[en] The response of a cadmium zinc telluride (CZT) detector to X-rays with energies around the Zn, Cd and Te K-absorption edges was investigated. The energy non-linearity in the detector response at the K-edges is less than 0.1%, within the experimental errors. No abrupt variation in both the w-value and the detector energy resolution was observed at the K-edges, a behaviour consistent with the absence of intrinsic non-linearity effects in CZT. Within the accuracy of our measurements, we conclude that there are no non-linearity effects in CZT semiconductors at the Zn, Cd and Te K-edges

[en] Performance characteristics are evaluated for a xenon driftless gas proportional scintillation counter (GPSC), for which detector pulses are formatted using very short shaping-time constants (∼50 ns), and directly analyzed by the MCA without previous pulse time duration analysis and amplitude correction. The present detector and method allow the achievement of detector energy linearity and energy resolution similar to those of conventional GPSCs, reducing background levels and maximizing the detector count-rate capability. However, the obtained peak tails can be somewhat larger than those obtained with conventional GPSCs for X-ray energies above ∼30 keV. Energy resolutions of 7.7%, 4.5% and 3.8% can be achieved for 5.9, 22.1 and 59.6 keV X-rays, respectively

[en] A Gas Proportional Scintillation Counter filled with pure krypton was studied. Energy resolution below 10% for 5.9-keV X-rays was obtained with this prototype. This value is much better than the energy resolution obtained with proportional counters or other MPGDs with krypton filling. The krypton electroluminescence scintillation and ionisation thresholds were found to be about 0.5 and 3.5 kV cm⁻¹bar⁻¹, respectively.

No abstract available

[en] The performance of a new VUV photosensor, based on an micro-hole and strip plate (MHSP) electron multiplier with a CsI photocathode deposited on its top electrode, is described. This photosensor presents gains above 10⁴ when operating in an Ar-5%Xe gas mixture at 1 atm. Although the gain of a single MHSP is not sufficient for efficient detection of single photons, this simple UV photosensor may be useful for the detection of higher light levels, such as primary- and secondary scintillation in noble gases

[en] We present the first operation of the VUV-sensitive avalanche photodiode (APD) from Hamamatsu to xenon scintillation light and to direct X-rays of 22.1 keV and 5.9 keV. A large non-linear response was observed for the direct X-ray detection. At 415 V APD bias voltage it was of about 30% for 22.1 keV and about 45% for 5.9 keV. The quantum efficiency for 172 nm photons has been measured to be 69±15%.

[en] The search for neutrinoless double beta decay (0νββ) is an important topic in contemporary physics with many active experiments. New projects are planning to use high-pressure xenon gas as both source and detection medium. The secondary scintillation processes available in noble gases permit large amplification with negligible statistical fluctuations, offering the prospect of energy resolution approaching the Fano factor limit. This Letter reports results for xenon secondary scintillation yield, at room temperature, as a function of electric field in the gas scintillation gap for pressures ranging from 2 to 10 bar. A Large Area Avalanche Photodiode (LAAPD) collected the VUV secondary scintillation produced in the gas. X-rays directly absorbed in the LAAPD are used as a reference for determining the number of charge carriers produced by the scintillation pulse and, hence, the number of photons impinging the LAAPD. The number of photons produced per drifting electron and per kilovolt, the so-called scintillation amplification parameter, displays a small increase with pressure, ranging from 141±6 at 2 bar to 170±10 at 8 bar. In our setup, this parameter does not increase above 8 bar due to non-negligible electron attachment. The results are in good agreement with those presented in the literature in the 1 to 3 bar range. The increase of the scintillation amplification parameter with pressure for high gas densities has been also observed in former work at cryogenic temperatures.

[en] The NEXT neutrinoless double beta decay (ββ0ν) experiment will use a high-pressure gas electroluminescence-based TPC to search for the decay of Xe-136. One of the main advantages of this technology is the possibility to reconstruct the topology of events with energies close to Q_β_β. The rejection potential associated to the topology reconstruction is limited by our capacity to properly reconstruct the original path of the electrons in the gas. This reconstruction is limited by different factors that include the geometry of the detector, the density of the sensors in the tracking plane and the separation among them, etc. Ultimately, the resolution is limited by the physics of electron diffusion in the gas. In this paper we present a series of molecular additives that can be used in Xenon gas at very low partial pressure to reduce both longitudinal and transverse diffusion. We will show the results of different Monte-Carlo simulations of electron transport in the gas mixtures from wich we have extracted the value of some important parameters like diffusion, drift velocity and light yields. These results show that there is a series of candidates that can reduce diffusion without affecting the energy resolution of the detector and they should be studied experimentally. A comparison with preliminary results from such an ongoing experimental effort is given

[en] We report on results obtained with the NEXT-DEMO prototype of the NEXT-100 high-pressure xenon gas time projection chamber (TPC), filled with pure xenon gas at 10 bar pressure and exposed to an alpha decay calibration source. Compared to our previous measurements with alpha particles, an upgraded detector and improved analysis techniques have been used. We measure event-by-event correlated fluctuations between ionization and scintillation due to electron-ion recombination in the gas, with correlation coefficients between −0.80 and −0.56 depending on the drift field conditions. By combining the two signals, we obtain a 2.8% FWHM energy resolution for 5.49 MeV alpha particles and a measurement of the optical gain of the electroluminescent TPC. The improved energy resolution also allows us to measure the specific activity of the radon in the gas due to natural impurities. Finally, we measure the average ratio of excited to ionized atoms produced in the xenon gas by alpha particles to be 0.561± 0.045, translating into an average energy to produce a primary scintillation photon of W_e_x=(39.2± 3.2) eV