Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of¹⁴⁰Ce and¹⁴¹Pr

Abstract

The neutron capture cross sections and capture ')'-ray spectra of 14°C e and 141 Pr were measured in the neutron energy region of 10 to lOOkeV and at 550keV. Prompt 1' rays from a capture sample were detected with a large anti-Compton NaI(Tl) spectrometer, employing a neutron time-of-flight method with a 1.5-ns pulsed neutron source by the 7 Li(p, n)7Be reaction. A pulse-height weighting technique was applied to observed capture ')'-ray pulse-height spectra to extract capture yields. The capture cross sections were derived with the error of about 5% by using the standard capture cross sections of 197 Au. The present results were compared with evaluated values in JENDL-3.2 and previous measurements. The capture ')'-ray spectra were obtained by unfolding the observed capture ')'-ray pulse-height spectra. An anomalous bump was observed around 1.5 MeV in each ')'-ray spectrum of 14°C e and 141 Pr, and its energy position was consistent with the systematics obtained in our previous work. The multiplicities of the observed capture 1' rays were derived from the ')'-ray spectra.

Evaluation of neutron nuclear data of praseodymium-141 and -143

“…We first discuss particularly the capture and (n, 2n) reaction cross sections which differ from JENDL-4.0 significantly by referring new experimental data after the release of JENDL-3.2. model parameters so as to follow the recent experimental data measured by Voss [13], Harnood [31], and Yoon [35] in the lower energy region up to 0.2 MeV and Zhu [36] from 0.2 to 1.6 MeV. From 1.6 to 3.0 MeV, Zaikin's data [37] are supported.…”

“…The parameters for electric giant dipole resonance (GDR) for 141 Pr are determined so as to reproduce measured capture γ -ray spectrum [31]. Additional small E1 resonances around 1.5 and 6.5 MeV are needed to explain the shape of γ -spectra emitted from 142 Pr produced by the capture reaction channel.…”

“…The parameters determined for the GDR and additional resonances are listed in Table 4. The calculated capture cross section of 141 Pr is normalized to the experimental data of Harnood et al [31] by multiplying the γ -ray strength function of 142 Pr by a factor of 0.502. We multiply the same factor in the γ -ray …”

“…The calculated capture γ -ray spectra are compared in Figure 11 with the experimental data of Harnood et al [31], who measured the spectra with incident neutron energies of 15-100 (average: 57.5 keV) and 550 keV (multiplied by a factor of 10). The evaluated data of ENDF/B-VII.1 in the case of neutron incident energy E = 57.5 and 550 keV are also shown.…”

Evaluation of Neutron Capture Gamma-ray Spectra for 89Y, 93Nb, 127I, 133Cs, 141Pr, 197Au, natTl, and 209Bi

“…The representative example is the anomalous bump shown in the experiments of the capture gamma-ray spectra. [7][8][9][10][11][12][13] According to a theoretical analysis and experiments, the bump could be considered to have the electric or magnetic properties of decaying gamma similar to the giant electric or magnetic resonances. So far, the bump has not been regarded as an essential nuclear property because it does not TECHNICAL MATERIAL affect significantly the capture cross sections, nor does it provide a sufficient enhancement of the high energy gammarays observed in the experiments.…”