319 research outputs found
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
Investigating the hard X-ray emission from the hottest Abell cluster A2163 with Suzaku
We present the results from Suzaku observations of the hottest Abell galaxy
cluster A2163 at . To study the physics of gas heating in cluster
mergers, we investigated hard X-ray emission from the merging cluster A2163,
which hosts the brightest synchrotron radio halo. We analyzed hard X-ray
spectra accumulated from two-pointed Suzaku observations. Non-thermal hard
X-ray emission should result from the inverse Compton (IC) scattering of
relativistic electrons by the CMB photons. To measure this emission, the
dominant thermal emission in the hard X-ray band must be modeled in detail. To
this end, we analyzed the combined broad-band X-ray data of A2163 collected by
Suzaku and XMM-Newton, assuming single- and multi-temperature models for
thermal emission and the power-law model for non-thermal emission. From the
Suzaku data, we detected significant hard X-ray emission from A2163 in the
12-60 keV band at the level (or at the level if a
systematic error is considered). The Suzaku HXD spectrum alone is consistent
with the single-T thermal model of gas temperature keV. From the XMM
data, we constructed a multi-T model including a very hot ( keV)
component in the NE region. Incorporating the multi-T and the power-law models
into a two-component model with a radio-band photon index, the 12-60 keV energy
flux of non-thermal emission is constrained within . The 90% upper limit of detected IC
emission is marginal ( in the
12-60 keV). The estimated magnetic field in A2163 is .
While the present results represent a three-fold increase in the accuracy of
the broad band spectral model of A2163, more sensitive hard X-ray observations
are needed to decisively test for the presence of hard X-ray emission due to IC
emission.Comment: 7 pages, 7 figures, A&A accepted. Minor correctio
DIOS: the dark baryon exploring mission
DIOS (Diffuse Intergalactic Oxygen Surveyor) is a small satellite aiming for
a launch around 2020 with JAXA's Epsilon rocket. Its main aim is a search for
warm-hot intergalactic medium with high-resolution X-ray spectroscopy of
redshifted emission lines from OVII and OVIII ions. The superior energy
resolution of TES microcalorimeters combined with a very wide field of view
(30--50 arcmin diameter) will enable us to look into gas dynamics of cosmic
plasmas in a wide range of spatial scales from Earth's magnetosphere to
unvirialized regions of clusters of galaxies. Mechanical and thermal design of
the spacecraft and development of the TES calorimeter system are described. We
also consider revising the payload design to optimize the scientific capability
allowed by the boundary conditions of the small mission.Comment: 10 pages, 11 figures, Proceedings of the SPIE Astronomical
Instrumentation : Space Telescopes and Instrumentation 2014: Ultraviolet to
Gamma Ra
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
Development of Large area Gamma-ray Camera with GSO(Ce) Scintillator Arrays and PSPMTs
We have developed a position-sensitive scintillation camera with a large area
absorber for use as an advanced Compton gamma-ray camera. At first we tested
GSO(Ce) crystals. We compared light output from the GSO(Ce) crystals under
various conditions: the method of surface polishing, the concentration of Ce,
and co-doping Zr. As a result, we chose the GSO(Ce) crystals doped with only
0.5 mol% Ce, and its surface polished by chemical etching as the scintillator
of our camera. We also made a 1616 cm scintillation camera which
consisted of 9 position-sensitive PMTs (PSPMTs Hamamatsu flat-panel H8500), the
each of which had 88 anodes with a pitch of 6 mm and coupled to
88 arrays of pixelated 613 mm GSO(Ce) scintillators.
For the readout system of the 576 anodes of the PMTs, we used chained resistors
to reduce the number of readout channels down to 48 to reduce power
consumption. The camera has a position resolution of less than 6mm and a
typical energy resolution of 10.5% (FWHM) at 662 keV at each pixel in a large
area of 1616 cm. %to choose the best scintillator for our project.
Furthermore we constructed a 1616 array of 313 mm
pixelated GSO(Ce) scintillators, and glued it to a PMT H8500. This camera had
the position resolution of less than 3mm, over an area of 55 cm,
except for some of the edge pixels; the energy resolution was typically 13%
(FWHM) at 662 keV.Comment: Proceedings of PSD7 appear in NIM
PROSAC: A Submillimeter Array Survey of Low-Mass Protostars. I. Overview of Program: Envelopes, Disks, Outflows and Hot Cores
This paper presents a large spectral line and continuum survey of 8 deeply
embedded, low-mass protostellar cores using the Submillimeter Array. Each
source was observed in high excitation lines of some of the most common
molecular species, CO, HCO+, CS, SO, H2CO, CH3OH and SiO. Line emission from 11
species originating from warm and dense gas have been imaged at high angular
resolution (1-3"; typically 200-600 AU) together with continuum emission at 230
GHz (1.3 mm) and 345 GHz (0.8 mm). Compact continuum emission is observed for
all sources which likely originates in marginally optically thick circumstellar
disks, with typical lower limits to their masses of 0.1 M_sun (1-10% of the
masses of their envelopes) and having a dust opacity law with beta
approximately 1. Prominent outflows are present in CO 2-1 observations in all
sources: the most diffuse outflows are found in the sources with the lowest
ratios of disk-to-envelope mass, and it is suggested that these sources are in
a phase where accretion of matter from the envelope has almost finished and the
remainder of the envelope material is being dispersed by the outflows. Other
characteristic dynamical signatures are found with inverse P Cygni profiles
indicative of infalling motions seen in the 13CO 2-1 lines toward
NGC1333-IRAS4A and -IRAS4B. Outflow-induced shocks are present on all scales in
the protostellar environments and are most clearly traced by the emission of
CH3OH in NGC1333-IRAS4A and -IRAS4B. These observations suggest that the
emission of CH3OH and H2CO from these proposed "hot corinos" are related to the
shocks caused by the protostellar outflows. Only one source, NGC1333-IRAS2A,
has evidence for hot, compact CH3OH emission coincident with the embedded
protostar.Comment: Accepted for publication in ApJ (52 pages; 9 figures). Abstract
abridge
Development of an ASD IC for the Micro Pixel Chamber
A new amplifier-shaper-discriminator (ASD) chip was designed and manufactured
for the Micro Pixel Chamber (-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 5-times longer than that of the
TGC-ASD, and some other modifications have been made in order to improve the
signal-to-noise ratio of the -PIC. The ASD IC uses SONY Analog Master
Slice bipolar technology. The IC contains 4 channels in a QFP48 package. The
decay time constant of the preamplifier is 80 ns and its gain is approximately
0.8 V/pC. The output from the preamplifier is received by a shaper
(main-amplifier) with a gain of 7. A baseline restoration circuit is
incorporated in the main-amplifier, and the current used for the baseline
restoration is 5-times smaller than that of the TGC-ASD. The threshold voltage
for the discriminator section is common to the 4 channels and their digital
output level is LVDS-compatible. The ASD IC also has an analog output of the
preamplifier. The equivalent noise charge at the input capacitance of 50 pF is
around 2000 electrons. The power dissipation with LVDS outputs (100
load) is 57 mW/ch. Using this ASD, the analog output voltage from the signal of
the -PIC is about 2-times higher than the case of using the TGC-ASD.As a
consequence, the MIPs tracking performance of the Time Projection Chamber (TPC)
with the -PIC was improved.The performance of the ASD IC and an improved
tracking performance of the TPC are reported.Comment: 6 pages, 14 figures, submitted for IEEE/TNS 200
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