Hidenobu Ijiri

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.

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.

Semi-microscopic formula for gas gain of proportional counters

Abstract A semi-microscopic formula of Townsends first ionization coefficient α is proposed for the gas gain of a proportional counter. The electron movement in a counter is expressed in terms of cross sections of inelastic and ionization collisions with gas molecules by introducing a simple model which has four fixed parameters for a gas. The model parameters have been determined for typical counter gases. The results of gas gain calculated by the obtained formula indicate good agreement with experimental results for several filling gas mixtures at a variety of mixing ratios and for various counter geometries.

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.

Characterization of H–Y zeolite modified by a radio-frequency CF4 plasma

Abstract H–Y zeolite modified by a radio-frequency CF 4 plasma has been characterized using X-ray diffraction, nitrogen adsorption, magic angle spinning nuclear magnetic resonance, ethanol adsorption, energy dispersive X-ray and infrared absorption techniques. The ethanol adsorption measurements indicated that the hydrophobic character of the zeolite was enhanced by the plasma treatment. The energy dispersive X-ray experiments showed that the plasma-treated zeolite contained 7.91 at% of carbon and 9.93 at% of fluorine. The infrared absorption measurements clarified that replacement of –OH groups by –CF 3 or –F groups on the micropore surface of the zeolite was responsible for the hydrophobic surface.

Fragmentation of neutron-hole strengths in 59Ni observed in the 60Ni(p,d) 59Ni reaction at 65 MeV

Abstract The 60Ni(p, d) 59Ni reaction has been studied with 65 MeV polarized protons. Angular distributions of the differential cross section and analyzing power have been measured for neutron hole states in 59Ni up to the excitation energies of 7 MeV. The data analysis with a standard distorted-wave Born approximation theory provides transferred angular momenta l, j and spectroscopic factors for thirty-nine transitions. The nuclear damping mechanism of the single hole states is discussed.