Development of a high resolution liquid xenon imaging chamber for gamma-ray astronomy

The objective was to develop the technology of liquid xenon (LXe) detectors for spectroscopy and imaging of gamma rays from astrophysical sources emitting in the low to medium energy regime. In particular, the technical challenges and the physical processes relevant to the realization of the LXe detector operated as a Time Projection Chamber (TPC) were addressed and studied. Experimental results were obtained on the following topics: (1) long distance drift of free electrons in LXe (purity); (2) scintillation light yield for electrons and alphas in LXe (triggering); and (3) ionization yield for electrons and gamma rays in LXe (energy resolution). The major results from the investigations are summarized

A liquid xenon imaging telescope for 1-30 MeV gamma-ray astrophysics

A study of the primary scintillation light in liquid xenon excited by 241 Am alpha particles and 207 Bi internal conversion electrons are discussed. The time dependence and the intensity of the light at different field strengths have been measured with a specifically designed chamber, equipped with a CaF sub 2 light transmitting window coupled to a UV sensitive PMT. The time correlation between the fast light signal and the charge signal shows that the scintillation signals produced in liquid xenon by ionizing particles provides an ideal trigger in a Time Projection type LXe detector aiming at full imaging of complex gamma-ray events. Researchers also started Monte Carlo calculations to establish the performance of a LXe imaging telescope for high energy gamma-rays

A high resolution liquid xenon imaging telescope for 0.3-10 MeV gamma-ray astrophysics: Construction and initial balloon flights

An instrument is described which will provide a direct image of gamma-ray line or continuum sources in the energy range 300 keV to 10 MeV. The use of this instrument to study the celestial distribution of the (exp 26)Al isotope by observing the 1.809 MeV deexcitation gamma-ray line is illustrated. The source location accuracy is 2' or better. The imaging telescope is a liquid xenon time projection chamber coupled with a coded aperture mask (LXe-CAT). This instrument will confirm and extend the COMPTEL observations from the Compton Gamma-Ray Observatory (CGRO) with an improved capability for identifying the actual Galactic source or sources of (exp 26)Al, which are currently not known with certainty. sources currently under consideration include red giants on the asymptotic giant branch (AGB), novae, Type 1b or Type 2 supernovae, Wolf-Rayet stars and cosmic-rays interacting in molecular clouds. The instrument could also identify a local source of the celestial 1.809 MeV gamma-ray line, such as a recent nearby supernova

A High Resolution Liquid Xenon Imaging Telescope for 0.3-10 MeV Gamma Ray Astrophysics: Construction and Initial Balloon Flights

The results achieved with a 3.5 liter liquid xenon time projection chamber (LXe-TPC) prototype during the first year include: the efficiency of detecting the primary scintillation light for event triggering has been measured to be higher than 85%; the charge response has been measured to be stable to within 0.1% for a period of time of about 30 hours; the electron lifetime has been measured to be in excess of 1.3 ms; the energy resolution has been measured to be consistent with previous results obtained with small volume chambers; X-Y gamma ray imaging has been demonstrated with a nondestructive orthogonal wires readout; Monte Carlo simulation results on detection efficiency, expected background count rate at balloon altitude, background reduction algorithms, telescope response to point-like and diffuse sources, and polarization sensitivity calculations; and work on a 10 liter LXe-TPC prototype and gas purification/recovery system

Vacuum ultraviolet light source utilizing rare gas scintillation amplification sustained by photon positive feedback

A source of light in the vacuum ultraviolet (VUV) spectral region includes a reflective UV-sensitive photocathode supported in spaced parallel relationship with a mesh electrode within a rare gas at low pressure. A high positive potential applied to the mesh electrode creates an electric field which causes drifting of free electrons occurring between the electrodes and producing continuous VUV light output by electric field-driven scintillation amplification sustained by positive photon feedback mediated by photoemission from the photocathode. In one embodiment the lamp emits a narrow-band continuum peaked at 175 nm

Final Technical Report for Award DE-FG02-05ER41389 A New Electrostatically-Focused, UV HPD for Liquid Xenon: A Direct Comparison with APD, PMT, SiPM in an Integrated Database

Within the scope of the project, a LXe detector and associated gas handling and purification system were set up to study the response of various photodetectors to the VUV Xe light. In particular we tested an Advanced Photonix Large Area Avalanche Photodiode (APD), Silicon Photomultipliers (SiPMs) from two different sources and an Hamamtsu Photonics APD. As part of the XENON Dark Matter project, sponsored by the National Science Foundation, we have accumulated independent knowledge of the response of compact metal channel photomultipliers. At this stage, we conclude that the last are far superior in terms of reliability and performance in a LXe detector environment. More studies are needed with APDs and SiPMs in LXe, taking advantage of the improved performance of these sensors with time. We could not test a hybrid PMT (HPD) since the only available unit on loan from one manufacturer lacked the mechanical stability and was packaged in a form not compatible with LXe purity requirements. Meanwhile, within the XENON collaboration, we are developing with Hamamatsu a hybrid PMT which is named QUPID (Quartz Photon Intensifying Detector) which promises to solve the problems of radioactivity and purity encountered with previous HPDs. We attach to this report two papers which summarize in detail the experimental st-ups, procedures and results obtained with different APDs and SiPMs operated in LXe. We continue our investigations of APDs in view of their potential appication in large arrays for LXe detectors. We intend to publish the results once we complete tests of newly acquired Hamamatsu APDs