Target Normal Sheath Acceleration as a Technique for Measuring Nuclear Cross-Sections

Abstract

A Multi-Terawatt Laser (MTW) experiment was performed at the Laboratory for Laser Energetics (LLE) to test the feasibility of using Target Normal Sheath Acceleration (TNSA) to measure 0.1-10 MeV light-ion cross sections, especially those involving tritium. In this initial experiment using deuterium, laser pulses (∼22 J, 7 ps) struck a 0.25 mm2 deuterated polyethylene (CD2) target, ejecting TNSA deuterons that hit a ~2 μm thick natural Li target film on a 25 µm thick stainless-steel substrate, causing the 7Li(d,p)8Li reaction. The Short-Lived Isotope Counting System (SLICS), consisting of the phoswich scintillator, light guide, and photomultiplier, was placed immediately behind the Li target, and a high-speed CAEN Digitizer was used to count the 840 ms half-life beta decay of 8Li, starting a few milliseconds after the laser shot. The phoswich detector consisted of a fast thin and slow thick scintillator sandwiched together to allow incident particles to be identified by their different rates of energy loss. Incident deuteron energy spectra were measured using time-of-flight (TOF) to a small scintillator in front of the Li target and, for comparison, with a Thompson parabola spectrometer.