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Radiation hardness of lead glasses TF1 and TF101
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH
Nuclear Instruments and Methods in Physics Research A 345 (1994) 210-212 North-Holland
Section A
Letter to the Editor Radiation hardness of lead glasses TF1 and TF101
Masaaki Kobayashi ",*, Yuri Prokoshkin b, Alexandre Singovsky " KEX National Laboratory for High Energy Physics, Oho, Tsukuba 305, Japan
b,
Kunio Takamatsu
a
b Institute for High Energy Physics, Protuino 142284, Russian Federation (Received 14 December 1993)
We have measured the radiation hardness of two types of lead glasses, TFl and TF101, for low energy -y-rays from 60 Co . TF101 containing cerium is a few tens times radiation harder than TFl which contains no cerium . The radiation hardness, or the tolerable accumulated dose, of TF101 is 2 x 10 3 rad when the degradation of the transmittance is required to be less than 1% for the unit radiation length X0 = 2 .8 cm . When the present result is compared with the work of Inyakin et al ., the radiation hardness of TF101 glass should be similar for both y-rays and for high energy hadrons.
Two types of lead glasses have been successfully used in the GAMS Cherenkov detectors [1], i.e . TFl (SF2 class) and TF101 (radiation-hardened by adding 0.2% of cerium). Their radiation hardness has already been studied by Inyakin et al . [2] for 70 GeV protons and 30 GeV-rr - mesons . In the course of efforts to develop new dense and radiation-hard materials which could be used for upgrading the GAMS detector and in the GLUON detector [3], we have measured the radiation hardness of the lead glasses for low energy -y-rays. The result is presented below. The lead glasses were caused at the Lytkarino factory, Moscow, and machined and polished at IHEP . Test samples with a size of 1 x 1.2 x 3.8 cm 3 were cut from spare modules for GAMS with a size of 3.8 x 3.8 x 45 cm 3. Optical transmission across 1 cm thickness was measured with a spectrophotometer (Hitachi 330) before and after irradiation. Irradiation by 60 Co -y-rays was carried out at Japan Atomic Energy Research Institute (JAERI). Four cycles of irradiation followed by transmission measurements were carried out to cover the accumulated dose #t from 10 3 to 10 6 rad by increasing the accumulated dose by a factor of 10 per cycle. Each cycle (irradiation, measurement and mailing of samples between KEK and JAERI) took about a week . Each irradiation period took 10 min, 1 h, 3 h and 1 h for an * Corresponding author . Tel. +81 298 64 1171, e-mail masaakiCjpnkekvx.bitnet, kekvax : :masaaki . #t We use an approximate conversion from 1 R (Ribntgen of 60 Co y-ray exposure to 0 .88 rad (=0.0088 Gy) of the adsorbed dose in lead glasses.
accumulated dose of 10 3, 10 °, 10 5 and 10 6 rad, respectively, by mounting the samples at different distances from a calibrated 60 Co source . Since recovery of radiation damage upon exposure to UV light is known in many materials such as PbFZ [4], CsI : Tl [5], BaF2 [6] and GSO : Ce [7], we paid attention for safety lest a sample should be exposed to strong UV light, including sunshine, during any course of the irradiation-measurement cycle. All the samples were wrapped in aluminium foil except during a short period of the transmission measurement which took about 10 to 15 min per measurement per sample . Figs . 1 and 2 show the radiation damages of standard TFl (TFl-00, 99 .9% pure) sample and highest purity one (TF1-000, 99 .99% pure), respectively, caused by 6° Co y-rays . No sizeable difference is seen in the results between the above two samples, indicating that the observed radiation damage should not dominantly come from the impurity in the raw material . The radiation damage in TFl observed at 33 h after irradiation by 10 5 rad is a little smaller than that observed by Yoshimura et al . [8] in a SF2 glass 3 h after irradiation by the same dose . From the present result, however, we cannot conclude whether the radiation damage itself should be smaller in TF1 than in SF2, or the recovery in SF2 is not yet saturated 3 h after irradiation . Fig. 3 shows the radiation damages of a TF101 sample . Although two TF101 samples were irradiated, there was no sizeable difference in the result between them . Comparing Fig. 3 with Fig. 2, we see that TF101 is radiation harder by about 20 times than TFl . After irradiation by 10 6 rad, the TF101 glass turned visibly bright brownish with a tint of red.
0168-9002/94/$07 .00 C 1994 - Elsevier Science B .V. All rights reserved SSDI 0168-9002(94)00234-X
M. Kobayashi et al. INucl. Instr. and Meth . in Phys. Res. A 345 (1994) 210-212
0.8
w zZ Q
0 .6
Z
N E
Z Q 0 .4
0.2
0
300
400 WAVELENGTH
500
600
400
(nm)
WAVELENGTH
500
600
(nm)
Fig. 1 . Transmission spectra of a TFl-00 lead glass across 1 cm thickness for different accumulated doses of 60 Co y-rays . Numbers in parentheses give the time elapse after irradiation .
Fig. 3. Transmission spectra of a TF101 lead glass across 1 cm thickness for different accumulated doses of 6O Co -y-rays. For the other items, see the captions of Figs . 1 and 2.
Recovery in TF101 (TFl) was studied after irradiation by 10 6 (105) rad. As seen in Fig. 3 (Fig . 2), the recovery is not complete even after 100 days, showing
stopped after one hour since the recovery was saturated after half an hour . Although the recovery due to UV exposure is significant, substantial damage still
saturation in recovery . Annealing by UV exposure was also examined at 105 (113) days after irradiation by exposing the irradiated sample close to a UV fluorescent lamp (National GL-10, 10W) . The exposure was
remains unrecovered (Figs. 2 and 3). The annealing effect of UV exposure is larger in cerium-containing glass (TF101) than in ordinary one (TF1). If we require the decrease of the transmission to be less than 1% per unit radiation length Xo = 2.8 cm in Cherenkov detectors read out by photomultipliers with
a bialkali or a multialkali photocathode, the tolerable accumulated dose in TF101 should be about 2 x 10 3 rad from Fig. 3. If, instead, we require the decrease of the transmission over the detector depth of 45 cm to be less than 1/e, the tolerable accumulated dose should be about 10 4 rad or a little higher . Writing the transparency of a 45 cm long module being R = exp[-(number of pions)/b] for 30 GeV Tr -
z
injection, Inyakin et al . [2] obtained b = (4 ± 1) x 10' 2 ,rr - for TF101 viewed by a photomultiplier (FEU-84)
with a multialkali photocathode (S20). Taking into account the cross section of the test module (3 .8 x 3.8 em'), the density of 3.8 g/cm 3 and the energy deposit
of about 1.5 MeV/g/cm 2 for 30 GeV -rr -, the above b corresponds to a tolerable accumulated dose of (7 ± 2) x 10 3 rad for the degradation of transmittance of 1% per X0. 400
500
600
WAVELENGTH (nm)
Fig. 2. Transmission spectra of a TFl-000 lead glass across 1 cm thickness for different accumulated doses of 60 Co y-rays. For the other items, see the caption of Fig. 1 . UV means exposure to UV light for one hour (see the text).
Comparing the tolerable dose of TF101 for high energy-rr- with that for -y-rays, we find that both are of the same order of magnitude . This feature of TF101, i.e . the radiation hardness being of the same order of magnitude for both -y-rays and hadrons, is similar to Cs [9], but significantly different from GSO : Cc [7] and
212
M. Kobayashi et al. /Nucl. Instr. and Meth . in Phys. Res. A 345 (1994) 210-212
BGO [10], in which the radiation hardness is two orders of magnitude smaller for hadrons than for grays . Acknowledgements The authors are deeply thankful to all the colleagues of the GAMS experimental program for their interest in and support to the present work . References [1] F. Binon et al., Nucl . Instr. and Meth . A 248 (1986) 86; in : Cherenkov Detectors and Their Application to Science and Technology (Nauka, Moscow, 1990) p. 149.
[2] AN . Inyakin et al ., Nucl . Instr. and Meth . 215 (1983) 103. [3] Yu .D . Prokoshkin, Proc. Workshop on the Experimental Program at UNK, Protvino, September 1987, p. 214. [4] D.F. Anderson et al ., Nucl . Instr . and Meth . A 290 (1990) 385. [5] M. Kobayashi and S. Sakuragi . Nucl. Instr . an d Meth . A 254 (1987) 275. [6] D-A. Ma and R-Y. Zhu, On Optical Bleaching of Barium Fluoride Crystals, CIT report, CALT-68-1812 (1992) . [7] M. Kobayashi et al ., Nucl. Instr. and Meth . A 330 (1993) 115. [8] Y. Yoshimura et al ., Nucl . Instr. and Meth . 126 (1975) 541. [9] M. Kobayashi et al., Nucl . Instr. and Meth . A 328 (1993) 501. [10] M. Kobayashi et al ., Nucl . Instr. and Meth . 206 (1983) 107.
Nuclear Instruments and Methods in Physics Research A 345 (1994) 210-212 North-Holland
Section A
Letter to the Editor Radiation hardness of lead glasses TF1 and TF101
Masaaki Kobayashi ",*, Yuri Prokoshkin b, Alexandre Singovsky " KEX National Laboratory for High Energy Physics, Oho, Tsukuba 305, Japan
b,
Kunio Takamatsu
a
b Institute for High Energy Physics, Protuino 142284, Russian Federation (Received 14 December 1993)
We have measured the radiation hardness of two types of lead glasses, TFl and TF101, for low energy -y-rays from 60 Co . TF101 containing cerium is a few tens times radiation harder than TFl which contains no cerium . The radiation hardness, or the tolerable accumulated dose, of TF101 is 2 x 10 3 rad when the degradation of the transmittance is required to be less than 1% for the unit radiation length X0 = 2 .8 cm . When the present result is compared with the work of Inyakin et al ., the radiation hardness of TF101 glass should be similar for both y-rays and for high energy hadrons.
Two types of lead glasses have been successfully used in the GAMS Cherenkov detectors [1], i.e . TFl (SF2 class) and TF101 (radiation-hardened by adding 0.2% of cerium). Their radiation hardness has already been studied by Inyakin et al . [2] for 70 GeV protons and 30 GeV-rr - mesons . In the course of efforts to develop new dense and radiation-hard materials which could be used for upgrading the GAMS detector and in the GLUON detector [3], we have measured the radiation hardness of the lead glasses for low energy -y-rays. The result is presented below. The lead glasses were caused at the Lytkarino factory, Moscow, and machined and polished at IHEP . Test samples with a size of 1 x 1.2 x 3.8 cm 3 were cut from spare modules for GAMS with a size of 3.8 x 3.8 x 45 cm 3. Optical transmission across 1 cm thickness was measured with a spectrophotometer (Hitachi 330) before and after irradiation. Irradiation by 60 Co -y-rays was carried out at Japan Atomic Energy Research Institute (JAERI). Four cycles of irradiation followed by transmission measurements were carried out to cover the accumulated dose #t from 10 3 to 10 6 rad by increasing the accumulated dose by a factor of 10 per cycle. Each cycle (irradiation, measurement and mailing of samples between KEK and JAERI) took about a week . Each irradiation period took 10 min, 1 h, 3 h and 1 h for an * Corresponding author . Tel. +81 298 64 1171, e-mail masaakiCjpnkekvx.bitnet, kekvax : :masaaki . #t We use an approximate conversion from 1 R (Ribntgen of 60 Co y-ray exposure to 0 .88 rad (=0.0088 Gy) of the adsorbed dose in lead glasses.
accumulated dose of 10 3, 10 °, 10 5 and 10 6 rad, respectively, by mounting the samples at different distances from a calibrated 60 Co source . Since recovery of radiation damage upon exposure to UV light is known in many materials such as PbFZ [4], CsI : Tl [5], BaF2 [6] and GSO : Ce [7], we paid attention for safety lest a sample should be exposed to strong UV light, including sunshine, during any course of the irradiation-measurement cycle. All the samples were wrapped in aluminium foil except during a short period of the transmission measurement which took about 10 to 15 min per measurement per sample . Figs . 1 and 2 show the radiation damages of standard TFl (TFl-00, 99 .9% pure) sample and highest purity one (TF1-000, 99 .99% pure), respectively, caused by 6° Co y-rays . No sizeable difference is seen in the results between the above two samples, indicating that the observed radiation damage should not dominantly come from the impurity in the raw material . The radiation damage in TFl observed at 33 h after irradiation by 10 5 rad is a little smaller than that observed by Yoshimura et al . [8] in a SF2 glass 3 h after irradiation by the same dose . From the present result, however, we cannot conclude whether the radiation damage itself should be smaller in TF1 than in SF2, or the recovery in SF2 is not yet saturated 3 h after irradiation . Fig. 3 shows the radiation damages of a TF101 sample . Although two TF101 samples were irradiated, there was no sizeable difference in the result between them . Comparing Fig. 3 with Fig. 2, we see that TF101 is radiation harder by about 20 times than TFl . After irradiation by 10 6 rad, the TF101 glass turned visibly bright brownish with a tint of red.
0168-9002/94/$07 .00 C 1994 - Elsevier Science B .V. All rights reserved SSDI 0168-9002(94)00234-X
M. Kobayashi et al. INucl. Instr. and Meth . in Phys. Res. A 345 (1994) 210-212
0.8
w zZ Q
0 .6
Z
N E
Z Q 0 .4
0.2
0
300
400 WAVELENGTH
500
600
400
(nm)
WAVELENGTH
500
600
(nm)
Fig. 1 . Transmission spectra of a TFl-00 lead glass across 1 cm thickness for different accumulated doses of 60 Co y-rays . Numbers in parentheses give the time elapse after irradiation .
Fig. 3. Transmission spectra of a TF101 lead glass across 1 cm thickness for different accumulated doses of 6O Co -y-rays. For the other items, see the captions of Figs . 1 and 2.
Recovery in TF101 (TFl) was studied after irradiation by 10 6 (105) rad. As seen in Fig. 3 (Fig . 2), the recovery is not complete even after 100 days, showing
stopped after one hour since the recovery was saturated after half an hour . Although the recovery due to UV exposure is significant, substantial damage still
saturation in recovery . Annealing by UV exposure was also examined at 105 (113) days after irradiation by exposing the irradiated sample close to a UV fluorescent lamp (National GL-10, 10W) . The exposure was
remains unrecovered (Figs. 2 and 3). The annealing effect of UV exposure is larger in cerium-containing glass (TF101) than in ordinary one (TF1). If we require the decrease of the transmission to be less than 1% per unit radiation length Xo = 2.8 cm in Cherenkov detectors read out by photomultipliers with
a bialkali or a multialkali photocathode, the tolerable accumulated dose in TF101 should be about 2 x 10 3 rad from Fig. 3. If, instead, we require the decrease of the transmission over the detector depth of 45 cm to be less than 1/e, the tolerable accumulated dose should be about 10 4 rad or a little higher . Writing the transparency of a 45 cm long module being R = exp[-(number of pions)/b] for 30 GeV Tr -
z
injection, Inyakin et al . [2] obtained b = (4 ± 1) x 10' 2 ,rr - for TF101 viewed by a photomultiplier (FEU-84)
with a multialkali photocathode (S20). Taking into account the cross section of the test module (3 .8 x 3.8 em'), the density of 3.8 g/cm 3 and the energy deposit
of about 1.5 MeV/g/cm 2 for 30 GeV -rr -, the above b corresponds to a tolerable accumulated dose of (7 ± 2) x 10 3 rad for the degradation of transmittance of 1% per X0. 400
500
600
WAVELENGTH (nm)
Fig. 2. Transmission spectra of a TFl-000 lead glass across 1 cm thickness for different accumulated doses of 60 Co y-rays. For the other items, see the caption of Fig. 1 . UV means exposure to UV light for one hour (see the text).
Comparing the tolerable dose of TF101 for high energy-rr- with that for -y-rays, we find that both are of the same order of magnitude . This feature of TF101, i.e . the radiation hardness being of the same order of magnitude for both -y-rays and hadrons, is similar to Cs [9], but significantly different from GSO : Cc [7] and
212
M. Kobayashi et al. /Nucl. Instr. and Meth . in Phys. Res. A 345 (1994) 210-212
BGO [10], in which the radiation hardness is two orders of magnitude smaller for hadrons than for grays . Acknowledgements The authors are deeply thankful to all the colleagues of the GAMS experimental program for their interest in and support to the present work . References [1] F. Binon et al., Nucl . Instr. and Meth . A 248 (1986) 86; in : Cherenkov Detectors and Their Application to Science and Technology (Nauka, Moscow, 1990) p. 149.
[2] AN . Inyakin et al ., Nucl . Instr. and Meth . 215 (1983) 103. [3] Yu .D . Prokoshkin, Proc. Workshop on the Experimental Program at UNK, Protvino, September 1987, p. 214. [4] D.F. Anderson et al ., Nucl . Instr . and Meth . A 290 (1990) 385. [5] M. Kobayashi and S. Sakuragi . Nucl. Instr . an d Meth . A 254 (1987) 275. [6] D-A. Ma and R-Y. Zhu, On Optical Bleaching of Barium Fluoride Crystals, CIT report, CALT-68-1812 (1992) . [7] M. Kobayashi et al ., Nucl. Instr. and Meth . A 330 (1993) 115. [8] Y. Yoshimura et al ., Nucl . Instr. and Meth . 126 (1975) 541. [9] M. Kobayashi et al., Nucl . Instr. and Meth . A 328 (1993) 501. [10] M. Kobayashi et al ., Nucl . Instr. and Meth . 206 (1983) 107.