Updated: June 14, 2000

The Hall D detector is optimized for incident photons in the energy range from 8 to 9 GeV to access the desired meson mass range. The use of a solenoidal spectrometer allows for the measurement of charged particles with excellent efficiency and momentum determination while at the same time containing the shower of unwanted electron-positron pairs associated with the photon beam. Photons will be produced using a "coherent bremsstrahlung" technique by passing a fine electron beam from the CEBAF accelerator though a wafer-thin diamond crystal: At special settings for the orientation of the crystal, the atoms of the crystal can be made to recoil together from the radiating electron leading to an enhanced emission at particular photon energies and yielding linearly polarized photons. With the planned photon fluxes of 10^7/sec and the continuous CEBAF beam, the experiment will accumulate statistics during the first year of operation which will exceed extant data with pions by at least an order of magnitude.

Please see the report of the Cassel Committee - the last page of this report presents a table which compares the proposed Hall D Detector with the LASS Spectrometer used as SLAC.

The need for sufficient energy, flux and degree of linear polarization dictates that we use a coherent bremsstrahlung beam.

1. More details are given in Chapter 4 of the Hall D Design Report (ver 2)
2. See also the notes by Richard Jones on the Photon Beam.

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The MEGA/LASS magnet is a 2.5 T superconducting solenoid originally built for the LASS spectrometer at SLAC. It was later moved to LANL for use in the MEGA experiment. We have requested that it be transferred to JLab for use in the Hall D detector.

1. More details are given in Chapter 5 of the Hall D Design Report (ver 2).
2. See the report of the Magnet Assessment Team which visited LANL in March,2000.
3. Paul Brindza wrote this note on magnet refurbishing plans.
4. Other information on the magnet on this Hall D website.

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We plan on using a 30-cm LH₂ target. There also has been some discussion about using nuclear targets.

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The tracking system will consist of cylindrical and planar drift chambers and a scintillating fiber "start" counter. We are also exploring the option of using a TPC.

1. More details are given in Chapter 5 of the Hall D Design Report (ver 2).
2. See tracking notes by Curtis Meyer (Notes 1, 2, 4, 5, 6, 7 and 24 ) on the CMU site
3. Please visit the FIU/ODU site for details on the "start" counter

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The barrel calorimeter will be similar to the design of KLOE detector in DAPHNE.

1. More details are given in Chapter 5 of the Hall D Design Report (ver 2).

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The TOF will consist of a Cerenkov counter and time-of-flight wall. The Cerenkov counter will use either C4F10 or aerogel as a radiator.

1. More details are given in Chapter 5 of the Hall D Design Report (ver 2).
2. See PID notes by Curtis Meyer (Notes 14 and 15) on the CMU site.
3. See this compilation of PID information from Alex Dzierba

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The lead glass detector (LGD) was originally built for the E852 experiment at Brookhaven lab and is being transferred to JLab.

1. A picture of the LGD
2. More details are given in Chapter 5 of the Hall D Design Report (ver 2).
3. A 3000 ELEMENT LEAD-GLASS ELECTROMAGNETIC CALORIMETER
   Nucl.Instrum.Meth.A387:377-394,1997
4. A STUDY OF TWO PROTOTYPE LEAD GLASS ELECTROMAGNETIC CALORIMETERS
   Nucl.Instrum.Meth.A332:419-443,1993
5. Details about the custom-built ADC's and Cockcroft-Walton PM bases here

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The Hall D detector will use on-board electronics and a digital pipeline.

1. More details are given in Chapter 7 of the Hall D Design Report (ver 2).

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The Hall D DAQ will be based on the JLab CODA system.

1. More details are given in Chapter 7 of the Hall D Design Report (ver 2).

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These drawings were produced by Eric Scott in consultation with Curtis Meyer. Curtis and Paul Eugenio have a CMU website where you can find these drawings as well as MCFast databases for this geometry.

units in cm - download an eps version of this drawing

units in cm - download an eps version of this drawing

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