Fundamental research for rare gas MRI

点击翻译按钮获取中文摘要

A cylindrical sapphire single crystal cell has been developed for 3He nuclear polarization for a MRI study. The cell was filled with 4-atm 3He gas, a small amount of rubidium droplet and 100 Torr nitrogen gas. The c axis of the single crystal was parallel to the disk of the cylinder. The disk worked as a widow for a laser beam for and optical pumping of rubidium atomic polarization. The sapphire single crystal has birefringence. The refractive index depends on the direction of the wave oscillation. The phase shift upon passage through the birefringence window depends on the oscillation direction. The circular polarization of incident laser is depolarized because of the phase shift. A same size of sapphire plate compensated for the phase shift. The rubidium polarization is transferred to 3He nuclear polarization upon atomic collision via a hyperfine interaction. The 3He nuclear polarization was monitored by a NMR detection. After the buid-up of the 3He nuclear polarization, the laser was switched off for an observation of 3He polarization relaxation. The relaxation time of the 3He polarization was 40 h. In the case of glass cell, we usually obtained one such cell from 10 cells. The result shows the sapphire is good material for 3He polarization. This is the first test of 3He polarization in sapphire cell