Sets monochromator d-spacing.
Usage: DM=[Spacing].
[Spacing] is a float (default is 3.354). Alternatively, one of predefined constants can be given:
CU: Cu (220), i.e., 1.2780 A
PG: Graphite (002), i.e., 3.35416 A
PG2: PG (004), i.e., 1.67708 A
HS: Heusler Alloy (111), i.e., 3.445 A
Note: DM is related to the following commands:
Instrument SetMonoSpacing, DA