Modeling All-sky Compton Telescopes for Nuclear Astrophysics
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
To further efforts in medium energy gamma-ray detector design, the goal of this thesis period was to model a new type of Compton Telescope for nuclear astrophysics. This involved defining several 3D detector geometry models, simulating far field point source fluxes, and analyzing the results for angular resolution, effective area, and mean area per kilogram of detector. As a prerequisite task, a new Monte Carlo analysis program called MEGAlib was installed at CESR (Center for Study of Space Radiation, Toulouse, France) to complete the modeling and will be available for future simulation work. Abstract The principal investigation was expanding the field of view (FOV) by a factor of 2 to 10 to increase the exposure (observation time multiplied by effective area) and fulfil angular resolution requirements without increasing detector size and mass. A very wide FOV (i.e. 4π) telescope would be exposed to every source at once for longer time, instead of looking at few sources with larger effective areas for shorter observation times. Using MEGAlib, three different detector configurations were modeled. A two-plate classical (similar to COMPTEL), a more compact five-plate stack, and a new six-plate omnidirectional cube geometry. Different detector plate sizes were tested at zenith angles from 0-90° degrees to evaluate off-axis performance. All configurations had similar on-axis angular resolutions (3°) but the new cube configuration had a larger mean effective area exposed to the whole sky, 17 cm^2 compared to 14 cm^2 of the next best geometry. However, it also had a mass nearly two times larger, giving the stack geometry the best exposed area to mass ratio. Because the stack geometry had surprisingly good off-axis effective area and was significantly lighter, it is possible that the large FOV concept could be applied to it by opening both its top and bottom to the sky (normally the bottom is shielded and faces the spacecraft) and using the low effective area side regions as feeds for electronics.
Place, publisher, year, edition, pages
2011. , 51 p.
Technology, Compton telescopes, gamma-ray detector, MEGAlib, Monte Carlo
IdentifiersURN: urn:nbn:se:ltu:diva-56196Local ID: cfaa1981-6f88-48f6-a318-792daff93862OAI: oai:DiVA.org:ltu-56196DiVA: diva2:1029583
Subject / course
Student thesis, at least 30 credits
Space Engineering, master's level
von Ballmoos, PeterJean, Pierre
Validerat; 20110915 (anonymous)2016-10-042016-10-04Bibliographically approved