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

Abstract

Application experiments with laser plasma-based accelerators (LPA) for protons have to cope with the inherent fluctuations of the proton source. This creates a demand for non-destructive and online spectral characterization of the proton pulses, which are for application experiments mostly spectrally filtered and transported by a beamline. Here, we present a scintillator-based time-of-flight (ToF) beam monitoring system (BMS) for the recording of single-pulse proton energy spectra. The setup’s capabilities are showcased by characterizing the spectral stability for the transport of LPA protons for two beamline application cases. For the two beamline settings monitored, data of 122 and 144 proton pulses collected over multiple days were evaluated, respectively. A relative energy uncertainty of 5.5% (1$$\upsigma$$ σ ) is reached for the ToF BMS, allowing for a Monte-Carlo based prediction of depth dose distributions, also used for the calibration of the device. Finally, online spectral monitoring combined with the prediction of the corresponding depth dose distribution in the irradiated samples is demonstrated to enhance applicability of plasma sources in dose-critical scenarios.

Dosimetry for radiobiological in vivo experiments at laser plasma-based proton accelerators

“…Alternatively, dose-rate independent dosimeters can be applied (Togno et al 2022). Moreover, novel beam monitoring systems such as the presented ToF spectrometer, which can be calibrated for proton numbers, might open new paths for multi-10Gy, ultra-high dose rate pulse characterization (Reimold et al 2022).…”

“…Additionally, potential beamline malfunctions can be identified immediately. This novel development for LPA proton beam monitoring represents an important step towards enabling the first in vivo LPA irradiation study, the interested reader can find more details on the ToF spectrometer in Reimold et al (2022). Since irradiation studies ultimately require information about the depth dose profile, the depth dose profile is calculated in a virtual RCF stack at the irradiation site via FLUKA Monte Carlo simulations (Battistoni et al 2016) based on the measured proton energy spectrum together with the proton beam diameter and divergence.…”

Three-dimensional acoustic monitoring of laser-accelerated protons in the focus of a pulsed-power solenoid lens

“…After exiting the vacuum chamber, the bunch travels through an air gap of 6.5 cm in length. Then, the proton bunch passes either an aperture equipped with a time-of-flight (TOF) spectrometer [ 11 , 19 , 20 ] and a parallel plate ionization chamber (IC, X-Ray Therapy Monitor Chamber 7862, PTW Freiburg) positioned behind the aperture connected to a dosemeter (UNIDOS, PTW Freiburg) to deduce the proton bunch particle number or a collimator of variable diameter between 1 and 5 mm. The bunch then enters the I-BEAT 3D detector, which is positioned 8 cm behind the aperture or the collimator, respectively.…”

miniSCIDOM: a scintillator-based tomograph for volumetric dose reconstruction of single laser-driven proton bunches

“…As application-readiness is reached for LPA protons, technological developments not only focus on the primary source and according diagnostics but have also diversified to a broad range of dedicated setups for the specific application fields. For radiobiological studies, these developments include dedicated beamlines for protons [5][6][7][8][9] , dosimetric systems [10][11][12][13] and beam monitoring approaches [14][15][16][17] , all contributing to the ability to perform sophisticated experimental studies.…”