arXiv subjects

K. Giboni

Publications and source records attributed to K. Giboni.

4 recordsLinked to original sources

arXiv2011

Limits on the release of Rb isotopes from a zeolite based 83mKr calibration source for the XENON project

The isomer 83mKr with its half-life of 1.83 h is an ideal calibration source for a liquid noble gas dark matter experiment like the XENON project. However, the risk of contamination of the detector with traces of the much longer lived mother isotop 83Rb (86.2 d half-life) has to be ruled out. In this work the release of 83Rb atoms from a 1.8 MBq 83Rb source embedded in zeolite beads has been investigated. To do so, a cryogenic trap has been connected to the source for about 10 days, after which it was removed and probed for the strongest 83Rb gamma-rays with an ultra-sensitive Germanium detector. No signal has been found. The corresponding upper limit on the released 83Rb activity means that the investigated type of source can be used in the XENON project and similar low-background experiments as 83mKr generator without a significant risk of contaminating the detector. The measurements also allow to set upper limits on the possible release of the isotopes 84Rb and 86Rb, traces of which were created alongside the production of 83Rb at the Rez cyclotron.

astro-ph.IM↗

arXiv2007

Secondary Scintillation Yield in Pure Xenon

The xenon secondary scintillation yield was studied as a function of the electric field in the scintillation region, in a gas proportional scintillation counter operated at room temperature. A large area avalanche photodiode was used for the readout of the VUV secondary scintillation produced in the gas, together with the 5.9 keV x-rays directly absorbed in the photodiode. The latter was used as a reference for the determination of the number of charge carriers produced by the scintillation pulse and, thus, the number of VUV photons impinging the photodiode. A value of 140 photons/kV was obtained for the scintillation amplification parameter. The attained results are in good agreement with those predicted, for room temperature, by Monte Carlo simulation and Boltzmann calculations, as well as with those obtained for saturated xenon vapour, at cryogenic temperatures, and are about a factor of two higher than former results measured at room temperature.

physics.ins-det↗

arXiv2000

Performance of the Light Trigger System in the Liquid Xenon Gamma-Ray Telescope LXeGRIT

LXeGRIT is a balloon-borne Compton telescope for MeV gamma-ray astrophysics, based on a liquid xenon time projection chamber with charge and light readout. The energy and direction of an incident gamma-ray is reconstructed from the three-dimensional locations and energy deposits of individual interactions taking place in the homogeneous detector volume. While the charge signals provide energy information and X-Y positions, the fast xenon scintillation light signal is used to trigger the detector. The drift time measurement, referred to the time of the trigger signal, gives the Z-position with the known drift velocity. The light is detected by four UV-sensitive photomultiplier tubes (PMTs). The logical OR of the PMT signals triggers the data acquisition system with an efficiency which depends on the event energy and location, as well as on the discriminator thresholds used on the individual PMTs. Results from experiments with a tagged 22Na source give the spatial distribution of the light trigger efficiency for 511 keV gamma-rays. When averaged over the whole sensitive volume amd all PMTs, the trigger efficiency is 47% or 40% for two discriminator windows used during the LXeGRIT balloon flight of 1999. These values are strongly affected by the different sensitivity of each PMT. The corresponding average efficiency at 511 keV for the best of the four PMTs is in fact 63%, and approaches 100% for interactions taking place in a small volume right above the PMT.

astro-ph↗

arXiv2000

An Upgraded Data Acquisition System for the Balloon-Borne Liquid Xenon Gamma-Ray Telescope LXeGRIT

LXeGRIT is a balloon-borne Compton telescope for MeV gamma-ray astrophysics, based on a liquid xenon time projection chamber (LXe-TPC) with charge and light readout. The first balloon flights in 1997 revealed limitations of the trigger electronics and the data acquisition (DAQ) system, leading to their upgrade. New electronics was developed to handle the xenon scintillation light trigger. The original processor module was replaced by a commercial VME processor. The telemetry rate was doubled to 2 x 500 kbps and onboard data storage on hard disks was implemented. Relying on a robust real-time operating system, the new DAQ software adopts an object oriented design to implement the diverse tasks of trigger handling, data selection, transmission, and storage, as well as DAQ control and monitor functions. The new systems performed well during two flights in Spring 1999 and Fall 2000. In the 2000 flight, the DAQ system was able to handle 300-350 triggers/s out of a total of about 650 Hz, including charged particles.

astro-ph↗