40,139 research outputs found
Gamma ray induced radiation damage in PWO and LSO/LYSO crystals
This paper compares Îł-ray induced radiation damage
effect in two kinds of heavy crystal scintillators: PWO and
LSO/LYSO. Scintillation emission, optical transmission, light output,
decay kinetics and light response uniformity were measured
for PWO and LSO/LYSO crystal samples of large size before and
after Îł-ray irradiations. Îł-ray induced phosphorescence was also
measured, and the corresponding readout noise was determined
Effects of Neutron Irradiations in Various Crystal Samples of Large Size for Future Crystal Calorimeter
In this paper, we report an investigation on the
radiation damage effects induced by neutrons in large size crystal
scintillator: BGO, CeF_3, LYSO:Ce and PWO. The irradiations
were carried out by using fast neutrons from one ^(241)Am-Be
and two ^(252)Cf sources. The optical and scintillation properties
of these samples, including UV excitation and emission spectra,
longitudinal transmission, light output, decay kinetics and light
response uniformity, were measured before and after the irradiations.
The neutron induced photo-current was also measured,
and was used to estimate the readout noise under the neutron
flux expected by an electromagnetic calorimeter at a very severe
radiation environment. Because of its high light output and
excellent radiation resistance LYSO:Ce crystal is found to have
the smallest neutron induced readout noise as compared to other
large size crystals, indicating it is a good candidate material for
a future crystal calorimeter in a severe radiation environment
Emission Spectra of LSO and LYSO Crystals Excited by UV Light, X-Ray and Îł-ray
Because of their high stopping power (X_o = 1.14 cm, R_(Moliere) = 2.07 cm) and fast (~ 40 ns) bright (4 times of BGO) scintillation, cerium doped lutetium oxyorthosilicate (LSO) and cerium doped lutetium-yttrium oxyorthosilicate (LYSO) crystals have attracted a broad interest in the high energy physics community. This paper presents a comparative study on emission spectra measured for large size BGO, lead tungstate (PbWO_4), LSO and LYSO samples excited by UV light (photo-luminescence) with and without internal absorption, X-ray (X-luminescence) and gamma-ray (radio-luminescence). A red shift was observed between the emission spectra with internal absorption as compared to that without. An additional red shift and a significant red component were observed in the radio-luminescence spectra measured for LSO samples but not LYSO samples, which were disappeared after a gamma-ray irradiation with an accumulated dose of 5 x 10^3 rad. This is the only significant difference observed between the large size LSO and LYSO samples. The origin of these red shifts and the consequence to their light output and applications in the high energy and nuclear physics experiments are discussed
Large size LYSO crystals for future high energy physics experiments
Because of their high stopping power and fast bright scintillation, cerium doped silicate based heavy crystal scintillators, such as GSO, LSO, and LYSO, have been developed for medical instruments. Their applications in high energy and nuclear physics, however, are limited by lacking high quality crystals in sufficiently large size. The optical and scintillation properties, including the transmittance, emission and excitation spectra and the light output, decay kinetics and light response uniformity, as well as their degradation under /spl gamma/-ray irradiation were measured for two long (2.5/spl times/2.5/spl times/20 cm) LYSO samples from CPI and Saint-Gobain, and were compared to a BGO sample of the same size from SIC. Possible applications for crystal calorimetry in future high energy and nuclear physics experiments are discussed
Polarization Decomposition Algorithm for Detection Efficiency Enhancement
In the paper, a new polarization decomposition of the optimal detection algorithm in the partially homogeneous environment is presented. Firstly, the detectors Matched Subspace Detector (MSD) and Adaptive Subspace Detector (ASD) are adopted to deal with detection problems in the partially homogeneous environment. Secondly, the fitness function with polarization parameters is equivalently decomposed to enhance time detection efficiency in the algorithm. It makes the multiplication number of the fitness function from square to a linear increase along with the increase in parameters. Simulation results indicate that the proposed decomposition is much more efficient than direct use of the fitness function
Performance of the Monitoring Light Source for the CMS Lead Tungstate Crystal Calorimeter
Light monitoring will play a crucial role in maintaining energy resolution for the CMS lead tungstate crystal calorimeter at LHC. In the last several years, a laser based monitoring light source was designed and constructed at Caltech, and was installed and commissioned at CERN. This paper presents the design of the CMS ECAL monitoring light source and its performance during beam tests. Issues related to the monitoring precision are discussed
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