COMPET is a MRI compatible preclinical PET scanner aiming towards a high sensitivity and a high point source resolution (PSR) by implementing a novel block detector geometry. Layers of matrices ...consisting of long LYSO crystals and wavelength shifter (WLS) fibers are used to determine the point of interaction (POI) of the
γ
‐ray
within the LYSO crystal. This reduces the parallax error to a minimum and allows for a high PSR and a high sensitivity, while keeping a low number of readout channels. Simulations show that the detector achieves a PSR below 1
mm in the transaxial plane and a sensitivity of up to 16%.
The MAGIC Cerenkov telescope has observed very high energy (VHE) g-ray emission from the active galactic nucleus 1ES 1959+650 during 6 hr in 2004 September and October. The observations were carried ...out alternating with observations of the Crab Nebula, whose data were used as a reference source for optimizing g -ray/hadron separation and for flux comparison. The data analysis shows VHE g-ray emission of 1ES 1959+650 with 68 s significance, at a time of low activity in both optical and X-ray wavelengths. An integral flux above 6180 GeV of about 20% that of the Crab Nebula was obtained. The light curve, sampled over 7 days, shows no significant variations. The differential energy spectrum between 180 GeV and 2 TeV can be fitted with a power-law of index -2.72 c 0.14. The spectrum is consistent with the slightly steeper spectrum seen by HEGRA at higher energies, also during periods of low X-ray activity.
FADC signal reconstruction for the MAGIC telescope Albert, J.; Aliu, E.; Antoranz, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2008, Letnik:
594, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Until April 2007 the Major Atmospheric Gamma ray Imaging Cherenkov (MAGIC) telescope used a 300
MSamples/s flash analog-to-digital converter (FADC) system to sample the shaped photomultiplier tube ...(PMT) signals produced by the captured Cherenkov photons of air showers. Different algorithms to reconstruct the signal from the read-out samples (extractors) have been implemented and are described and compared. Criteria based on the obtained charge and time resolution/bias are defined and used to judge the different extractors, by applying them to calibration, cosmic and pedestal signals. The achievable charge and time resolution have been derived as functions of the number of incident photo-electrons.
The long-duration g-ray burst GRB 050713a was observed by the MAGIC Telescope 40 s after the burst onset and followed up for 37 minutes, until twilight. The observation, triggered by a Swift alert, ...covered energies above -175 GeV. Using standard MAGIC analysis, no evidence of a g-ray signal was found. As the redshift of the GRB was not measured directly, the flux upper limit estimated by MAGIC is still compatible with the assumption of an unbroken power-law spectrum extending from a few hundred keV to our energy range.
Based on MAGIC observations from 2007 June to July, we have obtained an integral upper limit to the VHE energy emission of the globular cluster M13 of F(E > 200 GeV) < 5.1 X 10-12 cm-2 s-1, and ...differential upper limits for E > 140 GeV. Those limits allow us to constrain the population of millisecond pulsars within M13 and to test models for acceleration of leptons inside their magnetospheres and surrounding. We conclude that in M13 either millisecond pulsars are fewer than expected or they accelerate leptons less efficiently than predicted.
All but three (M87, BL Lac, and 3C 279) extragalactic sources detected so far at very high energy -rays belong to the class of high-frequency-peaked BL Lac objects. This suggested to us a systematic ...scan of candidate sources with the MAGIC telescope, based on the Donato et al. compilation of X-ray blazars. The observations took place from 2004 December to 2006 March and cover northern sky sources visible under small zenith distances image at culmination, constraining the declination to -2 degree to +58 degree . The sensitivity of the search was planned for detecting X-ray-bright image sources emitting at least the same energy flux at 200 GeV as at 1 keV. To avoid strong -ray attenuation close to the energy threshold, source redshift was constrained to image. Of the 14 sources observed, 1ES 1218+304 (for the first time at VHE) and 1ES 2344+514 (strong detection in a low flux state) were detected in addition to the known bright TeV blazars Mrk 421 and Mrk 501. A marginal excess of 3.5 capital sigma from the position of 1ES 1011+496 was observed and then confirmed as a VHE -ray source by a second MAGIC observation triggered by a high optical state. For the remaining sources, we present 99% c.l. upper limits on the integral flux image200 GeV. We characterize the HBL sample (including all HBLs detected at VHE so far) by looking for correlations between their multifrequency spectral indices determined from simultaneous optical, archival X-ray, and radio luminosities, finding that VHE-emitting HBLs do not seem to constitute a unique subclass. The HBLs' absorption-corrected -ray luminosities at 200 GeV are generally not higher than their X-ray luminosities at 1 keV.
We report on the observation of the region around supernova remnant G65.1+0.6 with the stand-alone MAGIC-I telescope. This region hosts the two bright GeV gamma-ray sources 1FGL J1954.3+2836 and 1FGL ...J1958.6+2845. They are identified as GeV pulsars and both have a possible counterpart detected at about 35 TeV by the Milagro observatory. MAGIC collected 25.5 hr of good quality data and found no significant emission in the range around 1 TeV. We therefore report differential flux upper limits, assuming the emission to be point-like (<=01) or within a radius of 03. In the point-like scenario, the flux limits around 1 TeV are at the level of 3% and 2% of the Crab Nebula flux for the two sources, respectively. This implies that the Milagro emission is either extended over a much larger area than our point-spread function or it must be peaked at energies beyond 1 TeV, resulting in a photon index harder than 2.2 in the TeV band.
We present a project for a novel camera using Geiger-mode Avalanche Photodiodes (G-APDs), to be installed in a small telescope (former HEGRA CT3) on the MAGIC site in La Palma (Canary Island, Spain). ...This novel type of semiconductor photon detector provides several superior features compared to conventional photomultiplier tubes (PMTs). The most promising one is a much higher Photon Detection Efficiency.
We report on very high energy gamma -ray observations with the MAGIC Telescope of the pulsar PSR B1951+ 32 and its associated nebula, CTB 80. Our data constrain the cutoff energy of the pulsar to be ...less than 32 GeV, assuming the pulsed gamma -ray emission to be exponentially cut off. In the case that the cutoff follows a superexponentlal behavior, the cutoff energy can be as high as similar to 60 GeV. The upper limit on the flux of pulsed gamma -ray emission above 75 GeV is 4.3 x 10 super(-11) photons cm super(-2) s super(-1), and the upper limit on the flux of steady emission above 140 GeV is 1.5 x 10 super(-11) photons cm super(-2) s super(-1). We discuss our results in the framework of recent model predictions and other studies.
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