Undergraduate Research at Jefferson Lab

Optimization of Spin-Polarization of Helium-3 Target Cell by Thermal Convection Processes

Student: Stacy E. Karthas

School: University of New Hampshire

Mentored By: Patricia Solvignon

Spin-polarized Helium-3 (3He) cells have been used in many experiments at Jefferson Lab as effective neutron targets to get access to the neutron properties. To reduce the polarization gradient within the cell we studied the new convection system and its effects on adiabatic fast passage (AFP) polarization loss that results from measuring the polarization of 3He with Nuclear Magnetic Resonance (NMR). A Kapton flexible heater was used to induce convection within the cell. By methods of NMR polarimetry, the convection speed and AFP loss was found for multiple heater powers. It was found that an appropriate gas velocity of 6.05 cm/min was easily achievable with an absolute AFP loss below one percent in both the pumping and target chambers. These results indicate that this heater will be able to be used to induce convection in the new cell with small AFP losses.