Inter-strip Interpolation in a High Purity Germanium Double-sided Strip Detector
Topic: Inter-strip Interpolation in a High Purity Germanium Double-sided Strip Detector Speaker: Dr. Jason Hayward Assistant Professor University of Tennessee Nuclear Engineering Department When: 1:30 2:30 p.m., Wednesday, September 10, 2008 Where: 308 Pasqua Engineering Building Webcast: http://www.engr.utk.edu/nuclear/colloquia Viewers of the live webcast may submit questions and/or comments to the speaker either before or during the live webcast via an email message to utne@utk.edu. Please include your name and affiliation in your email message. Viewers who miss the live webcast can view the archived webcast, which is usually posted within 24 hours, at http://www.engr.utk.edu/nuclear/colloquia/Archive/. Viewers may also receive the speaker's slides in PDF format via email request to Kim Scarbrough (kscarbro@utk.edu) after the live webcast. ABSTRACT: Germanium has long been known as the gold standard for gamma ray detection because it possesses excellent energy resolution and detection efficiency. Double-sided strip detectors (DSSDs) provide the advantage of excellent position resolution, which has been demonstrated to be better than 1 mm FWHM for some designs. Excellent position resolution improves gamma ray imaging performance. Additionally, gamma-ray imaging has shown to yield improved detection, localization, and identification of sources, even if the source or the detector itself is in motion. Imaging also gives a significant advantage in long range, low signal-to-noise, and complex radiation field applications. For these reasons, high-purity germanium (HPGe) DSSDs are being researched for applications in astrophysics, nuclear physics, homeland security, medical imaging, and environmental remediation. One fundamental design issue in the HPGe double-sided strip detector is the gap between strips, which makes up 1/6 of the 3 mm strip pitch in the UM HPGe strip detector. When an interaction occurs in the gap between strips, charge-carriers from the resulting charge cloud may be split between adjacent strips. Additionally, up to 6% of the carriers may be lost. Furthermore, use of the signals obtained for interactions that occur in gaps is complicated by their sensitivity to the change in charge cloud geometries and the difficulty of distinguishing single interactions from multiple close interactions. A Bayesian method for inter-strip interpolation is described for interactions which fall in detector gaps. This method exploits charge-splitting and charge loss, yielding interaction position with lateral resolution of ~200 mm FWHM at 356 keV and ~300 mm FWHM at 662 keV. The method may also be applied when a second interaction falls beneath an adjacent strip. For interactions that occur in the gap between strips, the 3D position resolution and the ability to discriminate single interactions from multiple close interactions are limited by the depth resolution of the detection system. Additionally, a novel method for assessing the depth resolution is presented. All students and faculty are invited to attend. UTNE Graduate Students who hold Assistantships or Fellowships are required to attend in person Refreshments will be provided in 219 Pasqua immediately following the colloquium.
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