Neutron Radiative Capture in Na, Al, Fe, and Ni from 1 to 200 keV

Abstract

Neutron radiative capture in Na, Al, Fe, and Ni has been measured from 100 eV to 200 keV with a 1.25-m-diam liquid scintillator detector at the Rensselaer LINAC Laboratory. Radiation widths were determined for those resonances whose neutron widths are well known, while the resonance capture areas (<roI\) were determined for most of the other resonances. Considerably more resonances were observed in the capture measurements upon Fe and Ni than had been observed in total cross-section measurements. It is reasonable to assign most if not all of these previously undetected resonances to ^>-wave neutrons, and from these data />-wave strength functions of (O.lOrLO.04) XlCr~4 and (0.04±0.03) X 10~4 were determined, respectively, for 58 Fe and 58 Ni. These strength functions are probably just upper limits to the true ^-wave strength functions and are an order of magnitude smaller than optical-model predictions.* Taken in part from the thesis submitted to Rensselaer Polytechnic Institute by R. W. Hockenbury in August, 1967, in partial fulfillment of the requirements for the Ph.D. degree.

keV Resonance Neutron Capture in Iron

“…The time of flight spectrum, using the NaI detector, a thin sample, and 4 ns timing resolution, is shown in Figure 2 (b). The improved timing resolution shows all the known resonances in this region (Hockenbury et al 1969). The proton energy above threshold and the experimental geometry are such that the neutron energy range in Figure 2 (a) extends to 90 keY, while that in Figure 2 (b) cuts off at 60 keY.…”

“…The high spin transitions are stronger at 52 and 72 keY than at lower neutron energies and this suggests that these resonances are higher l-wave or that there are S-, p-, or d-wave resonances close to one another. Hockenbury et al (1969) argue that d-wave resonances are not significant since computation of the d-wave strength function for these yields a value that is an order of magnitude larger than that expected from theory and the strength of the smallest observed resonance is adequate to account for the entire calculated d-wave strength function. If this interpretation is correct and the high spin transitions follow p-wave capture, then the present data show a major Ml enhancement.…”

“…Neutron radiative capture in iron has been reported by Hockenbury et al (1969) for the neutron energy range from 0·1 to 200 ke V. Several previously unknown resonances were found and most were assigned as p-wave on strength function estimates. The reported resonances were: 54Fe 7·82, 9·48,14·4, 52keV 56Fe 11·2, 22·7, 27·7, 34·1, 36·6, 38·3, 45·8, 51·9, 53·3, 59·0, 63·1, 72·6keV…”

“…The results of Hockenbury et al (1969) (Section IV(a)) show that there are at least 10 resonances in the neutron energy range covered and, since the data have been analysed for four neutron energy groups, a distribution similar to v = 2 or 3 might be expected. With the limited data available, statistical variations of 50% or more might be expected in the distribution.…”

Neutron cross section measurements of elemental molybdenum and resonance parameter analysis

“…This machine has been used in conjunction with neutron-producing targets to make these measurements [1][2][3].…”