Response of radiochromic film dosimeters to gamma rays in different atmospheres

Radiat. Phys. Chem. Vol. 25. Nos. 4--6, pp. 793-S05. 19S5

0146---572,t,'85 $3.00 + .00 Pergamon Press Ltd

Printed in Great Britain.

RESPONSE OF RADIOCHROMICFILM DOSIMETEP~S~O GAF~IARAYS RI DIFFERENT ATMOSPHERES~,~

W. L. McLaughlin and J. C. Humphreys Radiation Physics Division National Bureau of Standards Gaithersburg, MD 20234, USA Chen Wenxiu3 Laboratory for Radiation and Po|ymer Science University of Maryland College Park, MD 20742, USA ABSTRACT The high-dose gamma ray response (103 - 5x10s Gy) of radiochromic film dosimeters, with ten kinds of plastic matrices (polychlorostyrene containing 1 or 25% C£, polybromostyrene containing 2 or 43% Br, nylon, polyvinyl chloride, cellulose triacetate, and an aromatic polyamide) were investigated when irradiated under certain conditions in vacuum and in different atmospheres ( a i r , oxygen, nitrogen, and nitrous oxide). In addition, the s t a b i l i t y of the films was studied for storage periods up to one month after i r r a d i a t i o n under these conditions. The responses and s t a b i l i t i e s of the polyhalostyrene and nylon films were only s l i g h t l y affected by the different atmospheres of i r r a d i a t i o n , but there were marked differences of response for the other film types. The dyed cellulose triacetate films and polyvinylchloride films are generally more sensitive in N20 and 02-deprived atmospheres than in a i r or in 02, but the opposite is true for the dyed polyvinyl butyral and aromatic nylon films. The dyed cellulose triacetate and dyed polychlorostryrene with 1% C£ are the most stable films for a l l conditions of i r r a d i a t i o n . For accurate routine radiation processing dosimetry, i t is important to know the conditions of irradiation so that appropriate dosimetry systems and procedures may be used and so that suitable correction factors can be applied. Emphasis must be given to differences in atmospheric conditions encountered by dosimeters in practical industrial situations, which may cause marked differences in ultimate response factors. KEYWORDS Atmospheric effects; dosimetry; gamma radiation; plastic films; polymer dosimeter; radiochromic films; vacuum effects. INTRODUCTION Some plastic films and sheets, in which are dissolved dyes or dye precursors, are known to be useful dosimeters for the routine determination of radiation absorbed doses ( I - 3 ) . They have a r e l a t i v e l y convenient method of analysis (spectrophotometry), are easily calibrated, and are usually commercially available in large reproducible batches (3). Radiochromic dosimeter films are p a r t i c u l a r l y successful for routine dosimetry and have been used extensively in industrial radiation processing more than ten years. In order to guarantee that values of dose interpretation under various radiation processing conditions are accurate, we must study in detail the variations of response with environmental conditions (temperature, l i g h t , relative humidity, the presence of gases, etc.) both during i r r a d i a t i o n and during storage. ~Work carried out as part of Research Agreement No. 3712/CF between the International Atomic Energy Agency and the US National Bureau of Standards. 2The description of commercial products here is for technical reasons only, and does not imply endorsement or recommendation. 3Visiting scientist from Department of Chemistry, Beijing Normal University, Beijing, China.

793

794

W . L . ,~IcL.~LGIILI~. J. C. HL'~IPHREYS ~ D CHE:~ VVE~XlL"

The present study is to examine the variations of gamma-ray response of some radiochromic dosimeter films irradiated in vacuum and in the atmospheres of different gases.' Such variations might occur during radiation processing. The present work also shows the s t a b i l i t y of radiation-induced optical density after i r r a d i a t i o n . The results are for particular lots and batches of commercially available radiochromic dosimeters. I t should be noted that there may be s l i g h t differences in the effects from one batch of dosimeter films to another. EXPERIMENTAL MATERIALAND PROCEDURES I.

Material

The ten types of dosimeter films used in this study are listed in in Table I . 2.

Irradiation and Gas-Filling Procedure

These dosimeter films were irradiated with gamma radiation using the University of Maryland BOCo source (approximate a c t i v i t y 25 kCi) at room temperature, the maximum dose rate being 9.5 kGy per hour. The dose had been checked using Fricke dosimetry. The dosimeter films were studied under f i v e atmospheric conditions: a i r , vacuum, nitrogen, oxygen and nitrous oxide. Every f i l m sample was wrapped loosely between black polyethylene films, each separated by lens paper, and the loose stack of ten was put into a glass tube and evacuated to ~5 x l0 -G t o r r a i r pressure overnight. Then the tube could be l e f t evacuated or f i l l e d with gas. N20 f i l l i n g did not involve flowing, rather recirculation, because of t o x i c i t y . Any conditioning was completed about one hour prior to i r r a d i a t i o n . After i r r a d i a t i o n the films were removed before spectrophotometric readout and were stored for various times in the dark in a i r at room temperature and at 50 to 60% relative humidity (which were the storage conditions prior to conditioning with d i f f e r e n t atmospheres). These conditionings in d i f f e r e n t atmospheres before and during i r r a d i a t i o n are not meant to achieve saturation conditions, rather to simulate typical extreme atmospheric conditions that might occur during radiation processing. In many practical situations, such as during electron-beam i r r a d i a t i o n in vacuum or in N2 atmosphere, the period of vacuum or gas conditioning is often much shorter than those used here, with the result that the effects of d i f f e r e n t atmospheres on varying dosimeter response to scanned electron beams may be less severe than the present findings with gamma-rays and with longer pre-irradiation storage periods. No attempt was made to treat the films with heat following the irradiations. Such heat treatment may be used (-45 ° to 60°C for ~2 or 3 minutes) in order to accelerate slower components of dye formation, p a r t i c u l a r l y after short-term electron beam i r r a d i t i o n

(4).

3.

Optical Density and Thickness Measurement

Before and at various times after i r r a d i a t i o n , each f i l m was analyzed using a Beckman Model 25 spectrophotometer set at selected wavelengths, which corresponded to maximum changes induced by i r r a d i a t i o n . Except for the time during spectrophotometry, the films were stored in the dark under moderate relative humidity (~ 50% r . h . ) and ambient room temperature (~ 22°C). 4.

Measurement of Absorption Spectra and Selection of Absorption Band Maxima

The absorption spectra of the irradiated dosimeter films #i through #i0 were plotted as shown in Figures la, lb, Ic, for specified values of absorbed dose, i r r a d i a t i o n in these instances being in a i r . The selected wavelengths for analysis of dosimeter response curves are those corresponding to the maxima of absorption bands in Figures la, ib, and lc.

Gamma Rays in Different Atmospheres

795

Table 1 Radiochromic Dye Dosimeter Films Code No.

Description

Analysis Wavelengths (nm)

Approximate NBS Thickness Batch Dosimeter (mm) No, Supplier

#I

Malachitegreen methoxide in polychlorostyrene (MG-OCH3 in PS-C&) (containing I% C&)

630,430

0.120

FWT*

#2

Malachitegreen methoxide in polychlorostyrene (MG OCH3 in PS-C&25) (containing 25% C~)

630,430

0.083

FWT*

#3

Malachitegreen methoxide in polybromostyrene (MC-OCH3 in PS-Br 43) (contaifiing 2% Br)

630,430

0.077

FWT*

#4

Malachitegreen methoxide in polybromostyrene (MG-OCH~ in PS-Br 43) (contai6ing 43% Br)

630,430

0.090

FWT*

#5

Hexa(hydroxyethyl) pararosaniline cyanide in nylon film (HPR-CN in nylon)

605

0.053

118

FWT*

#6

Hexa(hydroxyethyl) pararosaniline cyanide in polyvinyl butyral (HPR-CN in PVB)

600

0.059

37

FWT*

#7

Hexa(hydr~'xyethyl) pararosaniline cyanide in polyvinyl pyrrolidone (HPR-CN in PVP)

598

0.134

109

FWT*

#8

Hexa(hydroxyethyl) pararosaniline cyanide in cellulose triacetate (HPR-CN in CTA)

595

0.13

#9

New fuchsin cyanide in polyvinyl chloride (NF-CN in PVC)

565

0.041

#10

New fuchsin cyanide in Trogamid (NF-CN in TGM Caromatic Nylon)

563

0.053

3CR2 HQ I l l

Ris~*

108

FWT*

*FWT films from Far West Technology, Inc., Goleta, CA; Ris6/National Laboratory, Roskilde, Denmark.

FWT*

796

W.L.

LO

NOt

0.~

I

~r~

McLAuGHLIN. J. C. HU'MPHREYS AND CHEN WENXIU

INO Z ;

"~I

0..~

~ o I z uJ

I

400

500

.=II.C_INo

~00

.....L ~ 700

i

I

L

~O.,31 MPR.~N in Nylon

/

0.e

0.z ),.

I

500

400

500

[--I.o,

I

i

I NO. 6 I /HPR -CN O.$t-- in PVB

1

.j

0.6I L( )-

~-o'

0.2 I

SO0

"tO0 BOO

.J

~ 0 . 71

3 r

I

0 0.$_HP~-CN

4 I

MG°OC~

~ NO. 8i HPR-CN "in CTA

in PS- lar 2

0

04

I

|

.0.~

O; o

OJ

I ~00 500

I

600

_L. 400 WAVELENGTH,

, ,,I

,i 700 800

I 500 nm

600

I'00

Fig. l a . Radiation-induced optical absorption spectra for dosimetry films #1, #2, #3, #4; Dose 9.6 kGy.

I

I

Ieo. 9

Nr "CN ,n PVC

O4

NO. ~o I NF'CN

I

~,00

,500

SOD

I

t

700 800 400 5CO WAVELENGTH, nm

800

Dose 9.6 kGy

1

E

Film f

MG * OCHs ,n P5- C~ !

•

-~

m

o.:

= -VaCuu -N z ~, . 0 z

0 O.t

o

o

oI

7 0

Fig. l b . Radiation-induced o p t i c a l absorption spectra for dosimeter f i l m s , #5, ,#6, #7, #8;

,~ T t e q e m , ~

= o..~ o

.a

I

5oo

400

"LO0

600

T

700 400 = 500 WAVELENGTH. nm

I

IO0

- NzO J

I

T00

Fig. Ic. Radiation-induced optical absorption spectra for dosimeter films #9 and lO; Dose 144 kGy.

O

ABSORBED

5Q

' I~00

Dose IN wATER,

' WGy

' ")

Fig. 2. Response curves (AOD/mm versus dose) for dosimeter film #1 (MG-OCH3 in PS-C~I) irradiated with 6°Co gamma radiation in different atmospheres and analyzed at 630 nm and 430 nm wavelengths,

Gamma Rays in Different Atmospheres

797

RESULTS 1.

Response Curves in Different Atmospheres.

The effects of various atmospheres during i r r a d i a t i o n are shown in Figs. 2 through 11, in terms of response curves, that is, increase in optical density per unit thickness (aOD/mm) at the indicated wavelengths of analysis as a function of absorbed dose. Polxhalostxrene Films The variations of response from one atmosphere to another are s i g n i f i c a n t , and are d i s t i n c t l y different with different types of dosimeter films. The radiochromic dye films #I, #2, #3, and #4 are polyhalostyrene films using two optical wavelengths of analysis (630 nm and 430 nm). For a given radiation absorbed dose, the aOD/mm values of films #1 and #2 in N20 atmosphere are somewhat lower than in 02 or a i r , as indicated in Figs. 2 and 3 (chlorinated), but the aOD/mm values of #3 and #4 (brominated) in N20 are higher than in 02 or a i r , as indicated in Figs. 4 and 5. Dosimeter film #4, which contains the greater amount of bromine (see Fig. 5 for Br43), shows less difference due to different atmospheres relative to the effects on #1 through #3 (C~I, C~25, and Br2). N~lon~ PVB~ PVP~ and CTA Films The radiochromic dye films #5, #6, #7 and #8 matrix materials are hydrocarbon polymers (nylon, PVB, PVP, and CTA bases, respectively). There are much greater differences in response between d i f f e r e n t atmospheres for PVB, PVP, and CTA base films, with s e n s i t i v i t y in 02 noticeably diminished for all three f i l m types. This is similar to the effect of 02 lowering the radiation chemical y i e l d of radiochromic dye in polar organic solutions (5). The response curve shape of dosimeter f i l m #6 (PVB) in N2 atmosphere, as indicated in Fig. 7, is d r a s t i c a l l y changed with dose, showing marked saturation at doses >40 kGy. PVC and Tro~amid Films The aOD/mm values of #9 and #10 (PVC-base and Trogamid respectively), where dye precursor concentrations are low, are suitable for very high dose measurement. As indicated in Figs. 10 and 11, the aOD/mm values of dosimeter (PVC) show a much diminished s e n s i t i v i t y in 02 atmosphere, especially at very high doses. The PVC film becomes b r i t t l e at the 470 kGy doses, but the Trogamid f i l m retains i t s f l e x i b i l i t y even up to 600 kGy. General Findings Note that the responses of films #1 through 5 (polyhalostyrene and nylon) in general do not show much difference in different atmospheres. On the other hand, films #6 (PVB) and #10 (Trogamid) are considerably more sensitive in the presence of 02 than in N2 or N20, although PVB response d r a s t i c a l l y changes shape at high doses. Films #8 (CTA) and #9 (PVC) are more sensitive in the reducing gas (N20) and in 02-deprived atmospheres, than in a i r or 02. The r e l a t i v e l y small differences in the gamma-ray response of the nylon-base f i l m in oxygenated environments and oxygen-deprived environments have the same trend as the results of Gehringer et al. (6), but are less severe, perhaps because of the r e l a t i v e l y high humidity of f i l ~ o n - d i t i o n i n g (50-60% r . h . ) in the present work, and the r e l a t i v e l y brief conditioning period. 2. S t a b i l i t y of Films Irradiated in Different Atmospheres and Stored in Air In general, all the radiochromic films stored in the dark in a i r after i r r a d i a t i o n are known to show f a i r l y good long-term (several weeks) s t a b i l i t y , as long as temperatures are not excessive (>40°C) (7-10). The present results indicate, on the other hand, that when i r r a d i a t i o n with gamma rays takes place in different atmospheres (see Figs. 1225), there is a d i s t i n c t i n s t a b i l i t y of optical density reading during the radiochromic films. This is especially true for nylon and aromatic nylon base films irradiated in vacuum, N2, or N20, and PVB, PVP, PVC films irradiated under a l l conditions.

798

W.L.

MCLAUGHLIN. J, C. HU,'W4PHREYSAND CHEN WENXIU

2O

12

I/

IRRAOIATIO

oo..£,,,o~

II/

12

I/#

/#

CONOI'fION • -Aft

4 -

~ --OI

H

,

20

,

80 DOSE IN WATER, kGy 40

ABSORBED

Fig. 3. Response curves (AOOlmm versus dose) for dosimeter film #2 (MG-OCH3 in PS-C~25) irradiated with S°Co gamma radiation in different atmospheres, and analyzed at 630 nm and 430 nm wavelengths.

= -Vocuum L

4

V "N l

O ~NtO (

0

//I/

I

I

t

I

I

l

I

I

Iy l

l

//

.o-otto

I #

I

Fig. 4. Response curves (AOD/mm versus dose) for dosimeter film #3 (MG-OCH~ in PS-Br2) irradiated with S°Co gamma radiation and in different atmospheres, and analyzed at 630 nm and 430 nm wavelengths.

SO

I

,l

50 iO0 ABSORBED DOSE IN WATER, WGy

"'"""

//

605 nm

HPR'CN

l I/I

IRRADIATI

I/

'°1-//I '/

CONDITION

t

: -v':<.,; ~# --N l

!;i!0

'

01~_ o

Ll --O i

20

40

ABSORBED DOSE IN WATER,

in Nylon

E ,,(; E o o ,~/'~

ZC

RA01ATION CON01TION

J

i-'"

• ~VocuUfA '~ --N l

/

i

kGy

--Oi -NzO

•

'

2o

:

50

ABSORBED DOSE IN WATER, kGy

Fig. 5. Response curves (AOO/mm versus dose) for dosimeter film #4 (MG-OCH3 in PS-Br43) irradiated with SOCo gamma radiation in different atmospheres, and analyzed at 630 nm and 430 nm wavelengths.

Fig. 6 • Response curves (aOD/mm versus dose) for dosimeter film #5 HPR-DN in nylon) irradiated with OCo gamma radiation in different atmospheres, and analyzed at 605 nm wavelength.

I

G a m m a Rays in Different Atmospheres

IRRADIATION CONE,ITtON • --Ai, D --Vocuum 30 -- ~ - N z ~, -O t

799

I HPR-CN in PV6

IRRADIATION COND T ON •--Air a -- V a c u u m

[

I

Hl~R;gN in P

X7 --N~

o-NO ~ / f

-O:o

..o.

E

E Zo

8<3

o IC

T

50 ABSORBED

I

iOO DOSE IN W A T E R ,

I

I

I

MPR "CN in CTA

I0

~50

Fig. 8. Response curve (AOD/mmversus dose) for dosimeter film #7 HPR-CN in PVP) irradiated with oCo gamma radiation in different atmosphere, and analyzed at 598 nm wavelength.

Fig. 7. Response curve (AOD/mm versus dose) for dosimeter film #6 (HPR-CN in PVB) irradiated with SOCo gamma radiation in different atmospheres, and analyzed at 600 nm wavelength

I

I

50 tOO A B S O R B E D DOSE IN W A T E R , WOy

150 kGy

40--

I IRRADIATION

CONO T ON

i NF r'~ • -'."."

J

I ~/ / /

-

- - Vacuum

V --N z

30- ~_02

O--Nz0

5gS.m

E E "~ 2C c~

O / --

CONDIiI'dN'" • ~Aif a -Vacuum ~-- 0 z

O -- NzO r 50

ABSORBED

f I00 DOSE IN W A T E R ,

150 kGy

Fig. 9, Response curve (AOD/mm versus dose) for dosimeter film #8 (HPR-CN in CTA) irradiated with SOCo gamma radiation in different atmospheres and analyzed at 595 nm wavelength.

O

I00 ABSORBED

200 300 DOSE IN WATER,

400 kGy

500

Fig. I0, Response curve (AOD/mmversus dose) for dosimeter film #9 NF-CN in PVC) irradiated with OCo gamma radiation in different atmosphere and analyzed at 565 nm wavelength.

I

800

W . L . McLAUGHLIN. J. C. HUMPHREYS ArID CHEN WENXIU

Pol~halost~rene Films Figures iz and 13 show that the values of OO of dosimeter film #i (MG-OCH3 in PS-C1) is essentially stable for different storage times up to a month after irradiation in different atmospheres. Dosimeter film #2 (PS-C125) is somewhat unstable for readings at 630 nm, the OD values increasing slightly with storage time, as indicated in Figs. 14 and 15. Dosimeterfilm #3 (PS-Br2) is stable for readings at 630 nm and somewhat unstable during the f i r s t day at 430 nm after high-dose irradiation, as indicated in Figs. 16 and 17. The OD values of dosimeter film #4 (PS-Br43) increase approximately exponentially with storage times for readings at 630 nm as indicated in Figs. 18 and 19. These results agree with earlier results by Bishop et al (8). N~1on Film Film #5 (nylon-base) shows excellent, long-term s t a b i l i t y , but during the f i r s t day after irradiation, there is some i n s t a b i l i t y when irradiated in vacuum, N2, (increase in optical density) and N20 (decrease in optical density). PVB, PVP) and CTA Films The OO values of the dosimeter films #8 (CTA) are the most stable of all (see Fig. 23). Figures 21 and 22 show that the OD values of dosimeter films #6 (PVB) and #7 (PVP) increase rapidly during f i r s t day, and then increase slowly, especially after irradiation to the higher doses. In the case of the PVP film (Fig. 22), the increase in optical density during the f i r s t day after high-dose irradiation in vacuum or N20 is especially pronounced. PVC and Tro~amid Films Figures 24 and 25 show that the OD value of dosimeter films #9 (PVC) and #10 (Trogamid) are relatively stable during storage, except for very high-dose (~ 50 kGy) irradiations, whereupon they became unstable during storage. For Trogamid film this is especially true when irradiated in N2, vacuum, or N20, where there is extensive increase in OD during the f i r s t day's storage, and when irradiated in air or 02, there is fading following irradiation. The f i r s t day decrease in OD following high-dose irradiation of PVC-base film and subsequent increase may involve overlapping absorption bands of the film base materials (PVC), which show such characteristics. CONCLUSIONS The gamma-ray response under different atmospheric conditions and the s t a b i l i t y of optical density after irradiation of different types of dosimeter films irradiated under different atmospheres have been investigated. The different responses depend on the matrix materials of dosimeter films and on the atmospheres of irradiation. Dosimeter film #8 (CTA) is the most stable type and #10 (Trogamid) is more suitable for very high absorbed doses (~ 106 Gy),but deaerated, deoxygenated, or N20 atmospheres at such high doses cause considerable loss in sensitivity of Trogamid film. From the present results with gammarays, in choosing a radiochromic dosimeter film, i t is important to consider the matrix material material (and also the dye composition) according to given atmospheric conditions of irradiation. Accurate dose measurements with radiochromic materials thus depend on careful planning of irradiation and storage conditioning. The next phase of this work w i l l be to investigate the effects of various environmental conditions on the electron beam responses of these routine high-dose dosimeters. Acknowledgement The authors are grateful to Arne Miller of the Accelerator Department of the Ris~ National Laboratory of Denmark for suggestions and discussions concerning this work; we also acknowledge the assistance of Thomas Preisinger of the NBS Radiation Physics Division for making the dosimeter calibrations. REFERENCES (i)

McLaughlin, W. L. (1974) "Solid-phase chemical dosimeters," Sterilization by lonizin~ Radiation. Proc. Int. Conf., Vienna, 1974 (E. R. L. Gaughran and A. J. Goudie, Eds.) Multiscience. Publ. Ltd. Montreal, pp. 219-252.

(2)

McLaughlin, W. L., Miller, A., Fidan, S., Pejtersen, K. and Pedersen, W. Batsberg "Radiochromic plastic films for accurate measurement of radiation absorbed dose and dose distributions," Radiat. Phys. Chem. 10, 119 (1977).

Gamma Rays in Different Atmospheres

-

I IR R,.1.DI~TION ~ONOIT~ON

i

I

I

801

!

NF - CN

m Troqomi4

= --VOCuum 9 --N 2

E E

8 <3

;'T;i;i'"

0

I00 200 300 A B S O R B E D DOSE IN W A T E R ,

400

1

'~00

kGy

Fig. I I , Response curve (AOD/mmversus dose) for dosimeter film #10 (NF-CN in Trogamid) irradiated with S0Co gamma radiation in different atmospheres and analyzed at 563 nm wavelength.

I/_ ,

, ..............

,,o..li._. '.... .......

~ ':'P,/:f,T,'J ca- ,~.~.

Ii

T;ME AFTER IRRADIATION. OA'r s

Fig. 12. Change in OD of dosimeter film #1 (MG-OCH3 in PS-C~I) for different storage times after BOCo gamma-ray irradiation at different doses in various atmospheres using optical wavelength 430 nm for analysis.

~ t~&OIITEO

430 . .

<

!

1

'oI~°°~o ;......... Co.

'} J

,*qJO,~t(O

°

,* o~

I ,**AOIAT(O

I ,o

o

a

I

~

'.

'o

/iii: ~*lAo~,t[o

O~l$ *4r

I ,t

:

;

;o I

'rIME A~T~! I~R~IATI~N. ~Ay~

11~041T(O

Fig. 13. Change in OD 3f dosimeter film #1 (MG-OCH~ in PS-C~I) for different storage ti~es after 6OCo gamma-ray irradiation at different doses in various atmospheres using optical wavelength 630 nm for analysis.

9 --~e • --t,$

'

~!

I

I

,

.

~.%.,=~,Tto I:-II;

=

o

m

o

[o TIM( e F t ( ~ tt'~AOJAtlON,

'

Days

Fig. 14, Change in OD of dosimeter film #2 (MG-OCH3 in P S - C ~ ) for different storage times after 6°Co gamma-ray irradiation at different doses in various atmospheres using optical wavelength 430 nm for analysis.

802

W . L . McLAuGHLIN, J'. C .

HUMPHREYS A N D

CHEN WENXIU

|

I

p

C|.,

L,,

} ®.

!

t......

~ •g,

I T

~,,,,

"D

0

C

"t ,InAo*~(o O - ,s ,o,

i

X. _ ~~:'"° '

< S

r

if .... -,

I

,.

;I

)

........ i

?........

l

.-,.z,g,

i

. . . .+. . . . . .

D - ,qo ,o,

", o r,~*( ~ t ( m

~

~oo

I~q~IAOIATION. OATS

Fig. 15. Change in 0D of dosimeter film #2 (MG-0CH~ in PS'C~25) for different storage times after ~OCo gamma-ray irradiation at different doses in various atmospheres using optical wavelength 630 nm for analysis.

Fig. 16, Change in OD of dosimeter film #3 (MG-0CH~ in PS-Br2) for different storage times after SOCo gamma-ray irradiation at different doses in various atmospheres using optical wave, length 430 nm for analysis•

maA~o

sso~

.......

?

-

:f ~:lF~,

1

....L

I

t.........

~

....... •

'

I

--

•

/,

,,,. "%lP~

i

O-- ,t .~, O,

o

t

o |

[

I

I I

• --9 S .~.

o;"

~a

~o

,oo

Fig. 17, Change in 0D of dosimeter film #3 (MG-0CH~ in PS-Br2) for different storage times after S°Co gamma-ray irradiation at different doses in various atmospheres using optical wavelength 630 nm for analysis.

T,M[ AST(~[AIq..,o,~'ro ;. D~Y$

Fig. 18. Change in 0D of dosimeter film #4 (MG-0CH3 in PS-Br43) for different storage times after 6OCo gamma-ray irradiation at different doses in various atmospheres using optical wave, length 430 nm for analysis,

Gamma Rays in Different Atmospheres

...... °-I

803

T

r

I

i

-~ ; 2 " ; . . 2

,i i

:

°

°

,~1

1

I

I

-~ ......... zz

o

l;

o-,,

0

o

1

, o

o

o.-..-.o

I '* %o

-~

,

.

'

n.;_,~o.,

.

.

.

.I

,!o

Fig. 19. Change in OD of dosimeter film #4 (MG-OCH3 in PS-Br43) for different storage times after 6OCo gamma-ray irradiation at different doses in various atmospheres using optical wavelength 630 nm for analysis.

,I

!o

Fig. 20. Change in OD of dosimeter film #5 HPR-CN in Nylon for different storage times after 6oco gamma-ray irradiation at different doses in various atmospheres using optical wavelength 605 nm for analysis. ....

........ I •

...........

.~,

,°4

ii!i! ' ]

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~,.

o

o

10

,4t

o i

J r

' T,

'

.

"

..... ~[._. "'°;°""~°

I ~

QT , ; ,

C t t ;G, i- ts,~

,If J,'

'o

~0

,;o

Fig. 21 o Change in OD of dosimeter film #6 (HPR-CN in PVB) for different storage times after 6°Co gamma-ray irradiation at different doses in various atmospheres using optical wavelength 600 nm for analysis.

"J......... I

Fig.

22.

F

I

'

Change i n OD o f d o s i m e t e r

film

#7

(HPR-CN in PVP) for different storage times after 6oCo gamma-ray irradiation at different doses in various atmospheres using optical wavelength 5,98 nm for analysis.

~J'

W.L.

McLAt:OHL[N.

~. C . H L ' ~ , I P H R E Y S A N D C H E N

WF~NXIU

-

~

,. vac~u. ....

,

:g:

1

"

I

r

,I j • ,,~ .~,

."

T~ME~rT~R IA~a01a? ON 0~Ys

,~

Fig. 23, Change in OD of dosimeter film #8 (HPR-CN in CTA) for different storage times after SOCo gamma-ray irradiation at different doses in various atmospheres using optical wavelength5g5 nm for analysis.

Fig. 24.Change in OD of dosimeter film #9 NF-CN in PVC for different storage times after ~OCo gamma-ray irradiation at different doses in various atmospheres using optical wavelength 565 nm for analysis.

J

....

2 g .....

! .~ o l

:2

o.

,o

,o

..........

,co

Fig. 25, Change in OD of dosimeter film #I0 (NF-CN in Trogamid) for different storage times after6OCo gamma-ray irradiation at different doses in various atmospheres using optical wavelength 563 nm for analysis.

Gamma Ra~s in Different Atmospheres

(3)

Kantz, A. D. and Humphreys, K. C. "Radiochromics, a radiation monitoring system," Radiation Processing, Trans. Ist. Int. Meeting on Radiation Processing, Puerto Rico, 1976 (J. Silverman and A. Van Dyken, Eds.) Pergamon Press, Oxford, UK; Radiation Phys. Chem. 9, 737 (1977).

(4)

Chappas, W. J., "Temperature and humidity effects on the response of radiochromic dye films," Trans. of 3rd Int. Meeting on Radiation Processing, Tokyo, 1980 (Ed. Silverman, J.); Radiat. Phys. Chem. 1_~8, 1017 (1981).

(5)

McLaughlin, W. L. and Kosani~, M. M., "The gamma-ray response of pararosaniline dosimeter solutions," Int. J. Appli. Radiat. Isotopes 2_~5,249 (1974).

(6)

Gehringer, P., Proksch, E., and Eschweiler, H., "Oxygen effect on the y-radiation response of FWT-60 radiochromic film dosimeters," Report No. 4159, Osterreichisches Forschungszentrum Seibersdorf GesmbH., Lenagasse 10, Vienna, Austria (1982).

(7)

Humpherys, K. C. and Kantz, A. D., "Radiochromic Note 4," Far West Technology, Inc., Goleta, CA, USA (1972).

(8)

Bishop, W. P., Humphreys, K. C. and Radntke, P. T., "Poly(halo) styrene thin-film dosimeters for high doses," Rev. Sci. Instr. 44, 443 (1973).

(9)

Levine, H., McLaughlin, W. L. and Miller, A., "Temperature and humidity effects on the gamma ray response and s t a b i l i t y of plastic and dyed plastic dosimeters," Trans. of 2nd Int. Meeting on Radiation Processing, Miami, USA, 1978 (Ed. Silverman, J.); Rad. Phys. Chem., 14, 571 (1979).

805

(IO) McLaughlin, W. L., Uribe, R. M. and M i l l e r , a., "Megagray dosimetry (or monitoring of very large radiation doses)," Trans. of 4th Int. Meeting on Radiation Processinq, Dubrovnik, Yugoslavia, 1982 (Ed. Markovic, V. M.); Rad. Phys. Chem. 22, 333 (1983). ""