Font Size: a A A

Development of A LXe-TPC Compton telescope for gamma-ray astronomy

Posted on:1999-12-10Degree:Ph.DType:Dissertation
University:Columbia UniversityCandidate:Xu, FangFull Text:PDF
GTID:1462390014969270Subject:Physics
Abstract/Summary:
A Liquid Xenon Time Projection Chamber (LXe-TPC) Compton telescope has been developed. It will be used as a balloon borne instrument to perform astronomical observations in the low and medium energy {dollar}gamma{dollar}-ray range between 0.3 and 30 MeV, with an angular resolution of 1-3 degrees and a field-of-view of {dollar}40spcirc .{dollar}; The feasibility of large volume LXe detectors was first demonstrated with a 3.5 liter gridded ionization chamber. Several liters of LXe were successfully purified and the charge and the scintillation light response of LXe to {dollar}gamma{dollar}-rays were measured. The lifetime of the drifting electrons in LXe was measured to be {dollar}{lcub}sim{rcub}1{dollar} ms, using both cosmic ray tracks and light triggered {dollar}gamma{dollar}-ray events. An energy resolution of 5.9% FWHM at 1 MeV was achieved for a drift gap of 4.5 cm. Using the scintillation light of LXe, the trigger efficiency was measured to be better than 85% for 662 keV {dollar}gamma{dollar}-rays.; The LXe-TPC flight prototype has been developed with a sensitive area of 400 {dollar}rm cmsp2{dollar} and an effective LXe layer of 7 cm (or 21 g {dollar}rm cmsp{lcub}-2{rcub}).{dollar} A non-destructive multiwire structure for the three-dimensional sensitivity to {dollar}gamma{dollar}-ray interactions in LXe has been implemented. The prototype has been tested in laboratory for its cryogenics, mechanical and electrical stability and its performance as both a {dollar}gamma{dollar}-ray spectrometer and an imager. The prototype has been operated with a stable charge response for periods longer than 10 days. Good energy resolution, comparable to that of the gridded ionization chamber, has been achieved. The spatial resolution has been measured to be 0.34 mm in the drift direction (Z), and better than 1 mm in the X-Y direction. Event reconstruction based on the Compton mechanism has also been studied.; Extensive simulations have been carried out to study the performance of the proto-type at the balloon altitude. The detection efficiency for the telescope was estimated to be 2%-4% for 0.5-4 MeV {dollar}gamma{dollar}-rays in the Compton scattering mode. The instrumental background rates from various sources for a 3 g {dollar}rm cmsp{lcub}-2{rcub}{dollar} balloon altitude have been derived. The estimated {dollar}3sigma{dollar} continuum sensitivity for a nominal {dollar}3times 10sp4{dollar} sec observation time is {dollar}1.8times 10sp{lcub}-7{rcub}{dollar} ph {dollar}rm cmsp{lcub}-2{rcub}secsp{lcub}-1{rcub}keVsp{lcub}-1{rcub}{dollar} at 1-3 MeV.
Keywords/Search Tags:Lxe, Compton, Telescope, {dollar}rm, Mev
Related items