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Relative intensities of gamma rays from 166mHo
NUCLEAR INSTRUMENTS AND METHODS 150 (1978) 3 6 1 - 3 6 3 ; ©
NORTH-HOLLAND PUBLISHING CO.
RELATIVE INTENSITIES OF GAMMA RAYS FROM 166mH0 T. E. SAMPSON
Los Alamos Scienti.lic Laboratory, Universityof Cal(/brnia, Los Alamos, NM 87545, U.S.A. Received 16 August 1977 Relative intensities for gamma rays from the decay of 166mHo are reported,
166mHo is a long-lived (T~/2= 1200 y) source with many gamma rays in the range from 80 to 1400 keV that can be used for efficiency calibration of high resolution semiconductor detectors. Several measurements of the relative intensity of gamma rays from 166mHo have been published since 19701-4). Earlier references may be found in these papers. The source used in these measurements was purchased commercially (ICN, lrvine, California) in 1974. The source consisted of 24 mg of Ho203 with an activity of about 8/zCi sealed in a thin Lucite disk. The source activity covered a diameter of 8 mm giving a thickness of 47.7 mg/cm 2. Trace contaminants of '54Eu and ~55Eu were found in the source. The Ge(Li) detector used in these 'measurements had a relative efficiency of 8%, a resolution of 1.8 keV at 1332 keV and a resolution of less than 750 eV at 122 keV. All efficiency measurements were done at a source to end cap distance of 22.3 cm to minimize coincidence sum effects. No corrections were made for coincidence summing. Detector calibration was accomplished with numerous sources spanning the energy range from 60 to 1800keV. A commercial set of sources (24,Am ' ]33Ba ' 137Cs ' 60C0 ' 88y, 22Na' 54Mn' 203Hg' 57Co, TRC, Amersham, England) gave 20 lines in the range from 60 to 1836 keV. Two sources from the National Bureau of Standards, a mixed nuclide source (l°gCd, 57Co, 139Ce, 2°3Hg, tl3Sn, SSSr, 137Cs, 60Co' 88y) and a ~S2Eu source added an additional 24 lines in this range. The efficiencies determined from the same line in different sources generally agreed to about 1%, with the worst agreement being 2.3%. Calibration and source measurements were done at gains of 0.22 keV/ch and 0.5 keV/ch. All photopeak intensities were derived from the fitting re-
sults of the LASL version 5) of GAMANAL6). An efficiency calibration curve for the 0-2000 keV range is shown in fig. 1. Efficiencies for t66mHO gamma rays were determined by log-log interpolation between measured efficiency calibration points. Consideration of the source calibration errors and peak fitting errors led to an assignment of an error of 2% (I a) to the calibration efficiency data. Data from separate 166taRo runs were combined with the arbitrary choice of l/tr weighting where tr is the error from the peak fitting results. This weighted peak fitting error was combined in quadrature with the 2% efficiency curve error to give the absolute intensity error for the 166rnHo s o u r c e emissions.
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IOO E (keV)
Fig, 1. Measured detector efficiency.
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IOOO
362
T.E.
SAMPSON
TABLE 1 Relative intensities of gamma rays from 166mHo as compared with previous values. Er(keV)
80.573 94.653 119.038 121.161 135.238 140.618 160.064 161.748 184.407 190.711 214.763 215.875 231.282 259.716 280.456 300.744 339.78 365.739 410.941 451.524 464.825 529.813 570.998 594.48 611.552 639.770 644.45 670.509 691.211 711.693 736.67 752.265 778.817 810.309 830.560 875.64 950.94 1010.25 1120.31 1146.82 1241.44 1282.12 1400.72 1427.05
Present data
17.51 _+0.50 0.221 _+0.011 0.222__+0.011 0.337_+0.013 0.126_+0.010 0.059___0.009 0.109-+0.008 0.135_+0.008 100.0 -+2.0 0.304±0.014 0.586_+0.020 / 3.54 ±0.10 j 0.284±0.014 1.446±0.043 40.79 ±1.15 5.12 ±0.15 0.234_+0.015 3.327_+0.096 15.25 -+0.43 4.02 ±0.12 1.651 _+0.051 13.10 -+0.37 7.53 -+0.22 0.773±0.030 1.951 ±0.061 0.122_+0.016 0.213_+0.019 7.37 _+0.21 1.871 _ + 0 . 0 5 8 74.48 -+2.11 0.506_+ 0.024 16.57 _+0.47 4.17 -+0.12 78.66 -+2.23 13.34 _+0.38 0.993_+0.029 3.71 _+0.11 0.096-+0.007 0.327-+0.013 0.271 -+0.013 1.142_+0.034 0.246-+0.012 0.686-+0.021 0.667+_0.021
Gehrke et al. (ref. 1)
Lingeman et al. (ref. 2)
16.72_+0.86
16.83_+0.42 0.21 _+0.03 0.23_+0.03 0.54-+0.05
14.48___0.48 0.3
0.16±0.03 0.16___0.03 100.0 0.31 _+0.04
0.36_+0.15
100.0-+3.0
4.06±0.16
40.2 _+ 1.3 4.97_+0.16 3.30-+0.03 15.27±0.16 3.99±0.04 12.78 _+0.13 7.45 _+0.08
7.37 _+0.08 1.805-+0.018 74.5 _+0.8 16.57 -+0.16 4.13 _+0.04 78.13 _+0.78 13.26 _+0.13 0.979-+0.010 3.68 -+0.040
0.274_+0.003 1.098_+0.013 0.241 -+0.004 0.670-+0.007 0.666±0.010
To obtain relative intensities, a self-absorption correction was made for the 166mHO source. The magnitude of this correction ranged from I!% at 80 keV, i.5% at 184 keV, to 0.2% at 810 keV. A small correction was also made for absorption in the 0.6 mm thick Lucite source window. The relative intensity values were normalized to 100.0 at
Lavi (ref. 3)
0.78_+0.18
I00.0
3.96±0.08 0.31 _+0.04 1.52-+0.05 39.63_+ 1.26 4.92-+0.12 0.23_+0.04 3.25-+0.10 14.77_+0.30 3.84-+0.13 1.50_+0.08 12.36-+0.25 7.04±0.14 0.70-+0.05 1.67_+0.09
3.94-+0.09 0.36_+0.03 1.77_+0.12 38.61-+0.46 4.77-+0.09
6.98±0.16 1.60-+0.10 71.10_+1.42 0.45 -+0.05 15.98-+0.32 4.16-+0.12 75.71_+1.51 12.83+_0.26 1.00+_0.09 3.74+_0.16
7.01-+0.25 1.85±0.09 71.65_+0.68 0.46_+ 0.04 16.06-+0.40 3.72-+0.07 76.38_+0.82 12.07-+0.25 1.14+_0.07 3.5 _+0.14
1.17-+0.12 0.24_+0.05
0.30 0.38___0.05 1.22±0.05 0.38-+0.04 0.86+_0.05 0.65±0.03
2.93_+0.06 15.50-+0.19 3.48___0.07 2.00-+0.07 10.16_+0.32 6.77_+0.14 1.28_+0.18 1.48-+0.27
Reich and Cline (ref. 4) 17.1 _+0.8 0.19 _+0.01 0.25 -+0.03 0.36 _+0.04 0.14 _+0.01 0.059-+0.014 0.134_+_+0.014 0.15 -+0.01 100.0 -+5.1 0.30 -+0.03 0.75 _+0.10 3.6 -+0.3 0.33 -+0.03 1.50 -+0.08 40.7 -+2.0 5.12 -+0.26 0.23 -+0.03 3.44 ___0.18 15.8 _+0.8 4.18 _+0.20 1.68 _+0.11 13.9 -+0.7 7.86 _+0.40 0.96 _+0.05 1.90 _+0.11 0.22 _+0.07 0.25 _+0.03 7.88 _+0.40 2.09 -+0.11 80.2 -+4.0 0.14 _+0.04 17.9 _+1.0 4.51 _+0.23 85.7 _+4.2 14.5 -+0.8 1.08 -+0.08 4.15 -+0.20 0.12 _+0.01 0.31 -+0.03 0.30 -+0.03 1.37 ±0.07 0.31 +_0.03 0.75 _+0.04 0.81 -+0.04
184.4 keV and the 2% uncertainty in the 184.4 keV intensity was again combined in quadrature with the uncertainties in the absolute intensity data to give the final uncertainties for the relative intensities of the gamma rays from 166rnHo. These results are compared with those from refs. 1-4 in table 1. The present data are in best
GAMMA RAYS FROM 166mHo o v e r a l l a g r e e m e n t w i t h t h e r e c e n t precise m e a s u r e m e n t s o f G e h r k e et al. t) a l t h o u g h t h e errors ass i g n e d to t h e p r e s e n t d a t a are larger t h a n t h o s e o f ref. 1.
References I) R. J. Gehrke, R. G. Helmer and R. C. Greenwood, to be published in Nucl. Instr. and Meth.
363
2) E. W. A. Lingeman, F. W. N. de Boer and B. J. Meijer, Nucl. Instr. and Meth. 118 (1974) 609. 3) N. Lavi, Nucl. Instr. and Meth. 109 (1973) 265. 4) C. W. Reich and J. E. Cline, Nucl. Phys. A159 (1970) 181. 5) B. R. Erdal, private communication. 6) R. Gunnink and J. B. Niday, Computerized quantitative analysis by gamma-ray spectrometry, vol. 1, Description of the GAMANAL Program, UCRL-51061, Lawrence Livermore Laboratory (1972).
NORTH-HOLLAND PUBLISHING CO.
RELATIVE INTENSITIES OF GAMMA RAYS FROM 166mH0 T. E. SAMPSON
Los Alamos Scienti.lic Laboratory, Universityof Cal(/brnia, Los Alamos, NM 87545, U.S.A. Received 16 August 1977 Relative intensities for gamma rays from the decay of 166mHo are reported,
166mHo is a long-lived (T~/2= 1200 y) source with many gamma rays in the range from 80 to 1400 keV that can be used for efficiency calibration of high resolution semiconductor detectors. Several measurements of the relative intensity of gamma rays from 166mHo have been published since 19701-4). Earlier references may be found in these papers. The source used in these measurements was purchased commercially (ICN, lrvine, California) in 1974. The source consisted of 24 mg of Ho203 with an activity of about 8/zCi sealed in a thin Lucite disk. The source activity covered a diameter of 8 mm giving a thickness of 47.7 mg/cm 2. Trace contaminants of '54Eu and ~55Eu were found in the source. The Ge(Li) detector used in these 'measurements had a relative efficiency of 8%, a resolution of 1.8 keV at 1332 keV and a resolution of less than 750 eV at 122 keV. All efficiency measurements were done at a source to end cap distance of 22.3 cm to minimize coincidence sum effects. No corrections were made for coincidence summing. Detector calibration was accomplished with numerous sources spanning the energy range from 60 to 1800keV. A commercial set of sources (24,Am ' ]33Ba ' 137Cs ' 60C0 ' 88y, 22Na' 54Mn' 203Hg' 57Co, TRC, Amersham, England) gave 20 lines in the range from 60 to 1836 keV. Two sources from the National Bureau of Standards, a mixed nuclide source (l°gCd, 57Co, 139Ce, 2°3Hg, tl3Sn, SSSr, 137Cs, 60Co' 88y) and a ~S2Eu source added an additional 24 lines in this range. The efficiencies determined from the same line in different sources generally agreed to about 1%, with the worst agreement being 2.3%. Calibration and source measurements were done at gains of 0.22 keV/ch and 0.5 keV/ch. All photopeak intensities were derived from the fitting re-
sults of the LASL version 5) of GAMANAL6). An efficiency calibration curve for the 0-2000 keV range is shown in fig. 1. Efficiencies for t66mHO gamma rays were determined by log-log interpolation between measured efficiency calibration points. Consideration of the source calibration errors and peak fitting errors led to an assignment of an error of 2% (I a) to the calibration efficiency data. Data from separate 166taRo runs were combined with the arbitrary choice of l/tr weighting where tr is the error from the peak fitting results. This weighted peak fitting error was combined in quadrature with the 2% efficiency curve error to give the absolute intensity error for the 166rnHo s o u r c e emissions.
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IOO E (keV)
Fig, 1. Measured detector efficiency.
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IOOO
362
T.E.
SAMPSON
TABLE 1 Relative intensities of gamma rays from 166mHo as compared with previous values. Er(keV)
80.573 94.653 119.038 121.161 135.238 140.618 160.064 161.748 184.407 190.711 214.763 215.875 231.282 259.716 280.456 300.744 339.78 365.739 410.941 451.524 464.825 529.813 570.998 594.48 611.552 639.770 644.45 670.509 691.211 711.693 736.67 752.265 778.817 810.309 830.560 875.64 950.94 1010.25 1120.31 1146.82 1241.44 1282.12 1400.72 1427.05
Present data
17.51 _+0.50 0.221 _+0.011 0.222__+0.011 0.337_+0.013 0.126_+0.010 0.059___0.009 0.109-+0.008 0.135_+0.008 100.0 -+2.0 0.304±0.014 0.586_+0.020 / 3.54 ±0.10 j 0.284±0.014 1.446±0.043 40.79 ±1.15 5.12 ±0.15 0.234_+0.015 3.327_+0.096 15.25 -+0.43 4.02 ±0.12 1.651 _+0.051 13.10 -+0.37 7.53 -+0.22 0.773±0.030 1.951 ±0.061 0.122_+0.016 0.213_+0.019 7.37 _+0.21 1.871 _ + 0 . 0 5 8 74.48 -+2.11 0.506_+ 0.024 16.57 _+0.47 4.17 -+0.12 78.66 -+2.23 13.34 _+0.38 0.993_+0.029 3.71 _+0.11 0.096-+0.007 0.327-+0.013 0.271 -+0.013 1.142_+0.034 0.246-+0.012 0.686-+0.021 0.667+_0.021
Gehrke et al. (ref. 1)
Lingeman et al. (ref. 2)
16.72_+0.86
16.83_+0.42 0.21 _+0.03 0.23_+0.03 0.54-+0.05
14.48___0.48 0.3
0.16±0.03 0.16___0.03 100.0 0.31 _+0.04
0.36_+0.15
100.0-+3.0
4.06±0.16
40.2 _+ 1.3 4.97_+0.16 3.30-+0.03 15.27±0.16 3.99±0.04 12.78 _+0.13 7.45 _+0.08
7.37 _+0.08 1.805-+0.018 74.5 _+0.8 16.57 -+0.16 4.13 _+0.04 78.13 _+0.78 13.26 _+0.13 0.979-+0.010 3.68 -+0.040
0.274_+0.003 1.098_+0.013 0.241 -+0.004 0.670-+0.007 0.666±0.010
To obtain relative intensities, a self-absorption correction was made for the 166mHO source. The magnitude of this correction ranged from I!% at 80 keV, i.5% at 184 keV, to 0.2% at 810 keV. A small correction was also made for absorption in the 0.6 mm thick Lucite source window. The relative intensity values were normalized to 100.0 at
Lavi (ref. 3)
0.78_+0.18
I00.0
3.96±0.08 0.31 _+0.04 1.52-+0.05 39.63_+ 1.26 4.92-+0.12 0.23_+0.04 3.25-+0.10 14.77_+0.30 3.84-+0.13 1.50_+0.08 12.36-+0.25 7.04±0.14 0.70-+0.05 1.67_+0.09
3.94-+0.09 0.36_+0.03 1.77_+0.12 38.61-+0.46 4.77-+0.09
6.98±0.16 1.60-+0.10 71.10_+1.42 0.45 -+0.05 15.98-+0.32 4.16-+0.12 75.71_+1.51 12.83+_0.26 1.00+_0.09 3.74+_0.16
7.01-+0.25 1.85±0.09 71.65_+0.68 0.46_+ 0.04 16.06-+0.40 3.72-+0.07 76.38_+0.82 12.07-+0.25 1.14+_0.07 3.5 _+0.14
1.17-+0.12 0.24_+0.05
0.30 0.38___0.05 1.22±0.05 0.38-+0.04 0.86+_0.05 0.65±0.03
2.93_+0.06 15.50-+0.19 3.48___0.07 2.00-+0.07 10.16_+0.32 6.77_+0.14 1.28_+0.18 1.48-+0.27
Reich and Cline (ref. 4) 17.1 _+0.8 0.19 _+0.01 0.25 -+0.03 0.36 _+0.04 0.14 _+0.01 0.059-+0.014 0.134_+_+0.014 0.15 -+0.01 100.0 -+5.1 0.30 -+0.03 0.75 _+0.10 3.6 -+0.3 0.33 -+0.03 1.50 -+0.08 40.7 -+2.0 5.12 -+0.26 0.23 -+0.03 3.44 ___0.18 15.8 _+0.8 4.18 _+0.20 1.68 _+0.11 13.9 -+0.7 7.86 _+0.40 0.96 _+0.05 1.90 _+0.11 0.22 _+0.07 0.25 _+0.03 7.88 _+0.40 2.09 -+0.11 80.2 -+4.0 0.14 _+0.04 17.9 _+1.0 4.51 _+0.23 85.7 _+4.2 14.5 -+0.8 1.08 -+0.08 4.15 -+0.20 0.12 _+0.01 0.31 -+0.03 0.30 -+0.03 1.37 ±0.07 0.31 +_0.03 0.75 _+0.04 0.81 -+0.04
184.4 keV and the 2% uncertainty in the 184.4 keV intensity was again combined in quadrature with the uncertainties in the absolute intensity data to give the final uncertainties for the relative intensities of the gamma rays from 166rnHo. These results are compared with those from refs. 1-4 in table 1. The present data are in best
GAMMA RAYS FROM 166mHo o v e r a l l a g r e e m e n t w i t h t h e r e c e n t precise m e a s u r e m e n t s o f G e h r k e et al. t) a l t h o u g h t h e errors ass i g n e d to t h e p r e s e n t d a t a are larger t h a n t h o s e o f ref. 1.
References I) R. J. Gehrke, R. G. Helmer and R. C. Greenwood, to be published in Nucl. Instr. and Meth.
363
2) E. W. A. Lingeman, F. W. N. de Boer and B. J. Meijer, Nucl. Instr. and Meth. 118 (1974) 609. 3) N. Lavi, Nucl. Instr. and Meth. 109 (1973) 265. 4) C. W. Reich and J. E. Cline, Nucl. Phys. A159 (1970) 181. 5) B. R. Erdal, private communication. 6) R. Gunnink and J. B. Niday, Computerized quantitative analysis by gamma-ray spectrometry, vol. 1, Description of the GAMANAL Program, UCRL-51061, Lawrence Livermore Laboratory (1972).