Development of a Polarized Lanthanum Target with Perovskite Crystals

It is widely known that a solid polarized target is a powerful device in research of spin physics, such as investigations of spin structure of nucleons, spin correlation in nuclear reactions, and precise measurements of discrete symmetries. In practical beam experiments, the solid polarized targets are limited to protons and deuterons since a relaxation time of nuclei with a large quadrupole moment is very short under a typical magnitude of external magnetic field. A possible method for overcoming such a problem is to perform the Dynamic Nuclear Polarization(DNP) with perovskite crystals, which is expected as a new way for opening up further possibilities in spin physics. The NOPTREX collaboration applies this method for the development of a polarized lanthanum ($^{139}$La) target, which is a core device for discovery of Time-reversal violating effects with a slow neutron. We will introduce a basic concept and some features of the method, and also show the current status on Research and Development(R\&D) of the polarized $^{139}$La target in the NOPTREX project.