Characterization of Diamond and Silicon Carbide Detectors With Fission Fragments

Experimental fission studies for reaction physics or nuclear spectroscopy can profit from fast, efficient, and radiation-resistant fission fragment (FF) detectors. When such experiments are performed in-beam in intense thermal neutron beams, additional constraints arise in terms of target-detector interface, beam-induced background, etc. Therefore, wide gap semi-conductor detectors were tested with the aim of developing innovative instrumentation for such applications. The detector characterization was performed with mass- and energy-separated fission fragment beams at the ILL (Institut Laue Langevin) LOHENGRIN spectrometer. Two single crystal diamonds, three polycrystalline and one diamond-on-iridium as well as a silicon carbide detector were characterized as solid state ionization chamber for FF detection. Timing measurements were performed with a 500-mu m thick single crystal diamond detector read out by a broadband amplifier. A timing resolution of similar to 10.2 ps RMS was obtained for FF with mass A = 98 at 90 MeV kinetic energy. Using a spectroscopic preamplifier developed at INFN-Milano, the energy resolution measured for the same FF was found to be slightly better for a similar to 50-mu m thin single crystal diamond detector (similar to 1.4% RMS) than for the 500-mu m thick one (similar to 1.6% RMS), while a value of 3.4% RMS was obtained with the 400-mu m silicon carbide detector. The Pulse Height Defect (PHD), which is significant in silicon detectors, was also investigated with the two single crystal diamond detectors. The comparison with results from alpha and triton measurements enabled us to conclude that PHD leads to similar to 50% loss of the initial generated charge carriers for FF. In view of these results, a possible detector configuration and integration for in-beam experiments has been discussed.</p>