Helium-3 Density Measurements Using Atomic Pressure Broadening

Abstract

Helium-3 (3He) gas is used as an effective neutron target at many particle accelerators studying the neutron spin structure. Its nucleus usually has two protons of opposite spin and one neutron determining the overall spin of the nucleus. Typically, the gas is polarized using optical pumping and spin exchange through the use of potassium (K) and rubidium (Rb). A density measurement of the 3He within such a mixture of gases is important before accelerator experiments can begin. This paper describes how such a 3He density measurement can be obtained through pressure broadening of K D2 absorption lines. This research shows the absorption lines were broadened by directing a Titanium Sapphire (Ti:Sapph) laser through a heated oven holding the 3He gas mixture. The 3He density of the neutron target named Fini at the College of William and Mary was measured to be 7.12 +/- 0.83 amg due to fitting errors. Experimental error could be minimized in the future with an automated frequency tuner, more absorption measurements per wavelength, and a focusing lens in front of each photodiode