See also newpsd
Define the integration formula for selecting the specular ridge and background for an instrument configuration. Return pixel ranges to integrate over:
{spec_lo spec_hi bkgm_lo bkgm_hi bkgp_lo bkgp_hi}
To suppress the backgrounds, use {} {} instead.
Available variables: >S1: slit widths (mm) >A,B: sample and detector angles (degrees) >dd: distance from sample to detector (mm) >w: pixel width (mm) >rec: the record structure >point: the current point
Use [Td_to_pixel $result $B] to convert offset from specular into pixel
Here is an example from a detector with simultaneous beams:
# slit D >set rec(centerpixel) 354 >set rec(index) D >set lo [expr -3.2*\$S1-9] >set hi [expr 5.5*\$S1+3] >return [list \$lo \$hi {} {} {} {}]
Note that the integration region expands with the slit opening. Since the formula is intimately tied with the center pixel for the beam, also set the center pixel. Background for the slit scan is ignored.
The following example defines the corresponding specular:
# spec D >set_center_pixel \$rec(id) 354 >set rec(index) D >set lo [expr -3.2*\$S1-9] >set hi [expr 5.5*\$S1+3] >return [list \$lo \$hi [expr \$lo-64] [expr \$hi-64] {} {}]
Note that the background is the same width as the specular and shifted by a multiple of 32. The particular detector in use when this documentation was written happened to have a periodic nonuniformity 32 pixels across.
Regions can also be fixed:
return [list -16 16 -64 -48 {} {}]; # uncomment for fixed integration width
Use the key combination control+enter to update the integration after editing the integration region formula.
2006-02-24