A novel approach to electron data background treatment in an online wide-angle spectrometer for laser-accelerated ion and electron bunches

Abstract

Laser-based ion acceleration is driven by electrical fields emerging when target electrons absorb laser energy and consecutively leave the target material. A direct correlation between these electrons and the accelerated ions is thus to be expected and predicted by theoretical models. We report on a modified wide-angle spectrometer, allowing the simultaneous characterization of angularly resolved energy distributions of both ions and electrons. Equipped with online pixel detectors, the RadEye1 detectors, the investigation of this correlation gets attainable on a single shot basis. In addition to first insights, we present a novel approach for reliably extracting the primary electron energy distribution from the interfering secondary radiation background. This proves vitally important for quantitative extraction of average electron energies (temperatures) and emitted total charge.

Geant4 Monte Carlo simulation study of the secondary radiation fields at the laser-driven ion source LION

“…It is worth mentioning here that we are not aware of any measured electron energy distributions in parallel to the proton energy distributions. In future, such measurements (as proposed, for example in Lindner et al 23 ) could provide valuable input to more accurate simulations. Therefore, within this work, a simple model of an exponentially shaped electron source is used.…”

A feasibility study of zebrafish embryo irradiation with laser-accelerated protons

“…After automated target positioning, the microscope was removed from the beam path of protons that could then enter a wide angle magnetic spectrometer through a 250 μm wide horizontal slit. 12 The permanent magnet dipole field dispersed the proton beam perpendicular to the slit orientation, and the two-dimensional energy-angular distribution map was registered with a 10 × 5 cm 2 CMOS sensor array composed of four RadEye detectors. 13 This configuration was used to measure the proton spectrum for optimizing the source.…”

Time-of-flight spectrometry of ultra-short, polyenergetic proton bunches

“…For comparison, the spectra of the proton bunches were measured using a magnetic spectrometer. 30 After the passive energy degraders, the scattered protons are collimated by a 30 µm narrow slit between two 1 cm thick aluminum blocks before they enter a 9 cm long dipole magnet (B = 600 mTesla). Due to the Lorentz force, protons are deflected in the magnetic field perpendicular to the initial beam direction according to their kinetic energy.…”

“…After a drift space in vacuum of 34 cm, they are detected by the pixelated CMOS detector RadEye. 31 Isoenergy curves were drawn in the detector plane, and with them the signal in each pixel was converted to a proton number according to Lindner et al 30 The slit configuration used in this setup translates to a full acceptance angle of the spectrometer of 6 mrad, resulting in a slight smearing of the signal in the detector plane and hence a broadening of the measured energy spectrum. The additional broadening was compensated by deconvolving the acceptance angle induced spread from the raw signal.…”