Measurements of neutron total and capture cross sections of ²⁴¹Am with ANNRI at J-PARC

Figures & data

Figure 1. Present status on total cross sections of ²⁴¹Am.

Table 1. Characteristics of the samples

Sample	^241Am	Dummy
Inclusion	AmO2 + Y2O3	Y2O3
Activity (MBq)	957.4 ± 0.5	–
Weight of Y2O3 (mg)	46.0	66.2
Composition (%)
^241Am	100.0000(4)	–
Other	$<0.0004$	–
Diameter (mm)	10.0 ± 0.1	10.0 ± 0.1
Thickness (mm)	0.50 ± 0.05	0.50 ± 0.05

Figure 2. PH spectra of the ⁶Li detector and the ⁷Li detector.

Figure 3. Gated TOF spectra of the ²⁴¹Am and the dummy samples measured with the ⁶Li-glass and the ⁷Li-glass detectors. The red and the green lines show the neutron TOF spectra measured by the ⁶Li-glass detector. The black and the blue lines show the gamma-ray backgrounds measured by the ⁷Li-glass detector, which are nearly equal to each other. Each TOF spectrum was normalized with the number proton beam pulses.

Figure 4. The gated neutron TOF spectra and the frame-overlap background of the ²⁴¹Am sample. The red line shows the gated neutron TOF spectra measured by the ⁶Li-glass detector. The black line shows the deduced frame-overlap background.

Figure 5. The neutron transmission ratio of ²⁴¹Am.

Figure 6. The derived neutron total cross sections of ²⁴¹Am (red points) with comparison to the results by Adamchk [13] (black points), the evaluated values in JENDL-4.0 [4] (blue line), and JEFF-3.2 [43] (black line).

Table 2. Measuring times

Samples	Measuring time (h)
^241Am	41
Dummy	26
^197Au	5
^10B	5
^208Pb	12
Blank	9

Figure 7. The correction factor of the neutron self-shielding and multiple scattering in the ¹⁰B sample.

Figure 8. Incident neutron energy spectrum determined by measuring the 478 keV gamma-ray from the ¹⁰B(n, $\alpha \gamma$)⁷Li reactions.

Figure 9. A comparison between calculated and measured response functions for a ⁶⁰Co source. The calculated response function was normalized with the number of emitted gamma-rays. Differences of the peak areas on the 1173 and 1332 keV between the experiment and the calculation were less than 2%.

Figure 10. The calculated weighting function for the ²⁴¹Am sample without the normalization.

Figure 11. The PH spectra of the ²⁴¹Am (red), dummy (black), ²⁰⁸Pb (blue), and ²⁴¹Am decay (green) measurements. These PH spectra were normalized using the number of proton beam pulses. Sample-independent background estimated from the PH spectra for the blank measurement was subtracted.

Figure 12. The weighted sum TOF spectra of the ²⁴¹Am, dummy, ²⁰⁸Pb, and blank. These weighted sum TOF spectra were normalized with the number of proton beam pulses. Red line is the ²⁴¹Am, black line is the dummy, green line is the ²⁰⁸Pb, and blue line is blank.

Figure 13. The dead-time corrections for the weighted TOF spectra of the ²⁴¹Am and dummy measurements.

Figure 14. The background of frame-overlap neutrons compared with the weighted TOF spectrum of the ²⁴¹Am sample.

Figure 15. The correction for neutron self-shielding and multiple-scattering on the ²⁴¹Am sample.

Figure 16. The correction for neutron self-shielding and multiple-scattering on the ¹⁹⁷Au sample.

Figure 17. The correction for the fission reaction of ²⁴¹Am.

Table 3. Details of uncertainties for the derived thermal capture cross section of ²⁴¹Am

Uncertainties	(%)
Statistics	0.5
Capture cross-section standard	0.1
Sample mass	0.2
Weighting function	1.0
Dead time	< 0.1
Self-shielding and multiple-scattering
^241Am	< 0.1
^197Au	0.2
^10B	2.3
Extrapolation of PH spectra
^241Am	2.7
^197Au	1.6
Fission	<0.1
Total	4.1

Table 4. The thermal neutron capture cross sections (${\sigma }_{0,\mathrm{g}+\mathrm{m}}$) of ²⁴¹Am

Year	${\sigma }_{0,\mathrm{g}+\mathrm{m}}$(b)	Author	Refs.
2017	$707\pm 29$	Present
2014	$678\pm 58$	Fraval et al.	[35]
2013	$750\pm 35$	Lampoudis et al.	[34]
2013	$725\pm 34$	Genreith et al.	[33]
2013	$711\pm 28$	Genreith et al.	[33]
2012	$591\pm 35$	Belgya et al.	[32]
2008	$665\pm 33$	Jandel et al.	[31]
2007	$702\pm 25$	Nakamura et al.	[30]
2007	$705\pm 23$	Bringer et al.	[29]
2001	$672\pm 10$	Maidana et al.	[28]
2001	$696\pm 48$	Fioni et al.	[27]
1997	$754\pm 58$	Shinohara et al.	[26]
1976	$625\pm 30$	Kalabin et al.	[17]
1976	$853\pm 52$	Gavrilov et al.	[25]
1973	$612\pm 25$	Harbour et al.	[24]
1969	$654\pm 104$	Dovbenko et al.	[23]
1967	$740\pm 60$	Bak et al.	[22]
1955	$629\pm 35$	Pomerance et al.	[21]

Figure 18. The determined neutron capture cross sections of ²⁴¹Am. (a) 0.01 - 2eV, (b) 2 - 10 eV and (c) 10 - 100eV.

Figure 19. The uncertainties of the derived neutron capture cross sections of ²⁴¹Am. A step appeared at neutron energy of 2.4 eV following a change of the TOF bin width.

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