Abstract:

Polarimetry is an important part of a polarized ³He system. This work describes a laser detection setup which measures the free induction decay nuclear magnetic resonance (FID NMR) signal in the spin-polarized ³He system. The setup provides a novel approach to the high precision real-time polarization measurement of the polarized ³He systems. This laser detection method is based on Faraday rotation effect, which utilizes a linearly polarized laser beam to detect the FID signal of the magnetic moment of ³He atoms which precess along the direction of the main magnetic field. Compared with traditional pick-up coils, experimental results demonstrate that the laser detection method has a signal-to-noise ratio improvement of 106% and consequently higher precision in ³He polarization measurement. The laser detection method proposed in this paper can replace the pickup coils, and it has various applications in the polarization measurement of ³He systems or in precision measurement experiments.

Key words: polarized ³He, free induction decay nuclear magnetic resonance (FID NMR), laser detection, Faraday optical rotation effect