Time of Flight based diagnostics for high energy laser driven ion beams

Abstract

A: Nowadays the innovative high power laser-based ion acceleration technique is one of the most interesting challenges in particle acceleration field, showing attractive characteristics for future multidisciplinary applications, including medical ones. Nevertheless, peculiarities of optically accelerated ion beams make mandatory the development of proper transport, selection and diagnostics devices in order to deliver stable and controlled ion beams for multidisciplinary applications. This is the main purpose of the ELIMAIA (ELI Multidisciplinary Applications of laser-Ion Acceleration) beamline that will be realized and installed within 2018 at the ELI-Beamlines research center in the Czech Republic, where laser driven high energy ions, up to 60 MeV/n, will be available for users. In particular, a crucial role will be played by the on-line diagnostics system, recently developed in collaboration with INFN-LNS (Italy), consisting of TOF detectors, placed along the beamline (at different detection distances) to provide online monitoring of key characteristics of delivered beams, such as energy, fluence and ion species. In this contribution an overview on the ELIMAIA available ion diagnostics will be briefly given along with the preliminary results obtained during a test performed with high energy laser-driven proton beams accelerated at the VULCAN PW-laser available at RAL facility (UK). K: Ion diagnostics; high energy laser-driven protons; time of flight.A X P : 1234.56789

Diagnostics and Dosimetry Solutions for Multidisciplinary Applications at the ELIMAIA Beamline

“…The main advantages of these detectors compared with FCs or ICs are their large band-gap, which cuts out of the high intensity visible and UV light emission from the plasma and their fast response to detect fast particles in TOF. These features coupled with high signal-to-noise ratio, typical of diamond and silicon carbide detectors, make these detectors more attractive than other devices, such as FCs or ICs, for timing measurement of high-pulsed and high-energy ion beams [20,21].…”

“…These detectors were tested at high power laser facilities in TOF measurements of the high energy laser-driven proton beams generated by the PW Vulcan laser system at the Rutherford Appleton Laboratory (RAL). The experiment was aimed at test diamond detector performances, using TOF technique, with high-energy (up to several tens of MeV) laser-accelerated protons in a laser environment characterized by strong EMP pulse, and compared the results with well-established diagnostics and techniques [21].…”

“…The short peak appearing at the beginning of time axis (7-12 ns) corresponds to the so-called photo-peak and fixes the starting point for the acquisition, that is, the trigger signal. As one can see in Figure 5a, the low sensitivity of the diamond detector to the plasma visible and soft-UV radiation reflects in a narrow photo-peak compared with other detectors such as Faraday cups and ion collectors, allowing to disentangle the high-energy proton component, characterized by short TOF, also at short flight path as in this case [18,21]. The Al filter allows selecting a TOF interval in which the signal, being uniquely generated from protons, can be directly converted in energy distribution using the analysis procedure developed for high-energy (up to 100 MeV level) proton spectrum reconstruction, which takes into account the detector response and the proton energy loss inside the detector thickness A TOF signal structure consisiting of a peak arising from UV, X-rays, and fast electrons emitted from the target and a peak generated by the fast proton group can be observed in Figure 5a.…”

A new energy spectrum reconstruction method for time-of-flight diagnostics of high-energy laser-driven protons

“…As it is reported in 16,17,21 a typical TOF signal displays the temporal evolution of the radiation and particles reaching the detector after being emitted from the laserirradiated target: UV/X-rays promptly emitted when the laser hits the target surface generate the trigger signal in the detector, i.e. the so-called photo-peak which is typically followed by a tail originated from fast electrons.…”

“…The Time-of-Flight (ToF) technique, so far used as on-line diagnostics for low-energy laser accelerated proton and ion beams, enables measurement of the ion maximum energy (cut-off), spectrum and flux 10,11 . As discussed in literature [11][12][13][14][15][16][17] , detectors as Faraday Cups (FC), ion collectors (IC) and semiconductor-like detectors such as diamond and silicon carbide, are typically placed at a finite distance from the target to measure TOF of accelerated particles. The TOF signal generated in such devices results from the contribution of the different ion species incoming with a specific TOF and, as a consequence, kinetic energy.…”