Osamu Konno

Photoproduction of neutral kaons on a liquid deuterium target in the threshold region

The photoproduction process of neutral kaons on a liquid deuterium target is investigated near the threshold region, E{sub {gamma}}=0.8-1.1 GeV. K{sup 0} events are reconstructed from positive and negative pions, and differential cross sections are derived. Experimental momentum spectra are compared with those calculated in the spectator model using a realistic deuteron wave function. Elementary amplitudes as given by recent isobar models and a simple phenomenological model are used to study the effect of the new data on the angular behavior of the elementary cross section. The data favor a backward-peaked angular distribution of the elementary n({gamma},K{sup 0}){lambda} process, which provides additional constraints on current models of kaon photoproduction. The present study demonstrates that the n({gamma},K{sup 0}){lambda} reaction can provide key information on the mechanism of the photoproduction of strangeness.

Outgassing characteristics and surface analysis of pure aluminum plates under electron beam irradiation

In order to develop aluminum with suitable surface properties for use in beam lines and scattering chambers, where ultrahigh vacuum is required; tests were carried out on aluminum samples with two different surface preparations. For one sample (specimen N) the surface was milled with a diamond cutter while in an atmosphere of dry nitrogen; for the other (specimen EP), the surface was electropolished. The surface properties and the outgassing of each sample were studied, after the samples had been irradiated with a flux of 60 MeV electrons. The outgassing from specimen N was found to be the lower. The surface composition was studied using x‐ray photoelectron spectroscopy, and indicated that the surface hydration of specimen N was lower than for specimen EP; this was true both before and after irradiation. It is shown that, before irradiation, both specimens had surface layers of a mixture of Al2O3(H2O) and Al2O33(H2O); after irradiation the surface of specimen N contained only Al2O3(H2O) while the surface ...

DOUBLE PION PHOTOPRODUCTION EXPERIMENT AT LNS–TOHOKU

The total cross sections for the π+π− photoproduction on the deuteron were measured in an energy range of 0.8 to 1.1 GeV. The obtained total cross section for the quasi-free π+π− photoproduction on the deuteron was about 60 % of those on the free proton. The cross section for Δ++Δ− photoproduction was derived from the non-quasi-free π+π− photoproduction events. It was smaller than the previous data.

Development of optical-pumping polarized deuteron target

An optical-pumping system of rubidium atoms for a laser-driven polarized deuteron target was constructed. The density and polarization of the rubidium atoms were measured using Faraday rotation. The rotation angle was determined within an error of 0.01°. Our preliminary result showed a polarization of 0.4 at a gas thickness of 4×1013 atoms/cm2.

Outgassing characteristics and composition analysis of aluminum alloy extrudate under electron beam irradiation

Outgassing characteristics and a combined surface analysis of two kinds of aluminum alloy extrudate produced in both a dry nitrogen shrouding and in air have been examined to investigate their suitability for a beam duct of an electron linear accelerator. Under conditions closely simulating the environment in the accelerator, the outgassing rate and partial pressure have been measured. Auger electron spectroscopy and secondary ion mass spectroscopy have been used to examine the surface composition and depth profile. The maximum outgassing rates per current during 55 μA irradiation were 9.1×10−8 and 1×10−8 (Torr l/s cm2)/μA for the aluminum alloy extrudates produced in air and nitrogen shrouding processes, respectively. There were significant differences in partial pressure of H2, H2O, CO, and CO2 for the two extrudates, which were found to depend on the thickness of the oxide layer on the surface and the surface composition. The Auger and secondary‐ion depth profile analysis revealed that after irradiatio...