Characterisation of the first p-type Segmented Inverted-coaxial Germanium Detector, SIGMA

Pearce, Fiona Jane
(2020) Characterisation of the first p-type Segmented Inverted-coaxial Germanium Detector, SIGMA. PhD thesis, University of Liverpool.

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The Segmented Inverted-coaxial GerMAnium (SIGMA) detector is a large volume High Purity Germanium (HPGe) gamma-ray detector that aims to demonstrate superior en- ergy and position resolution over other large volume segmented germanium detectors. The SIGMA prototype detector is the first p-type detector of its kind to be produced. Due to the low noise of the point contact, the SIGMA detector can provide excellent energy resolution and, through the use of Pulse Shape Analysis (PSA), excellent po- sition resolution. Accurate and precise energy and position determination are the key factors in effective gamma-ray tracking making SIGMA particularly suited for use at Radioactive Ion Beam (RIB) experiments such as DESPEC. The SIGMA prototype detector has been characterised and tested at the Univer- sity of Liverpool. SIGMA showed excellent energy resolution with the point contact achieving 0.89 keV at 122 keV and 2.21 keV at 1332 keV and a relative efficiency of 40.9%. A collimated beam of 241Am and 137Cs gamma rays were scanned across the detector in 1 mm steps to investigate the crystal size, structure and position and the active area of the individual segments. The 241Am data was used to produce a risetime matrix displaying the change in drift time across the front face of the crystal. The detector was also operated alongside BGO detectors in coincidence mode and data acquired using the 137Cs beam to investigate pulse shape behaviour in the crystal at a range of positions. The pulses from all functioning segments were collected, includ- ing both real charge and image charge pulses, and used to produce an average response from each segment for individual x-y-z locations in the crystal. The average pulses were compared to investigate the position response of the detector. A measurable difference in pulse shape was seen in multiple segments for a separation of as little as 2 mm in one dimension.

Item Type: Thesis (PhD)
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 04 Jun 2021 11:07
Last Modified: 18 Jan 2023 22:44
DOI: 10.17638/03124117
  • Harkness-Brennan, Laura
  • Page, Robert
  • Judson, Daniel