X-RAY AND GAMMA-RAY INTENSITY MEASUREMENTS IN 177Lu AND 2l0Pb DECAYS

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X-RAY AND GAMMA-RAY INTENSITY

MEASUREMENTS IN 177Lu AND 2l0Pb DECAYS

D. Mehta, B. Chand, S. Singh, M. Garg, N. Singh, T. Cheema, P. Trehan

To cite this version:

D. Mehta, B. Chand, S. Singh, M. Garg, N. Singh, et al.. X-RAY AND GAMMA-RAY INTENSITY

MEASUREMENTS IN 177Lu AND 2l0Pb DECAYS. Journal de Physique Colloques, 1987, 48 (C9),

pp.C8-657-C8-659. �10.1051/jphyscol:19879113�. �jpa-00227221�

JOURNAL DE PHYSIQUE

Colloque C9, supplt5ment au n012, Tome 48, dgcembre 1987

X-RAY AND GAMMA-RAY INTENSITY MEASUREMENTS IN 1 7 7 AND ~ ~'lopb DECAYS

D. MEHTA, B. CHAND, S. SINGH, M.L. GARG, N. SINGH, T.S. CHEEMA and P.N. TREHAN

Department of Physics, Panjab University, Chandigarh 160014, India

Abstract:- Relative intensities of X- and gamma-rays emitted in the radioactive decays of 177~u and 210~b were precisely measured using a 28.27 mm2 x 5.5 mm vertical Si(Li) detector, a 28.27 mm2 x 5.0 mm vertical planar HPGe detector and a 96.0 cm3 coaxial HPGe detector. The measured intensities of X-rays have been compared with the values deduced by using physical parameters from internal conversion and sequential atomic processes.

Introduction:- The radionuclides 177~u (TI = 6.7 d) and 'lOpb (Tt = 22.3 y) undergo $-- decay to the excited states ofi '17'~f and 210~i respectively with subsequent emission of intense and well separated X- and gamma-rays in the energy region below 320 keV. Therefore, with the knowledge of precise X- and gamma-rays intensities, it will be convenient to use these sources for efficiency calibration of low energy photon-detectors. However, the earlier intensity measurements for L X-rays and gamma-ray in 210~b decay [l] and for the gamma-rays in 1 7 7 ~ ~ decay [2-41 are not precise and bear lar e errors in intensity values.

Also, no measured K and L X-ray intensities in 177Lu decay are available in literature These points prompted us to reinvestigate the radioactive decays of 177~u and IlOpb by making precision measurements of intensities of emitted X- and gamma-rays with the aid of high resolution detectors.

Experimental Procedure:- The present X- and gamma-ray intensity measurements were performe5 using three semiconductor detectors : a vertical Si(Li) detector (volume 28.27 mm x 5.5 mm, resolution 165 eV at 5.9 keV

,

1

a vertical planar HPGe detector (volume 28.27 mm x 5.0 mm, resolution 459 eV at 122 keV4, used over energy region 20-400 keV and coaxial HPGe detector (volume 96.0 cm

,

These detectors were coupled to a 4096 channels analyser (ND-66B) through a spectroscopy amplifier (ORTEC 572). The details of the detector set-ups and efficiency calibration procedures have been described in our earlier paper [5,6].

The source-to-detector distances were kept to 2.7, 4.0 and 25.0 cm with the vertical Si(Li), vertical HPGe and coaxial HPGe detectors respectively.

Radioactive liquid sources of 17'~u in HC1 and 210~b in HN03 were procured from BARC, Trombay, India. For intensity measurements, thin and uncovered radioactive sources were prepared by drying the source solution on mylar backing (thickness 2 mg/cm2) treated with an insulin drop. The count rates for different sources were kept betwen 50-200 counts/s with the vertical HPGe/Si(Li) det ors and about800 covntsls with coaxial W G e detector. Ten spectra were taken forF5'Lu

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19879113

C9-658 JOURNAL DE PHYSIQUE

source using all the three detectors and Pb source with Si(Li) detector for time 210 duration of 10,000-40,000 s. The spectra were analysed as described in our

earlier paper [6], The peak areas in the spectrum taken by using coaxial HPGe detectors were corrected for summing due to various cascading and cross-over gamma rays by the method suggested by Gerkhe et al [7]. The summing corrections for example, are found to be 0.4% and -2.8% for 136 keV and 321 keV gamma rays from 17'Lu decay. The summing corrections for peaks in the spectra measured by vertical HPGe/Si(Li) detectors are neglegibly small because of their low detection efficiency.

Results and Discussion:- The present measured X- and gamma-ray relative intensities for 177Lu and 210pb decays are shown in Tables 1 and 2 respectively. The overall uncertainty in the intensity measurement includes uncertainties due to statistics and peak area evaluation (less than 1%), efficiency calibration errors (1.0-3.5%) and other systematic errors (0.3%). All these uncertainties are added in quadr- ature to give final errors in the intensity results.

The intensities of different K and L X-rays relative to the measured intensity of gamma rays emitted in t h e £ - decay of 177LU and 210pD have been calculated using the formulation given elsewhere [6] and are also given in Tables 1 and 2.

For the present calculations, the values of internal conversion coefficients are taken from ref. [8], The values of the number of primary L^ subshell (i = 1,2,3) vacancies produced in the decay of one K shell vacancy are taken from Rao et al [9]. Coster-Kronig transition probabilities and fluorescent yields are taken from Krause et al [10]. Theoretical X X-ray relative intensities are taken from Storm and Israel [11].

The measured intensity values for L X-rays from Pb decay and for K X-rays 210 from l''Lu decay were found to be in general agreement with the calculated ones.

However, the measured L X-ray intensities in 1 7 7 LU decay were found to be higher by about 20% than the calculated ones. The present measured gamma-ray intensity results from 177Lu decay are in good agreement with the earlier measured results [2,3]. But in case of 2 1 0Pb decay, the present measured results are found to be higher by about 20% than those of Freund and Fink [1],

In conclusion, the relative intensities of X- and gamma-rays in the Lu and

°Pb decays have been measured precisely and these sources are recommended as efficiency calibration of high resolution low energy photon detectors.

Table 1: Relative Intensities of X-rays and Gamma-rays emitted in the decay of 210pb.

Energy (keV)

9.42 10.83 11.71 13.02 15.25 16.28 46.5

Radiation type

Ll

L

n

LP

L*123

L/4 y

Relat Experimental

(present) 13.73(41) 241.6 (72) 1.73(9) 273.7 (82)

54.9 (16) 7.12(28) 100.0 (18)

ive intensity(%) Theoretical

(present) 12.30 227.2

2.30 247.9

49.8 5.8 100

Freund and Fink [1]

9.21(58) 199.9 (100) 214.2 (100) 48.1 (24) 100.0 (28)

C9-659

Table 2 : Relative Intensities of X-rays and Gamma-rays in the decay of Lu.

Energy (keV)

6.96 7.89 9.02 10.52 54.61 55.79 63.14 64.93 71.66 112.9 136.7 208.3 249.7 321.3

Radiation type

H

L

«,n.

Lp

Ly

s

Ktf,,

% , 3 K*2

y

y Y y y y

Relative Intensity (%) Expt.

(present) 1.41 (8) 25.7 (10) 28.4 (11) 4.73 (19) 26.7 (4) 45.9 (7) 14.86 (24) 4.08 (7) 2.87 (8) 100.0 (13)

0.750(10) 167.2 (20) 3.28 (4) 3.54 (5)

Theor.*

(present) 0.94 20.9 22.5 3.59 24.8 43.4 13.7 3.52

- - - - - -

Haverfield et al [3]

- - - - - - - - 2.4 (1) 100

0.92(6) 164 (10)

3.0 (2) 3.6 (2)

Agnihotry et al [2]

- - - - - - - - 2.5 (2) 100 (8)

0.87(8) 167

3.2 (3) 3.3 (3)

___ — — — —

X-ray intensity values calculated using present measured gamma ray intensities.

References:

1. Freund and Fink Phys. Rev. 178 (1969) 1952.

2. A.P. Agnihotry, K.P. Gopinathan and H.C. Jain Phys. Rev. C9 (1974) 336.

3. A.J. Haverfield, F.M. Bernthal and J.M. Hollander Nucl. Phys. A 94 (1967) 337.

4. P. Alexander, F. Boehm and E. Kankect Phys. Rev. 133 (1964) B 284.

5. Devinder Mehta, M.L. Garg, Jasbir Singh, Nirmal Singh, T.S. Cheema and P.N. Trehan Nucl. Instru. and Meth. A 245 (1986) 447.

6. Devinder Mehta, Surinder Singh, H.R. Verma, Nirmal Singh and P.N. Trehan Nucl. Instru. and Meth. A 254 (1987) 578.

7. R.J. Gerkhe, R.J. Helmer and R.C. Greenwood Nucl. Instru. and Meth. 147 (1977) 405.

8. C M . Lederer and V.S. Shirley (eds.), Table of Isotopes, 7th ed.

(Wiley, New York, 1978).

9. P.V. Rao, M.H. Chen and B. Crasemann, Phys. Rev. A5 (1972) 997.

10. M.0. Krause, C.W. Nestor Jr., C.J. Sparks and E. Ricci, Oak Ridge National Laboratory Report No. 0RNL-5399 (1978).

11. Storm and Israel, Nucl. Data Tables A7 (1970) 668.