract

International audienceThis 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

Charge Diagnostics for Laser Plasma Accelerators

“…The electron energy dependence of the Lanex light yield was not observed in previous works [ 19,20,21 ]. Since the previously explored energy range was small enough for the difference to be within the measurement error, the observed energy dependence is not contradictory to them.…”

“…Laser plasma accelerators (LPAs) [ 1 ] have shown remarkable progress over the past decade along with the advances in laser technology In 2006, the production of GeV electron beams was demonstrated in just a few centimeters [2,3], by using a discharge capillary based guiding structure [4] Several injection schemes have been proposed to improve stability and quality of e-beams [5,6,7], and initial experiments have showed promising results [8,9,10] This progress is making LPAs attractive as a driver for a light source ranging from THz [11] to x-ray [12,13] A precise measurement of electron beam (e-beam) charge is essential for any kind of accelerator Numerous technologies have been studied for LPA produced e-beam charge detection, such as Faraday cups, integrating current transformers (ICTs) [14], activation based measurements [15], imaging plates (IPs), and scintillating screens with cameras Since an LPA can provide e-beams with a wide range of the energy spread and divergence, a charge diagnostic with imaging capability is desired, leading to detailed studies of the IPs [16,17,18] and scintillating screens [19,20,21] Among many kinds of scintillating screens from various manufactures, ones with Terbium doped Gadox (Gd202S Tb) as an active layer have been commonly used in the LPA community The light yield from the screens has been experimentally calibrated against the ICT by using e-beams from rf-accelerator (RFA) with 3-8 MeV electron energy [19] and 40 MeV electron energy [21] By using broadband electron beams from an LPA, sensitivity for 1 to 80 MeV electrons was experimentally calibrated against the IP [20] Although simulations suggested that the scintillating screens were energy insensitive above a few MeV [19], a detailed experimental study with electrons above 80 MeV has not been reported yet Since recent progress in the LPA research has pushed attainable energy to a GeV level, it is important to experimentally explore the applicable energy range of the screens above a GeV A Faraday cup and ICT have been used as reliable charge diagnostics in the RFA community Since the Faraday cup has to physically capture electrons, the size can be an issue for high energy e-beams In contrast, the ICT is a non-destructive, energy independent and compac...…”

Design of a compact spectrometer for high-flux MeV gamma-ray beams

“…10(b) and 10(c). [18][19][20] The spectral resolution of this magnetic spectrometer will depend upon a series of parameters, namely, the strength B and spatial extent L m of the magnetic field, the angular divergence θ s and source size D s of the beam, and the distance D d between the entrance of the magnet and the detector. The relative energy resolution δE/E of a magnetic spectrometer in the ultra-relativistic regime (E 0.5MeV) thus …”

Pico-coulomb charge measured at BELLA to percent-level precision using a Turbo-ICT

“…In order to reduce the charge measurement error, devices not susceptible to EMP, such as imaging plates and scintillating screens, have been widely used in LPAs [3][4][5]. In addition to the beam charge, they can measure the beam profile and pointing as well.…”