CHESS X-ray measurements 5/2011

This was the first true production run, with scans of the entire current inventory of Hall D diamonds being carried out. A new custom monochromator built for us by Ken Finkelstein was installed and aligned already when we arrived. The beam spot was about 10mm x 10mm, very uniform and stable, with a b factor of about 8. There were really no issues with the monochromator throughout this run.

Instead of gluing them to a stretch wire mount, this time Jim McIntyre built for us a pair of stretched mylar target holders. These consisted of a pair of aluminum hoops with mylar sheets stretched very tight and glued to them. The diamond target was sandwiched in the middle between the two mylar sheets, and stuck naturally to the mylar by van der Waals forces so that no adhesive was required. Changing out the targets was as simple as separating the two hoops, scooping up the diamond with a thread loop, and replacing it with another. The fundamental mode of the stretched membrane was close to 1kHz, high enough that the amplitude of its oscillations due to noise pickup was very small. Samples studied were:

• Sinmat-9 : a 9 micron diamond thinned for us by Sinmat, Inc. This was originally a 3.5mm x 3.5mm x 100 micron CVD diamond from Element 6, that Sinmat had thinned to a final thickness close to 9 microns. It was already in 2 pieces where we received it, and the X-ray images showed that the larger piece had begun to fracture further in two new places.
• E6-10 : a 10 micron diamond thinned for us by Element 6. This was purchased by Jefferson Lab in 2010, for use in Hall D.
• pristine A,B : two pristine type III (CVD electronic grade) single-crystal diamonds from Element 6, purchased by UConn to be the beginning of an inventory of radiators for GlueX. Both of these were 3.5mm x 3.5mm x 300 microns.
• plate A,B,C,D : four pristine type II (CVD single-crystal plate) 3mm x 3mm x 300 microns plates from Element 6, ordered online from their catalog.

All data from this run have been archived at UConn. A summary of what was learned from this run and a sampling of the results were presented at the May, 2011 GlueX collaboration meeting in a talk by R. Jones.