Dormenev, V.

Eissner, T.

Novotny, R. W.

Schubert, R.

Tarasov, I.

GSI Repository

Quality of PbWO4 Crystals Manufactured at SICCAS∗V. Dormenev†1, T. Eissner1, R. W. Novotny1, R. Schubert1, I. Tarasov1,2, and for the PANDAcollaboration11II. Physikalisches Institut, Justus-Liebig-Universita¨t Gießen, Germany; 2GSI, Darmstadt, GermanyThe electromagnetic target calorimeter of the futurePANDA detector is based on PbWO4 scintillator crystalsof improved, so called PWO-II quality. These crystals pro-vide a nearly doubled luminescence output and a superiorradiation hardness comparad to PWO-I quality. These im-provements are mandatory for the challenging aim to de-tect high energy photons from 15 GeV down to a few tensof MeV. To reach this goal, the calorimeter has to be op-erated at a low temperature of T = -25◦C. The extremelyhigh radiation hardness of the crystals is required sincethermally activated recovery processes are drastically sup-pressed. Therefore, the maximum loss of light output dueto the deterioration of the optical transparency is primarilydetermined by the concentration of intrinsic defects createdduring the growing process. One can overcome or at leastsignificantly compensate the damage by the recently dis-covered new effect of stimulated recovery [1].Before completing the production of the total number of≈11,000 PWO crystals for the barrel part of the calorime-ter the former manufacturer BTCP (Bogoroditsk TechnicalChemical Plant) in Russia went out of business due to lackof funding for the missing 8,350 crystals. The barrel sec-tion comprises 11 different geometries in two symmetricversions. Presently, the company SICCAS at Shanghai isthe only active manufacturer of PWO crystals. Therefore,an R&D project has been restarted to inspect and furtherimprove the quality of crystals to meet the PANDA-EMCrequirements. Tab. 1 summarizes the relevant parametersof the quality specifications.Parameter Unit LimitLight yield LY phe/MeV ≥16.0measured at T = +18◦C, polished crystalLY(100 ns)/LY(1µs) > 0.9light yield integrated over 100 ns and 1 µsInduced absorption coefficient Δk m−1 ≤ 1.1measured at RT, integral dose: 30 GyTable 1: Some relevant quality specifications.Within this project 25 full size crystals of geometry type11L have been produced and completely tested at the fa-cilities at Giessen and CERN. In the latter case, the semi-automatic testing machine ACCOS has been used to deter-mine the geometrical dimensions, the optical performance,luminescence parameters like the relative light yield anddecay kinetics. At the detector laboratory and radiation fa-cility at Giessen, the absolute light yield at different oper-ating temperatures as well as the radiation hardness were∗This work was supported by BMBF (grant no. 05P12RGFP7), andHIC for FAIR.† valery.dormenev@physik.uni-giessen.detested with gamma rays originating from a set of 60Cosources.LY in phe/MeV8 10 12 14 16 18 20 22 24 26 28Samples per 1 phe/MeV00.511.522.53Figure 1: Distribution of absolute light yield measured atT = +18◦C for all 25 PWO crystals.Time in ns0 500 1000 1500 2000 2500 3000 3500 4000Light Yield in phe/MeV2030405060708090C°T=+18 C°T=0 C°T=-25 Figure 2: Light yield of one PWO sample (#120904) asfunction of and integration time for selected temperatures.Figs. 1 and 2 illustrate the determined light yield at+18◦C and the increase at lower temperatures as a functionof integration time. Most of the crystals reach the limits andshow no dominant slow scintillation components. The op-tical performance delivers sufficient transmittance over therelevant wavelength region. However, the required radia-tion hardness, expressed by the change of absorption coef-ficient at 420 nm due to an integral radiation dose of 30 Gyneed further improvement of the used raw material or thegrowing technology. Fig. 3 shows the distribution of theobtained Δk values.References[1] V. Dormenev et al., Nucl. Instr. and Meth. in Phys. Res. A623 (2010) 1082-1085.HSD-09 GSI SCIENTIFIC REPORT 201386 doi:10.15120/GR-2014-1-HSD-09-1 k in mΔ0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6-1Samples per 0.2 m0246810Figure 3: Distribution of the measured Δk values at420 nm.GSI SCIENTIFIC REPORT 2013 HSD-09doi:10.15120/GR-2014-1-HSD-09 87

Quality of $PbWO_4$ Crystals Manufactured at SICCAS

http://repository.gsi.de/record/67814/files/HSD-09.pdf

Quality of $PbWO_4$ Crystals Manufactured at SICCAS

Abstract

Similar works

Full text

Available Versions

GSI Repository

Quality of PbWO4PbWO_4PbWO4​ Crystals Manufactured at SICCAS

Abstract

Similar works

Full text

Available Versions

GSI Repository

Quality of $PbWO_4$ Crystals Manufactured at SICCAS