310

Nuclear Instruments and Methods m Physics Research A273 (1988) 310-314North-Holland. Amsterdam

PRECISION MEASUREMENTS OF K X- AND GAMMA-RAY INTENSITIESIN 103 Ru, 13'Ba,'3°Cs AND '66'Ho DECAYS

Bakhshish CHAND, Jatinder GOSWAMY, Devinder MEHTA, Surinder SINGH, M.L . GARG,Nirmal SINGH and P.N . TREHAN

Department of Physics, Panlab Unroersttv, Chandigarh-] 60014, India

Received 3 February 1988 and in revised form 4 May 1988

The intensities of K X-rays relative to gamma rays emitted m the decays of 103Ru,' 31 Ba,' 34 Cs and 166mHo have been measuredprecisely using a 96 .0 cm3 coaxial HPGe detector. a 28 27 mm2 x 5.0 mm vertical planar HPGe detector and a 28 .27 mm- x 5 5 mmSi(Li) detector The intensities of different K X-rays m these decays have been measured for the first time .

1 . Introduction

The radionuclides 166"Ho(Tt12 = 1 .2 X 10 3yr),

134CS(T1,12 = 2.06 yr), '31Ba

(T112 = 11.8 d) and t°3 Ru(T,z2 = 39 .2 d) provide a set of valuable efficiencycalibration sources for semiconductor photon detectors.For this purpose, the intensity of gamma rays emittedfrom these sources must be known precisely. Only a fewreports about the intensity measurements of gammarays in'03Ru [1,21 and 13'Ba decays [3-51 are availablein literature . However, these measurements were notprecise and the previous results were found to disagreeconsiderably with respect to the presence and intensityof several gamma rays. Recently, precise measurementsof gamma-ray intensities in '34Cs [6,71 and '66'Ho [81decays have been reported by some workers and theirintensity results are quite consistent . To the best of ourknowledge, it is found that K X-ray intensity measure-ments have not been done in all the above mentioneddecays so far . Keeping these points in view it was foundworthwhile to measure the relative intensities of differ-ent K X-rays and gamma rays emitted to '°3Ru and13'Ba decays using well calibrated, high resolution de-tectors . Also the intensities of K X-rays relative to someimportant gamma rays in the 134Cs and 166m Ho decayshave been measured using the same high resolutiondetectors.

2. Experimental procedure

The present K X-ray and gamma-ray intensity mea-surements were performed using three semiconductordetectors: a coaxial HPGe detector (active volume 96.0cm3 , FWHM = 1.7 keV at 1332 keV), a vertical HPGe

0168-9002/88/$03.50 C Elsevier Science Publishers B.V.(North-Holland Physics Publishing Division)

detector (active volume 28.27 mm2 X 5.0 mm, FWHM=459 eV at 122 keV) and a vertical Si(Li) detector(active volume 28.27 mm2 X 5.5 mm, FWHM = 170 eVat 5.9 keV) coupled to a 4096-channel analyser (ND66B) through a spectroscopy amplifier (Ortec 572) .

Radioactive sources of 103Ru, 131Ba and 134CS inHCl were procured from BARC, Bombay, India. The166m Ho radioisotope was obtained from the NBS inWashington, DC, USA. For intensity measurements ofphotons above 80 keV with the coaxial HPGe detector,the radioactive sources were prepared by drying thesource solution on the mylar backing supported on analuminium annulus. The counting rates for differentsources were kept to about 1200 counts/s for a 25 cmsource-to-detector distance . Thin and uncovered sourceswere prepared by the same method on perspex discs forlow energy measurements with vertical HPGe and Sj(Li)detectors . The counting rates for these sources werekept to about 250 counts/s with vertical HPGe/Si(Li)detectors. The source-to-detector distance was kept at 4cm by mounting a perspex cup on the vertical HPGedetector, while for the Si(Li) detector this distance waskept at 2.7 cm by using a special annular source geome-try detailed elsewhere [9] .

The relative efficiency curves for the coaxial HPGedetector in the energy region 80-1400 keV, for thevertical HPGe detector in the energy region 20-600 keVand for vertical planar Si(Li) detector in the energyregion 4-90 keV were generated as explained in ourearlier papers [10,111 .

For gamma-ray intensity measurements in the caseof 166' Ho, ' 34Cs, 13 t Ba and '°3 Ru decays, seven spectrawere taken with each source and detector combinationfor time intervals ranging from 10000 to 150000 s .Gamma ray spectra were analysed to obtain the areas of

3. Results and discussion

B.

different gamma ray peaks using the computer programSAMPO [121 on a DEC-20 system at the RegionalComputer Centre, Chandigarh . The spectra in the X-rayregion were analysed by adding the counts under thepeak, and background counts were subtracted by ex-trapolating the background from above and below thepeak graphically . The summing corrections for variouscrossover and cascading gamma rays, suggested byGehrke et al . [13], were calculated, and present gamma-ray intensity values were corrected for these effects . Thetotal efficiency curve for the coaxial HPGe detectorrequired in the estimation of summing corrections wasobtained from a knowledge of the absorption coeffi-cients for gamma rays in germanium, and the size of thedetector [141 . The summing corrections in the case ofmeasurements using the 96 .0 cm3 HPGe detector (withsource-to-detector distance =25 cm) for example, arefound to be 0.2% and 0.3% for the 113 and 293 keVgamma rays in 103 Ru, 0.7% and -4.2% for the 351 and620 keV gamma rays in ' 3'Ba and 0.6% and 0.4% for the326 and 569 keV gamma rays in ' 34Cs decays .

The present measured K X- and gamma ray intensi-ties in the 103Ru, 131 Ba, 134Cs and 166'Ho decays areshown in tables 1-4 respectively . The intensity valuesfor different gamma rays as well as K X-rays measured

Table 1Relative intensities of K X- and gamma rays m the decay of 103Ru

Chand et al. / Precision measurements of KX- and y -ray intensities

with different detectors in the energy region 20-600keV were found to be consistent with each other and theweighted averages of these intensity results are given intables 1-4. The overall uncertainty in the intensitymeasurements includes the uncertainties due to statis-tics and peak area evaluation (less than 0.5% for intensepeaks), the efficiency calibration error (1.5-2.5% overthe energy region 4-100 keV and 0.5-1 .5% over theenergy region 100-1400 keV) and other systematic er-rors (0.3%) . All of these uncertainties are added inquadrature to give the final error in the intensity results .

The present gamma-ray intensity results in ' °3 Rudecay agree well with those of Macias et al . [1] for thestrong gamma rays, but for the weak gamma rays theresults are inconsistent (table 1) . We believe that thepresent results are more reliable and better determinedcompared to previous results because of very goodstatistics collected under weak peaks and using threedifferent well calibrated detectors. The intensities of KX-rays in the decay of 103 Ru have been measured forthe first time and are found to be higher than thetheoretical values [16] (table 1) .

In the case of 131 Ba decay, the present gamma-rayintensities agree well with those of Gehrke et a] . [31 forboth strong and weak gamma rays (table 2) . The inten-sity results by Sharma et al . [4] and Hesselgren et al . [5]are found to be in general inconsistent with the presentvalues . The gamma rays of 550, 563, 703, 1125, 1208and 1342 keV energy reported only by Gehrke et al . [3]

Energy[keV]

Relative intensities

Experimental(present)

Theoretical[16]

Macias et al .[1]

Raeside et al[21

20.17 (K j 9.35(20) 810(24)22.78 (K p) 192(4) 1.54(12)39 .73 0.098(9) 0.079(2) 0.037(9)42 .6 0.0057(6) 0.0012(2) -53 .29 0487(11) 0.420(20) 0.34(6)

113 .25 0.0039(8) 0.0040(8) -11497 0.0081(5) 0.0089(8) -241 .9 0.0198(14) 0.0165(17) -292.7 0.0063(19) 0.003(3) -294.98 0.333(5) 0.280(9) 0.30(3)317.8 0.021(10) 0006(l) -357.4 0.0103(6) 0010(3) < 0.05443.8 0.379(4) 0.36(1) 034(2)497.1 100.0(11) 100.0(26) 100(3) 1005146 0.0125(16) 00054(15) -557.1 0.954(11) 0.93(3) 0 88(7)5679 00031(l) 0.0018(8) -6103 6.33(5) 6.30(20) 6.24(31)612.02 0.118(3) 0.089(10) -651.7 0.0076(25) 0.0002 -

312

Table 2Relative intensities of K X- and gamma rays in the decay of 131 Ba

have been observed in the present measurements andthe results are quite consistent . However, the gammarays of 334 and 1170 keV energy observed by Gehrke etal . [3] could not be seen by us as well as by any of the

B. Chand et al / Precision measurements of K X- and y -ray intensities

previous workers [4,5] . Also, the 82 and 323 keV gammarays observed by Gehrke et al . [3] and Hesselgren et al .[5] could not be seen in the present measurements . The128.2, 369, 546.3, 795 .5 and 919.5 keV gamma rays

Energy[keV]

Relative intensitiesExperimental(present)

Theoretical[16]

Gehrke et al .[31

Sharma et al .[4]

Hasselgren et al .[5]

30 .851 (K a) 160.3(30) 181 .4(41)34 .987 (Kß I ) 31 .65(70) 32 .30(90)35 .813 (Kß 2 ) 7.25(20) 7 .89(27)54 .96 0.223(4) 0 .198(10) - 0.290(50)78 .76 1.606(26) 1560(50) - 1 .70(8)82 .0 - < 0 .4 - 0 .045(3)92 .25 L231(12) 1.37(18) 1 .52(4) 1 .85(8)12180 60.69(49) 61 9(18) 66.3(15) 66 .4128.08 0.030(2) 0.037(12) 0.039(15) -133.62 4.53(4) 4.61(13) 4.82(9) 4 .51(25)137.37 0.082(2) 0 .068(4) 0.102(5) -157.17 0.361(4) 0 .406(11) 0527(10) 0 .58(4)216.07 42.49(34) 42 .2(9) 4878 514(3)239.64 5 184(45) 5 .13(9) 6.26(13) 6 .26(24)246.91 1 .343(15) 1 .37(4) 1683(14) 1.54(12)249.44 5 .98(5) 603(12) 7.059(14) 7 3(5)294.52 0.341(7) 0 .356(9) 0.463(10) 0 .375(21)35123 0.187(4) 0218(14) 0.278(10) 0 .38(9)369 .04 0.026(3) 0.051(10) 0.073(34) -373 .24 29.58(26) 29 .90(80) 34 .0(7) 31 .0(20)4040 2.79(3) 279(3) 3 .59(7) 3 .00(23)427.52 0.205(2) 0.210(6) 0.263(5) 0 .233(27)451 .43 0 .086(1) 0.088(4) 0117(15) 0106(20)461 .23 0 .199(4) 0.220 0.122(10) 0.250(40)48037 0.703(7) 069](17) 0.932(24) 1 .03(9)486.48 4 .46(4) 443(5) 5.27(10) 4.29(21)496 .31 100 .0(8) 100(9) 100 100 .0(20) 100.0(47)546 .40 0.0074(5) 0011(2) 0.010(5) -550 .54 0.0040(6) 0.009(2) - -562 .88 00070(6) 0.009(2) - -572 .67 0 .333(3) 0.332(9) 0 .400(10) 043(4)585 .03 2 .54(3) 2.61 310(7) 2.64(16)620 .1 3 .08(3) 2.91(18) 3 .79(7) 297(16)674.43 0 .282(3) 0.285(7) 0 .322(15) 0.300(40)696 .49 0 .454(7) 0.317(10) 0 .361(15) 0.310(40)703 .33 0 .0126(9) 0015(l) - -795 .8 - 0.016(4) 0 .010(10) -797,45 OA76(2) 0075(4) 0.093(24) -831 61 0 .483(5) 0494(13) 0.595(20) 0.510(80)914 .1 0 .099(1) 0.098(3) 0 .102(29) 0.100(19)91973 0.021(2) 0.019(4) 0 .015(5) -923 .89 1 .556(17) 1 .56(4) 1 89(7) 1 .61(24)954 .6 0 .070(1) 0.071(2) 0078(49) -968 .95 0 .056(3) 0.072(2) 0 .127(29) 0087(15)

1047 .56 2 .826(28) 284 3.51(8) 2.91(25)1125 .82 0 .0070(2) 00051(13) - -1207 .98 0 .0027(2) 0.0047(10) - -1341 .57 0 .0016(9) 0.0027(8) -

Table 3Relative intensities of K X- and gamma rays m the decay of 134CS

Energy

Relative intensitieskV][

observed by Gehrke et al . [3] and later confirmed bySharma et al. [4] were also seen clearly in the presentmeasurements except the one at 795.5 keV.

The K X-ray spectrum in the successive decay of131Ba

(T1,12=11 .8 d) _131 Cs (T1,12 =9.7 d)-->>31Xe is

shown in fig . 1 . It is clear from this figure that the KX-rays from two decays are well separated from eachother, except that the Kp, line of 131Xe overlaps the Kp 1line of 131Cs . These peaks were separated by the least-squares fitting of the combined area of both the peaks

Z 4ZQSU

Wa

z0U

3

B Chand et al. / Precision measurements ofK X- and y -ray intensities

mô

N

200

250

300

350

400 570 600 800CHANNEL NUMBER

as a function of area of K,(Cs) and K,(Xe) in variousspectra taken over a period of 10 d. The ratio ofintensities Kp(Cs)/K,(Cs)=0.243 from 131 Ba decaywas also confirmed from the 133Ba decay (KO(Cs)/K,(Cs) = 0.235) [15] . The intensities of the K X-rays of131 Cs are being reported for the first time and aregenerally in good agreement with the theoretical values[16] presented m table 2.

The intensity values of K X-rays relative to gammarays in 134Cs and 166' Ho decays agree reasonably well

X200 " .. .^~: .: . .. x50

Fig. 1 . Low energy spectrum for 131Ba and 131 Cs decays taken with the vertical HPGe detector .

UU

313

. . . . .

:. . . .. ... . . ... .. . . . . .,. . . . .. . .. . .~ . . .% I

. ..... .. . . .. . . . . . ..L-900 1320 1350

1400

1450

1500

x 10 5xY

6 r

5 Uâz

32 .0636 .3837 .25

242 .9

Experimental(present)

(Kj 0.740(15)(Kp,) 0.142(4)(Kd2) 0.032(4)

0 .0294(20)

Theoretical[16]0.707(13)0 .127(3)0 .032(9)

Wang et al .[6]

0.0269(54)

Yoshizawa et al .[7]

0 .0215(8)3264 0.0170(17) - 0.0164(16) 0 .0148(6)475 .4 1 .52(2) - 1.52(1) 1 .50(4)563 .3 8 .54(7) 8 .56(3) 8 .59(9)569 .3 15 .75(3) 15 .76(5) 15 .80(20)604 .7 100.0(7) 100(3) 100 .0(2) 100.0(3)

Table 4Relative intensities of K X- and gamma rays m the decay of1668,Ho

References

Chand et al / Precision measurements ofKX- and y -ray intensities

This gamma ray of energy 184.5 keV was also used forefficiency calibration of the HPGe detectors

with the theoretical values [16] (tables 3 and 4) . These KX-ray intensity values are also being reported for thefirst time .

In conclusion, the relative intensities of K X-raysand gamma rays in the decays of 166'Ho, t34C s, t3'Baand ' °3 Ru have been measured precisely. These radio-nuclides can therefore be used to obtain accurate ef-ficiency values for semiconductor detectors in the en-ergy region 20-1400 keV.

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[21 D.E. Raeside. J.J . Reidy and M.L Wiedenbeck, NuclPhys . A134 (1969) 347.

[3] R.J. Gehrke, R.G. Helmer, C.W Reich, R.C . Greenwood

Nucl Instr. and Meth . 203 (1982) 339.M L. Garg . Jasbir Smgh, H.R. Verma, Nirmal Smgh, P.C .Mangal and P.N . Trehan, J Phys B: At Mol. Phys . 17(1984) 577.

[101 Devmder Mehta. M.L . Garg, Jashir Singh, Nirmal Singh,T.S. Cheema and P N Trehan, Nucl Instr. and Meth .A245 (1986) 447

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[12] J.T Routti and S.G . Prussm, Nucl. Instr. and Meth . 72(1969) 125

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Greenwood. NuclInstr and Meth 147 (1977) 405.

[14] R Griffiths, Nucl . Instr and Meth . 91 (1971) 377.[15] B Chauvenet, J Morel and J. Legrand. Int J Appl

Radiat . Isot . 34 (1983) 479.[16] Table of Radioactive Isotopes, eds. E Browne and R B

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48.22 (K,,) 15 .1(3) 14 .9(5) Nucl Phys. A153 (1970) 625

49.13 (Kn') 25 .4(4) 26.5(l0) [6] G Wang, D.E. Alburger and K.E . Warburton. Nucl

55.67 (Kß) 7.86(l2) 8 .21(32) Instr. and Meth . A260 (1987) 413 .

56 .08 (K~) 1.94(4) 2.32(9) [7] Y. Yoshizawa, Y. Iwata, T. Kaku, T. Katoh, J. Ruan, T

90.5762

172(2) Kolima and Y Kawada, Nucl . Instr. and Meth . 174

184.5 ') 100(1) 100(4) (1980) 109.[8] S S. Sooch, Ravmder Kaur, Nirmal Smgh and P N. Trehan,