Development and calibration of a Thomson parabola with microchannel plate for the detection of laser-accelerated MeV ions

Abstract

This article reports on the development and application of a Thomson parabola (TP) equipped with a (90x70) mm(2) microchannel-plate (MCP) for the analysis of laser-accelerated ions, produced by a high-energy, high-intensity laser system. The MCP allows an online measurement of the produced ions in every single laser shot. An electromagnet instead of permanent magnets is used that allows the tuning of the magnetic field to adapt the field strength to the analyzed ion species and energy. We describe recent experiments at the 100 TW laser facility at the Laboratoire d'Utilization des Lasers Intenses (LULI) in Palaiseau, France, where we have observed multiple ion species and charge states with ions accelerated up to 5 MeV/u (O(+6)), emitted from the rear surface of a laser-irradiated 50 microm Au foil. Within the experiment the TP was calibrated for protons and for the first time conversion efficiencies of MeV protons (2-13 MeV) to primary electrons (electrons immediately generated by an ion impact onto a surface) in the MCP are presented.

MeV ion beams generated by intense pulsed laser monitored by Silicon Carbide detectors

“…The spectrometer uses a 0.06 T horizontal magnetic deflection and + 2.8 kV (from the top) voltage for the vertical electric deflection. The distance between the electric deflectors and the MicroChannel Plate (MCP) plane detector of the parabola ions is D=16.5 cm, as in similar apparatuses reported in literature [12].…”

Influence of fs-laser desorption on target normal sheath accelerated ions

“…The measurement and the analysis of the accelerated ions were done by a Thomson parabola spectrometer [28] under 0 from target normal with a ð90 Â 70Þ mm 2 microchannel plate (MCP) for an online measurement. Radiochromic films in stack configuration [29] were used as a second independent diagnostics for the registration of the accelerated protons.…”

Recent developments in the Thomson Parabola Spectrometer diagnostic for laser-driven multi-species ion sources

“…Where most of the physical parameters of the TPS can be easily measured, it is paramount to map the magnetic field accurately, whether using permanent magnets or electromagnets [23][24][25], accounting in particular for non-uniformities in the field along the beam axis. The magnetic field inside a yoke can either be mapped empirically using a Hall probe [25,26], or modelled numerically as described in Refs.…”

“…Since the response of the detectors for different charged particles depends heavily on the ion species and energy, calibration functions for the most common types of TPS detectors and particles have been obtained experimentally by different groups. Some of the relevant works include calibration of Image Plates [30] for protons [31][32][33], deuterons [34,35], alpha particles [35,36] and carbon ions [37], and the calibration of MultiChannel Plates for protons [23,38] and carbon ions [39].…”