Structure of glasses for ³He neutron spin filter cells

In spin-exchange optical pumping, there is unknown excess relaxation, called the X-factor, that limits attainable ³He polarization. It is known that the X-factor depends on the glass containers. Hence, it is expected that there are cell-to-cell variations in microscopic structure among the cells and that these variations affect the attainable ³He polarization. However, microscopic structure of the glasses for ³He neutron spin filters has not been clarified yet. In this paper, we have performed precise X-ray diffraction measurements for the glasses at SPring-8 using synchrotron radiation. The structural differences are observed between several types of glasses, and also, between the GE180 glass pieces with different thermal treatment. Based on the results, the structural influence on the performance of ³He neutron spin filters is discussed.