A TNSA Technique to Measure Light-Ion Cross Sections Using the MTW Laser

An experiment was performed using the Multi-Terawatt Laser (MTW) 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. Laser pulses (∼22 J, 7 ps) struck a 0.25 mm² deuterated polyethylene (CD₂) target, ejecting TNSA deuterons that hit a thin natural Li target film on a 25 µm thick stainless-steel substrate, causing the ⁷Li(d,p)⁸Li reaction. The phoswich scintillator, light guide, and photomultiplier tube of the Short-Lived Isotope Counting System (SLICS) were placed immediately behind the Li target, and a CAEN Digitizer was used to count the 840 ms half-life beta decay of ⁸Li, beginning 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.