Hi Mike, 

  Here's an edited version of your DRAFT.

    -Dan
- - -

Analysis of the Diffraction Efficiency (DE) data on the gratings which
were exposed to a proton beam is on-going and there are some
conclusions so far:

1) Proton exposure will not cause catastrophic failure of HETG.
2) There are no obvious, common signatures in the data to suggest
which set of gratings were exposed.
3) If calibration changes caused by protons are linear with the dosage, then
at the current proton dose rate, proton induced HETG calibration drift
appears to be less than 1%/year at any energy.

The current analysis objective is to uncover any basis for deciding
which gratings may have been exposed.

Because the effect of proton exposure is subtle, the data analysis has
proven to be more labor intensive than if the effect were clear. In
addition, some outliers seen in the results are not due to changes in
the gratings, but instead due anomalies in the automated analysis of
the large amount of data and slight variations in the instrumentation
properties.  Tracking down these anomalies may take several additional
weeks.

Data analysis began by processing the test data (of order 100 files
per grating) with the custom IDL analysis software used in pre-flight
calibration.  The final output of this processing is five model fits
to the grating DE in five strips across the grating active area.  A
comparison of these pre- and post- exposure DE model fits is a measure
of proton induced calibration changes.  Using this approach, there
were some apparent changes as great as 14% observed.  Investigation
showed that the 14% change was attributed to the efficiency model
fitting procedure accentuating small changes or drop outs in the
measured data affecting the fits.

A new script was written to plot the individual pre- and post-
exposure DE measurements (rather than model fits to the ensemble of
measurements) and their ratios as a function of grating position,
X-ray energy, and diffraction order.  Using this approach, many
first-order data points are in agreement within 5% and/or the
statistical measurement uncertainties.  Some apparent changes as great
as 20% are still observed, however.  Manually examination of the data
files and pulse-height analysis fits for these measurements is in
process; validating and/or reprocessing each of the results is taking
time.


Michael McGuirk, Ph.D.	Voice: 617-253-3722
Research Technical Staff	Fax: 617-253-0861
MIT 37-491			Cellular Phone: 508-735-6927
77 Massachusetts Avenue
Cambridge, MA 02139-4307