Effects of nuclear radiation on the optical properties of cerium-doped glass

NUCLEAR

INSTRUMENTS

AND

METHODS

I35

0976) 93-97;

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NORTH-HOLLAND

PUBLISHING

CO.

EFFECTS OF N U C L E A R R A D I A T I O N O N THE OPTICAL P R O P E R T I E S OF C E R I U M - D O P E D GLASS B. M c G R A T H , H. S C H O N B A C H E R and M. V A N D E V O O R D E

CERN, Geneva, Swttzerland Received 5 February 1976 Some twenty types o f glass containing 0.5-4% CeO2 have been lrradmted in a 6°Co g a m m a cell and m the mixed neutrong a m m a field o f a nuclear reactor, at total integrated doses of up to 5 × 109 Rad (CH). The resulting colouratlon has been assessed quantltahvely by measuring the light transmtssion with reference to air, in the range 360-510 nm. F r o m the results, certain types of glass statable for apphcatJons m nuclear engineering can be selected. Specifically, it was found that 1-2°/'o CeO2 content is usually sufficient to obtain radlatlon-resmtant optical glass: the reducUon in hght transmission above 450 n m is nd at 108 Rad (CH), below 10% at 109 Rad (CH), and below 20% at 5 x 109 Rad (CH); the post-irradiation fading Is negligible.

1. Introduction

Glass is used in accelerators for various applications, for example viewing windows in vacuum chambers, TV camera objectives, insulation of rf cavities, electron tubes, etc., or for dosimetry. Colour changes are produced in normal glass during exposure to ionizing radiation. This colouration, which

starts around 5 x 10 5 Rad (CH)* and is very dark at 10 7 Rad (CH), can either a) hamper operation if it occurs in the glass components of systems where maximum optical transmission is essential, or * 1 Rad ( C H ) = e n e r g y absorption of material (e.g. polyethylene).

100erg/g

in

(CH)n-

TABLE 1 Types o f glass and reduction o f light transmission at 1 x l0 s, 1 x 109, and 5 × 109 Rad (CH) (2 = 450 nm). (Manufacturer' Schott, except nos. 9, 10 Pllkington ) No.

Glass type

CeOz content

9 16 18 19 3 12 5 14 15 8 1 7 17 10 11 2 4 6 13

RSF SF 19 G7 SF 8 G7 SF 1 G7 W G 9 G9 SK 10 G10 B A K 1 G12 F 2 G12 SF 16 G12 SK 4 G I 3 BK7GI4 LF 5 G I 5 L A K N9 G I 5 O W 10 F2G20 BK 7 G25 G G 375 G34 L F 4 G34 F 6 G40

0.5 0.7 0.7 0.7 0.9 1.0 1.2 1.2 1.2 1.3 1.4 1.5 1.5 1.7 20 2.5 3.4 3.4 4.0

a Reactor irradiation position Ebene 1. b Reactor irradiation position 11.

Reduction of light transmission ( 2 > 4 5 0 nm) at dose of 1 × l0 s Rad (CH) a 1 × 109 Rad (CH) b 5 × 109 Rad (CH) b

84 13 11 0 4 10 2 3 3 7 2 0 18 14 0 0 1 3 2

86 26 12 22 20 23 12 5 3 28 13 1 64 40 1 13 8 11 9

95 30 12 21 29 37 13 6 12 49 21 6 74 54 3 16 24 15 11

Figure

1, 11 2

3, 12 4

5, 1

6 7 8 9

94

B. M C G R A T H

et al.

TABLE 2 Characteristics of radiation sources and total doses to glass samples.

]rra&atmn s o u r c e

6°Co Ycell SNIF

Nuclear reactor Position 1

Fast neutron flux (E> 1 MeV) (nf/cm 2 s)

3 X 1 0 9 - - 5 X 109

2 X 1 0 1 2 - - 3 X 1012

2 X 1 0 1 ° - - 3 X 10 lo

Thermal neutron flux (nth/cm 2 s)

1X 1 0 9 - - 2 X 1 0 9

4 X 1 0 1 2 - - 5 X 1012

3X 10tl--4X

dose rate (Rad (CH)/h)

l X 10 6

HI

x

104

Ebene 1

1 x 10s--2 x 108

1 X 107

Irradmtmn temperature (°C)

20

~30

~30

~30

Irradiation medium

air

air

water

air

1 X l09 5 X 10 9

1 x l0 s 5 X l0 8

y dose to samples (Rad (CH))

5 X 10 6 1 X 10 7 5 × 10 7 1 xl0 8

1011

1 x 109 2.5 x 1014 7 x 1014"

Fast neutron fluence to samples (nf/cm2) a

a 1018nr/cm2 = 1 x 109 Rad (CH). b) be utihzed for radiation dose measurements (dosimetry). Therefore, in order to avoid case (a) above, types of radiation-resistant glass have been developed which overcome the colouring effects produced by radiation. Glass can be protected from colouring by the addition of certain polyvalent ions called "protective a g e n t s " of which cerium is the best known. A d d i t i o n of 1-2% C e O 2 suppresses the radiation-induced colour in cerium glass due to the Ce 4+ ion, which is such a powerful electron acceptor that it removes the radiation-created free electrons in the matter which would otherwise form colour centres. In this report we present the radiation test results of some types of cerium-doped glass studied, which could be of interest for nuclear engineering. The glass samples have been irradiated in a 6°Co g a m m a cell and in a nuclear reactor up to a total integrated dose of 5 × 109 R a d (CH).

45 x 10 m m 2 or 30 × l0 m m 2 faces highly pohshed, flat a n d parallel. In order to assess the c o l o u r a t i o n induced by radiation, the percentage change in spectral transmission in the near ultraviolet/visible region of the electromagnetic spectrum was measured using a 100 g

¢ s0

0 350

2. Materials, test samples and test methods The types of glass which have been studied were m a n u f a c t u r e d by Jenaer Glaswerke Schott, G e r m a n y (45 × 10× 2.5 m m 3) a n d by C h a n c e - P i l k l n g t o n , England ( 3 0 x 1 0 × 1 0 m m 3 and 3 0 x 1 0 x 5 m m 3 ) . "[able 1 shows the types of glass and their CeO2 content, which varies between 0 5 a n d 4%. Each sample of glass was prepared with the

4.00

450

500 Wove(ength

550 h (nm)

Fig. 1 Changeofoptlcaltransmlsslonas afunctlonofwavelength for different ra&ation doses. Reference medmm: air Radiation doses [in Rad (CH)], (1) unlrradlated glass; (2) 2.5 × 10s, (3) 7× l0 s, (4) 5× 106; (5) 107; (6) 5.5× l07, (7) l l × 10s; (8) 10s; (9) 5 x 108, (10) 109, (11) 109; (12) 5 x 10a. The Irradiations were done as follows' (2) and (3), at SNIF; (4) to (7), with 6°Co; (8) to (10), at Ebene 1; (11) and (12), at Posmon 11.9-Pllkmgton type RSF; CeO2 content 0.5%.

OPTICAL I

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Fig. 2. Same as fig. 1, for 16-Schott type SF 19 G7; CeO2 content 0.7%. 100

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Fig. 3. Same as fig. 1, for 3-Schott type W G 9 G9; CeO2 content 0.9%.

Fig. 6. Same as fig. 1, for 10-Pdkmgton type O W 10; CeOz content 1.7%.

1,30

100

g E c o

o

'50

5O

ol 350

400

450

500 550 Wavelength X (nm)

Fig. 4. Same as fig. 1, for 5-Schott type B A K 1 G12, CeO2 content 1.2%.

350

400

450

500 550 Wavelength X { nmJ

Fig. 7. Same as fig. 1, for 2-Schott type B K 7 G25; CeO2 content 2.5%.

96

B. M C G R A T H

Beckman DB-GT spectrophotometer. Measurements were made against air as reference. The glass samples were scanned over the spectrum from about 510 to 360 nm with a scan speed of 5 nm/min. Measurements from 510 to 800 nm showed no difference in spectral transmission and have therefore been omitted. The direct linear transmission recordings were made on a Beckman potentiometric recorder. 3. Irradiation conditions The irradiations were carried out in a 60Co gamma cell and in three different irradiation positions, i.e. SNIF, Ebene 1, and Position 11 of the A S T R A Reactor near Vienna. Table 2 summarizes the radiation sources, their characteristics, and the doses with which the glass samples have been irradiated. Further details

et al.

about the irradiation facilities, dosimetry methods, etc., can be found in Sch/Snbacher et al)). 4. Results Since many of the specially developed types of glass listed in table 1 show similar results, we only present in this report those types which show characteristic behaviour, for example those with low and high alteration of optical transmission after irradiation. A complete summary of all the test results is given in a report by McGrath2). The results are presented in the form of graphs, which are self-explanatory, namely:

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400

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500

550 Wovelength ;~ (nm)

Fig. 8. Same as fig. 1, for 4-Schott type G G 375 G34; CeO2 content 3 4 % .

20

3B /,o Ce0z content %

Fig. 10. C h a n g e o f optical transmission as a function o f CeO2 content 410 n m

Reference m e d m m '

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umrradmted glass. Wavelength'

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ol

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400

450

500 Wovelenqth

550 ;~ (nrn]

Fig. 9. S a m e as fig. 1, for 13-Schott type F 6 G40; CeO2 content 4%.

400

z,50

500 Wovelenqth

550 X (nm)

Fig. 11. Post-~rradmtlon fading effects m 9 - P d k m g t o n type R S F glass. Reference medium' air. (1) U m r r a d l a t e d ; (2) 5.5 × 108 Rad (CH); (3) 4 h m h g h t at r o o m temperature; (4) 2½ h at 100°C; (5) 2½h at 1 0 0 ° C + I h at 200°C; (6) 2½h at 1 0 0 ° C + 4 h at 200°C; (7) 2½ h at 100°C + 4 h at 2 0 0 ° C + 4 h at 300°C.

OPTICAL

100

PROPERTIES

OF

CERIUM-DOPED

GLASS

97

been found which are not at all affected by nuclear radiation up to 1 × 108 Rad (CH), - show a reduction in light transmission of less than 10% at 1 × 10 9 Rad (CH) ( 2 > 4 5 0 n m ) , - show a reduction of light transmission of less than 20% at 5 x 10 9 Rad (CH) ( 2 > 4 5 0 n m ) .

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zoo

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•'50

r t I I _~

500 Wovelength

1

I J t [ IJ

550 ),. (nm)

Fig. 12. Post-irradmtlon fading effects in 3-Schott type W G 9 G9 glass. Reference medium: air. (1) Unirradlated; (2) 5.5 × 10 s Rad (CH); (3) 2k h at 100°C + 4 h at 200°C; (4) 2½ h at 100°C + 4 h at 200 °C + 4 h at 300 °C.

1) Figs. 1 to 9: change of optical transmission as a function of wavelength. 2) Fig. 10: change of optical transmission as a function of CeO2 content. 3) Figs. 11 and 12: post-irradiation fading effects. In table 1 we summarize the reduction of light transmission at 1 x 108 Rad (CH), 1 × 10 9 Rad (CH), and 5 x 109 Rad (CH) (2 = 450 nm). 5. Analysis

of results and conclusions

1) Among the tested samples, types of glass have

2) A CeO 2 content of 1.0-2.0% seems, in general, to be sufficient to obtain radiation-resistant optical glass. A CeO2 content higher than 2% does not necessarily improve the properties of a glass under irradiation (see fig. 10). 3) The colouration of the glass depends on the irradiation conditions. The damage parameter is greater with neutrons than with 60Co ?-irradiation for glass exposed to identical dose levels. 4) The post-irradiation fading effect of the glass at room temperature two months after irradiation is negligible, whereas heating the glass for several hours at 300°C anneals the created colour centres (see figs. 11 and 12). 5) The light transmission with reference to air of samples of unirradiated cerium-doped glass is 80-90% (e.g. they appear slightly yellowy brown). References

1) H. Schonbacher, M. Van de Voorde, A. Burtscher and J. Casta, Kerntechnik 17 (1975) 268. 2) B. McGrath, Internal report LAB II-RA/TM/75-34 (1975).