Candidate: Philip Ugorowski

Degree of: Doctor of Philosophy

Department: Physics

Title: A New Type of Particle Detector for Nuclear Scattering Experiments

Committee:
Dr. Paul Pancella, Chair
Dr. Dean Halderson
Dr. Gerald Hardie
Dr. Robert Shamu
Dr. Dennis Pence

Date: Thursday, May 23, 2002 3:00 p.m. - 5:00 p.m.
202 Everett Tower, Bradley Commons Room

Abstract:
A new detector was needed for counting recoil protons resulting from proton-proton (pp) elastic scattering during pion production experiments by the Polarized Internal Target Experiments (PINTEX) group at Indiana University Cyclotron Facility (IUCF). The previous silicon detectors were only usable up to 12 MeV, and a stopping power of at least 40 MeV was needed. In addition, the detector had to operate in nanotorr vacuum, and near strong varying magnetic fields, ruling out standard organic plastic scintillators and photomultiplier tubes. We needed to find the most suitable inorganic scintillator and another method of detecting the photons produced when a proton entered the detector. We used a photodiode for light collection, which can be made to work with the right choice of preamplifier. CsI scintillator gave the best light output, and the signal risetime (1 ms) was sufficient to handle the expected event rate. We wanted to eventually use the signal to trigger the data collection electronics, which required a risetime of ~100 ns or less. This required a switch to BiGeO as a scintillator, with much less light output. The minimum required energy detection thresholdto is to detect 12MeV incident protons. Using the Tandem Van De Graff Accelerator at WMU, a minimum sensitivity of 5 MeV was achieved. During subsequent experiments at IUCF the new detector was tested, with good results.

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