CHESS X-ray measurements 11/2007

In November, 2007 we had a second week of beam time at CHESS in Cornell University. Participating in this run were CHESS staff scientist Ken Finkelstein, and GlueX collaborators Richard Jones, Guangliang Yang, and Stuart Fegan. Ken had mounted a new pair of silicon crystals in the primary monochromator box. These crystals were only a couple mm thick, and about 10cm x 10cm in size. Each bounce gave an expansion factor close to 4, with a combined b in the range 16-18. This expanded the beam vertically to about 1.5 cm. The monochromator design is described in a separate document linked here. The monochromated beam is dispersion-matched to the diamond 220 reflection, so that an ideal crystal will all diffract at the same angle, from the top to the bottom of the exposed area.

We measured rocking curves for several good diamond crystals (100 microns thick) during this run and demonstrated rocking curve resolution better than 10 μr RMS. The diamonds studied were taken from the Glasgow collection, and brought to CHESS by Yang. Here is a list.

• Mainz-new : type IIA synthetic (HPHT), thickness 100 microns, had been used at Mainz so had significant radiation damage.
• giant2 : type IB synthetic (HPHT), thickness 100 microns, never been in a beam.
• giant3 : type IB synthetic (HPHT), thickness 100 microns, never been in a beam.
• s1 : type IB synthetic (HPHT), thickness 100 microns, never been in a beam.
• s2 : type IB synthetic (HPHT), thickness 100 microns, never been in a beam.
• s3 : type IB synthetic (HPHT), thickness 100 microns, never been in a beam.
• q1 : type IB synthetic (HPHT), thickness 100 microns, never been in a beam.