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Proceedings Paper

Results from the characterisation of Advanced GAmma Tracking Array prototype detectors and their consequences for the next-generation nuclear physics spectrometer
Author(s): M. R. Dimmock; A. J. Boston; H. C. Boston; J. R. Cresswell; L. Nelson; P. Nolan; S. Rigby; C. Unsworth; I. Lazarus; J. Simpson; P. Medina; C. Parisel; C. Santos
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Paper Abstract

The Advanced GAmma Tracking Array (AGATA) is a European project that is aiming to construct a complete 4π High Purity Germanium (HPGe) gamma-ray spectrometer for nuclear structure studies at future Radioactive Ion Beam (RIB) Facilities. The proposed array will utilise digital electronics, Pulse Shape Analysis (PSA) and Gamma-Ray Tracking (GRT) algorithms, to overcome the limited efficiencies encountered by current Escape Suppressed Spectrometers (ESS), whilst maintaining the high Peak-to-Total ratio. Two AGATA symmetrical segmented Canberra Eurisys (CE) prototype HPGe detectors have been tested at the University of Liverpool. A highly collimated Cs-137 (662keV) beam was raster scanned across each detector and data were collected in both singles and coincidence modes. The charge sensitive preamplifier output pulse shapes from all 37 channels (one for each of the 36 segments and one for the centre contact) were digitised and stored for offline analysis. The shapes of the real charge and image charge pulses have been studied to give detailed information on the position dependent response of each detector. 1mm position sensitivity has been achieved with the parameterisation of average pulse shapes, calculated from data collected with each of the detectors. The coincidence data has also been utilised to validate the electric field simulation code Multi Geometry Simulation (MGS). The precisely determined 3D interaction positions allow the comparison of experimental pulse shapes from single site interactions with those generated by the simulation. It is intended that the validated software will be used to calculate a basis data set of pulse shapes for the array, from which any interaction site can be determined through a χ2 minimisation of the digitized pulse with linear combinations of basis pulseshapes. The results from this partial validation, along with those from the investigation into the position sensitivity of each detector are presented.

Paper Details

Date Published: 24 September 2007
PDF: 12 pages
Proc. SPIE 6706, Hard X-Ray and Gamma-Ray Detector Physics IX, 670613 (24 September 2007); doi: 10.1117/12.738297
Show Author Affiliations
M. R. Dimmock, Univ. of Liverpool (United Kingdom)
A. J. Boston, Univ. of Liverpool (United Kingdom)
H. C. Boston, Univ. of Liverpool (United Kingdom)
J. R. Cresswell, Univ. of Liverpool (United Kingdom)
L. Nelson, Univ. of Liverpool (United Kingdom)
P. Nolan, Univ. of Liverpool (United Kingdom)
S. Rigby, Univ. of Liverpool (United Kingdom)
C. Unsworth, Univ. of Liverpool (United Kingdom)
I. Lazarus, STFC Daresbury Lab. (United Kingdom)
J. Simpson, STFC Daresbury Lab. (United Kingdom)
P. Medina, Institut de Recherches Subatomiques (France)
C. Parisel, Institut de Recherches Subatomiques (France)
C. Santos, Institut de Recherches Subatomiques (France)

Published in SPIE Proceedings Vol. 6706:
Hard X-Ray and Gamma-Ray Detector Physics IX
Ralph B. James; Arnold Burger; Larry A. Franks, Editor(s)

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