Radiative neutron capture cross sections on ${}^{176}\mathrm{Lu}$ at DANCE

The cross section of the neutron capture reaction ${}^{176}\mathrm{Lu}\left(n,\gamma \right)$ has been measured for a wide incident neutron energy range with the Detector for Advanced Neutron Capture Experiments at the Los Alamos Neutron Science Center. The thermal neutron capture cross section was determined to be $\left(1912\pm 132\right)$ b for one of the Lu natural isotopes, ${}^{176}\mathrm{Lu}$. The resonance part was measured and compared to the Mughabghab's atlas using the $R$-matrix code, sammy. At higher neutron energies the measured cross sections are compared to ENDF/B-VII.1, JEFF-3.2, and BRC evaluated nuclear data. The Maxwellian averaged cross sections in a stellar plasma for thermal energies between 5 keV and 100 keV were extracted using these data.

Figure 1

Correction factor calculated from formula in [28] and applied to data taken in the segmented acquisition mode.

Figure 2

Comparison of the capture yield obtained from data acquired in segmented mode, the cyan (light gray) line, and in continuous mode, the black line. The segmented mode needs a dead-time correction performed using the analytic method given in [27, 28, 29].

Figure 3

Normalized capture yield for the ${}^{176}\mathrm{Lu}\left(n,\gamma \right)$ reaction using the $R$-matrix code, sammy [35]. The fit of sammy is represented by the cyan (light gray) line.

Figure 4

Normalized capture yield for the ${}^{176}\mathrm{Lu}\left(n,\gamma \right)$ reaction and a fit, the cyan (light gray) line, of the $R$-matrix code, sammy [35].

Figure 5

Some thermal neutron capture cross sections on ${}^{176}\mathrm{Lu}$ from Baston [37], Albert [38], Young [39], Mughabghab [36], [33], and this work. The dotted lines represent limits from the errors of the last reference Mughaghab compilation value [33].

Figure 6

Radiative capture yield of the ${}^{176}\mathrm{Lu}\left(n,\gamma \right)$ in the resonance energy range. The cyan (light gray) lines are the fit obtained using the sammy code [35].

Figure 7

Expected values of $\langle g{\mathrm{\Gamma }}_n/\sqrt{E}\rangle$ for $s$ waves, the red (upper) line, and $p$ waves, the blue (lower) line [33]. Black circles represent resonance parameters extracted from the DANCE data for the ${}^{176}\mathrm{Lu}\left(n,\gamma \right)$ reaction. Dotted lines are for DANCE values of $\langle g{\mathrm{\Gamma }}_n/\sqrt{E}\rangle$ determined in this work, respectively for $s$ waves (upper line) and $p$ waves (lower line).

Figure 8

Number of observed resonances whose reduced neutron width is larger than a threshold as a function of this threshold. Resonances observed in the DANCE experiment are shown by the black line. The cyan (light gray) line represents a fit using formula (2). The extrapolated curve (dotted line) indicates the real number of levels, $N_0=N(x_t=0)$.

Figure 9

The cumulative sum of the reduced neutron widths as a function of neutron energy is shown in (a). The cyan (light gray) line is the fit using formula (3). The averaged value of $\langle S_0\rangle$ calculated from the cumulative sum up to a neutron energy is presented in (b).

Figure 10

Radiative neutron capture cross section on ${}^{176}\mathrm{Lu}$ in the 0.5 to 70 keV region. These DANCE data (the black square), are compared to the previous measurements of Wisshak [5] [the green square (gray)], and recent data evaluations: JEFF-3.2 [31] [the cyan (upper) line], BRC [32] [the light gray line], and ENDF/B-VII.1 [30] [the red (dark gray) line].