Ohio University Qweak Status Report: 03/18/2004

• Add floor, the front and back walls of the shielding hut to Qweak.euclid file, as well as the windows on the front wall.
  
  
  1. Side view of the Qweak Spectrometer
     
     
  2. View of the Qweak Spectrometer from upstream of the beamline
     
     
  
  
• Study the elastic scattering electron envelop at different Z positions along the beamline, to determine the size and position of the windows on the front wall.
  
  
  1. Electron envelop at different Z positions
     
     
  2. Projection of electron envelop on X direction
     
     
  3. Projection of electron envelop on Y direction
     
     
  What we learned from our studies:
  
  
  • The magnet changes the 8 deg scattering angle to ~ 21.5 deg. This means the Region 3 chambers should hang at ~ 23.5 deg from the vertical (with the edge closest to the beamline more upstream) to get electrons going through them at 45 deg.
    
    
  • The electrons are being focussed in the radial direction (X direction) and defocussed in the phi direction (Y direction).
    
    
  • Figuring out the active area of the Region 3 chambers and the trig scintillator should probably be done by looking at the electron envelope at the desired Z position since the geometry of the focussing and defocussing are not straightforward.
    
    
  • If the Region 3 chambers are going to extend ~ 40 cm in Z, we need to know this so we can put the front wall of the hut in the correct place, and figure out the suitable size and position of the windows on the wall.
    
    
  • The asymmetry has little sensitivity to the width of the Cerenkov bar and the amount of the radiative tail accepted in that width. There is no requirement on the width other than it should not cut into the main portion of the elastic peak. (Learned from Jim Birchall's studies)