[en] A P10-filled microstrip gas chamber (MSGC) is used to replace the conventional photomultiplier tube (PMT) as the photosensor for a Gas Proportional Scintillation Counter (GPSC). The Vacuum Ultra-Violet (VUV) scintillation light produced in the xenon-filled GPSC is transmitted through a 1 mm thick high-purity quartz window to the MSGC where it is converted to photoelectrons by a CsI photocathode deposited directly onto the surface of a microstrip plate (MSP). These photoelectrons are afterwards multiplied near the microstrip plate anodes with a charge gain of about 10³. The energy resolution achieved for 5.9 keV X-rays is 11.5% which, while not yet as good as the 8% figure for standard GPSC (instrumented with a PMT), is already better than the energy resolution obtained for standard proportional counters. Experimental results are presented and discussed. With this design a compact GPSC is obtained which has the further advantage of being much less sensitive to magnetic fields than PMT-based GPSCs

[en] A P10 filled microstrip gas chamber (MSGC) is used to replace the conventional photomultiplier tube as the photosensor for a gas proportional scintillation counter (GPSC). The VUV scintillation light produced in the xenon gas of the GPSC is transmitted through a high-purity quartz window to the MSGC where it is converted to photoelectrons by a CsI photocathode deposited directly onto the surface of a microstrip plate (MSP). The microstrip plate also provides the charge amplification in a gas selected for high gain and quenching. Preliminary experimental results of a study of the performance of this concept are presented

[en] A simple system is described that allows the study of the photoelectron collection and quantum efficiency uniformity, i.e. the output response of a photomultiplier as a function of the angle of incidence of the light for a variety of wavelengths. Results are presented for the EMI 9956QQB and discussed for both this model and the 9956QB photomultipliers, tubes frequently used in gas proportional scintillation counters. It is shown that the response uniformity is better for the shorter wavelengths and for incidence angles not too large

[en] Digital signal processing techniques have been developed to analyze the signals from a gas proportional scintillation counter (GPSC). Compared to analog systems, the digital technique is a very simple and powerful tool for manipulating and improving pulse-height distributions with no additional electronic components. Among the features inherent in digital signal processing are pulse risetime discrimination, pulse pileup correction and rejection, and background rejection. By allowing the rejection of signal pulses from x-ray interactions within the scintillation region and for near insensitive regions of the detector, an improvement in the pulse-height distribution has been effectively achieved Using this technique the energy resolution for the 22.1 keV line of a ¹⁰⁹Cd x-ray source improves from 5.6 to 5.1 % and the peak-to-background ratio increases from 30 to 170

[en] The response of a YAP, NaI(Tl) and BaF₂ scintillators to X-rays with energies around the Y, I, and Ba K-absorption edges, respectively, was investigated. For all the scintillators, the amplitude response follows different linear trends for X-ray energies below and above the respective K-edges, presenting a discontinuity at these energies. An abrupt decrease of about 3%, 5% and 2% were observed in the detector amplitude at the K-edges, for the YAP, the NaI(Tl) and the BaF₂ scintillator, respectively, corresponding to a decrease of 0.5±0.1, 1.7±0.3 and 0.8±0.2 keV in the energy calibration line. These discontinuities result in a region within 0.5±0.1, 1.6±0.3 and 0.9±0.2 keV where the X-ray energy cannot be obtained unambiguously. The scintillation yields for X-rays present abrupt decreases of about 3%, 4% and 2%, respectively, at the K-edges. The measured non-linearity effects are significantly larger than those obtained for gaseous and semiconductor detectors. The higher amplitude non-linearity observed in NaI(Tl) is attributed to the larger light yield non-linearity in the electron response of this crystal

[en] The results of a comparative study of a xenon gas proportional scintillation counter instrumented with photosensors based on two variants of a CsI photocathode and a microstrip plate are reported. The photosensors were isolated from the gas proportional scintillation counter by a quartz window and operated in P-10 gas at one atmosphere. The CsI photocathode is deposited either in the reflective or semitransparent mode. In the reflective mode, the CsI is deposited directly onto the micro strip plate and we observe gain fluctuations due to a geometric factor that degrades the energy resolution. In the semitransparent mode, the CsI is deposited onto the surface of the quartz window. Both modes of operation were evaluated and their performance characteristics reported

[en] The response of an argon proportional counter to X-rays with energy in the range of 1.5-8 keV was investigated. The response to full-energy absorption events was found to follow different trends for X-ray energies this facility and project RIBRAS follows.oacpresenting a discontinuity at this energy. An abrupt decrease of (2.2±0.3)% in the detector amplitude at the K-edge (3.203 keV) was measured, corresponding to a region within±(70±10) eV around the edge where the X-ray energy cannot be obtained unambiguously. This discontinuity corresponds to an abrupt increase of about 0.5 eV in the argon w-value and results in a sudden increase in the energy resolution from about 17% to about 19%. The detector response to escape peak events follows a linear trend over the entire energy range, very close to the response for full-energy absorption of X-rays with energies above the K-edge

[en] New methods are presented that allow the design the non-focused gas proportional scintillation counters (GPSC) with window areas that approximate the photomultiplier window area. These methods are alternatives to a previously reported technique that uses a non-uniform electric field produced by a curved grid to compensate for the radial decrease of the scintillation light collected in the photosensor due to solid angle and reflection effects. The present work reverts to a uniform electric field and compensation is achieved with a mask with a radially-decreasing density of opaque dots that are deposited onto the windows of the photosensor. The variation in the density of opaque dots is calculated to produce radially-independent light collection in the photosensor. An implementation of this new design is presented for a 52-mm-diameter photomultipler tube with a 46-mm-effective diameter. The variation in pulse amplitude as a function of radial position was observed to be reduced from 18% to only 3.5% over the area contained within the central 19 mm radius. For a 38-mm-diameter window, the energy resolution for 5.9 keV x-rays was improved from 18% to 10% with the addition of the compensating mask

[en] We present the results of a study of an argon gas proportional scintillation counter instrumented with a CsI-coated microstrip plate placed in the argon envelope. Although the measured light amplification gain and the photoelectron collection efficiency are 70% and 30-40% higher than those obtained in a similar xenon detector, the charge gain achieved in argon for the avalanches produced by the photoelectrons at the microstrip anodes is a factor of ten lower than in xenon. In both cases, these gains are limited by optical positive feedback. The energy resolution achieved for 5.9 keV X-rays was 14.8% compared to 12% in xenon

[en] A new method for pulse analysis of driftless-gas proportional scintillation counters (GPSCs) is presented. With this method the requirement for additional analog or digital signal time-analysis and pulse-amplitude correction currently used is eliminated. In contrast to conventional- and driftless-GPSCs that have always relied on long shaping-time constants (several μs), the use of very short linear amplifier shaping-time constants (∼50 ns) enables pulse shapes to closely represent the scintillation light-pulse time-profile. Since the number of detected photons in the photosensor increases continuously with depth due to the increase in the solid angle subtended by the photosensor, a maximum is achieved when the primary electron cloud is closest to the anode. This maximum depends only on the number of primary electrons in that cloud, regardless of where the X-ray absorption took place, and is proportional to the X-ray energy