136 research outputs found
The Successful Operation of Hole-type Gaseous Detectors at Cryogenic Temperatures
We have demonstrated that hole-type gaseous detectors, GEMs and capillary
plates, can operate up to 77 K. For example, a single capillary plate can
operate at gains of above 10E3 in the entire temperature interval between 300
until 77 K. The same capillary plate combined with CsI photocathodes could
operate perfectly well at gains (depending on gas mixtures) of 100-1000.
Obtained results may open new fields of applications for capillary plates as
detectors of UV light and charge particles at cryogenic temperatures: noble
liquid TPCs, WIMP detectors or LXe scintillating calorimeters and cryogenic
PETs.Comment: Presented at the IEEE Nuclear Science Symposium, Roma, 200
A High Position Resolution X-ray Detector: an Edge on Illuminated Capillary Plate Combined with a Gas Amplification Structure
We have developed and successfully tested a prototype of a new type of high
position resolution hybrid X-ray detector. It contains a thin wall lead glass
capillary plate converter of X-rays combined with a microgap parallel-plate
avalanche chamber filled with gas at 1 atm. The operation of these converters
was studied in a wide range of X-ray energies (from 6 to 60 keV) at incident
angles varying from 0-90 degree. The detection efficiency, depending on the
geometry, photon energy, incident angle and the mode of operation, was between
5-30 percent in a single step mode and up to 50 percent in a multi-layered
combination. Depending on the capillary geometry, the position resolution
achieved was between 0.050-0.250 mm in digital form and was practically
independent of the photon energy or gas mixture. The usual lead glass capillary
plates operated without noticeable charging up effects at counting rates of 50
Hz/mm2, and hydrogen treated capillaries up to 10E5 Hz/mm2. The developed
detector may open new possibilities for medical imaging, for example in
mammography, portal imaging, radiography (including security devices),
crystallography and many other applications.Comment: Presented at the IEEE Nuclear Science Symposium, Roma, Octber 200
The Ulysses Supplement to the BATSE 3B Catalog of Cosmic Gamma-Ray Bursts
We present Interplanetary Network localization information for 218 gamma-ray
bursts in the 3rd BATSE catalog, obtained by analyzing the arrival times of
these bursts at the Ulysses and Compton Gamma-Ray Observatory (CGRO)
spacecraft. For any given burst observed by these two spacecraft, arrival time
analysis (or "triangulation") results in an annulus of possible arrival
directions whose half-width varies between 7 arcseconds and 32 arcminutes,
depending on the intensity and time history of the burst, and the distance of
the Ulysses spacecraft from Earth. This annulus generally intersects the BATSE
error circle, resulting in an average reduction of the error box area of a
factor of 30.Comment: Accepted for publication in the Astrophysical Journal Supplemen
Decay Properties of Bh and Db Produced in the Cm + Na Reaction
Decay properties of an isotope Bh and its daughter nucleus Db
produced by the Cm(Na, 5\textit{n}) reaction were studied by
using a gas-filled recoil separator coupled with a position-sensitive
semiconductor detector. Bh was clearly identified from the correlation
of the known nuclide, Db. The obtained decay properties of Bh
and Db are consistent with those observed in the 113 chain,
which provided further confirmation of the discovery of 113.Comment: Accepted for publication in J. Phys. Soc. JPN., to be published in
Vol.78 No.
A Single-Year Cosmic Ray Event at 5410 BCE Registered in C-14 of Tree Rings
The annual C-14 data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, 992/993 CE, and similar to 660 BCE. Here, we report another rapid increase of C-14 concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These C-14 data series show a significant increase of similar to 6 parts per thousand in 5411-5410 BCE. The signature of C-14 variation is very similar to the confirmed three SEP events and points to an extreme short-term flux of cosmic ray radiation into the atmosphere. The rapid C-14 increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand C-14 excursion during 5481-5471 BCE. The similarity of our C-14 data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event.Peer reviewe
CANGAROO-III Search for Gamma Rays from SN 1987A and the Surrounding Field
Optical images of SN 1987A show a triple ring structure. The inner (dust)
ring has recently increased in brightness and in the number of hot spots
suggesting that the supernova shock wave has collided with the dense
pre-existing circumstellar medium, a scenario supported by radio and X-ray
observations. Such a shocked environment is widely expected to result in the
acceleration of charged particles, and the accompanying emission of very high
energy gamma-rays. Here, we report the results of observations made in 2004 and
2006 which yield upper limits on the TeV gamma-ray flux, which are compared
with a theoretical prediction. In addition, we set upper limits on the TeV flux
for four high energy objects which are located within the same field of view of
the observation: the super-bubble 30 Dor C, the Crab-like pulsar PSR
B054069, the X-ray binary LMC X-1, and the supernova remnant N157B.Comment: 5 pages, 5 figures, Accepted for publication in Ap
Search for TeV gamma-rays from SN 1987A in 2001
We searched for TeV gamma-rays from the remnant of SN 1987A around 5400 days
after the supernova. The observations were carried out in 2001, from November
16 to December 11, using the CANGAROO-II Imaging Atmospheric Cherenkov
Telescope. In total, 708 minutes of ON- and 1019 minutes of OFF-source data
were obtained under good conditions. The detection threshold was estimated to
be 1 TeV, due to the mean zenith angle of 39. The upper limits for the
gamma-ray flux were obtained and compared with the previous observations and
theoretical models. The observations indicate that the gamma-ray luminosity is
lower than erg s at TeV.Comment: 8 pages, 3 figures, submitted for publication, style file adde
Observation of Very High Energy Gamma Rays from HESS J1804-216 with CANGAROO-III Telescopes
We observed the unidentified TeV gamma-ray source HESS J1804-216 with the
CANGAROO-III atmospheric Cerenkov telescopes from May to July in 2006. We
detected very high energy gamma rays above 600 GeV at the 10 sigma level in an
effective exposure of 76 hr. We obtained a differential flux of
(5.0+/-1.5_{stat}+/-1.6_{sys})\times 10^{-12}(E/1 TeV)^{-\alpha}
cm^{-2}s^{-1}TeV^{-1} with a photon index \alpha of 2.69 +/- 0.30_{stat} +/-
0.34_{sys}, which is consistent with that of the H.E.S.S. observation in 2004.
We also confirm the extended morphology of the source. By combining our result
with multi-wavelength observations, we discuss the possible counterparts of
HESS J1804-216 and the radiation mechanism based on leptonic and hadronic
processes for a supernova remnant and a pulsar wind nebula.Comment: 11 pages, 12 figures, Accepted in Ap
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