NB : this material is not part of the official distribution
11.1-ter HPGSPC event corrections
In the case of the HPGSPC there is one correction needed to be applied to raw events in order
to normalize their energy information. The implementation of this correction
in XAS is done for analogy to that of the
MECS,
which is partially unlike the way SAXDAS does it.
As for the MECS all corrections are handled on request, transparently during the
primary accumulation of images, spectra, time profiles or
photon lists.
These are the kind of corrections and a very brief description of their nature.
Time dependency of gain
This optional correction multiplies the PHA of each event
by a correcting factor. This takes into account the
gain history
described elsewhere (relative gain vs time) and effectively normalizes to a common
energy scale (so-called PI channels).
This is important after July 1999, when the instrument started being operated
at reduced gain, in order to use the same energy scale as before
In order for correction to be applied during
primary accumulations
it must currently be explicitly enabled. Otherwise one obtains uncorrected files using
raw PHA. Enabling occurs as for the MECS
xasset correction Enabled
But for the HPGSPC they must not be applied when accumulating
gain histories !!!
Additionally all primary accumulations programs will
currently require an additional argument following all others.
THIS IS PROVISIONAL AND WILL BE CHANGED IN THE FUTURE TO USE ENVIRONMENT VARIABLES.
This extra arguments is a seed for a random number generator.
Time dependency of gain
The correction of the time dependency of gain (and gain normalization) is enabled as for the MECS:
xasset gainhistory gainfile
where gainfile is a gain history produced by the
appropriate command