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Planar LAAPDs: temperature dependence, performance, and application in low-ener...
Ludhova, L.; Amaro, F. D.; Antognini, A.; Biraben, F.; Cardoso, J. M. R.; Conde, C. A. N.; Covita, D. S.; Dax, A.; Dhawan, S.; Fernandes, L. M. P.An experiment measuring the 2S Lamb shift in muonic hydrogen ([mu]-p) was performed at the Paul Scherrer Institute, Switzerland. It required small and compact detectors for 1.9 keV X-rays (2P-1S transition) with an energy resolution around 25% at 2 keV, a time resolution better than 100 ns, a large solid angle coverage, and insensitivity to a 5 T magnetic field. We chose Large Area Avalanche Photodiodes (LAAPDs...
Detection of VUV photons with large-area avalanche photodiodes
Monteiro, C. M. B.; Fernandes, L. M. P.; Lopes, J. A. M.; Veloso, J. F. C. A.; Santos, J. M. F. dosThe room-temperature response of large-area avalanche photodiodes (LAAPDs) to 128- and 172-nm light pulses is investigated. The minimum detectable number of photons, which can produce a signal just above the noise level, is found to be around 1300 and 600 photons, respectively. The LAAPD relative statistical fluctuations in the detection of 15 000 photons of 128 nm and 25 500 photons of 172 nm were found to be ...
A curved-grid gas proportional scintillation counter instrumented with a 25-mm ...
Monteiro, C. M. B.; Morgado, R. E.; Santos, J. M. F. dos; Conde, C. A. N.The curved-grid technique provides a simple method to compensate for the variation in solid angle viewed by the PMT in large-area gas proportional scintillation counters (GPSC), improving their performance. The scintillation region is delimited by a planar grid and a curved one, whose shape is calculated to produce a radially increasing scintillation yield, compensating for the decrease in the solid angle. In t...
The gas proportional scintillation counter/microstrip gas chamber hybrid detector
Freitas, D. S. A. P.; Veloso, J. F. C. A.; Monteiro, C. M. B.; Santos, J. M. F. dos; Conde, C. A. N.The gas proportional scintillation counter/microstrip gas chamber (GPSC/MSGC) hybrid detector for X-ray spectrometry is described. The detector uses a CsI-coated microstrip plate placed in direct contact with the gas-filling as the photosensor readout for the GPSC scintillation substituting for the photomultiplier tube (PMT). Usable photosensor maximum gain is limited by optical positive feedback due to the add...
Energy non-linearity effects in argon gaseous detectors in the region of the Ar...
Monteiro, C. M. B.; Simões, P. C. P. S.; Veloso, J. F. C. A.; Santos, J. M. F. dos; Conde, C. A. N.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 below and above the argon K-absorption edge presenting 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 ...
The gas proportional scintillation counter/microstrip gas chamber hybrid detect...
Monteiro, C. M. B.; Veloso, J. F. C. A.; Freitas, D. S. A. P.; Santos, J. M. F. dos; Conde, C. A. N.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 a...
Non-linear behaviour of large-area avalanche photodiodes
Fernandes, L. M. P.; Lopes, J. A. M.; Monteiro, C. M. B.; Santos, J. M. F. dos; Morgado, R. E.The characterisation of photodiodes used as photosensors requires a determination of the number of electron-hole pairs produced by scintillation light. One method involves comparing signals produced by X-ray absorptions occurring directly in the avalanche photodiode with the light signals. When the light is derived from light-emitting diodes in the 400-600 nm range, significant non-linear behaviour is reported....
The performance of the GPSC/MSGC hybrid detector with argon-xenon gas mixtures
Monteiro, C. M. B.; Veloso, J. F. C. A.; Santos, J. M. F. dos; Conde, C. A. N.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...
The response of high-purity germanium detectors to X-rays with energy in the re...
Santos, J. M. F. dos; Monteiro, C. M. B.The response of a high-purity germanium detector to X-rays in the 8-15-keV energy region has been investigated. The w-value and energy resolution dependencies on the X-ray energy have been studied. No abrupt variation of w is observed at the germanium K absorption-edge (11.104-keV). The detector energy resolution follows a characteristic linear dependence on Ex-1/2 over the whole energy range. Both features are...
Energy linearity of high-purity germanium detectors in the region of the Ge K-a...
Santos, J. M. F. dos; Monteiro, C. M. B.; Morgado, R. E.; Conde, C. A. N.Non-linearities in the energy response of gas detectors in the regions of the absorption edges of the detection medium are well documented. Monte Carlo calculations show that the non-linearity results from differences in efficiencies for converting absorbed radiation into ionisation for different atomic sub-shells. Energy non-linearity in germanium-based solid-state detectors in the region of the germanium 11.1...
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