TJNAF Hall A HRS VDCs (Vertical Drift Chambers)

• detailed description in JLab-TN-00-016
• 368 wires per plane / 4 planes per spectrometer (UV + UV)
• no guard wires
• UV wire orientation (45 degrees relative to frame)
• 4.24 mm wire spacing (6 mm along frame edge)
• 20um Au plated Tungsten sense wires
• The wire spacing is 6 mm along the frame edge which translates to 4.24 mm perpendicular distance between wires. The distance from H.V. plane to H.V. plane is 1 inch = 25.4 mm. The projection of the track into the wire plane and within the gas volume is therefore L = 25.4 mm/tan(theta) = 19.6 to 32.9mm long. Since the wires are oriented at 45 degrees relative to X and Y this track will intercept L/(sqrt(2)x4.24) = 3.3 to 5.5 cells.
• some measured wire tensions
• Notes on VDC operating conditions (on 04-23-09)
• Right Arm VDCs
• gas flowing at a setting of 26 on the rotameters for both the top and bottom VDC
• 12V at about 5A for the cooling fans.
• About 0.2A on each threshold supply.
• 5.65V at 51.16A on the Agilent supply.
• 5.3V at 24A on the Acopian supply.
• On the top of the Right Arm top VDC, I put a layer of Reynolds 624 Heavy Duty Foil (aluminum)
• Left Arm VDCs
• gas flowing at a setting of 26 on the top and 24 on the bottom.
• measured gas gain for argon/ethane 62%/38% (premix, not from the mixing system)
• Additional material in the acceptance envelope (as noted in JLab-TN-00-016 and observation on 04/09/02 by me)
  • Left Arm (from the top to the bottom)
    • 15.75 mil of woven carbon fiber
    • 1 mil of aluminum foil (flush with VDC frame)
    • 6 um of mylar, aluminized on inner surface
    • 6 um of mylar, 850 angstroms gold on inner surface
    • wire plane
    • 6 um of mylar, 850 angstroms gold on both surfaces
    • wire plane
    • 6 um of mylar, 850 angstroms gold on inner surface
    • 6 um of mylar, aluminized on inner surface
    • air gap between VDCs
    • 10 mil of mylar (flush with VDC frame)
    • 6 um of mylar, aluminized on inner surface
    • 6 um of mylar, 850 angstroms gold on inner surface
    • wire plane
    • 6 um of mylar, 850 angstroms gold on both surfaces
    • wire plane
    • 6 um of mylar, 850 angstroms gold on inner surface
    • 6 um of mylar, aluminized on inner surface
    • 10 mil of mylar (flush with VDC frame)
    • 1 mil of aluminum foil (flush with VDC frame)
  • Right Arm (from the top to the bottom)
    • 15.75 mil of woven carbon fiber
    • 1 mil of aluminum foil (flush with VDC frame)
    • 6 um of mylar, aluminized on inner surface
    • 6 um of mylar, 850 angstroms gold on inner surface
    • wire plane
    • 6 um of mylar, 850 angstroms gold on both surfaces
    • wire plane
    • 6 um of mylar, 850 angstroms gold on inner surface
    • 6 um of mylar, aluminized on inner surface
    • air gap between VDCs
    • 10 mil of mylar (flush with VDC frame)
    • 6 um of mylar, aluminized on inner surface
    • 6 um of mylar, 850 angstroms gold on inner surface
    • wire plane
    • 6 um of mylar, 850 angstroms gold on both surfaces
    • wire plane
    • 6 um of mylar, 850 angstroms gold on inner surface
    • 6 um of mylar, aluminized on inner surface
    • 10 mil of mylar (flush with VDC frame)
    • 1 mil of aluminum foil (flush with VDC frame)