The study presented in this paper aims to explain the influence of scintillation detector size on spectrometric parameters. For this purpose, a setup composed of 1.5”×1.5”, 2”×2” and 3”×3” NaI(Tl) ...detectors from the same manufacturer was performed. Furthermore, the linearity of detector response to gamma-ray energy was examined for all detectors. Our results show that the energy resolution presents a remarkable dependency to detector size, governed by a second order polynomial function. Thus, the energy resolution shows a significant decrease for almost all energies. As expected, full-energy peak efficiency and Peak-to-Total coefficients have a notable correlation with NaI(Tl) crystal size. In order to study a larger range of crystal sizes, we have developed a Monte Carlo (MC) simulation model using Geant4 (V 10.05). The obtained results were presented using ROOT (V 6.14/08) data analysis framework. The statistical uncertainties were below 4% for all obtained spectra. The comparison of simulated and measured results shows an excellent agreement. The accuracy of our model and the real detector responses has been quantified by applying statistical tests. In this context, a negligible deviation within 4.1% and 3.96% was found, for the obtained response functions and efficiency curves, respectively. An important improvement of intrinsic efficiency and photoelectric effect probability was observed for larger crystals. However, our study shows that CPU-time increases with increasing the active volume of the detector.
The Outer Tracker detector of the HERA-B experiment—Part I: Detector Albrecht, H.; Bauer, Th.S.; Beck, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2005, Letnik:
555, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The HERA-B Outer Tracker is a large system of planar drift chambers with about 113
000 read-out channels. Its inner part has been designed to be exposed to a particle flux of up to
2
×
10
5
cm
-
2
s
...-
1
, thus coping with conditions similar to those expected for future hadron collider experiments. Thirteen superlayers, each consisting of two individual chambers, have been assembled and installed in the experiment. The stereo layers inside each chamber are composed of honeycomb drift tube modules with 5 and
10
mm
diameter cells. Chamber aging is prevented by coating the cathode foils with thin layers of copper and gold, together with a proper drift gas choice. Longitudinal wire segmentation is used to limit the occupancy in the most irradiated detector regions to about 20%. The production of 978 modules was distributed among six different laboratories and took 15 months. For all materials in the fiducial region of the detector good compromises of stability versus thickness were found. A closed-loop gas system supplies the Ar/CF
4/CO
2 gas mixture to all chambers. The successful operation of the HERA-B Outer Tracker shows that a large tracker can be efficiently built and safely operated under huge radiation load at a hadron collider.
The detection of gamma rays from the source HESS J1745-290 in the Galactic Center (GC) region with the High Energy Spectroscopic System (HESS) array of Cherenkov telescopes in 2004 is presented. ...After subtraction of the diffuse gamma-ray emission from the GC ridge, the source is compatible with a point source with spatial extent less than 1.2;{'}(stat) (95% C.L.). The measured energy spectrum above 160 GeV is compatible with a power law with photon index of 2.25+/-0.04(stat)+/-0.10(syst) and no significant flux variation is detected. It is finally found that the bulk of the very high energy emission must have non-dark-matter origin.
We report the detection of a point-like source of very high energy (VHE) γ-rays coincident within $1'$ of Sgr A*, obtained with the HESS array of Cherenkov telescopes. The γ-rays exhibit a power-law ...energy spectrum with a spectral index of $-2.2 \pm 0.09 \pm 0.15$ and a flux above the 165 GeV threshold of $(1.82 \pm 0.22) \times 10^{-7}$ m-2 s-1. The measured flux and spectrum differ substantially from recent results reported in particular by the CANGAROO collaboration.
Aims.We study the efficiency and reliability of cluster mass estimators that are based on the projected phase-space distribution of galaxies in a cluster region. Methods.We analyse a data-set of 62 ...clusters extracted from a concordance ΛCDM cosmological hydrodynamical simulation. We consider both dark matter (DM) particles and simulated galaxies as tracers of the clusters gravitational potential. Two cluster mass estimators are considered: the virial mass estimator, corrected for the surface-pressure term, and a mass estimator (that we call $M_{\sigma}$) based entirely on the velocity dispersion estimate of the cluster. In order to simulate observations, galaxies (or DM particles) are first selected in cylinders of given radius (from 0.5 to 1.5h-1 Mpc) and $\simeq$$200h^{-1}$ Mpc length. Cluster members are then identified by applying a suitable interloper removal algorithm. Results.The virial mass estimator overestimates the true mass by $\simeq$10% on average, for sample sizes of $\ga$60 cluster members. For similar sample sizes, $M_{\sigma}$ underestimates the true mass by $\simeq$15%, on average. For smaller sample sizes, the bias of the virial mass estimator substantially increases, while the $M_{\sigma}$ estimator becomes essentially unbiased. The dispersion of both mass estimates increases by a factor ~2 as the number of cluster members decreases from ~400 to ~20. It is possible to reduce the bias in the virial mass estimates either by removing clusters with significant evidence for subclustering or by selecting early-type galaxies, which substantially reduces the interloper contamination. Early-type galaxies cannot however be used to improve the $M_{\sigma}$ estimates since their intrinsic velocity distribution is slightly biased relative to that of the DM particles. Radially-dependent incompleteness can drastically affect the virial mass estimates, but leaves the $M_{\sigma}$ estimates almost unaffected. Other observational effects, like centering and velocity errors and different observational apertures, have little effect on the mass estimates.
The HERA-B Outer Tracker is a large detector with 112,674 drift chamber channels. It is exposed to a particle flux of up to
2
×
10
5
cm
-
2
s
-
1
thus coping with conditions similar to those expected ...for the LHC experiments. The front-end readout system, based on the ASD-8 chip and a customized TDC chip, is designed to fulfil the requirements on low noise, high sensitivity, rate tolerance, and high integration density.
The TDC system is based on an ASIC which digitizes the time in bins of about 0.5
ns within a total of 256 bins. The chip also comprises a pipeline to store data from 128 events which is required for a deadtime-free trigger and data acquisition system.
We report on the development, installation, and commissioning of the front-end electronics, including the grounding and noise suppression schemes, and discuss its performance in the HERA-B experiment.
In this paper we discuss the energy losses of magnetic monopoles and of dyons in the earth's core and mantle over a large range of velocities. The calculations are used to compute the maximum ...fractional geometrical acceptance for a detector located in one of the underground halls at the Gran Sasso laboratory in central Italy.
Very high energy (> 100 GeV) gamma-ray emission has been detected for the first time from the composite supernova remnant G0.9+0.1 using the H.E.S.S. instrument. The source is detected with a ...significance of 13 sigma, and a photon flux above 200 GeV of (5.7+/-0.7 stat +/- 1.2 sys) * 10^-12 cm^-2 s^-1, making it one of the weakest sources ever detected at TeV energies. The photon spectrum is compatible with a power law (dN/dE \propto E^-Gamma) with photon index Gamma = 2.40 +/- 0.11 stat +/- 0.20 sys. The gamma-ray emission appears to originate in the plerionic core of the remnant, rather than the shell, and can be plausibly explained as inverse Compton scattering of relativistic electrons.
The HERA-B outer tracker Ouchrif, Mohamed
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2003, Letnik:
513, Številka:
1
Journal Article
Recenzirano
In this paper, we report about the actual status of the HERA-B Outer Tracker (OTR) detector. The OTR of HERA-B is a gaseous detector that provides tracking of charged particles over a wide volume. ...Since January 2000, the completed OTR is being commissioned and totally included in the regular datataking of HERA-B.
Very high energy (>100 GeV) gamma-ray emission has been detected for the first time from the composite supernova remnant G 0.9+0.1 using the HESS instrument. The source is detected with a ...significance of ≈$13\sigma$, and a photon flux above 200 GeV of ($5.7\pm0.7_{\rm stat}\pm1.2_{\rm sys})\times10^{-12}$ cm-2 s-1, making it one of the weakest sources ever detected at TeV energies. The photon spectrum is compatible with a power law (${\rm d}N/{\rm d}E \propto E^{-\Gamma}$) with photon index $\Gamma = 2.40\pm0.11_{\rm stat}\pm0.20_{\rm sys}$. The gamma-ray emission appears to originate in the plerionic core of the remnant, rather than the shell, and can be plausibly explained as inverse Compton scattering of relativistic electrons.
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