Tsutomu Nagayoshi

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The physical processes of charge collection and gas multiplication of a Micro Pixel Chamber (μ-PIC) were studied in detail using a three-dimensional simulation. The collection efficiencies of primary electrons and gas multiplication factors were calculated for several electrode structures. Based on those studies, we analyzed the optimization of the(More)
MeV gamma-ray imaging has become an indispensable technology in many fields, especially medical science. A full ray-tracing of MeV gamma-rays, however, has not been realized because of its intrinsic difficulty. Collimation is one of the conventional quasi-imaging methods and is used in SPECT, although the quality of the image is not satisfying. The Compton(More)
We propose an electron-tracking Compton telescope with a gaseous time projection chamber (TPC) and a position-sensitive scintillation camera. In this detector, both the energy and direction of the Compton recoil electron are precisely measured by the gaseous TPC, while those of the Compton scattered gamma ray are also measured by the scintillation camera.(More)
Revealing the nature of dark matter is one of the most interesting tasks in astrophysics. Measuring the distribution of recoil angles is said to be one of the most reliable methods to detect a positive signature of dark matter. We focused on measurements via spin-dependent interactions, and studied the feasibility with carbon tetrafluoride(CF4) gas, while(More)
A conventional Compton camera reconstructs initial gamma-rays direction as circle. A Compton gamma-ray camera which we have developed can detect electron tracks. So our camera can reconstruct the initial gamma-rays as arc. It makes getting the low noise of image. In this paper, we report the results of three version of electron tracking camera. One is 10 x(More)
An MeV gamma-ray imaging detector for astrophysics, which enables us to reconstruct gamma-rays event by event by tracking both a Compton recoil electron and a scattered gamma-ray, has been developed. This detection method is powerful for background rejection. The prototype detector is a hybrid of a gaseous time projection chamber (micro-TPC) with 10 /spl(More)
We are developing an electron-tracking Compton imaging camera (ETCC) based on a gaseous time projection chamber (TPC) and a scintillation camera. The ETCC detects the energy and the direction of the incident gamma ray using the information of the recoil electron and the scattered gamma ray. We have developed the ETCC with a detection volume of 23 times 28(More)
For the readout of the time projection chamber with our developed micro-pattern gaseous detector (micro-PIC), we have developed a high-speed position encoding system operated at 100 MHz clock, by combination of multi-channel analog-ASIC preamplifiers, a position encoding system with FPGA processors, a VME-bus memory-board, and a VME-bus CPU. This system has(More)
We have been developing a micro-TPC (mu-TPC) based on a micro pixel chamber (mu-PIC) with a real-time readout system. The mu-PIC has micro-pixel electrodes with a pitch of 400 mum in an area of 10times10 cm<sup>2</sup>. The mu-TPC has high performances for tracking charged particles and measuring their energy deposition so that there are various developing(More)
A new amplifier-shaper-discriminator (ASD) chip was designed and manufactured for the micro pixel chamber (/spl mu/-PIC). The design of this ASD IC is based on the ASD IC (TGC-ASD) for the thin gap chamber in the LHC ATLAS Experiment. The decay time constant of the preamplifier is five times longer than that of the TGC-ASD, and some other modifications have(More)