Powder

SICS uses NeXus, based on HDF, as its raw dataformat. As first instrument DMC is using this new data format. A common task at DMC is to sum and concatenate measurements to a complete powder diagram. During this a detector efficiency correction needs to be performed. Users may also request an absorption correction to be performed. All this has been implemented as a set of operations in Tcl. This allows for scripting user interfaces to this process.

This package installs one new command powder in Tcl. The principle operation is that single diagrams are added into a list. Once this list is complete the operator finish will do the necessary calculations. powder understands the following operators:

• powder mur val. Sets the absorption coefficient to val.
• powder eff filename. Sets the detector efficiency file to use for efficiency correction. If none is specified no correction will be performed.
• powder add filename Adds a powder diagram in ASCII format from filename to the current list.
• powder addnx filename. Adds the powder diagram in NeXus format to the current list.
• powder sub filename Adds a powder diagram in ASCII format from filename to the current list. All counts are made neagtive in order to achieve a subtraction.
• powder subnx filename. Adds the powder diagram in NeXus format to the current list.All counts are made neagtive in order to achieve a subtraction.
• powder finish. Initiates the actual calculation of the concatenated powder diagram.
• powder abs. Performs absorption correction on the current powder diagram. A value for mur must have been specified.
• powder write filename. Writes the result powder diagram to an ASCII file in DMC format.
• powder clear. Deletes all internal buffers and lists prior to a new calculation.