TJNAF Hall A HRS Gas Cherenkov

• Thicknesses of materials:
  • Entrance window: 1.5mil PVF (Charcoal Tedlar)
  • Gas: 1.5m(e- arm)/1m(hadron arm) CO2 at atm
  • Mirrors: ten spherical with 90cm radius of curvature
    • 40nm MgF2
    • 80nm Al
    • 1mm lucite
    • 0.2mm carbon-epoxy
    • 10mm phenol honeycomb
    • 0.2mm carbon-epoxy
  • Exit window: 1.5mil PVF (Charcoal Tedlar)
  • 10 PMTs per spectrometer * 2 = 20 PMTs:
    • Burle 8854 - one per mirror (66ns transit time)
• Location in electron arm:
  • Between aerogel and scintillator plane 2
• Location in hadron arm:
  • Between 1st and 2nd polarimeter strawtube wire chambers
• Counter sizes (nominal)
  • Both electron and hadron arm counters assumed identical except for length.
    • Transverse: +/- 250mm active (1193mm(w/ PMT) total)
    • Dispersive: mm active (2547mm total)
• Gas connection required.
  • 1 of 1/2 inch for input per arm ( 2 total )
  • 1 of 1/2 inch for output per arm ( 2 total )