Difference between revisions of "CHESS X-ray measurements 11/2006"

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In November, we had a one week beam time at CHESS in Cornell University. We measured rocking curves for several diamond crystals there. Some interesting results are shown below.  
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In November, 2006 we had a one week beam time at CHESS in Cornell University. Participating in this run were: CHESS staff scientist Ken Finkelstein and GlueX collaborators Guangliang Yang, Richard Jones, and Franz Klein.  We measured rocking curves for several diamond crystals there. Franz brought with him the target ladder from Hall B, so we had quite a rich variety of samples to examine.
  
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* [[Results for the 20 micron diamond]]
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* HallB-G50 : type IA natural diamond, said to be 53 microns thick, mounted on the Hall B target ladder.  Experimenters from g8 call this diamond "good", hence the name G50.
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* [[Discussion about the X-ray beam divergence]]
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* HallB-B50 : type IIA natural diamond, said to be 40 microns thick, mounted on the Hall B target ladder.  Experimenters from g8 call this diamond "bad", hence the name B50.
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* [[How the crystal curvature affects the rocking curve width]]
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* HallB-20 : type IB synthetic (HPHT) diamond, said to be 18 microns thick, mounted on the Hall B target ladder.
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* twin-50 : type IA natural diamond, said to be 50 microns thick, thought to be a twin crystal, part of the Glasgow collection.
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* badboy-50 : type IIA natural diamond, said to be 50 microns thick, thought to have a large rocking curve width, part of the Glasgow collection.
  
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One of the challenges we faced during the 2006 feasibility measurements at CHESS was how to sufficiently collimate the beam to resolve the rocking curve structure of diamond on the scale of its natural Darwin width.  Using the C1 beam line Si(111) monochromator, the narrowest rocking curves we could obtain were of order 150 μr fwhm.  This width was understood as coming from dispersion, due to the large energy width of the monochromated beam.  The advantages of this setup were that the beam intensity was higher than we needed and the beam size filled the 15mm x 15mm beam line aperture.  With such a large beam it was possible to expose the entire diamond in a single scan.
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All data were archived at UConn.  Some interesting results for the 20 micron crystal are shown below.  
  
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As a means to narrow the energy distribution of the beam, a second monochromator was installed between the C1 monochromator and the diamond.  It was a symmetric channel-cut silicon (220) cyrstal.  We rotated the crystal about the (220) axis by a few degrees to get rid of the (224) and higher reflections.
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* [[Results for the 20 micron diamond]]

Latest revision as of 12:11, 29 November 2011

In November, 2006 we had a one week beam time at CHESS in Cornell University. Participating in this run were: CHESS staff scientist Ken Finkelstein and GlueX collaborators Guangliang Yang, Richard Jones, and Franz Klein. We measured rocking curves for several diamond crystals there. Franz brought with him the target ladder from Hall B, so we had quite a rich variety of samples to examine.

  • HallB-G50 : type IA natural diamond, said to be 53 microns thick, mounted on the Hall B target ladder. Experimenters from g8 call this diamond "good", hence the name G50.
  • HallB-B50 : type IIA natural diamond, said to be 40 microns thick, mounted on the Hall B target ladder. Experimenters from g8 call this diamond "bad", hence the name B50.
  • HallB-20 : type IB synthetic (HPHT) diamond, said to be 18 microns thick, mounted on the Hall B target ladder.
  • twin-50 : type IA natural diamond, said to be 50 microns thick, thought to be a twin crystal, part of the Glasgow collection.
  • badboy-50 : type IIA natural diamond, said to be 50 microns thick, thought to have a large rocking curve width, part of the Glasgow collection.

All data were archived at UConn. Some interesting results for the 20 micron crystal are shown below.

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