Fission cross-section measurements of ²³⁷Np, ^242mAm, and ²⁴⁵Cm with lead slowing-down neutron spectrometer

Figures & data

Figure 1. Top view of KULS. Photo-neutrons produced in the tantalum target are slowed down in the lead material. Fission fragments are detected with MLPPAC (multi-layered parallel-plate avalanche chamber) placed in one of the experimental holes provided to KULS.

Table 1. The number of atoms in each sample.

	MA sample	^235U reference
^237Np
Am		(A)
^245Cm		(A)
		(B)
Note: The errors are the statistics in the counting.

Figure 2. MLPPAC has two sets multi-layered electrode. Each consists of four foils of aluminized polyester. Two samples are located between them.

Figure 3. The correlation between the pulse heights of the first and the second anode signals observed in the measurement of ²⁴⁵Cm. The fission fragments are clearly separated from particles.

Figure 4. The thick and the thin solid lines show the pulse-height spectra for the reference sample of ²³⁵U(A) used in the measurements of Am and ²⁴⁵Cm, respectively. The dashed line shows that of ²³⁵U(B).

Figure 5. The open circles show the cross section for ²³⁷Np before subtracting the background from ²³⁹Pu. The result of the background subtraction performed using the JENDL-4.0 evaluation is shown by the closed circles.

Figure 6. The cross section for ²³⁷Np obtained in this work (closed circles) is compared with the other experimental data, Yamanaka et al. [1], Carlson et al. [3], Gerasimov et al. [2] and Tovesson and Hill [4].

Figure 7. The resulting cross section for Am shown by the closed circles is compared with other experimental data, Gerasimov et al. [2], Kai et al. [8] and Alekseev et al. [9].

Figure 8. The resulting cross section for ²⁴⁵Cm shown by the closed circles is compared with Block et al. [12], Gerasimov et al. [2], and Alekseev et al. [9].

Table 2. The cross-section values for ²³⁷Np.

En (eV)	(b)	En (eV)	(b)	En (eV)	(b)
0.100–0.112		2.81–3.16		79.4–89.1
0.112–0.126		3.16–3.54		89.1–100
0.126–0.141		3.54–3.98		100–112
0.141–0.158		3.98–4.46		112–126
0.158–0.178		4.46–5.01		126–141
0.178–0.200		5.01–5.62		141–158
0.200–0.251		5.62–6.31		158–178
		6.31–7.07		178–200
0.251–0.282		7.07–7.94		200–224
0.282–0.316		7.94–8.91		224–251
0.355–0.447		8.91–10.0		251–282
		10.0–11.2		282–316
0.316–0.355		11.2–12.6		316–355
0.447–0.501		12.6–14.1		355–398
0.501–0.562		14.1–15.8		398–447
0.562–0.631		15.8–17.8		447–501
0.631–0.708		17.8–20.0		501–562
0.708–0.794		20.0–22.4		562–631
0.794–0.891		22.4–25.1		631–708
0.891–1.00		25.1–28.2		708–794
1.00–1.12		28.2–31.6		794–891
1.12–1.25		31.6–35.5		891–1000
1.25–1.41		35.5–39.8		1000–1122
1.41–1.58		39.8–44.7		1122–1259
1.58–1.77		44.7–50.1		1259–1413
1.77–1.99		50.1–56.2		1413–1585
1.99–2.23		56.2–63.1		1585–1778
2.23–2.51		63.1–70.8		1778–1995
2.51–2.81		70.8–79.4		1995–2239
Note: The first and second errors are the statistical and the other experimental uncertainties, respectively.

Table 3. The cross-section values for Am.

En (eV)	(b)	En (eV)	(b)	En (eV)	(b)
0.100–0.112		2.82–3.16		79.4–89.1
0.112–0.126		3.16–3.55		89.1–100
0.126–0.141		3.55–3.98		100–112
0.141–0.158		3.98–4.47		112–126
0.158–0.178		4.47–5.01		126–141
0.178–0.200		5.01–5.62		141–158
0.200–0.224		5.62–6.31		158–178
0.224–0.251		6.31–7.08		178–200
0.251–0.282		7.08–7.94		200–224
0.282–0.316		7.94–8.91		224–251
0.316–0.355		8.91–10.0		251–282
0.355–0.398		10.0–11.2		282–316
0.398–0.447		11.2–12.6		316–355
0.447–0.501		12.6–14.1		355–398
0.501–0.562		14.1–15.8		398–447
0.562–0.631		15.8–17.8		447–501
0.631–0.708		17.8–20.0		501–562
0.708–0.794		20.0–22.4		562–631
0.794–0.891		22.4–25.1		631–708
0.891–1.00		25.1–28.2		708–794
1.00–1.12		28.2–31.6		794–891
1.12–1.26		31.6–35.5		891–1000
1.26–1.41		35.5–39.8		1000–1122
1.41–1.58		39.8–44.7		1122–1259
1.58–1.78		44.7–50.1		1259–1413
1.78–2.00		50.1–56.2		1413–1585
2.00–2.24		56.2–63.1		1585–1778
2.24–2.51		63.1–70.8		1778–1995
2.51–2.82		70.8–79.4		1995–2239
Note: The first and second errors are the statistical and the other experimental uncertainties, respectively.

Table 4. The cross-section values for ²⁴⁵Cm.

En (eV)	(b)	En (eV)	(b)	En (eV)	(b)
0.100–0.112		2.82–3.16		79.4–89.1
0.112–0.126		3.16–3.55		89.1–100
0.126–0.141		3.55–3.98		100–112
0.141–0.158		3.98–4.47		112–126
0.158–0.178		4.47–5.01		126–141
0.178–0.200		5.01–5.62		141–158
0.200–0.224		5.62–6.31		158–178
0.224–0.251		6.31–7.08		178–200
0.251–0.282		7.08–7.94		200–224
0.282–0.316		7.94–8.91		224–251
0.316–0.355		8.91–10.0		251–282
0.355–0.398		10.0–11.2		282–316
0.398–0.447		11.2–12.6		316–355
0.447–0.501		12.6–14.1		355–398
0.501–0.562		14.1–15.8		398–447
0.562–0.631		15.8–17.8		447–501
0.631–0.708		17.8–20.0		501–562
0.708–0.794		20.0–22.4		562–631
0.794–0.891		22.4–25.1		631–708
0.891–1.00		25.1–28.2		708–794
1.00–1.12		28.2–31.6		794–891
1.12–1.26		31.6–35.5		891–1000
1.26–1.41		35.5–39.8		1000–1122
1.41–1.58		39.8–44.7		1122–1259
1.58–1.78		44.7–50.1		1259–1413
1.78–2.00		50.1–56.2		1413–1585
2.00–2.24		56.2–63.1		1585–1778
2.24–2.51		63.1–70.8		1778–1995
2.51–2.82		70.8–79.4		1995–2239
Note: The first and second errors are the statistical and the other experimental uncertainties, respectively.

Table 5. The experimental uncertainties considered in the present analysis are listed (in percent).

Source of the uncertainty	^237Np	Am	^245Cm
Number of atoms of MA	12	7.2	2.4
Number of atoms of ^235U	4.9	5.2	4.9
Selection of fission of MA	0.3	0.1	0.1
Selection of fission of ^235U	0.1	10	0.2
Solid angle for MA	1.9	2.1	5.6
Solid angle for ^235U	1.9	2.1	3.9
Total	13	14	8.7

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