Extraction of a helium ion beam from an optically polarized helium source gas
Stockwell, Norman David
Walters, G. King
Master of Arts
Optical pumping techniques can be used to produce nuclear polarization in He3 gas excited by a weak electric discharge. By optically polarizing He3 to a polarization P0 and extracting ions from the gas, the resulting ion beam is expected to retain a polarization between P0 and P0 /2 depending on the experimental conditions. Such a polarized beam would have great utility in nuclear physics. An ion source using this principle has been built by straight-forward modifications of normal rf ion-source geometry to provide the higher pressure and lower flow rate needed for the optical pumping. The dependences of ion current upon source gas pressure and cleanli-ness, electrical discharge intensity, the axial magnetic field, and the extraction voltage are measured. He4 rather than He3 has been used to date and ion-beam polarization cannot be measured with the present apparatus. However, under discharge and flow conditions which appear suitable for He3 polarization, beam current of 1 /ua are attained. Methods for measuring beam polarization are proposed. Some future experiments in atomic physics are considered.