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Register a new userFirst study of radiation hardness of lead tungstate crystals at low temperatures
تحليل اولي لقوة الإشعاع للبلورات المحصولة من التنغستات الخام عند درجات حرارة منخفضة
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المحول الالكترومغناطيسي لباندا في مرفق فيئر سيعتمد على عملية بلورات السنتيلاسيون الخاصة بالتنغستين الرصاصي (PWO) عند درجات حرارة قريبة من -25 مئوية عشرة لتوفير دقة كافية للأشعة في نطاق الطاقة من 8 جيجا فولت إلى 10 ميكرو فولت. تم دراسة صلابة الإشعاع لبلورات PWO في مرفق إشعاع الإشعاع في إيهيب (بروتفينو) في نطاق الحرارة من درجة حرارة الغرفة إلى -25 مئوية عشرة. وأظهرت هذه الدراسات فرقاً كبيراً في تطور العمليات التلفية في درجات حرارة أقل من درجة حرارة الغرفة. وأظهرت النتائج المختلفة في مستوى فقدان الإشارة في نفس معدل الجرعة ولكن عند درجات حرارة مختلفة. وأظهرت النتائج تأثير تخفيض كبير في عملية استعادة البلور في درجات حرارة أقل من 0 مئوية عشرة.
The electromagnetic calorimeter of PANDA at the FAIR facility will rely on an operation of lead tungstate (PWO) scintillation crystals at temperatures near -25 deg.C to provide sufficient resolution for photons in the energy range from 8 GeV down to 10 MeV. Radiation hardness of PWO crystals was studied at the IHEP (Protvino) irradiation facility in the temperature range from room temperature down to -25 deg.C. These studies have indicated a significantly different behaviour 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 deg.C has been seen.
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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 40-GeV pion beam. After full recovery, the same crystals were irradiated using a $^{137}Cs$ $gamma$-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 crystals light output.
In the context of the ClearMind project, we measured the scintillating properties, as induced from from gamma ray interactions, of today available PbWO4 crystal. We measured scintillation s yields and time constants by measuring the signal shape measured on a fast photo-multiplier and deconvoluting it from the instrumental effects. For the doped crystals at room temperature, we measured a fast scintillation component, with time constants of 2 ns, 55 percent of the total light yield, and a slow component of 6 ns. We observe a significant increase of the light yield for the slow component when the temperature decreases and simultaneous increase of the time constants, but no increase in the fast component light yield. Our measurements reproduce the main qualitative features of PbWO4 crystals quoted in the literature. Quantitatively though, we measured significantly shorter time constants and larger light yields. This is explained by a rigorous treatment of the instrumental contributions in the measurements. Results are discussed and prospect for future developments, tailored for the ClearMind project, are presented.
This paper is devoted to the study of a degradation of CsI(Tl)crystals scintillation characteristics under irradiation with gamma-quanta at the uniformly distributed absorbed dose up to 3700 rad. The sample set consisted of 25 crystals of 30 cm long having a truncated pyramid shape and 30 rectangular crystals of the same length. A large difference in the light output deterioration caused by the radiation was observed for the samples of the same shape. A substantial dependence of the average light output loss from the sample shape is seen as well. On the other hand, the crystals from the same ingot behave very similarly under irradiation.
Lead fluoride ($PbF_{2}$) crystals represent an excellent and relatively innovative choice for high resolution electromagnetic calorimeters with high granularity and fast timing. During the R&D stages of the Crilin calorimeter, three pbfd crystals sized $5times 5 times 40 $ mm$^3$ were irradiated with $^{60}$Co photons up to $sim 4$ Mrad and with 14 MeV neutrons up to a $10^{13}$ n/cm$^2$ total fluence. Their loss in transmittance was evaluated at different steps of the photon and neutron irradiation campaign, and two optical absorption bands associated with the formation of colour centres were observed at $sim 270$ nm and $sim 400$ nm. Natural and thermal annealing in the dark, along with optical bleaching with 400 nm light, were performed on the irradiated specimens resulting in a partial recovery of their original optical characteristics.
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.
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