The effects of mis-alignment and background noise in a low energy gamma-ray telescope
The effects of mis-alignment and background noise in a low energy gamma-ray telescope
As a consequence of the nature of γ-ray interactions with matter, telescopes operating in the low energy γ-ray region of the spectrum tend to be massive, bulky instruments, and require a platform at or above the top of the atmosphere. This situation can lead to mechanical distortion of the structure, causing a translational or rotational mis-alignment between the various components of the telescope. Such distortion can lead to systematic errors in the reconstructed source position and a decrease in the significance of the source detection. The ZEBRA telescope is a balloon-borne coded aperture instrument designed to operate in the energy range 0.2-10 MeV. Its mechanical structure is such that the distortions described above can cause significant aberration in the images produced by the telescope. The results of simulations written to investigate the effects of mis-alignment on the image quality are presented, and a set of mechanical tolerances is derived. A system of deflection measuring devices was used on the ZEBRA platform during its first flight in May 1989 to enable the quantification of distortions to be carried out in real time. These devices, their calibration, and the associated software written to perform the data analysis are described in detail, together with the results obtained during the flight. The use of such a system on a future flight is discussed, as are some alternative methods. The reduction of background noise in γ-ray telescopes is of paramount importance due to the inherently low source to background ratio found in their operating environments. A study of the various background contributions is presented, with particular emphasis placed upon the reduction of background noise in actively shielded germanium spectrometers. The results of simulations are presented, and overall conclusions are reached concerning the optimisation of the shielding and orbit with regard to the background level in such instruments. A brief outline of the proposed INTEGRAL satellite is presented, with emphasis placed upon the relevance of this work to the design of the instrument.
University of Southampton
1990
Knight, Peter John
(1990)
The effects of mis-alignment and background noise in a low energy gamma-ray telescope.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
As a consequence of the nature of γ-ray interactions with matter, telescopes operating in the low energy γ-ray region of the spectrum tend to be massive, bulky instruments, and require a platform at or above the top of the atmosphere. This situation can lead to mechanical distortion of the structure, causing a translational or rotational mis-alignment between the various components of the telescope. Such distortion can lead to systematic errors in the reconstructed source position and a decrease in the significance of the source detection. The ZEBRA telescope is a balloon-borne coded aperture instrument designed to operate in the energy range 0.2-10 MeV. Its mechanical structure is such that the distortions described above can cause significant aberration in the images produced by the telescope. The results of simulations written to investigate the effects of mis-alignment on the image quality are presented, and a set of mechanical tolerances is derived. A system of deflection measuring devices was used on the ZEBRA platform during its first flight in May 1989 to enable the quantification of distortions to be carried out in real time. These devices, their calibration, and the associated software written to perform the data analysis are described in detail, together with the results obtained during the flight. The use of such a system on a future flight is discussed, as are some alternative methods. The reduction of background noise in γ-ray telescopes is of paramount importance due to the inherently low source to background ratio found in their operating environments. A study of the various background contributions is presented, with particular emphasis placed upon the reduction of background noise in actively shielded germanium spectrometers. The results of simulations are presented, and overall conclusions are reached concerning the optimisation of the shielding and orbit with regard to the background level in such instruments. A brief outline of the proposed INTEGRAL satellite is presented, with emphasis placed upon the relevance of this work to the design of the instrument.
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Published date: 1990
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Local EPrints ID: 458338
URI: http://eprints.soton.ac.uk/id/eprint/458338
PURE UUID: b3e8ca03-3cc8-4e03-883a-31ada601f9cc
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Date deposited: 04 Jul 2022 16:46
Last modified: 04 Jul 2022 16:46
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Author:
Peter John Knight
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