PrimEx meeting minutes 2/23/01


Dave Lawrence
  • Here are the transparencies shown by Dave.
  • HV Supplies:
    • The CAEN HV supplies have been ordered
    • We might expect to seethe first prototype module in April/May.
    • First final design module in May/June
    • First 10 modules by September
  • HV Cables:
    • No quote yet on the connectors. Old quote for similar connectors used for estimate of cost.

Sam Danagoulian

Dan Dale

Phil Cole
    g8 and PrimEx:

    g8 is a set of several experiments using a beam of highly-polarized Photons in Hall B through the process of coherent bremstrahlung. The beam will be highly collimated (2.0E6 photons/sec).

    The g8 run period is from June 1 through July 26.

  • PrimEx Pair Spectrometer
    • Positioning of hodoscope telescopes
      • 1.9 < Egam < 2.2 GeV
      • 1.6 < Egam < 1.9 GeV
    • Run at Highest Field Settings (10kGauss?)
    • Background into CLAS -- Shielding Structure?
  • Position of Harp (Photon Profiler)
  • Possibility of TASC upstream of CLAS?
  • How Can g8 Help?
    • Manpower
      • Geant Studies
      • Polishing of lightguides
    • Commision the Pair Spectrometer
      • can use spare Cerenkov electronics

Mark Ito
  • The dipole power supply was supposed to arrive in New York on February 23.

Abdellah Ahmidouch

Dave Kashy

Mahbub Khandaker
    Total Absorption Counter (TAC)

  • The four lead glass blocks (20 x 20 x 40 cm3) that have been acquired from Fermilab will be tested for performance during April, 2001. Specially, the time resolution of the blocks with the existing attached 5" photomultiplier tubes will be studied carefully. If need be, we will replace the existing pmt's with faster ones to facilitate the timing. One of the blocks will be installed at the current location of the existing TAC in the Hall B alcove before the g8 run period. Also, the possibility of installing a single block upstream of the CLAS detector for the g8 program is being looked into together with the help of Hall B engineering staff.

Eugene Pasyuk
  • Tagger status:
    During unscheduled down time new HV power supplies and cables were installed. That will provide individula HV for each E-counter. All the E-counter bases were replaced with the new one. Presumably these changes will iprove tagger stability. Beam test will be done diring comissioning time right before g8 run, in the beginning of June.

Rory Miskimen

Liping Gan
  • We found about 100% gain shift for 1"+1/8" Phillips PMT 2982 with VD119 HV divider at rate of 200kHz which is the operation condition for the pair spectrometer detectors during PrimEx running period. The best way to improve the situation wad found to be adding additional power supply with ratio of 120V:180V:240V on the last three dynodes, so that this shift could be reduced to about 25%. As Hamamatsu PMT usually have better rate stability, we ordered Hamamatsu 1+1/8" PMT R6427 for the front detectors and 1+1/2" PMT R580-17 for the back detectors. We will add additional power supply on the last three dynodes in the detector design.
  • We are still in process to negotiate with SIC in China to finalize the crystal specification.

Ashot Gasparian


David Lawrence
davidl@jlab.org
Wed Mar 21 10:39:58 EST 2001