• Based on the principle of spin exchange between optically pumped Rb vapor or Rb-K mixture and ³He gas.
• 40 (also 25) cm long sealed glass cell containing 10 atm ³He gas.
• Polarization ~ 55%, thickness 10²² atoms/cm².
• With 15 microA beam, the polarized luminorsity reaches 10³⁶particles/cm²/s. A World Record! .
• With no free polarized neutron target available, polarized ³He target provides a target close to a polarized neutron target since the spin of the two protons in ³He are almost all paired in opposite directions.

Status of the Polarized ³He Target Work and Safety Documents:

• Target OSP for the Gen experiment , LSOP for the Gen experiment .

  A briefing safety document for the target operator and procedures for the target operator.

• If you would like to contribute to the polarized ³He target effort, please contact the polarized ³He target program coordinator J. P. Chen at 269-7413. You will need laser training before you can work in the target lab. The training includes General Laser Safety Training (contact JLab laser safety officer Patty Hunt at 269-7039), an eye exam and the system specific training (read the safety documents Laser Safety Operation Procedure (LSOP) and Operation Safety Procedure (OSP), then contact the laser system superviser J. P. Chen at 269-7413).
• A new laser building was built in 2005 next to the Hall A counting house to allow setup and test the polarized ³He target for experiment(s). Optical fiber system will transport the lasers to the hall. OSP for the new laser building and LSOP for the new laser building .
• A permanent polarized ³He target lab was built in 1998 in EEL building. Many tests were done there while the target was not used for experiments. OSP for the EEL polarized ³He target lab and LSOP for the EEL polarized ³He target lab .
• A polarized ³He target was built in 1998 and has been undergoing upgrade and improvement continuously.

Progress and Status of the Polarized ³He Physics Program:

• Six experiments using the polarized ³He target have succesfully run from September 1998 to August 2003.
• Currently E02-013, Neutron Electric Form Factor G_En at High Q², is taking data. In-beam polarization reached all-time high of ~54% with the new hybrid (Rb-K miture) cell.
• A number of papers were published or submitted for publication (listed for each experiment, see Completed Experiments below).
• A number of students got their PhDs from the polarized He³ program (listed for each expeirment), including two (X. Zheng, MIT, for E99-117 in 2002 and K. Slifer, Temple, for E94-010 in 2004) received JLab/SURA Thesis award.
• A number of experiments using the polarized He³ target are approved to run in the near future.
• Experiments using the polarized He³ target are key components of the physics program for the JLab 12 GeV upgrade.

Polarized ³He Target Experiments in Hall A:

Completed Experiments:

• E94-010: Measurement of the Netron (³He) Spin Structure Function at Low Q²; a connection between the Bjorken and GDH sum rules.
• E95-001: Transverse Asymmetry A_T from ³He (e,e')at low Q.
• E99-117: Aⁿ₁ at Large x using JLab at 6 GeV.
• E97-103: Search for Higher Twist Effects in the Neutron Spin Structure Function gⁿ₂.
• E01-012: Neutron (³He) spin structure functiuons in the resonance region - spin duality.
• E97-110: The GDH Sum Sule and Spin Structure of ³He and the Neutron Using Nearly Real Photons.

On-going Experiment:

• E02-013: Neutron Electric Form Factor G_En at High Q².

Approved Experiments: (tentatively scheduled to run from fall 2007 to spring 2008)

• E06-010/06-011: Single Target-Spin Asymmetry in Semi-Inclusive Pion Electroproduction on a Transversely Polarized ³He Target.
• E06-014: Precision measurements of d_2n: color polarizabilities.
• E05-015: Target Single Spin Asymmetry in Quasi-Elastic ³He(e, e') Reaction.
• E02-108: A_x and A_z in Quasi-Elastic ³He(e, e'd) Reaction.

Related sites:

• Polarized ³He Target Lab at Temple University .
• Polarized ³He Target Lab at University of Virginia.
• Polarized ³He Target Lab at William and Mary.

This page is maintained by J. P. Chen. Last Update: April 21, 2006.
Email: jpchen@jlab.org, Phone: (757)269-7413.