Hydrogen Scattering                 Sep 27, 1999

      Helium elastic scattering will be used to measure the absolute target
   density. To measure the cross section very accurately, a study of the
   solid angle is required. The helium elastic will study the product of
   the target density and the solid angle. It is important to have a
   separate plan to study how well we understand the solid angle. The best
   way to do this is to use hydrogen scattering from the same target
   geometry at "optimized" kinematics.
  

  Target: 10 cm liquid hydrogen. The helium loop will be switched with the
  hydrogen loop. This feature is already built in and was used before
  (e.g. The deuterium experiment switched loop one and three in the middle
  of the experiment). It will take about one shift to achieve this.
         The coolant has to be changed from 5K to 15K. The cryogenic group
  will need about one shift to change the coolant. They would prefer a day
  shift (not on the weekend). Switching loops and changing coolants can be
  done at the same time. The cool down of the hydrogen target will take a
  couple of hours. 

 Beam: 5 microA at 1.245 GeV.

 When: At the end of March running. There will be no need to switch back
 to helium target.   

 Kinematics: Beam 1.245 GeV, same angles as the elastic helium calibration
 data. May be we should take coincidence data instead of single arm.

 Running time: The cross section is large. Need 6 runs 20 minutes each.

 Total time required: 3 shifts (target work + data taking).