158 research outputs found
Tracking and imaging gamma ray experiment (TIGRE) for 1 to 100 MEV gamma ray astronomy
A large international collaboration from the high energy astrophysics community has proposed the Tracking and Imaging Gamma Ray Experiment (TIGRE) for future space observations. TIGRE will image and perform energy spectroscopy measurements on celestial sources of gamma rays in the energy range from 1 to 100 MeV. This has been a difficult energy range experimentally for gamma ray astronomy but is vital for the future considering the recent exciting measurements below 1 and above 100 MeV. TIGRE is both a double scatter Compton and gamma ray pair telescope with direct imaging of individual gamma ray events.
Multiâlayers of Si strip detectors are used as Compton and pair converters CsI(Tl) scintillation detectors are used as a position sensitive calorimeter. Alternatively, thick GE strip detectors may be used for the calorimeter. The Si detectors are able to track electrons and positrons through successive Si layers and measure their directions and energy losses. Compton and pair events are completely reconstructed allowing each event to be imaged on the sky. TIGRE will provide an orderâofâmagnitude improvement in discrete source sensitivity in the 1 to 100 MeV energy range and determine spectra with excellent energy and excellent angular resolutions. Itâs wide fieldâofâview of Ï sr permits observations of the entire sky for extended periods of time over the life of the mission
FiberGLAST: a scintillating fiber approach to the GLAST mission
FiberGLAST is a scintillating fiber gamma-ray detector designed for the GLAST mission. The system described below provides superior effective area and field of view for modest cost and risk. An overview of the FiberGLAST instrument is presented, as well as a more detailed description of the principle elements of the primary detector volume. The triggering and readout electronics are described, and Monte Carlo Simulations of the instrument performance are presented
Calibration of the Milagro Cosmic Ray Telescope
The Milagro detector is an air shower array which uses the water Cherenkov
technique and is capable of continuously monitoring the sky at energies near 1
TeV. The detector consists of 20000 metric tons of pure water instrumented with
723 photo-multiplier tubes (PMTs). The PMTs are arranged in a two-layer
structure on a lattice of 3 m spacing covering 5000 area. The direction
of the shower is determined from the relative timing of the PMT signals,
necessitating a common time reference and amplitude slewing corrections to
improve the time resolution. The calibration system to provide these consists
of a pulsed laser driving 30 diffusing light sources deployed in the pond to
allow cross-calibration of the PMTs. The system is capable of calibrating times
and the pulse-heights from the PMTs using the time-over-threshold technique.
The absolute energy scale is provided using single muons passing through the
detector. The description of the calibration system of the Milagro detector and
its prototype Milagrito will be presented.Comment: 4 pages, submitted to the XXVI International Cosmic Ray Conferenc
First results of a study of TeV emission from GRBs in Milagrito
Milagrito, a detector sensitive to Îł-rays at TeV energies, monitored the northern sky during the period February 1997 through May 1998. With a large field of view and high duty cycle, this instrument was used to perform a search for TeV counterparts to Îł-ray bursts. Within the Milagrito field of view 54 Îł-ray bursts at keV energies were observed by the Burst And Transient Satellite Experiment (BATSE) aboard the Compton Gamma-Ray Observatory. This paper describes the results of a preliminary analysis to search for TeV emission correlated with BATSE detected bursts. Milagrito detected an excess of events coincident both spatially and temporally with GRB 970417a, with chance probability 2.8Ă10â5 within the BATSE error radius. No other significant correlations were detected. Since 54 bursts were examined the chance probability of observing an excess with this significance in any of these bursts is 1.5Ă10â3. The statistical aspects and physical implications of this result are discussed
Milagro: A TeV observatory for gamma-ray bursts
Observation of prompt TeV Îł-rays from GRBs requires a new type of detector to overcome the low duty factor and small field of view of current TeV observatories. Milagro is such a new type of very high energy (\u3e a few 100 GeV) gamma-ray observatory, which has a large field of view of \u3e1 steradian and 24 hours/day operation. Milagrito, a prototype for Milagro, was operated from February 1997 to May 1998. During the summer of 1998, Milagrito was dismantled and Milagro was built. Both detectors use a 80âmĂ60âmĂ8âm pond of water in which a 3âmĂ3âm grid of photomultiplier tubes detects the Cherenkov light produced in the water by the relativistic particles in extensive air showers. Milagrito was smaller and had only one layer of photomultipliers, but allowed the technique to be tested. Milagrito observations of the Moonâs shadow and Mrk 501 are consistent with the Monte Carlo prediction of the telescopeâs parameters, such as effective area and angular resolution. Milagro will have improved flux sensitivity over Milagrito due to larger effective area, better angular resolution and cosmic-ray background rejection
Study of the Shadows of the Moon and the Sun with VHE Cosmic Rays
Milagrito, a prototype for the Milagro detector, operated for 15 months in
1997-8 and collected 8.9 billion events. It was the first extensive air shower
(EAS) array sensitive to showers intiated by primaries with energy below 1 TeV.
The shadows of the sun and moon observed with cosmic rays can be used to study
systematic pointing shifts and measure the angular resolution of EAS arrays.
Below a few TeV, the paths of cosmic rays coming toward the earth are bent by
the helio- and geo-magnetic fields. This is expected to distort and displace
the shadows of the sun and the moon. The moon shadow, offset from the nominal
(undeflected) position, has been observed with high statistical significance in
Milagrito. This can be used to establish energy calibrations, as well as to
search for the anti-matter content of the VHE cosmic ray flux. The shadow of
the sun has also been observed with high significance.Comment: 4 pages, submitted to XXVI International Cosmic Ray Conference, Salt
Lake Cit
Search for Short Duration Bursts of TeV Gamma Rays with the Milagrito Telescope
The Milagrito water Cherenkov telescope operated for over a year. The most
probable gamma-ray energy was ~1 TeV and the trigger rate was as high as 400
Hz. We have developed an efficient technique for searching the entire sky for
short duration bursts of TeV photons. Such bursts may result from "traditional"
gamma-ray bursts that were not in the field-of-view of any other instruments,
the evaporation of primordial black holes, or some as yet undiscovered
phenomenon. We have begun to search the Milagrito data set for bursts of
duration 10 seconds. Here we will present the technique and the expected
results. Final results will be presented at the conference.Comment: submitted to XXVI International Cosmic Ray Conference, Salt Lake Cit
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