N. Horikawa

A new frozen-spin target for 4π particle detection

Abstract A new frozen-spin target has been developed, that allows the detection of emitted particles in an angular acceptance of almost 4π in the laboratory frame. The central part of this new target represents a 3He/4He dilution refrigerator that is installed horizontally along the beam axis. The refrigerator includes an internal superconducting holding coil to maintain the nucleon polarization in the frozen-spin mode longitudinally to the beam. The design of the dilution refrigerator and the use of an internal holding coil enabled for the first time the measurement of a spin-dependent total cross section in combination with a polarized solid state target. This new frozen-spin target was used successfully to measure the helicity asymmetry of the total photoabsorption cross-section at the Mainz accelerator facility MAMI. This experiment has been performed in order to verify for the first time the GDH sum rule.

A scintillating fiber tracker with high time resolution for high-rate experiments

A fast and precise scintillating fiber (SciFi) tracker, using 0.5-mm-diameter fibers (Kuraray SCSF-78MJ) and position-sensitive photomultiplier tubes (Hamamatsu H6568), has been developed for the COMPASS (NA58) experiment at CERN. Tests of a 16-channel prototype showed an excellent stability in time resolution, in spatial resolution, as well as in detection efficiency under different beam flux of up to 1.4 /spl times/ 10/sup 8/ muons/spill. Four SciFi tracker stations have been constructed and all of them are presently under operation in the experiment with high performances as expected from the prototype.

A profile and flux monitor for the few GeV neutron beam at KEK

Abstract We describe a neutron beam monitor in the few GeV region developed for an experiment of the n + p → d + γ differential cross section measurement at the KEK-PS. It was used to monitor the profile and the flux of the neutron beam. The detector is a 3-plane plastic scintillator hodoscope. We present the design and performance of the monitor. The detection efficiencies evaluated with various Monte Carlo simulation codes are compared to the results of the measurements.

On-line system for NMR polarization measurement

Abstract The on-line system of the SMC polarized target with emphasis on the NMR polarization measurement system is presented. Target subsystems are controlled or monitored by local processors and a host μ-VAX computer which collects all data and provides the user interface. The Global Section scheme is used as a common data block and achieves the synchronization between subsystems. The communication between the μ-VAX and a newly added SUN-VME based system is made by the Remote Procedure Call.

A gamma ray detector with lead-scintillator tiles and WLS fiber readout for the experiment at SPring-8 to study the GDH sum rule

Abstract A prototype gamma ray detector for the detection of π0 in the proposed experiment at SPring-8 to study the Gerasimov–Drell–Hearn (GDH) sum rule (GDH experiment) has been built and tested. The detector is fabricated with lead-scintillator tiles and wave length shifter fiber readout. This detector will be placed inside the bore of the superconducting magnet which supplies the polarized target with a 2.5 T magnetic field. High-detection efficiency (above 85%) for the gamma rays is the most important requirement for this detector to be employed in the proposed experiment. It has been tested with minimum ionizing particles, electrons and gamma rays. The results of the tests in comparison with some Monte Carlo simulations are presented. The evaluated efficiency for gamma rays ranging in energy above 50 MeV is higher than 90%.