Ultraviolet Photosensors Research Articles

The performance of the GPSC/MSGC hybrid detector with argon-xenon gas mixtures

The performance for X-ray spectrometry of argon-xenon gas proportional scintillation counters (GPSCs) using a CsI-coated microstrip plate in direct contact with the scintillation gas as a vacuum ultraviolet photosensor is investigated for different argon-xenon mixtures. The GPSC/microstrip gas chamber hybrid detectors filled with argon-xenon mixtures present superior performance when compared to those with pure argon and pure xenon fillings. For these mixtures, the signal amplification due to the scintillation processes and the detector energy resolution may achieve values of 15-18 and 11-10%, respectively. The best energy resolutions can be achieved for mixtures with a broad range of xenon concentration, 20-70% Xe, and for lower reduced electric fields in the scintillation region as the xenon concentration is reduced. As in pure argon or pure xenon gas-filling, the detector performance is limited by optical positive feedback resulting from additional scintillation produced in the electron avalanche processes around the microstrip plate anodes. The best energy resolutions are achieved for positive feedback gains of about 1.1.

The microhole and strip plate gas detector: Initial results

We report the initial performance of an argon gas proportional counter consisting of a microstructure: the microhole and strip plate (MHSP). The MHSP combines desirable features of both a gas electron multiplier (GEM) and a microstrip plate (MSP) into a single integrated microstructure. Like the GEM, the MHSP is fabricated with flexible printed-circuit technology. As implemented, the MHSP provides two charge-amplification stages: slotted holes that function as a GEM, and microstrip anodes that also function as the charge-collection electrode. With two stages of amplification the microstrip can be operated with bias voltages well below the breakdown threshold. Results for the operation of the MHSP in argon are presented. A charge amplification factor of seven was achieved in the microholes with a maximum electron transmission approaching 100%. The measured energy resolution for 5.9 keV x rays was 30%. Future plans include the incorporation of a photocathode into the MHSP for applications as an ultraviolet photosensor.

A comparative study of microstrip plate geometries as UV photosensors with reflective photocathodes: simulation

A numerical simulation of eight microstrip plate geometries operated in 760 torr of xenon was performed. The cathode widths and anode-to-cathode gaps were varied while the anode widths were held constant at 10 /spl mu/m. Avalanche multiplication factors as a function of position and total gains for all geometries were determined. Since optical positive feedback is a limiting factor in considering microstrip plates as vacuum ultraviolet (VUV) photosensors, the optical positive feedback of a CsI-coated microstrip plate used as a VUV photosensor for a gas proportional scintillator counter was estimated for all geometries. The geometry with the least optical positive feedback in this application was determined to have 160-/spl mu/m cathodes and cathode-to-anode gaps of 55 /spl mu/m.