31-May-2012

From Richard Schwartz:

Four routines have been changed to support better precision in the 
detector response around the instrumental K-edges for germanium, 
molybdenum (Grid 1 only), and tungsten.  They are


hsi_srm__define.pro
hsi_srm_control.pro
hsi_srm_control__define.pro
hsi_drm_mod__define.pro

There is a new control parameter for the 'hsi_srm' object, 
INSERT_KEDGE.  For the time prior to the SPD meeting its default will be 
0 so it will have no effect.  We'll change the default to 1 after the 
SPD meeting June 10-15, 2012.

With INSERT_KEDGE set(1), energy edges are introduced into the 
SRM (detector response matrix) at the edges where the cross-sections for 
x-ray photoelectric absorption has a jump.  Those jumps have been in the 
response tools for the SRM and grids but the calling routines have been 
using the default channel edges for photon energy edges.  That 
compromises the computation of the response at those energies.  The best 
solution is to insert edges at those energies and hence have the 
response computed more exactly.

While testing the change to the SRM generator we noticed an issue with 
hsi_drm_mod__define (used in OSPEX) where the code was assuming that in 
the low energy range the channel and photon edges were identical.  Not 
the case with this change, so hsi_drm_mod__define was also changed to 
support this.  It shouldn't change the results for any previous SRM fits 
files.  However, to take advantage of the INSERT_KEDGE  code you'll have 
to regenerate your SRM fits files with INSERT_KEDGE set.