M. Salete

Detection of soft X-rays with a xenon proportional scintillation counter

Abstract Soft X-rays were detected with a xenon proportional scintillation counter; for example, full widths at half maximum of 100 eV and 140 eV were obtained for the carbon and oxygen X-rays, respectively. Window sizes up to 100 mm2 were used. The measured value of the Fano factor, 0.170 ± 0.007, implies that the ultimate relative standard deviation of the pulses is 0.06 E − 1 2 (E in keV ) to be compared to the experimental determination 0.087 E − 1 2 .

Fano factors of rare gases and their mixtures

Abstract Measurements of FW (Fano factor × mean energy to make an ion-pair) for several non metastable Penning gas mixtures were made using the proportional scintillation process. Taking for W the values that correspond to 5.3 MeV alpha particles, upper limits of F were determined. The following results were obtained: 100% Xe, FW = 3.247, F ⩽ 0.15 ± 0.03 100% Ar, FW = 10.536, F ⩽ 0.40 ± 0.03 Ar + 80% Xe, FW = 4.635, F ⩽ 0.21 ± 0.03 Ar + 5% Kr, FW = 9.397, F ⩽ 0.37 ± 0.06 Ar + 24% Xe, FW = 5.093, F ⩽ 0.23 ± 0.02 Ar + 20% Kr, FW = 3.038, F ⩽ 0.12 ± 0.03 Ar + 20% Xe, FW = 3.582, F ⩽ 0.16 ± 0.02 Ar + 79% Kr, FW = 3.113, F ⩽ 0.13 ± 0.02 Ar + 5% Xe, FW = 3.204, F ⩽ 0.14 ± 0.03 100% Kr, FW = 4.584, F ⩽ 0.19 ± 0.02

The Energy Resolution and Window Area Capabilities of the Gas Proportional Scintillation Counter

The behaviour of xenon and argon-xenon gas proportional scintillation counters is con sidered. For X-rays, ranges of window area are defined showing competition with semiconductor detectors. Data for primary scintillation of X-rays and alpha particles are included. Relative efficiencies of tetraphenylbutadiene, p-terphenyl, diphenyl-stilbene, sodium salicylate and p-quaterphenyl were measured.

Fano factors of krypton-xenon mixtures

Abstract Measurements of FW (product of the Fano factor and the mean energy to make an ion pair) for several mixtures of krypton and xenon were made using the proportional scintillation method. The following results were obtained: Kr 100% FW = 5.472 F ⩽ 0.23±0.01 Kr + 1.3%Xe FW = 4.426 F ⩽ 0.19±0.02 Kr + 20%Xe FW = 4.659 F ⩽ 0.21±0.02 Kr + 40%Xe FW = 4.828 F ⩽ 0.22±0.01 Kr + 60%Xe FW = 4.587 F ⩽ 0.21±0.01 Kr + 95%Xe FW = 4.558 F ⩽ 0.21±0.01 Xe 100% FW = 3.244 F ⩽ 0.15±0.01

Self-Quenching Streamers in Mixtures with Photoionization Vapours

The basic properties of self-quenching streamers in a proportional counter with a thick anode wire are investigated. In particular, the influence of mixing benzene and triethylamine to argon-isobutane mixtures is studied regarding thresholds for streamer production, pulse shapes and dead time. There is a lowering of the high voltage threshold for streamer production associated with low concentrations of triethylamine and benzene. Higher concentrations of benzene increase that thre¿ shold. Triethylamine leads to narrower pulses. Stable operation is observed for a much broader range of high voltages than in the absence of photoionization vapours.

Dead Region Time Evolution and Afterpulses Development in SQS

The dead length, 6, for t > 20 ¿s is well approximated by ¿=¿0 exp(-t/¿) for mixtures of argon-isobutane with benzene or TEA. ¿0 varies in an approximate linear way with the streamer charge and the systematics of ¿ regarding the high voltage is also presented. Afterpulses are associated not only with wall effects but also with photoionization in the gas mixture itself. Interpretation of the data is attempted.

Detection of VUV photons with a photoionization proportional scintillation chamber

Abstract The VUV emission of Ar and Kr filled proportional scintillation counters (GSPC) has been detected by a gaseous photoionization detector with multianode proportional chamber configuration. Transfer efficiencies were measured for several photoionizing gases, and values of 30% and 41% were obtained for di-n-propylamine and di-iso-propylamine relatively to triethylamine (TEA) for the detection of Kr emission, and values of 61% and 47% were obtained for acetylacetone and cyclohexene relatively to benzene for the detection of Ar emission. Cross sections for photoabsorption were calculated from the experimental data: σ (TEA) ∼ 9 Mb (or σ P ∼ 450 Mb · Torr , P being the vapour pressure at room temperature), σ P (di-n-propy lamine) ∼ 400 Mb · Torr, σ P (di-iso-propylamine) ∼ 1500 Mb · Torr, σ P (acetylacetone) ∼ 200 Mb · Toor, σ P (cyclohexene) ∼ 103 Mb · Torr. Threshold fields for secondary light production were obtained as (0.92±0.02) V · cm− · Torr−1 and (0.77±0.02) V · cm−1 · Torr−1 for Ar and Kr respectively. Measurements of energy and spatial resolution, though of a preliminary nature, were undertaken.

The Gain Divergence on the Transition to the Self-Quenching Streamers

Based on the observed gain divergence characteris¿ tics occuring in a gaseous detector at the transition fran the proportional to the self-quenching streamers discharge (SQS), when adquate gas fillings are used and on the role played by photoionization, a mechanism is proposed to interpret quantitatively the process. The relevant intrinsic parameters, which determine the mechanism, are the number of photons emitted by electron per cm path near the anode, W, the mean free path of VUV radiation, L, the quantum efficiency, ¿, geometrical factors, g, which are interrelated. Fran the experimental data some of those parameters are computed for the mixtures argon-isobutane and argon-isobutane-triethylamine.

Photon breeding of self-quenching streamers (SQS)

A quantitative formalism for the photon breeding of the SQS is proposed and the number of breeding photons per electron is determined for argon-isobutane mixtures for concentrations of the quencher from 32% up to 60%. This number (probably in the region hv < 14 eV) is about 5 × 10−2.

Pressure dependence of light output in rare gases and their mixtures

Abstract The reduced secondary light output L / p from the gas proportional scintillation counter is studied as a function of the reduced electric field E / p for several rare gases and a few of their mixtures. Most data concern a spherical field geometry using p-terphenyl as a wavelength shifter, but some (Ar and Kr) refer also to a uniform field without wavelength shifter, using a photoionization chamber. All measurements were made in a charge mode. A weighted least square fit of the type L / p = a 2 ( E / p ) a 1 , a 1 and a 2 being free parameters, was made to the data with good results. a 1 and a 2 are constant for Xe, Ar–46%Xe and Xe–50%Ne, the values of a 1 being 1.55, 2.7 and 1.61, respectively. For Ar, Kr and Ar–75%Ne those parameters exhibit small variations with the pressure and the average values of a 1 are 2.65, 1.91 and 1.54, respectively.