Polarized 3He Pressurization Loop for an Electron Beam Target

The 12 GeV upgrade to the Continuous Electron Beam Accelerator Facility at Jefferson Lab will open a new program of nuclear physics experiments, some of which will be conducted with a polarized 3He target. The proposed developments will enable pressurizing polarized 3He from an external large-scale 3He polarizer and circulating it through a high-pressure target cell, allowing a factor of one-hundred improvement in data rates, reducing errors, shortening run times, and providing more experimental flexibility. New physics experiments to map Generalized Parton Distributions, presently under discussion, will only become feasible with this technology. We recently demonstrated a large-scale polarizer of 3He that offers polarization rates much higher than any worldwide. We will mate this polarizer with a diaphragm pump compressor with all wetted parts fabricated from non-ferrous metals, which will preserve 3He polarization and deliver polarized 3He at 50 liters per minute at 1000 psi and more. Gas returning to the polarizer will drop its pressure through a de Laval nozzle. Luminosity with a 100A electron beam in a 40cm long cell will be 1038. Commercial Applications and Other Benefits: The $330M allocation for the Jefferson Laboratory 12 GeV upgrade will allow the US to remain the leader in studying electromagnetic interactions in nuclear physics by accessing new kinematic regimes, increasing data rates, and reducing measurement uncertainties. This project will allow exactly those same improvements for a whole class of important experiments, those that use 3He. Also, new technologies for handling polarized gases facilitate other applications in neutron physics and medical imaging.