Full characterization of laser-accelerated ion beams using Faraday cup, silicon carbide, and single-crystal diamond detectors

Abstract

Multi-MeV beams of light ions have been produced using the 300 picosecond, kJ-class iodine laser, operating at the Prague Asterix Laser System facility in Prague. Real-time ion diagnostics have been performed by the use of various time-of-flight (TOF) detectors: ion collectors (ICs) with and without absorber thin films, new prototypes of single-crystal diamond and silicon carbide detectors, and an electrostatic ion mass spectrometer (IEA). In order to suppress the long photopeak induced by soft X-rays and to avoid the overlap with the signal from ultrafast particles, the ICs have been shielded with Al foil filters. The application of large-bandgap semiconductor detectors (>3 eV) ensured cutting of the plasma-emitted visible and soft-UV radiation and enhancing the sensitivity to the very fast proton/ion beams. Employing the IEA spectrometer, various ion species and charge states in the expanding laser-plasma have been determined. Processing of the experimental data based on the TOF technique, including estimation of the plasma fast proton maximum and peak energy, ion beam currents and total charge, total number of fast protons, as well as deconvolution processes, ion stopping power, and ion/photon transmission calculations for the different metallic filters used, are reported.

Laser-accelerated ion beam diagnostics with TOF detectors for the ELIMED beam line

“…Nevertheless, the low time and energy resolution of these detectors limit the time separation of the different accelerated species or/and charge states, required for the identification and the energy reconstruction, particularly, for high energy (> 10 MeV) proton beams. For all these reasons, SiC and diamond detectors, offering all these advantageous properties [24][25][26], are the most appropriate for high energy proton beam diagnostics along the ELIMED beamline. In particular, two different types of Chemical Vapour Deposition (CVD) diamond detectors, supplied by the CIVIDEC Instrumentation company [27], have been chosen for laser-accelerated beam diagnostics at ELIMAIA: a 100 µm thickness polycrystalline (pCVD) high radiation detector, specifically designed for high intensity loss measurements and a 500 µm thickness single crystal diamond detector (sCVD).…”

“…In spite of the short flight path (1.22 m), two time-separated peaks can be easily disentangled in the TOF signal, shown in figure 3, corresponding respectively to the fast accelerated proton component, about 20 MeV, and the slow ion contribution. As indicated in figure 3, a fitting procedure on the peak arising from the fast proton contribution has been performed using the wellknown Maxwell-Boltzmann shifted functions [24], in order to investigate the time response of the detector with such high energy pulsed beams. A rise time of 1.5 ns and a FWHM of about 3.5 ns have been measured, showing the fast response of the pCVD, which represents a promising result, in view of the expected 60 MeV protons at ELIMAIA.…”

Generation of high-energy neutrons with the 300-ps-laser system PALS

“…The clear-cut evidence that the fastest protons accelerated by the laser system PALS (1.315 µm, 300 ps, 3×10 16 W cm −2 ) have energies up to ∼4 MeV [20,21] creates a way to accelerate a high number of deuterons from the front side of a target and exploit them in the production of high-energy (∼15 MeV) neutrons through the 7 Li(d, xn) nuclear reaction even if the mean kinetic energy of the bunch of deuterons is <1 MeV. In addition, under these conditions up to 2 × 10 8 neutrons per laser shot have be generated with the laser system PALS through the D(d, n) 3 He reaction, which is scalable with energy of other laser systems [22] .…”

“…In contrast to ultra-short high-intensity lasers which allow the generation of beams of protons and deuterons possessing kinetic energies 1 MeV, sub-nanosecond lasers of the kJclass capable of delivering a moderate intensity onto a target make it possible to accelerate ions up to MeV energies per nucleon [19][20][21][22] . The clear-cut evidence that the fastest protons accelerated by the laser system PALS (1.315 µm, 300 ps, 3×10 16 W cm −2 ) have energies up to ∼4 MeV [20,21] creates a way to accelerate a high number of deuterons from the front side of a target and exploit them in the production of high-energy (∼15 MeV) neutrons through the 7 Li(d, xn) nuclear reaction even if the mean kinetic energy of the bunch of deuterons is <1 MeV.…”

Calibration and Performance Tests of Detectors for Laser-Accelerated Protons

“…For repeated measurements detectors with real-time readout are preferrable, such as Thomson parabola spectrometers [7], [8], silicon-based pixel detectors [9], and systems based on scintillators [10]- [12] or scintillating fibres [13]. A time-of-flight method for the measurement of proton and ion energies with Faraday cups and semiconductor detectors has been presented in [14].…”