604 research outputs found
Imaging Gaseous Detector based on Micro Processing Technology
The development of gaseous detectors has been exciting again since the
appearance of a MicroStrip Gas Chamber(MSGC) in 1988, which is made using a
micro-electronics technology. These days lots of variations of the advanced
gaseous detectors are being intensively studied in the world.
We have developed the two-dimensional MSGC having a 10 cm square detection
area and the ultra fast readout system for a real time X-ray imaging. The MSGC
was made using Multi-Chip Module (MCM) technology, and has a very thin
substrate of 17 m, lots of thin anodes and back strips both with 200
m pitches. This enables us to get fast digital X-ray images with recording
both the timing and an energy of each X-ray photon. In addition, an
intermediate gas multiplier has been realized using a capillary plate having a
conductive surface of a capillary. The MSGC combined with the conductive
capillary plate can be steadily operated with a high gain under intense
irradiation. Here we also report new approaches of X-ray crystal structure
analyses using timing information obtained by the MSGC.Comment: 14 papges, 10 figures, to appear in the proceedings of Solid State
Detectors for 21st Century (Nucl. Instru. and Meth. A
Particle Acceleration and Cosmic-Ray Origin in the Galaxy
In 1990's Very High Energy Gamma-ray Astrophysics has dramatically advanced
due to the Imaging Air \v{C}erenkov Telescopes(IACTs). After the first
detection of TeV gamma-ray emission from the Crab nebula in 1989, several type
of TeV gamma-ray sources, Active Galactic Nuclei(AGN), young pulsar, and
SuperNova Remnant(SNR), have been detected. In those discoveries, recent
detections of both synchrotron X-rays and TeV gamma-ray emissions from several
SNRs are very significant. SNR has been widely believed to be an unique
candidate of galactic cosmic-ray origin since the beginning of cosmic-ray
physics, whereas little observational evidences have been reported so far.
Those are expected to be a clue of not only the galactic cosmic-ray origin but
also the understanding of the particle acceleration due to a diffusive shock.
Here I present the recent results obtained by our group, CANGAROO, about the
evidences of electron and proton acceleration in SNRs.Comment: 9 pages, 9 figures, to appear in proceedings of the conference " The
International Symposium on Science of Super-Strong Field Interactions" held
in Japan Hayama, March 200
Reanalysis of Data Taken by the CANGAROO 3.8 Meter Imaging Atmospheric Cherenkov Telescope: PSR B1706-44, SN 1006, and Vela
We have reanalyzed data from observations of PSR B1706-44, SN 1006, and the
Vela pulsar region made with the CANGAROO 3.8 m imaging atmospheric Cherenkov
telescope between 1993 and 1998 in response to the results reported for these
sources by the H.E.S.S. collaboration. In our reanalysis, in which gamma-ray
selection criteria have been determined exclusively using gamma-ray simulations
and OFF-source data as background samples, no significant TeV gamma-ray signals
have been detected from compact regions around PSR B1706-44 or within the
northeast rim of SN 1006. We discuss reasons why the original analyses gave the
source detections. The reanalysis did result in a TeV gamma-ray signal from the
Vela pulsar region at the 4.5 sigma level using 1993, 1994, and 1995 data. The
excess was located at the same position, 0.13 deg. to the southeast of the Vela
pulsar, as that reported in the original analysis. We have investigated the
effect of the acceptance distribution in the field of view of the 3.8 m
telescope, which rapidly decreases toward the edge of the field of the camera,
on the detected gamma-ray morphology. The expected excess distribution for the
3.8 m telescope has been obtained by reweighting the distribution of HESS
J0835-455 measured by H.E.S.S. with the acceptance of the 3.8 m telescope. The
result is morphologically comparable to the CANGAROO excess distribution,
although the profile of the acceptance-reweighted H.E.S.S. distribution is more
diffuse than that of CANGAROO. The integral gamma-ray flux from HESS J0835-455
has been estimated for the same region as defined by H.E.S.S. from the
1993-1995 data of CANGAROO to be F(> 4.0 +/- 1.6 TeV) = (3.28 +/- 0.92) x
10^{-12} photons cm^{-2} s^{-1}, which is statistically consistent with the
integral flux obtained by H.E.S.S.Comment: Published in ApJ, minor improvement
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
Development of an advanced Compton camera with gaseous TPC and scintillator
A prototype of the MeV gamma-ray imaging camera based on the full
reconstruction of the Compton process has been developed. This camera consists
of a micro-TPC that is a gaseous Time Projection Chamber (TPC) and
scintillation cameras. With the information of the recoil electrons and the
scattered gamma-rays, this camera detects the energy and incident direction of
each incident gamma-ray. We developed a prototype of the MeV gamma-ray camera
with a micro-TPC and a NaI(Tl) scintillator, and succeeded in reconstructing
the gamma-rays from 0.3 MeV to 1.3 MeV. Measured angular resolutions of ARM
(Angular Resolution Measure) and SPD (Scatter Plane Deviation) for 356 keV
gamma-rays were and , respectively.Comment: 4 pages, 5 figures. Proceedings of the 6th International Workshop On
Radiation Imaging Detector
Studies of the performance of different front-end systems for flat-panel multi-anode PMTs with CsI(Tl) scintillator arrays
We have studied the performance of two different types of front-end systems
for our gamma camera based on Hamamatsu H8500 (flat-panel 64 channels
multi-anode PSPMT) with a CsI(Tl) scintillator array. The array consists of 64
pixels of which corresponds to the anode pixels of
H8500. One of the system is based on commercial ASIC chips in order to readout
every anode. The others are based on resistive charge divider network between
anodes to reduce readout channels. In both systems, each pixel (6mm) was
clearly resolved by flood field irradiation of Cs. We also investigated
the energy resolution of these systems and showed the performance of the
cascade connection of resistive network between some PMTs for large area
detectors.Comment: 9 pages, 6 figures, proceedings of the 7th International Workshop on
Radiation Imaging Detectors (IWORID7), submitted to NIM
- âŠ