Optics
Channel-cut Si(111) + KB focusing mirrors
The main XALOC optical elements are: a diamond window (not shown in figure); a removable diamond filter (which could also be used as a Laue monochromator); a channel-cut monochromator; and a Kirkpatrick-Baez (KB) focusing system.
| 25 March 2011 The optics are completely assembled. Efforts are being directed to controls. From left to right, XBPM+slits (blue), Horizontal Focusing Mirror (green), XBPM+slits (blue), Vertical Focusing Mirror (yellow), and the Monochromator (red) behind a temporary rack |
Monochromator
| Type | Si(111) channel-cut, cryocooled |
| Gap between crystals | 6 mm |
| Absorbed power | <100 W (in working conditions) |
| 460 W (in worst-case conditions) | |
| Bragg axis resolution (measured) | <1 urad (<0,2 arcsec) |
| Bragg axis stability (measured) | <1 urad/1 hour |
Status: Now operative. The Factory Acceptance Tests were done and approved in Summer 2008. The monochromator was installed at the beamline in 15-19 June 2009.
| Monochromator in Factory Acceptance Tests |
Detail of the Silicon block. System controlling the pitch of the second crystal is shown above. Black pieces are part of the interferometer used to evaluate the performance of the monochromator. Cooling pipes are seen on the left, Bremsstrahlung block is shown on the right. |
A typical error when commissioning channel-cut monochromators is to take a diffracted reflection which is not the designed one (e.g. Si442 instead of Si111). This error can be easily overcome, especially in the case of Si111, by varying the Bragg angle. Some info about this can be found here.
KB mirrors
| Vertical Focusing Mirror | Horizontal Focusing mirror | |
|---|---|---|
| Type | Elliptically bent mirror | Elliptically bent mirror |
| Substrate | Si | Si |
| Coating material | Si, Rh, Ir | Si, Rh, Ir |
| Angle of incidence | 4.1 mrad | 4.1 mrad |
| Optical length | 300 mm | 600 mm |
| rms slope error (bent, measured) | <0,1 urad |
<0,1 urad |
| Pitch stability (measured) | <4 urad/1 hour | N.A. |
Status: Now operative. The Factory Acceptance Tests were done and approved in November-December 2008. The mirror vessels and positioning systems were installed at the beamline 9-13 June 2009. Mirrors were installed in Oct-Dec 2010.
| Vertical focusing Mirror in Factory Tests
|
Horizontal |
Other Elements
Other optical elements are white beam attenuators, slits, photon shutter, fluorescent screens and x-ray beam positioning monitors. All these elements have been installed.
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