Hitoshi Kametani

Observation of Self-Quenching Streamers in Quenching Gases of Hydrocarbons and Carbon Dioxide

Basic properties of the self-quenching streamer transition have been studied for quenching gases of CH/sub 4/, C/sub 2/H/sub 6/, C/sub 3/H/sub 8/, isoC/sub 4/H/sub 10/ and CO/sub 2/ without argon. It is found that X-rays do not induce clearly the transition, but ..cap alpha..-rays, which are incident in normal to the counter anode, induce it evidently in all the quenching gases. This suggests that argon is important but is not essential to obtain the transition. Instead of energetic photons from excited argon molecular states for the transition, possible origins of energetic photons in the quenching gases are discussed.

Three Dimensional Monte Carlo Simulation of the Electron Avalanche Around an Anode Wire of a Proportional Counter

A three-dimensional Monte Carlo simulation code) has been written, which calculates physical characteristics of the electron avalanche around an anode wire of a proportional counter. The microscopic treatment of the avalanche development in a gas counter has been realized first using the present simulation code. Typical results of simulations are reported.

Characterization of Separation-by-Implanted-Oxygen Wafers with Monoenergetic Positron Beams

Defects in separation-by-implanted-oxygen wafers were studied with monoenergetic positron beams. Doppler broadening profiles of the positron annihilation radiation and lifetimes of positrons were measured as a function of incident positron energy for 200-keV O+-ion implanted Si specimens. For as-implanted specimens, the dominant defect species at a depth of ~20 nm was identified as vacancy-clusters and that in the region between ~200 nm and ~600 nm as vacancy-oxygen complexes. After annealing treatment, the formation of an oxide layer was observed in the region where a great number of vacancy-oxygen complexes formed. It was also found that interstitial Si atoms accumulated at the Si/SiO2 interface.

Charge-division type position sensing with a single-wire position sensitive counter in the self-quenching streamer mode☆

Abstract Using single-wire position sensitive counters with a stainless-steel anode wire of 25 μm diameter, position sensing has been performed in the self-quenching streamer (SQS) mode. Overall position resolutions of 0.26 mm and 0.69 mm fwhm for 4.5 keV X-rays were obtained for 100 mm long and 1.82 m long counters, respectively, by means of standard NIM electronic circuits and a new ratio-to-digital converter (RDC). Problems in the application of SQS mode to position sensing are discussed.

Realization of the concept of the ratio-to-digital converter (RDC)☆

Abstract The concept of the ratio-to-digital converter (RDC) has been realized. An RDC system based on a division circuit which utilizes linear discharge functions in memory condensers has been developed. The quotient from the division circuit is converted directly into a digital form. The accuracy in the quotient is better than 0.1% for the full scale, and a linearity better than 0.05% over a dynamic range of 1:20 is obtained. This performance corresponds to that of a digital division system using two 16000-channel ADCs.

Strength functions of deeply bound hole states in 111, 115, 119, 123Sn

Abstract Deeply bound hole states in 111,115,119,123Sn have been investigated with high resolution (p, d) experiments at the bombarding energy of 50 MeV. The fine structure and neutron number dependence of the strength functions of the 1 g 9 2 and 2 p (2 p 1 2 + 2 p 3 2 ) hole states have been determi The resulting strength functions and the spreading widths were compared with predictions of the nuclear damping calculations by Soloviev, Stoyanov and Vdovin and by Bortignon and Broglia.

Self-quenching streamers in magic gas mixtures

Abstract Self-quenching streamers (SQSs) are found to be essential to obtain large pulses in the magic gas mixtures of ArCH 4 , ArC 2 H 6 , ArC 3 H 8 , ArisoC 4 H 10 and ArCO 2 containing a small amount of electronegative freon13B1 vapour. The condition of the transition to the SQS mode is discussed on the basis of an estimation of the mean electron density of an avalanche and of the number of photoelectrons contributing to the transition. The mixture of ArCO 2 —freon13B1 shows clearly the magic gas behaviour in a single-wire gas counter as the other freon-containing mixtures found previously.

Position Resolution of a Gas Counter in the SQS Transition Region

Position resolutions around the transition region from the proportional to self-quenching streamer (SQS) modes in a gas counter has been measured. The counter used is of a strip-cathode type, which is filled with a mixed gas Ar70% + CH430% adding an adequate concentration of ethanol. Transition in the position resolution was clearly observed between the SQS mode and the double SQS mode in any concentration of the ethanol, while not so clearly between the proportional mode and the SQS mode. The best position resolution, 0.11mm (FWHM), was obtained in the double SQS mode operation.

Strength functions of deeply bound hole states in 115Sn

Abstract High-resoluution (p, d) experiments for the deeply bound hole states in 115Sn were performed at an incident proton energy of 50.4 MeV. The data gives new detailed information regarding the strength function of the deeply bound 1 g 9 2 and 2 p hole states in 115Sn. The comparison between experiment and theory suggests the necessity of refining the theoretical model on the nuclear damping mechanism of hole states.

Space charge effect in SQS transition in a gas counter

Abstract Systematic investigation of the gas multiplication characteristics in the transition region from the proportional to SQS mode in a cylindrical proportional counter has been performed. The property of saturation of the gas multiplication factor can be reproduced using the effective electric field which is corrected for the space charge related to the positive ion density in the avalanche. Photon-mediated gas multiplication can explain the large jump phenomenon of the SQS transition. It is shown that the effective electric field in the avalanche becomes almost zero near the anode surface (Meeks streamer condition) at the 50% transition voltage and the region of its maximum moves slightly away from the anode surface.