Main Magnetic Field Coil Optimization For ~3He Polarization

The nuclear spin-polarized³He gas has been deeply studied and widely used in various scientific experiments.The polarized³He gas can be used as a polar-ized neutron target to study the reaction of neutrons and charged particles or photon beams;On the other hand,spin polarized³He gas is good probe for the new interactions in the supernormal model.Such as searching the spin-dependent interaction quantitatively by measuring the NMR frequency shift,and measuring the relaxation time of polarized³He gas can also study the spin-dependent in-teraction;In addition,polarized³He gas can be applied to magnetometers and magnetic resonance imaging?MRI?;Finally,the highly polarized³He gas can be used as a neutron spin filter for neutron polarization and polarization analysis be-cause of the high correlation between the absorption cross section of the neutron in polarized³He nucleus and the spin orientation of both.At present,the three major domestic sources of neutron,CMRR,CARR,and CSNS,are conducting research on neutron polarization and polarization analysis techniques based on spin polarized³He gas.In³He polarization experiment,the relaxation process of³He is a key factor to maintain and limit its polarizability.In the past experiments of³He polariza-tion,in order to reduce the effect of magnetic field gradient on the longitudinal relaxation time for polarized³He gas with several hundred hours relaxation time,large size Helmholtz coils were usually constructed to provide a main magnetic field where the magnetic field center region homogeneity reaches 10^-4cm^-1.In order to obtain enough magnetic field homogeneity,some magnetic field systems size even exceeded 1.5m,but various experiments from the practicality and con-venience are expected to have a small magnetic field configuration.This work constructs a³He system based on Merritt coil.The length of the magnetic field system is?0.5 m,and the length of the section side is?0.4 m.Theoretical cal-culation and experimental measurement both prove that the magnetic field has enough region where the homogeneity reaches 10^-4cm^-1.However,for the³He cells for electron scattering experiments,the chamber length can be 40 cm,even with Merritt coil,the system length will exceed 1 m.In this work,a new six-coil system for³He polarization is obtained.Within coils,the uniformity of the m_?agnetic field in more than 30%of the space area satisfies the requirement that???,which is better than all the existing coil constructions used in polarized³He experiments and can be applied in future³He instruments for electron scattering experiment.