LRF Core Analysis

LRF Core Analysis

Go to HETG at XRCF

Results and Discussion

(updated 8/11/97)

The results to date suggest adopting the following calibration values:

Gratingdp/p rmserrorarc min rmserror
MEG 162. 50. 1.5 0.5
HEG 146. 50. 1.5 0.5

For the period variations I have used the sub-assembly value rss'ed with 100 ppm as an estimate, with an error of +/- 50ppm.

For the roll variations I have used 1.5 arc minute rms with an error of 0.5 arc minute. This is based on the MEG HSI FC data set described below which gives a measured MEG roll rms less than 2.07 arc minute (other effects have not been removed so this is an upper limit.)

Analysis chain

Sub-assembly Predictions

LR sub-assembly data predicts the values in the table below for dp/p rms and the grating roll rms values.
Gratingdp/p rmserrorarc min rmserror
MEG 127. ppm 10. ppm 0.42 0.1
HEG 106. ppm 10. ppm 0.42 0.1

The period and dp/p values measured with the LR system should be accurate - the main additional effect in going to the full flight model are any period variation effects due to the mounting process (aligning and screwing the frame to the HESS).

The existence of the "mis-aligned" MEG gratings shows that the polyimide can introduce polarization effects that can cause the X-ray roll angle to differ from the polarization-measured roll angle. The subassembly roll values are the polarization measured ones. It is possible that the same phenomenon is working to a smaller degree for all the MEGs and HEGs: polyimide polarization effects will lead to X-ray roll variations greater than the sub-assembly predicts.

XRCF very preliminary Results