For the first time, full size lead tungstate crystals of different suppliers, quality and dopant concentration have been irradiated with gamma-rays at low temperatures down to -25degC at IHEP ...Protvino. In contrast to the behavior at room temperature, increased damage and extremely slow recovery processes have been observed. These first results are discussed in the light of several very different interpretations. Further more sensitive measurements are under preparation. The outcome will have a strong impact on the presently assembled ALICE-PHOS detector and the design of the EM calorimeter of PANDA at the future FAIR facility.
A new experiment SPASCHARM devoted to a systematic study of polarization phenomena in hadron-hadron interactions in the energy range 10-70 GeV is under preparation at IHEP (Protvino). The physical ...observables will be single-spin asymmetries, hyperon polarizations and spin-density matrix elements. A universal setup will detect and identify various neutral and charge particles in the full azimuthal angle and a wide polar angle range. A polarized target is used to measure the SSA. The SPASCHARM sub-detectors are being designed and constructed now. The possibility of obtaining a polarized proton beam for the SPASCHARM experiment from Lambda decays is under study.
A highly stable monitoring system based on blue and red light emitting diodes coupled to a distribution network comprised of optical fibers has been developed for an electromagnetic calorimeter that ...uses lead tungstate crystals readout with photomultiplier tubes. We report of the system prototype design and on the results of laboratory tests. Stability better than 0.1% (r.m.s.) has been achieved during one week of prototype operation.
Radiation damage in lead tungstate crystals reduces their transparency. The calibration that relates the amount of light detected in such crystals to incident energy of photons or electrons is of ...paramount importance to maintaining the energy resolution the detection system. We report on tests of lead tungstate crystals, read out by photomultiplier tubes, exposed to irradiation by monoenergetic electron or pion beams. The beam electrons themselves were used to measure the scintillation light output, and a blue light emitting diode (LED) was used to track variations of crystals transparency. We report on the correlation of the LED measurement with radiation damage by the beams and also show that it can accurately monitor the crystal recovery from such damage.
Studies of the radiation hardness of lead tungstate crystals produced by the Bogoroditsk Techno-Chemical Plant in Russia and the Shanghai Institute of Ceramics in China have been carried out at IHEP, ...Protvino. The crystals were irradiated by a 40GeV pion beam. After full recovery, the same crystals were irradiated using a 137Csγ-ray source. The dose rate profiles along the crystal length were observed to be quite similar. We compare the effects of the two types of radiation on the crystal's light output.
We report on the performance of a monitoring system for a prototype calorimeter for the BTeV experiment that uses lead tungstate crystals coupled with photomultiplier tubes. The tests were carried ...out at the 70-GeV accelerator complex at Protvino, Russia.
Influence of irradiation on the light yield of PWO (lead tungstate, PbWO
4) scintillation crystals was studied in the temperature range from −25 °C to +60 °C. Light output and optical transmittance ...were simultaneously measured as a function of time under irradiation in PWO single crystals grown in first and second recrystallization cycle of raw material, doped with different lanthanides and annealed in different conditions. Increased sensitivity to irradiation and slower recovery of the initial light yield were observed at decreased temperatures. The model of tungsten oxide clusters in a regular PWO lattice is used to interpret the experimental results, and dynamics of the light yield under irradiation at different temperatures are qualitatively explained using rate equations describing composition changes in the clusters.
The energy dependence of the energy and position resolutions of the electromagnetic calorimeter prototype made of lead tungstate crystals produced in Bogoroditsk (Russia) and Shanghai (China) is ...presented. These measurements were carried out at the Protvino accelerator using a 1–
45
GeV
electron beam. The crystals were coupled to photomultiplier tubes. The dependence of energy and position resolutions on different factors as well as the measured electromagnetic shower lateral profile are presented.
We report on the effects of radiation on the light output of lead tungstate crystals. The crystals were irradiated by pure, intense high-energy electron and hadron beams as well as by a mixture of ...hadrons, neutrons and gammas. The crystals were manufactured in Bogoroditsk, Apatity (both Russia), and Shanghai (China). These studies were carried out at the 70-GeV proton accelerator in Protvino.
The electromagnetic calorimeter of PANDA at the FAIR facility will rely on the operation of lead tungstate (PbWO
4, PWO) scintillating crystals at temperatures near
-
25
∘
C
to provide sufficient ...resolution for photons in the energy range from 8
GeV down to 10
MeV. The radiation hardness of PWO crystals was studied at the IHEP (Protvino) irradiation facility in the temperature range from
+
20
∘
C
(room temperature) down to
-
23
∘
C
. These studies have indicated significantly different behavior in the time evolution of the damaging processes well below room temperature. Different signal loss levels at the same dose rate but at different temperatures were observed. The effect of a deep suppression of the crystal recovery process at temperatures below
0
∘
C
has been seen.
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