Online Charge Measurement for Petawatt Laser-Driven Ion Acceleration

Abstract

Laser-driven ion beams have gained considerable attention for their potential use in multidisciplinary research and technology. Pre-clinical studies into their radiobiological effectiveness have established the prospect of using laser-driven ion beams for radiotherapy. In particular, research into the beneficial effects of ultra-high instantaneous dose rates is enabled by the high ion bunch charge and uniquely short bunch lengths present for laser-driven ion beams. Such studies require reliable, online dosimetry methods to monitor the bunch charge for every laser shot to ensure that the prescribed dose is accurately applied to the biological sample. In this paper we present the first successful use of an Integrating Current Transformer (ICT) for laser-driven ion accelerators. This is a non-invasive diagnostic to measure the charge of the accelerated ion bunch. It enables online dose measurements in radiobiological experiments and facilitates ion beam tuning, in particular, optimization of the laser ion source and alignment of the proton transport beamline. We present the ICT implementation and the correlation with other diagnostics such as radiochromic films, a Thomson parabola spectrometer and a scintillator.

Time-of-flight spectroscopy for laser-driven proton beam monitoring

“…This efficient approach however comes at the prize of directly translating the LPA-inherent spectral fluctuations into fluctuations of the depth dose distribution in a sample. BMSs for volumetric irradiations consequently need to provide spectral information of the selected and transported proton pulse non-destructively with single pulse detection in order to complement the commonly monitored parameters like pulse intensity via ionization chambers (IC) 23 or integrating charge transformers (ICT) 24,37 .…”

Time-of-Flight spectroscopy for laser-driven proton beam monitoring

“…This efficient approach however comes at the prize of directly translating the LPA-inherent spectral fluctuations into fluctuations of the depth dose distribution in a sample. BMSs for volumetric irradiations consequently need to provide spectral information of the selected and transported proton pulse non-destructively with single pulse detection in order to complement the commonly monitored parameters like pulse intensity via ionization chambers (IC) 23 or integrating charge transformers (ICT) 24,37 . The unique combination of temporal and spectral structure of LPA proton pulses makes time-of-flight (ToF) spectrometry an ideal candidate for monitoring of volumetric irradiations: Spectrally filtered and transported proton pulses from state-of-the-art LPA beamlines typically feature ∼ 10 MeV spectral bandwidth.…”