| PARAMETER |
APS DCM |
UNI-CAT DCM |
| Beam offset |
35 mm upwards |
20 to 40 mm upwards |
| Energy scan |
6 to 24 keV with Si(111) |
4 to 40 keV with Si(111) |
| Range of scan travel |
0° to +35° |
-5° to +45° |
| Resolution of scan |
1 arc sec (5 microradians) |
0.5 arc sec (2.5 microradians) |
| First crystal pitch remote |
Yes |
Yes |
| First Pitch Encoder |
No |
Yes |
| First Pitch range |
± 1° |
± 3° |
| First crystal yaw manual |
-- |
Yes |
| First yaw Range |
-- |
± 5° |
| Y1 (normal to crystal) range |
0 - 20 mm |
0 - 20 mm |
| Y1 Remotely controllable |
Yes |
Yes |
| Second crystal pitch remote |
Yes |
Yes |
| Second Pitch Encoder |
No |
Yes |
| Second Pitch range |
± 1° |
± 0.0115° |
| Second crystal roll remote |
Yes |
Yes |
| Second crystal Roll Encoder |
No |
Yes |
| Second crystal Roll range |
± 5° |
± 7.5° |
| Second crystal yaw remote |
Yes |
No |
| Second crystal Yaw Encoder |
No |
-- |
| Second crystal Yaw range |
± 5° |
-- |
| X2 (parallel to pitch axis) |
No |
Yes |
| X2 Encoder |
-- |
Yes |
| X2 Range |
-- |
25 mm |
| Z2 (parallel to crystal surface) |
Yes |
Yes |
| Z2 Encoder |
Yes |
Yes |
| Z2 Range |
200 mm |
200 mm |
![[photo of 2 APS DCMs]](../images/aps_dcm.gif)
In the fall of 1996, PSL delivered two unique double crystal
monochromators to the Advanced Photon Source at Argonne. The DCMs are the
first in the world to operate at ultra-high vacuum and thus can be installed
directly on a beamline without a protective window. The DCMs can achieve a
vacuum in the 1 × 10-10 Torr range because they are constructed entirely
out of aluminum and stainless steel, without any high-torque or ferrofluidic
seals and gaskets which would contribute to the contamination of vacuum.
Both DCMs are capable of accepting inclined geometry, high heat load optics, and
sagittal focusing crystals through provisions of ample space for such optical
elements. The basic monochromator is a compact instrument. It has a single
rotational stage that does not require a track system to access the crystals
yet will fit into the confined back space at APS by having only 300 mm distance
between the beam centerline and the back of the instrument. All actuators are
hermetically sealed with all services to the actuator routed through a flexible
stainless steel corrugated hose. The scan drive uses a stepper motor and a glass
scale linear encoder. A large flange is located at the front of the chamber through
which the monochromator can be serviced. Motorized kinematic mounts are used
to adjust the position of the entire device.