Difference between revisions of "Monte Carlo simulation of the CHESS C1 beamline"
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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. | 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. | ||
| − | 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. | + | 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. The narrowest rocking curve width we saw with the second monochromator in place was about 20 μr fwhm, still larger than the intrinsic Darwin width of diamond (220) of 7 μr at 15 keV, but much better than before. However the vertical beam dimension was now reduced from 15mm down to |
| + | |||
| + | A Monte Carlo program has been written to simulate the behaviour of the C1 beam line for diamond rocking curve measurements. The Monte Carlo will be used to | ||
| + | * reproduce the observed | ||
Revision as of 11:16, 10 March 2007
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.
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. The narrowest rocking curve width we saw with the second monochromator in place was about 20 μr fwhm, still larger than the intrinsic Darwin width of diamond (220) of 7 μr at 15 keV, but much better than before. However the vertical beam dimension was now reduced from 15mm down to
A Monte Carlo program has been written to simulate the behaviour of the C1 beam line for diamond rocking curve measurements. The Monte Carlo will be used to
- reproduce the observed
