S. Fukui

Measurement of the asymmetry for π+ photoproduction from polarized protons between 300 and 900 MeV

Abstract The asymmetry of the cross section for π+ photoproduction from a polarized butanol target has been measured at a c.m. angle 90° and photon energies between 300 and 900 MeV by a single-arm spectrometer detecting positive pions. Our results indicate that the asymmetry has clear positive peaks at photon energies 400 and 700 MeV with a deep valley at about 600 MeV. The general feature of the results is well reproduced by the phenomenological analyses made by Walker and ourselves; however, the best fit to the polarized target asymmetry data seems to give a somewhat different set of parameters from that given by Walker.

Construction of GaAs Spin-Polarized Electron Source and Measurements of Electron Polarization

A simple and compact system for generation and detection of polarized electrons is constructed. Polarized electrons are extracted from negative electron affinity (NEA) surface of GaAs by optical pumping with circulary polarized light from GaAlAs laser diode. The maximum degree of the electron polarization measured by 90 keV Mott analyzer is about ±10%.

Channeling radiation emitted from planar channeled electrons at 350 MeV in silicon crystal

Abstract Spectra of the channeling radiation emitted by 350 MeV (HO)-planar channeled electrons in silicon crystals were observed and the dechanneling length was obtained as 31 μm. A photon spectrum, only from channeled electrons, deduced from observed aligned and random photon spectra, was compared with that calculated quantum mechanically, taking account of the experimental conditions and the efficiency of the photon detector. The result showed good agreement for the absolute intensity.

Tensor analyzing power T20 for cumulative pion production from deuterons in the GeV energy region

Abstract The tensor analyzing power T 20 for the reaction d ↑ + 12 C → π ± (0°) + X has been measured with a polarized deuteron beam from 6.2 to 9.0 GeV/ c at a pion momentum3.0 GeV/ c . This experiment is focused on “cumulatively produced pions”, which are produced beyond the kinematically allowed limit for free nucleon-nucleon collisions. The measured values of T 20 turn out to be close to zero. They are in disagreement with the results of our impulse approximation calculation which is based on a single NN → πNN interaction and takes into account the internal motion of nucleons in the deuteron. Possible explanations of the result are discussed.

Flexible Adiabatic Light Guide of Silicon Rubber

A certain type of silicon rubber (KE103RTV) is found to be a useful material as an adiabatic light guide for scintillation counters because of its mechanical flexibility. The refractive index of KE103RTV is measured to be 1.410±0.006. The transmission and the resolution of scintillation light pulses through it are comarable with those through acrylic resin light guides. This RTV has the resistivity against high dose of radiation.

First results on the tensor analyzing power Ayy in deuteron inclusive breakup at large transverse momenta of protons

The tensor analyzing power A yy in inclusive breakup of 9 GeV/c deuterons on carbon has been measured at 85 mrad of the detected proton angle using polarized beam of the Synchrophasotron of the Laboratory for High Energies of JINR. The analyzing power A yy remains positive at the highest measured momentum of the proton in definite contradiction with the predictions based on the standard nucleon-nucleon potentials.

Loss Mechanism of Electrons from a Magnetic Bottle

The motion of electrons in a static magnetic field of mirror geometry was investigated by injecting a beam of KeV electrons with a small electron gun in the central region of the magnetic bottle. The first order orbit theory was well verified by high vacuum experiment. The The mirror loss of KeV electrons was studied by filling the vaccum chamber with helium and argon gases. The mean lifetime of trapped electrons was measured by making use of the azimuthal drift of electrons as a function of gas pressure. The elastic scattering of single or plural type is concluded to be the most responsible for the mirror loss at pressure of 10 -4 mmHg or higher.

Fragmentation of polarized deuteron into high momentum mesons as source of spin information of deuteron core structure

Abstract A study of spin effects at fragmentation of 9 GeV polarized deuterons into high momentum pions d A → π (θ) X was for the first time performed at Dubna polarized deuteron facility. Large D -state effects were observed at fragmentation of tensor polarized deuterons into cumulative pions at non-zero emission angles.

Channeling radiation from 350 MeV electrons

Abstract The energy spectrum of channeling radiation from 350 MeV electrons was measured in the case of the (110) plane of silicon crystal. The result shows good agreement with the spectrum calculated by quantum theory and corrected for detector efficiency.

An Automatic Recorder of the Spark Chamber

An automatic digitizing-recording system of the spark chamber by means of television vidicon cameras is constructed. It is possible to record two spark columns in one gap simultaneously, and two cameras are used to define the position of a spark column. One picture is decomposed into 200 horizontal sweep lines in one vertical sweep; among them 40 sweeps are arbitrarily selected for the digitization according to the structure of the chamber. The digitization area (67% of the sweep length) is divided into 1000 scales and the position of the spark is represented by the 3 digital numbers. The capacity of the memory is just enough to memorize a set of stereoscopic pictures of an event. At present, the position of the spark is determined with an error of scale 2, the resolving power of two lines is about scale 7 and the linearity between the geometrical position and the digitized result is good.