Hall A Target System

* Cryogenic Target System:(JLab, CalStLa, Kent, UMD, ODU, W&M)
  • Three loops for liquid H2, D2 and one gasous target (3He or 4He)

  • LH2 and LD2 targets have been in stable operation since 9/29/97
  • Each Target can handle rastered beam up to 120 microAmps,
    Beam heating up to 700 Watts. A World Record!
  • LH2, LD2: each has 2 cells (15 cm, 4 cm): operation conditions: 20 K, 1.5 atm.

  • Helium target has been in stable operation since 1/2000
  • 3He, 4He: one cell, 10 cm, 5K, 15 atm.

  • Each of the three targets can be remotely moved in and out of beam.
  • Solid targets attached: Dummy targets (10cm, 15cm and 4 cm), 12C, Al, BeO, Empty.

* Polarized 3He Target: (Caltech, JLab, Kentucky, MIT, Temple, UVa and William and Mary)
  • Based on the principle of spin exchange between optically pumped Rb vapor and 3He gas.
  • 40 cm long sealed glass cell containing 10 atm 3He gas.
  • Polarization 40-50%, thickness 1022 atoms/cm2.
  • With 15 microA beam, the polarized luminorsity reaches 1036particles/cm2/s. Another 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.

* Solid Target Ladder:
  • Attached at the bottom of the cryotarget. Can hold 5 different targets; each can be remotely moved in and out of beam;

* Waterfall Target Assembly: (INFN)
  • Three parallel waterfall H2O targets each 200mg/cm2;
    Used for spectrometer calibration and 16O experiments.
  • Hydrogen in water provides a precision calibration.

This page is maintained by J. P. Chen. Last Update: Sept.24/2003.
Email: jpchen@jlab.org, Phone: (757)269-7413.