GlueX Target Meeting, May 17, 2011

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Location, Time

Tuesday, May 17, 2011
1:00 pm EST
JLab: CEBAF Center, Room F224/225


  1. Review minutes from previous meeting: all
  2. Target Work Reports: all
  3. MOU status: Mark



To connect by telephone:

  1. dial:
  2. enter access code followed by the # sign: 3421244#


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2011-2Q on the JLab CUE. This directory is accessible from the web at .


Present: Hovanes Egiyan, Jim Fochtman, Mark Ito, Chris Keith, Tim Whitlatch


We went over the target requirements list that Tim prepared. The following items came up in discussion:

  • Five hundred Gauss on the cold head is maximum according to the manufacturer. Is this OK?
  • We want to be able to cool the target in one shift.
  • The average diameter of the target is spec'ed at 2 cm. Is that OK?
  • Length of target is 40 cm: can this be finalized?
  • The maximum OD of the scattering chamber driven by start counter and that is driven in turn by the CDC.
  • What is the alignment requirement for target?
  • How well do we have to know the density of the liquid?

Additional requirements were raised in the discussion:

  • specification of quality of scattering chamber vacuum (prevent freezing material on target)
  • flammable gas compatibility of system
  • interlock of nearby electrical systems and/or ignition sources if target cell ruptures
    • hydrogen gas sensors will be needed
    • pressure switch on vacuum chamber
  • specify stainless steel tubing
  • specify welding whenever possible


Tim showed the current drawing of the target, scattering chamber, and start counter area from Slava.


We looked over the two versions of a piping and instrumentation diagram for the target that Chris prepared

  • Hydrogen and deuterium tanks outside connect to a single line going to the Hall.
  • A vent line goes outside hall; a manual valve is provided.
  • The vacuum pump needs an explosion-proof motor.
  • In the second version, the gas panel is mounted outside hall so changing gas could be done without access to the Hall. It would still be manual operation.

Other considerations:

  • We could put gas panel and control electronics in the "target" rack.
  • Electronics needed:
    • temperature controller
    • local visual read-back for pressure transducers would be nice to have
    • turbo controller for scattering chamber
    • vacuum gauge controller
  • These designs allow automatic transition to cold gas in the target cell, but not to vacuum.

Next Area of Work

  • The next step is to work on the mechanical design for target condenser, cell, scattering chamber.
  • We may not want to have the cold head provide any mechanical support; copper braid could provide flexible thermal coupling.
  • Jim will contact Chris to work out issues before the next meeting