Breakthrough in pulse-shape based particle identification with silicon detectors

Identification of charged particles is an important method in nuclear spect roscopy. We have achieved a major breakthrough that makes pulse-shape discr imination (PSD) method with a single solid-state detector comparable to and sometimes better than traditional telescope technique. By using rear-side injection in over-biased surface barrier n-type Si detectors made from homo geneously doped n-TD silicon, and extracting the pulse-shape information al ready at the preamplifier level we have reached improved Z and even A discr imination over a wide dynamic range. Previously good separation with PSD te chnique required major degradation of time resolution and inferior energy r esolution. Currently we have pushed down the dynamical time range to below 35 ns and reached time resolution of about 200 ps fwhm while maintaining go od energy resolution characteristic of silicon detectors. The lowest energy threshold for Z separation of intermediate mass fragments (IMF) achieved w ith a 250 mu m thick detector is equivalent to a range of about 20 mu m in silicon. For IMFs with ranges higher than 80 mu m of silicon we got full is otope separation. Details of this study are presented, and the application of our method in recent nuclear physics experiments is briefly discussed.