168 research outputs found
Performance of the TPC with Micro Pixel Chamber Readout: micro-TPC
Micro-TPC, a time projection chamber(TPC) with micro pixel chamber(-PIC)
readout was developed for the detection of the three-dimensional fine(sub-m
illimeter) tracks of charged particles. We developed a two-dimensional position
sensitive gaseous detector, or the -PIC, with the detection area of
1010 cm and 65536 anode electrodes of 400 m pitch. We
achieved the gas gain of over 10000 without any other multipliers. With the
pipe-line readout system specially developed for the -PIC, we detected
X-rays at the rate as high as 7.7 Mcps. We attached a drift cage with an 8 cm
drift length to the -PIC and developed a micro-TPC. We measured the basic
performances of the micro-TPC and took three-dimensional tracks of electrons.
We also developed a prototype of the MeV gamma-ray imaging detector which is a
hybrid of the micro-TPC and NaI(Tl) scintillators and confirmed its concept by
reconstructing the obtained data.Comment: 6 pages 16 figures, submitted for IEEE/TNS 200
Performance of large area Micro Pixel Chamber
A novel gaseous two-dimensional imaging detector "Micro Pixel Chamber
(micro-PIC)" has been developed. This detector is based on double sided printed
circuit board (PCB). We have developed large area (10cm x 10cm) micro-PICs with
65536 pixel anodes of 400um pitch on a 100um thick insulating substrate.
Achieved energy resolution was 30% (FWHM) at 5.9keV, and a gas gain of 7000 was
obtained with argon ethane (8:2) gas mixture. This gain is high enough to
detect minimum ionizing particles with such a small electrode pitch. Although
several discharges occurred during 65 hours continuous operation, the detectors
have kept stable operation with high gain. The micro-PIC is a useful detector
for many applications e.g. X-ray, gamma ray, and charged particle imaging. The
micro electrode structure allows us to measure directions of primary electrons
due to incident X-rays or gamma rays, which provide a strong method for X-ray
polarimetry and gamma-ray imaging.Comment: 4 pages, 8 figures, to appear in the proceedings of 6th International
Conference on Position Sensitive Detectors, 9-13 Sep 2002, Leicester, UK
(Nucl. Instr. and Meth. A
Performance of a micro-TPC for a time-resolved neutron PSD
We report on the performance of a micro-TPC with a micro pixel
chamber(-PIC) readout for a time-resolved neutron position-sensitive
detector(PSD). Three-dimensional tracks and the Bragg curves of protons with
energies of around 1 MeV were clearly detected by the micro-TPC. More than 95%
of gamma-rays of 511 keV were found to be discriminated by simple analysis.
Simulation studies showed that the total track length of proton and triton
emitted from the (n,p(573 keV)) reaction is
about 1.2 cm, and that both particles have large energy losses () in 1 atm Ar++He(). These values
suit the current performance of the micro-TPC, and we conclude that a
time-resolved neutron PSD with spatial resolution of sub-millimeters shall be
developed as an application of the micro-TPC.Comment: 13 pages, 10 figures, to appear in NIM
Development of a low-alpha-emitting {\mu}-PIC for NEWAGE direction-sensitive dark-matter search
NEWAGE is a direction-sensitive dark-matter-search experiment that uses a
micro-patterned gaseous detector, or {\mu}-PIC, as the readout. The main
background sources are {\alpha}-rays from radioactive contaminants in the
{\mu}-PIC. We have therefore developed a low-alpha-emitting {\mu}-PICs and
measured its performances. We measured the surface {\alpha}-ray emission rate
of the {\mu}-PIC in the Kamioka mine using a surface {\alpha}-ray counter based
on a micro TPC.Comment: 6 pages, 4 figure
Study of Negative-Ion TPC Using {\mu}-PIC for Directional Dark Matter Search
Negative-ion time projection chambers(TPCs) have been studied for low-rate
and high-resolution applications such as dark matter search experiments.
Recently, a full volume fiducialization in a self-triggering TPC was realized.
This innovative technology demonstrated a significant reduction in the
background with MWPC-TPCs. We studied negative-ion TPC using the {\mu}-PIC+GEM
system and obtained sufficient gas gain with CSgas and SF gas at
low pressures. We expect an improvement in detector sensitivity and angular
resolution with better electronics
Development of a time projection chamber with micro pixel electrodes
A time projection chamber (TPC) based on a gaseous chamber with micro pixel
electrodes (micro-PIC) has been developed for measuring three-dimensional
tracks of charged particles. The micro-PIC with a detection area of 10 cm
square consists of a double-sided printing circuit board. Anode pixels are
formed with 0.4 mm pitch on strips aligned perpendicular to the cathode strips
in order to obtain a two-dimensional position. In the TPC with drift length of
8 cm, 4 mm wide field cage electrodes are aligned at 1mm spaces and a uniform
electric field of about 0.4 kV/cm is produced. For encoding of the
three-dimensional position a synchronous readout system has been developed
using Field Programmable Gate Arrays with 40 MHz clock. This system enables us
to reconstruct the three-dimensional track of the particle at successive points
like a cloud chamber even at high event rate. The drift velocity of electrons
in the TPC was measured with the tracks of cosmic muons for three days, during
which the TPC worked stably with the gas gain of 3000. With a radioisotope of
gamma-ray source the three-dimensional track of a Compton scattered electron
was taken successfully.Comment: 4 pages, 7 figures, to appear in the proceedings of 6th International
Conference on Position Sensitive Detectors, 9-13 Sep 2002, Leicester, UK
(Nucl. Instr. and Meth. A
Simulation study of electron drift and gas multiplication in Micro Pixel Chamber
The physical processes of charge collection and gas multiplication of a Micro
Pixel Chamber (mu-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 electrode structure of
the mu-PIC, in order to obtain a high gas gain of more than 10^4 and a
simultaneous suppression of discharges. Consequently, we found that these
characteristics strongly depend on the substrate thickness and the anode
diameter of the mu-PIC. In addition, a gas gain of 10^5 would be expected for a
mu-PIC having a thick substrate of > 150um.Comment: 16 pages, 14 figures, Submitted to Nucl. Instr. Methods
Detecting the WIMP-wind via spin-dependent interactions
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() gas, while taking into
account the performance of an existing three-dimensional tracking detector. We
consequently found that it is highly possible to detect a positive signature of
dark matter via spin-dependent interactions.Comment: 14 pages, 5 figures, submitted for Physics Letters
ABCA7 Gene Expression and Genetic Association Study in Schizophrenia
Introduction: Although ATP-binding cassette sub-family A member 7 gene (ABCA7) is known to be associated with Alzheimer’s disease, the relationship between ABCA7 and schizophrenia has been unknown.
Methods: Schizophrenia patients (n = 50; 24 males, 62.1 ± 0.50 years old) and age- and sex-matched healthy controls (n = 50) were recruited for the mRNA analysis. Additionally, a case-control study for the rs3764650 genotypes was performed with 1308 samples (control subjects; n = 527, schizophrenia patients; n = 781). All participants were Japanese, unrelated to each other, and living in the same area.
Results: The distributions of the rs3764650 genotypes in schizophrenia patients were not different from that of controls. However, the ABCA7 mRNA expression levels in schizophrenia patients were significantly higher than those in controls by a logistic regression analysis. Additionally, the ABCA7 mRNA expression levels in schizophrenia patients were correlated with the rs3764650 genotypes in a dose-dependent manner.
Discussion: The ABCA7 mRNA expression levels in peripheral blood with the rs3764650 genotypes may be related to pathological mechanisms in schizophrenia and may be a biological marker for schizophrenia
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