Measurements of gamma-ray emission probabilities of ^{241, 243}Am and ²³⁹Np

Figures & data

Figure 1. Simplified decay scheme of ²⁴¹Am. Alpha-ray energies and intensities are described [30].

Figure 2. Alpha-ray spectrum of the ²⁴¹Am source.

Figure 3. Simplified decay scheme of ²⁴³Am. Alpha-ray energies and intensities are described. Transition intensities by beta minus decay are also shown [30].

Figure 4. Alpha-ray spectrum of the ²⁴³Am sample.

Figure 5. Gamma-ray spectrum of the ²⁴¹Am source.

Figure 6. Gamma-ray spectrum of the ²⁴³Am sample.

Figure 7. The full-energy-peak efficiency is plotted in the top figure (a). The filled points show measured efficiencies using the standard sources of ⁶⁰Co and ¹³³Ba at a source distance of 20.0 cm. The solid line indicates the calculated efficiencies from the Monte Carlo calculation. Differences between the measured efficiencies and the calculated values using the PHITS are compared in the bottom figure (b). Open circles represents the data obtained by using the ¹³⁷Cs source, which were normalized to unity at 662 keV. The estimated uncertainties of the efficiency curve were shown by the gray area in the figure.

Figure 8. Geometry of the HPGe detector in the PHITS calculations. The upper half of the detector is illustrated in the figure.

Table 1. Parameters of the HPGe detector. Specifications by the manufacturer are compared with the PHITS calculations. Uncertainties of these parameters estimated by the PHITS calculations are shown.

Parameter	Specifications	PHITS
Crystal radius, r (mm)	18	18.01 ± 0.04
Crystal length, l (mm)	13	14.00 ± 0.05
Dead layer thickness
Ion implantation, t1 (μm)	<0.3	1.6^+ 2.4− 1.6
Li diffusion, t2 (mm)	<0.7	0.70

Table 2. Gamma-ray emission probabilities of ²⁴¹Am.

Eγ (keV)	Iγ (%)
26.34	2.3 ± 0.1
59.54	35.64 ± 0.46

Table 3. Gamma-ray emission probabilities of ²⁴³Am.

Eγ (keV)	Iγ (%)
43.53	5.87 ± 0.09
74.66	67.72 ± 0.65

Table 4. Gamma-ray emission probabilities of ²³⁹Np.

Eγ (keV)	Iγ (%)
106.12 +106.47^a	26.01 ± 0.26
209.75	3.31 ± 0.04
228.18	11.18 ± 0.12
277.60	14.34 ± 0.16
285.46	0.76 ± 0.02
315.88	1.60 ± 0.03
334.31	2.05 ± 0.04

^a I_γ = 0.05% from ENSDF [30].

Table 5. Details of uncertainties for the gamma-ray emission probabilities of ²⁴³Am.

Uncertainties	%
Statistics	0.3
Fitting	0.3
Efficiencies of gamma rays	0.7–2.5 (25–1332 keV)
Activity determination	0.53
Corrections	<0.3

Figure 9. Comparison of the gamma-ray emission probabilities of 59.54 keV of ²⁴¹Am in chronological order. The gray area indicates the uncertainty of the evaluated value of ENSDF.

Figure 10. Comparison of the gamma-ray emission probabilities of 74.66 keV of ²⁴³Am in chronological order. The gray area indicates the uncertainty of the evaluated value of ENSDF.

Figure 11. Comparison of the gamma-ray emission probabilities of 277.60 keV of ²³⁹Np in chronological order. The gray area indicates the uncertainty of the evaluated value of ENSDF.

Evaluated Nuclear Structure Data File (ENSDF) for 241,243Am, 237,239Np and 239Pu. Database version of May 2015. Available from: www.nndc.bnl.gov/ensdf/index.jsp.

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