Thin diamond crystals (110-plates) 

are used as monochromators at three ID14 side stations: ID14-1, ID14-2 and ID14-3 beamlines. These stations are operated independently to allow four different user groups (forth group being active on the ID14-4 end station) to collect data simultaneously.

 

Diamond monochromator Energy   Wavelength 
ID14-1 Diamond (111), Laue geometry, 150 microns thin 13.27 keV 0.934 Å
ID14-2
Diamond (111), Laue geometry, 150 microns thin
13.29 keV
0.933 Å
ID14-3
Diamond (111), Laue geometry, 150 microns thin
13.32 keV
0.931 Å

Below is a photo of a diamond mounted on a copper block via indium-gallium.

diam

Since the diamond monochromators are essentially transparent for these energies and so absorb little of the beam, they are not cryogenically cooled. Only water cooling is used.

Energy calibration of diamond monochromators is performed via a theta scan with a thin platinium foil in the beam. This procedure is more less automatic (fully on ID14-3, see here for details) and working energies are set with respect to the Pt LII edge inflexion point = 13.1112 keV.

The crystalline quality of the ID14-2 diamond (as an example, diamonds of ID14-1 and ID14-3 being comparable) can be estimated from the topograph recorded in-situ just about 40cm from it.

white beam topograph of eh2 diamond

The vertical size of the image is about 3 mm. The black eliptical feature in the middle corresponds to the intense central beam. On the right side of the topograph a nice triangular growth sector can be seen as well as a quantity of growth striations. Fortunately they are not present in the part of the diamond crystal from which the beam is used. On the nearly perfect part of crystal some individual dislocations and small circular constrast features, as shown on detailed image below, can be observed. The circular contrasts are probably produced by (non?) polished beryllium window placed just after the diamond and resulting in phase modulations in the beam. The interference fringes visible (probably equal thickness fringes) in this detailed image demonstrate a high crystalline perfection (behaviour predicted by the dynamic theory) of the crystal.

white beam topograph of eh2 diamond: detail