M. Asai

Micro-discharge at strip edge of silicon microstrip sensors

Abstract We have investigated the micro-discharge (micro-breakdown) phenomenon which is potentially a serious problem in operating in a high radiation environment. Numerical calculation of field strength for the model structure of the microstrip sensor gives us a quantitative understanding of each different cause of micro-discharge. The structure of the microstrip sensor can be optimized through this field calculation for suppressing the micro-discharge. We propose a new strip structure to suppress the micro-discharge.

The Cherenkov correlated timing detector: beam test results from quartz and acrylic bars

Abstract Several prototypes of a Cherenkov correlated timing (CCT) detector have been tested at the KEK-PS test beam line. We describe the results for Cherenkov light yields and timing characteristics from quartz and acrylic bar prototypes. A Cherenkov angle resolution is found to be 15 mrad at a propagation distance of 100 cm with a 2 cm thick quartz bar prototype.

Timing optimization of thin gap chambers for the use in the ATLAS muon endcap trigger

The first level muon trigger in the endcap region of the ATLAS experiment requires the use of detectors with well defined high segmentation and good time resolution, to cope with high backgrounds at large rapidity. Thin gap chambers operating in a high gain mode have been proposed for this task due to its anode readout capability, that permits a well defined segmentation down to the two wire separation, combined with its good timing properties. An optimization of such a device for timing application has been performed using large (1.22 × 0.74 m2) detectors under different operating conditions. A time resolution better than 3.7 ns has been achieved for a single layer, showing no deterioration under background rates at as high as 170 kHz/cm2.

New polarimeter for high energy gamma-rays

Abstract A new type of polarimeter for gamma-rays of over a hundred MeV was built. It is based on a principle in which the polarization is obtained from the azimuthal angular distribution of recoil electrons in electron-positron pair productions in the Coulomb fields of electrons.

Beam tests of the prototype level-1 trigger system and drift tubes with field-shapers proposed for the SDC barrel muon system

Abstract Mini-tower beam tests were carried out at a test beam line of KEK-PS in order to study the performance of the prototype level-1 trigger system and drift tubes with field-shapers originally designed for the SDC barrel muon detector at the SSC. A mini-tower of 10 layers, 31 drift tubes in total, and a prototype level-1 trigger module were designed and fabricated for the tests. The spatial resolution of about 230 μm was obtained for the tubes. Relatively high rates of multi-pulse signals were observed for most of the tubes. The trigger module designed at KEK using a logic delta- T method was studied for various trigger logics and its performance was found to be very satisfactory.

A useful method to monitor outputs from a pulsed light source and its application to rate effect studies in a photomultiplier tube

Abstract In order to study short-term gain stability in a photomultiplier tube at high counting rate, we constructed an LED pulsed light source and its output monitoring system. For the monitoring system, we employed a photon counting method using a photomultiplier as a monitor photon detector. It is found that the method offers a simple way to monitor outputs from a pulsed light source and that, together with an LED light source, it provides a useful method to investigate photomultipliers rate effects.

Muon trigger electronics for hadron collider experiments

Abstract Trigger electronics designed and constructed for the SDC muon system are described briefly and results of beam tests carried out at KEK are presented. The implementation is based on custom VLSI designs in 1.2 μm CMOS. The performance characteristics of the circuits were measured and confirmed to meet specifications. Designs based on this approach are applicable to future collider experiments.