Gain Notes for Revolution 342


JEM-X1	
A completely ordinary revolution.Gain smoothing is fine. All data from this 
revolution should be useable.
This is the last of the revolutions to have a pre-switch on
with HV set three steps below nominal. The procedure was changed beginning with
revolution 343 because gain overshoot and decay at the beginning of each 
revolution was really only a problem at the beginning of the mission.
The large gain increase at the beginning of the revolution is due to the 
long time available for the plate to `relax' (ion migration) while the unit
was switched off during revolution 341.


Xe Line analysis: It is clear from the Xe line evolution that there has been
some gain suppression on the plate due to residual high background that kept the
unit deactivated throughout revolution 341. This is a problem
where the microstrip detector plate becomes charged due to the influx of
energetic particles so that the gain of the detector drops slightly. This is not
picked up by the calibration spectra unfortunately because the calibration
areas are always highly irradiated by the calibration sources themselves. Hence
no gain suppression occurs at the calibration areas. The wild swings in Xe line
position at the beginning of the revolution are due to gaussian misfits because
the line was both swamped by the Her X-1 source in the FOV, and there was strong
grey filtering of both the science data and the calibration data. Fits with a
width significantly greater or less than one indicate that the Xe analysis 
program failed to find the xenon line in that Science Window.



JEM-X2: There is no scientific data and no gain history for this unit during
revolution 342.


CAO 22/12/2006