Speaker
Description
The total angular momentum of resonance is one of the significant parameters in nuclear data, but the identification is difficult. The parameter has been determined by several methods: the measurement of the spin-dependent transmission ratio by polarized neutrons and a polarized target [1], the measurement of intensity ratio of cascade $\gamma$-rays emitted from neutron resonance captures [2], and the measurement of $\gamma$-cascade multiplicity [3]. In spite of these efforts, available data were limited, and estimated values of the parameter have often been recorded in the evaluated nuclear data libraries, such as JENDL-5 [4].
As an alternative, we are inventing a new method which determines the total angular momentum of resonances from the measurements of circular polarization of $\gamma$-rays emitted from capture reaction of polarized neutrons on a target [5]. This method relies on the fact that the circular polarization of $\gamma$-rays from polarized neutron capture depends on the total angular momentum. We aim to apply the experiments at the thermal region performed in the 1950s to 1970s [6-8] to the resonance region. In order to measure the circular polarization of $\gamma$-rays, a Compton polarimeter was developed. For its operation confirmation, $^{32}$S was selected as a target because its polarized thermal neutron capture is known to emit 5.4 MeV $\gamma$-rays whose circular polarization is 50%. The circular polarization of $\gamma$-rays was measured with Ge detectors at J-PARC$\cdot$MLF$\cdot$ANNRI, and the analyzing power at the $\gamma$-ray energy of 5.4 MeV was determined as about 2%. In this presentation, we will report on the details of the sulfur experiment and future prospects for circular polarization measurements at ANNRI.
This work is partially supported by the JSPS KAKENHI Grant No. JP20K14495 and JP21K04950.
[1] A. Stolovy, Phys. Rev. 118, 211 (1960). [2] K.J. Wetzeland and G.E. Thomas, Phys. Rev. C 1, 1501 (1970). [3] C. Cocovi et al., Nucl. Phys. A 117, 586 (1968). [4] O. Iwamoto et al., J. Nucl. Sci. Technol. 60, 1 (2023). [5] L. C. Bindenharn et al., Phys. Rev. 83, 683 (1951). [6] G. Trumpy, Nucl. Phys. 2, 664 (1956). [7] R. Schaub and W. Schuler, Nucl. Phys. A 107, 14 (1967). [8] F. Djadali and J. Elchler, Nucl. Phys. A 165, 560 (1971).
