Optics

From X6AWiki

Open Monochromator Tank

Mirror in the BNL Metrology Laboratory

Basic Optical Elements

* Si(111) channel cut monochromator

* Toroidal focusing mirror

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Specifications

* Energy range: 6-23 KeV
* Bandpass: 1.9 x 10^-4
* Intensity at sample position: 
        1.2 x 10¹⁰ photons/s

        (I=230mA, 200um slits, at 1.2 A)
* Spot size: 0.5 x 0.1 mm²(max)
* Epics/VME control system

X6A is a bending magnet beam line that has been specifically designed to pursue the structure determination of macromolecules using the Multiwavelength Anomalous Diffraction technique (MAD) in a user-friendly environment. A Si monochromator and an Oxford Danfysik focusing mirror are part of the basic optical elements in this beam line.

The Front End is a standard NSLS design and allows for an acceptance of 3 mrad. Machine vacuum is shared up to the first water cooled beryllium window 6.7 m down stream from the source. All of the hardware required for the construction of the beam line was build in house with the exception of two components that were procured from Oxford Instruments: the white-beam apertures and the focusing mirror. The Si (111) channel-cut monochromator (band pass: 1.9 x 10-4) located 7.6 m down stream from the source, is similar in design to monochromators found in other NSLS beam lines. The overall beam displacement at sample position over the whole energy range (7.0 to 20 keV) is on the order of 500 um. The Rh coated mirror, supplied by Oxford Danfisik and located 8.8 meters down stream from the source, can be bent into a toroidal figure for a standard 1:1 magnification-ratio. The maximum focal point at sample position, ~17 m from the source, is 0.1 x 0.5 mm2. The calculated intensity and flux at 2.8GeV, 320mA, is of the order of ~1011 photons/s and ~1.5 x 1013 ph./s/0.1%bw/mrad respectively.

Both optical elements are motorized and controlled by the beam line control system implemented in VME with software based on EPICS.