Vol. XVI. 1 REVISTA MEXICANA DE FISICA 1967

RELATIONSHIP BETWEEN E.S.R. SPECTRA AND DOSE IN

ELECTRON-IRRADIATED BOROSILICATE GLASSES:

S. Reyes L., tE. Muño, P., J. Reyes L.Instituto de Física, Universidad Nacional de México

(Recibido: 26 de octubre de 1966)

Se han I/el'ado a cabo estudios de la reSOlUZ'lcia del espín e/~c/rónico

(1(.1:".1:".) eu I'idriw. de borosilica/o ac/h'ados con cobalto e irradiados con elec-

trrm('s de 1.\lel'. Lm. "idrios e'xpuestos a dosis entre 103 rad exhihe'u un ('spee-

tro de R. 1:".1:"., /a I q ut' la inte llS idad de' la ú,Jica línea es f unCÍ";" ere c iente de la

dosis recibida y te"diente a la .<;(l/uración. A partir de las gráficas obtenidas se

discute el decaimiento de /05 centros paramagnéticos eTl el tiempo. .'1(' discut('

adt'má,,>, la posibilidad de usar /a relacir)n encontrada para utilizar los (Iidrios co.

nJ(~dos íme tro.'>. Se crnnparall los resultados con ('1 método cumún de transmitancia

óptica.

A preliminory report of thi~ paper was pre~ented 01 Ihe joint meeling of the physicol sacie.ties of Conodo. the United Slote~ onJ Mexico. Augusl 1966. Bull. Am. Phys. Soco 11. 11.777. (1966)

t Par! lime Associate Profesor. Facultad de Ciencias. U.N.A.M.

31

ABSTRACT

E lec/ron spin resonance (E.S. R.) spectra hove bl"eTJ obseTt)ed lar ('/"c/ron-

irradia/ed cobalt-activated borosilicate g/asses. Tlle glasses weTe exposed lo

doses between 103 and l06rad aud display an E.S.R. speclrtulI slJcb ,hal the ¡"terl-

sity o{ the on/y /¡'le is On increasing ¡une/ion o/ the Joses hOl1jllg a teudellc) /0

satura/ion. Graphs were ob/ained which show the de ca'!' o/ thf' paramaguC'tic C(,Tl/ers.

The relationship between in/ensity and Jos e operls tbe possihility o/ using Ihese

g/asses as dosime/ers. The resu/ts hove been compared with ¡he usual method o/aplical de nsity.

INTRODUCTION

Lorge-scale use of gomma ..•.ay or e lectron-beom doses in different products

mode it necessary ta develop a more convenient dosimeter than the uSLOI enes oosed

on sorne chemicol teehniques. Rodiotion~indueed chonges in absorption, luminescence

ond other properties of solids hove been used to measure low doses of ionizing rodi-

ation by Friedman ond Glover1 and Schulmon et al.2 For high doses, rodiotion-in-

duced obsorption chonges in glass are large enough to meosure doses direetly, as

Sehulmon, Kliek ond Robin4 have pointed out. In particular a cobolt-oetivated

borosilicote gloss has beenextensively usedS,with a linear response upto 106rad,

where saturation effeets begin to appeor. The dose reeeived by the irradiated

cobalt-glass plate is determined by eomporing the transmissivity of oir with thot of

the glass ot 500 mil in the Bausch ond Lomb Speetronic 20 Colorimeter Spectropho-

tometer.E lectron irradiation not only causes gloss coloration but a Iso poromognetie

centers. Coloration has been studied by Kreidl and Hens ler6 ond E.S. R. studies

of glasses containing boron were first reported by Yosaitis and Smaller7

ond

recently by Lee and Broy8 ond Karapetyon and Yudin9•

In the present work curves were obtained showing the creation of paromog-

netic centers os o function of dose and their de-excitotion in time. It is proposed,

32

by comparison with the colorimetric methods, ta use these curveS fa high-dose

meosurements ond the utilization of the de-excitation curves is discussed.

EXPERIMENTAL PROCEDURE

The opporatu'i used to obtain the E.S.R. spectro wos a Vorion V.4502.15

spectromerer operating at a microwave frequency in the X.band neor 9.4 GHz with

100kHz field modulation. The spectrometer provides o recader trocing of the

first derivative af the resononce absorption curve. E.S.R. doto were obtoined ot

room temperature.

The glasst~s uscJ were of the type F .•0621 P""ovided by Bousch and Lomb

Ca., with a nominal molor .•volume composition of: SiO 62%, B O 21%, No 011%,2 2 3 2

A 1203

6%, C03

04 0.1% ond the oppropiate d imens ioos (15 x 6 x 1.5 mm) to o lIow

readings to be token in the Spectronic 20 colorimeter with the adoptar. The gloss

plates exhibit the characteristic blue color af cobalt in a non.saturoted solutlon.

The glass samples were irrodiated ot room temperature with en electro"

beam of 1 MeV ond 10JlA, (the output of the Van de Grooff accelerator at the,lnsti •.

tute of Physics of the University of Mexica) during time intervals vorying from O

to 300, corresponding to doses as high as 160Krep. The E.S.R. spectra were de.

termined within the first hour aher irratiation.

The somples far the E.S. R. spectrometer were po-epored from the commer

mercial plates by cutting themwith o mechoni-col saw to final dimensions of

6x2.5x 1.5mm. No great difference was detected sowing the somples aher or

befare irradiation.

Because different samples were irrodiated for different time intervals, 011

the results were normalized by referring them to a standard somple.

Line width and 9 factor were meosured with the help of o nuclear mognetic

resonance indicotor, Magnion.Model G.•502, using os standard the D. P. P.H.

(g = 2.0036) reported by Holden et 01.10• A Varion 0.1% pitch in KCI wos used

as intens ity standard.

33

EXPERIMENTAL RESULTS

Before" irradiation no parcmagnetic resonance was observed in the somples.

After ¡rred ¡ation, the glasses showed o resonance peak and were colored to differ-

ent tones of green and brown.

The 9 value "f the resononce is 2.0144, measured ot the point where the

derivative curve crosses the horizontal base line, and the lioe width, ¡.e., the

separation between the positive and negative maximo points in the deri\Qtive curve,

II tiH = 49.41. 0.3 gauss where the error quoted corresponds to ene standard de-

viation.

Figure 1 shows the peak-to-Peok height agoinst irrodiation time ond dase.

Uling en equation s ¡milor to the one proposed by Rochll,

h = h : 1 _ e. ,lf )S

where h is the peak-ta-peak height token from the derivative curve, hs is the same

height at saturation, a is the slope at the origin and t the irradiation time, we

Htted the curve to the experimental points with hs = 7.0and a = 0.024::!:: 0.003.

Since the causes of errors are multiple, (amplifier and detector stability,

klystronepower variations, variation in the Qecavity when the sample is chonged,

etc.) we estimate an overeall error of 3% in the meosurements.

Figure 2 shows the decreose in time of the number of poramagnetic centers

measured by meOns of the variation in the peaketoepeak height ofter irradiation.

The samples were kept at room tempercture in closed ;ars. Studies of the temper-

ature"¿ependence of the de-excitation in time of the paramognetic centers ore being

carr ied out.

DISCUSSION

It is evident from the figures that the meosurements of dose as o function

of the height has the sorne choracteristics os measurements made by the colorie

34

metric method12 but with the odvantoge thot the determinotions con be mode more

occurotely. 11 is evident that this situotion is seriously dependent upon the quoliM

ty of the glass (homogeneity ond lock of mechonical stresses).

Fading of coloration of irradiated crystals and glosses in storoge is a well.

known phenomenon. Since de.-excitation of the p:::lramagnetic centers is app-eciable

in our case, means are required to prevent its interference with the usefulness of

the glass os o dosimeler. First one should standradize so that al! peak-to-peak

height meosurements are made al a given time aher Ihe irradiotion as we did.

Second, decay curves con be done ond a reduction factor can be obtoined lo be ap-

plied to glass plates reod days or weeks aher exposure.

ACKNOWLEDGMENTS

The authors would like to thonk Mr. Carlos Ruiz Mejío and Mrs. Mary Ann

M. de Valladares for proof reading the manuscript. They would 0150 like to ac-

knowledge Mr. Ariel A. Valladares C. and Mr. Héctor Riveros R. for his mony

helpfulsuggestions.

REFERENCES

1. H. Friedmon, C. P. Glover, Nucle.onics JO, 24, (1952).2. J.H. Schulman, W. Shurcliff, R.J. Ginther, F.H. Attix, Nucleonics 11,52,

(1953) •3. E.J. Henley, A. Miller, Nucleonics 9,62, (1951).

4. J.H. Schulman, e.e. Klick, H. Robin, Nucleonics 13,30, (1955)

5. J. Reyes, Tesis Profesional. Facultad de Ciencias. U.N.A.M. (1965).

6. N.H. Kreidl, J.R. Hensler, J. Am. Cerom. 38, 423, (1955).

7. E.L. Yosoi!is, B.Smoller, Phys. Rev. 92, 1068, (1953).

8. S. Lee, P.J. Broy, J. Chem. Phys. 40,2982, (1964).

9. G. O. Korope!yon, D. M. Yudin, Sov. Phys. Sol. SI. 4, 1943, (191\3).

35

10. A.W. Holden, C. Kittel, F.R. Merritt, W.A. Yoger, Phys. Rev. 77, 147, (1950).11. J. Roch, Ann. Phys., 5,1401, (1960).

12. Gloss Dosimetry, Bousch ond Lomb, p. 12, (1963).

36

dose D(krep)

h (cm)26 44 154 157 159 /61

7

I ~o

6.,=- .,~~ 5

_0 f I...c:.~ h 'hs(l-e-a:I)"" ~.- .,~"O 4

h,' 7.0~.,c'-' 0::'0.024:1: 0.003.,"""g

tS o 5: 3-~~e.,"- 2

00 50 100 150 200 250Irrodiolion time

300f (sec)

Height 01 fhe Resononce Derivofive as a Funcfion01 Dose In Cobolt-Aclivocfed Borosilicole Glosses

Fil. 1

w'"

h(cml7

~I-----,

~ 6~

ii't\.0; '" '\ ~~i~41\:"" ,; ~ 3 ~ \ '----.::::::::::--~ ~ + '" ,------ '~ 2}' o~ o+, o '-

.••.+

., ~CJ

•• ---, +"•

,o

,o

+

•

,o

,o

.+•

161krep

149krep132kre~

104 krep

61 krep

28 krep.

,-o-

0-

+-.-o O 100 200 300 400 500

Elapsed600

time700 600 900 1000

T (hr)

Decay Curves lar Electran-Irradiated Cobalt-ActivatedBorosilicote Glosses

Fig.2