BLTWG Meeting 9/27/2007

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The meeting was booked in VRVS on 27 Sept, from 10am to 12am (EST). Present for the meeting were Ken Livingston, Franz Klein, Yang Guangliang, and Richard Jones

Availability of diamonds for CHESS run 11/2007

Ken reiterated his concern that we not take the Hall B diamond crystal target ladder out of its mount in the Hall B gonimeter to carry out further tests on those diamonds at Cornell this year. Ken was told by a contact within Element 6 that he would be receiving a few diamonds, a mix of natural and synthetic types, within the past week. He has not received anything from them. Franz reported that the fragments from the broken 20 micron Hall B diamond are too small to use for X-ray tests. He had thought that there might have been a piece that was big enough, but that turns out not to be the case. Ken believes that he might be able to get a diamond from Mainz that has been exposed to a well-known amount of radiation. This diamond has been used in the CB beam line at Mainz for several months of beam time at a few tens of microamps. The Mainz beam spot area is a factor of ~20 smaller than the GlueX design, so the local rate of radiation damage is comparable to GlueX running at beam currents 20 times higher.

Plans and schedule for new Si(331) monochromator

Ken Finkelstein has looked over our design for the new asymmetric Si(331) monochromator and has proposed a small change that would employ two asymmetric crystals of somewhat smaller asymmetry b factor instead of using one asymmetric followed by one symmetric crystal. Yang and Richard have both run their calculations on this modified design and agree that it will work equally well. This enables Ken to re-use some silicon crystals that he already has in his inventory instead of cutting new slices from the large block. He reports that the cost of crystalline silicon has gone up a lot lately.

Goals for upcoming X-ray studies

  1. Check the performance of the new beamline configuration with the improved resolution for studies of Diamond(2,2,0).
  2. Test ideas for speeding up the data acquisition with the CCD camera.
  3. Test new means for reducing the effects of air disturbance on the mounted crystals during a measurement.
  4. Characterize the crystal quality of any new crystals that Ken Livingston obtains from Element 6.
  5. Study the effects of local radiation damage in the crystal that Ken will borrow from Mainz.

Discussion of engineering design package for tagger

Next week we plan to use the regular time slot for this meeting to discuss with Jlab the description of the engineering design package that will be going out in the near future.