Novel method for characterizing relativistic electron beams in a harsh laser-plasma environment

Abstract

Particle pulses generated by laser-plasma interaction are characterized by ultrashort duration, high particle density, and sometimes a very strong accompanying electromagnetic pulse (EMP). Therefore, beam diagnostics different from those known from classical particle accelerators such as synchrotrons or linacs are required. Easy to use single-shot techniques are favored, which must be insensitive towards the EMP and associated stray light of all frequencies, taking into account the comparably low repetition rates and which, at the same time, allow for usage in very space-limited environments. Various measurement techniques are discussed here, and a space-saving method to determine several important properties of laser-generated electron bunches simultaneously is presented. The method is based on experimental results of electron-sensitive imaging plate stacks and combines these with Monte Carlo-type ray-tracing calculations, yielding a comprehensive picture of the properties of particle beams. The total charge, the energy spectrum, and the divergence can be derived simultaneously for a single bunch.

Ultrafast Diagnostics for Electron Beams from Laser Plasma Accelerators

“…These discrepancies were attributed to the following potential problems: (1) that the ICT was not designed to measure sub-100 fs bunches, (2) the effect of electrons passing outside the core was not known, (3) that the electronic system was susceptible to electromagnetic noise generated in the interaction, and (4) that the ICT is sensitive to the large amount of low energy charge emitted at wide angles. In the second experiment [5], the ICT was found to overestimate the scintillating screen-based measurement by a factor of 3-4. The importance of ICTs to the LPA community combined with the doubt cast on them by these studies provides strong motivation for further detailed investigation into the applicability of ICTs to charge diagnosis in the harsh LPA environment.…”

“…Two recent studies [4,5] reported discrepancies between charge measurements done with ICTs and scintillating screens, questioning the suitability of ICTs for use in LPAs. In the first experiment [4], discrepancies of greater than an order of magnitude, were observed.…”

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

“…In LPA environments, ICTs can overestimate the charge by more than an order of magnitude [4,5] if not used under the proper conditions. However, a previous study using a gas-jet based LPA showed that, with special care to reduce the detrimental influence of the EMP and other noise sources described above, an ICT can provide accurate charge information for 5 pC and above [7].…”

“…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.…”

Escaping Electrons from Intense Laser-Solid Interactions as a Function of Laser Spot Size

“…Hidding et al [7] showed that interleaving multiple layers of image plate with filtering material in a stack behind a laser-solid interaction enables, the temperature and flux to be extracted from simple Monte Carlo modelling. Curving the image plate and also using multiple layers provides angular information on the flux and temperature [8,9].…”