Polarized ~3He System And The Polarization Measurement

The research of Spin-exchange optical pump(SEOP)with alkali vapors has existed since 1960.We have obtained polarized ~3He through SEOP.The ~3He nuclear spin polarization technology has been deeply studied in many fields of science and technology.Polarized ~3He can be used to study the reaction of neutrons with charged particles or photons;it can also be used to detect new interactions outside the standard model;spin polarized ~3He can also be used in the development of magnetometers.In the field of nuclear magnetic resonance imaging(MRI),there is great prospect;in addition,spin polarized ~3He can also be used to prepare polarized neutrons,which has a good application prospect for neutron detection.The highly polarized ~3He can also be used as a polarization analysis.The domestic neutron polarization analysis technology is in the research and development stage.At present,the three major neutron sources in China are doing related work.The polarized ~3He system mainly consists of four parts:a laser pumping system,a flirnace system,a magnetic field environment,and a polarizability measurement system.To obtain high polarization,each part must be very accurate,including:narrowing of the laser spectrum and design of the optical path,temperature stability of the heating system,uniformity of the main magnetic field,selection of special glass for ~3He polarized cavity(~3He will collide with the chamber to depolarize),and the ~3He polarizability measurement process affects the polarizability.In this paper,the whole polarization ~3He system is optimized from these aspects,and the ~3He polarization rate is improved.In order to maintain the polarizability of ~3He,the uniformity of the main magnetic field is maintained,and the influence of the magnetic field gradient on the longitudinal relaxation time is reduced.For the laser spectrum,the Zhou Jiu Bragg grating spectral narrowing technique is used to narrow the spectrum.The polarized cavity is made of GE180 special glass.This glass is very friendly to ~3He?and the relaxation caused by the collision is small,and it does not affect the transmission of the neutron beam.Nuclear magnetic resonance(NMR)and electron paramagnetic resonance(EPR)is usually used to obtain the polarizability of ~3He.Nuclear magnetic resonance measures give us the relative polarizability of ~3He,and the electron sequential resonance measures give us the absolute polarizability of ~3He.The method of measuring the electron paramagnetic resonance signal of an alkali metal is more accurate than the method of nuclear magnetic resonance method.My main work focuses on the construction of the entire system,the optimization of the laser beam path,and the calibration of the polarizability measurement system.Debug the laser beam path to obtain right-handed circularly polarized light,precisely ensuring that the polarization state of the laser is in a circularly polarized light.When the spin polarization direction of ~3He is flipped,the polarizability of ~3He is lost,and an optimal solution of the AFP coil needs to be obtained.In this paper,the loss of ~3He polarizability during the flipping process is reduced by a large number of experiments and optimized design,and the accurate ~3He polarizability signal is obtained.Compared with the data of foreign research institutions,our results are close to the world's advanced level.This paper contains 41 pictures and 56 references.