Study on Proton Energy Measurement by Using a Si(Li) Detector Stack

Abstract
Proton energy measurements using a Si(Li) detector stack composed oftwo 2-mm-thick and one 5-mm-thick Si(Li) detectors were performed atthe MC-50 cyclotron of KIRAMS (Korea Institute of Radiological andMedical Sciences). The maximum energy that could be measured withsemiconductor detector was limited by the thickness of the detector.In the case of the energy measurement using a 5-mm-thick Si(Li)detector, it was not possible to measure a proton energy above 30MeVcite{1}. This measurable range can be extended to 40 MeV byusing a Si(Li) detector stack with a 9-mm total thickness. Theproton energy from the cyclotron was 45 MeV, and the active areas ofthe 2-mm- and 5-mm-thick detectors were 150 mm$^{2}$ and 75mm$^{2}$, respectively. The electronic signals from the threedetectors were processed by using preamplifiers (ORTEC 142AH),shaping amplifiers (ORTEC 572A), attenuators and fastanalog-to-digital converter (VME FADC, 64 k). And a summing andanalysis process was performed using a ROOT-based data acquisition(DAQ) program developed by the European Council for Nuclear Research(CERN). The proton energy was changed from 6.9 MeV to 37.5 MeV byusing 0.5- $sim$ 5.7-mm-thick Al degraders. The proton energy wascalculated by using SRIM 2003. The response function of the Si(Li)detector stack had good linearity and agreed well with thecalculated results. Also, the experiments to measure the same protonenergy using multiple stacked Si(Li) detectors instead of a singleSi(Li) detector with a similar thickness showed no big difference orany problems. The maximum difference between these two cases wasless than 3 \%.
Keywords: Energy measurement, Si(Li) detector stack, Proton beam

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