Rad-exposed Grating Analysis

3/28/01, 4/4/01, 5/7/01, 5/21/01 dd

Summary

To test for effects of radiation exposure on HETG gratings, a sample of 12 facets were provided to MSFC for proton irradiation at energies of 40 keV to 640 keV. Six of the 12 facets received proton exposures and the other 6 did not. The facets were pre- and post- tested at MIT and only after analyzing the test data were the identities of the irradiated gratings provided to MIT personnel. There was no clear correlation between irradiation and any change in grating properties, we concluded:

Any proton induced performance change is small, and will be accommodated by the normal recalibration schedule.
There was no significant change in the resonant frequency of any grating.

Rad analysis Notes

mm_010522.txt <-- Summary note when rad gratings revealed
(Ressonant Frequency note)
proton_hetg.pdf <-- The irradiated gratings!
rad_note_010521.txt <-- Final note, includes rad_anom.txt
rad_note_010507.txt
mmdd_010405.txt
odell_notes.txt
rad_note_010313.txt
rad_note_010307.tx

List of Data Sets and Journal of Analysis Activities

rad_test.txt

Rad analysis output plots

Plots comparing the pre and post exposure diffraction efficiencies were made for each of the five regions of each of the 12 possibly-exposed gratings and are available here:

rad_anom.txt <--- Anomalies noted in the comparison plots
and the status of investigating them.
rad_allrad.ps and rad_allrad.pdf <--- Plots Compare Post/Pre Radiation Exposed Gratings
Earlier versions of these products
- 010507 -- rad_anom.txt
- 010404 -- rad_allrad.ps , rad_allrad.pdf , rad_anom.txt
- 010328 -- rad_allrad.ps , rad_allrad.pdf

A brief explanation of the two types of plots on these pages is given here...

Plot of the absolute efficiencies measured by X-GEF for a specific grating and region.
For each closely spaced pair of points, the left one is the "pre" value and the right one is the "post" value.
The diffraction order is indicated by "1st", "2nd", and "zo".

The second-order points are:
MEG: m= + - + - + - + - (8) E= 1.25 1.49 2.29 4.51 HEG: m= - - - + - + - (7) E= 1.25 1.49 2.29 4.51 6.40

Plot of the Ratio of "post"/"pre" exposure values.
The X-GEF date codes are given as well as the Chi-squared value for each order set.
The error bars shown are plus/minus one sigma.

Chi-squared Values

The plots above give the reduced Chi-squared value:

Chi^2/N = TOTAL{ ( Ratio - 1.0 )^2 / Error_in_ratio^2 } / N_points

for each region and type of data (zeroth, first, second orders). This value indicates the agreement of the measurements with the "no change" hypothesis (ratio = 1.0) for first-order (fo), second order (so) and zeroth-order (zo) measurements. For the 10 or 12 first-order ratio points, a value greater than about 2.2 would occur statistically only 1 per cent of the time.

The 5-region-averaged reduced Chi-squared values for each grating are given in the tables below. In this case, for the 50 to 60 first-order measurements, values greater than 1.5 would occur randomly in only about 1 per cent of the cases.

Rad-exposed Gratings "Post- / Pre-" (010507)

MA1025  Chi^2   fo:    1.3,   so:    1.2,   zo:    2.1
MA1026  Chi^2   fo:   0.95,   so:    1.0,   zo:    2.1
MB1148  Chi^2   fo:    1.4,   so:   0.80,   zo:    2.6
MB1158  Chi^2   fo:   0.66,   so:    2.3,   zo:   0.73
MA1022  Chi^2   fo:   0.71,   so:    1.3,   zo:    1.2
ME1409  Chi^2   fo:    1.2,   so:    2.8,   zo:   0.41

HC2214  Chi^2   fo:   0.59,   so:    2.5,   zo:    0.0
HC2259  Chi^2   fo:   0.90,   so:    7.2,   zo:    0.0
HB2104  Chi^2   fo:    2.3,   so:    3.8,   zo:    5.2
HE2426  Chi^2   fo:   0.71,   so:    2.1,   zo:   0.22
HE2412  Chi^2   fo:   0.45,   so:    2.8,   zo:    1.2
HF2517  Chi^2   fo:    1.3,   so:    2.0,   zo:    4.3

*** OLD 010404 Values *** Rad-exposed Gratings "Post- / Pre-"
MA1025  Chi^2   fo:    1.3,   so:    1.2,   zo:    2.1
MA1026  Chi^2   fo:   0.95,   so:    1.0,   zo:    2.1
MB1148  Chi^2   fo:    1.4,   so:   0.80,   zo:    2.6
MB1158  Chi^2   fo:   0.66,   so:    2.3,   zo:   0.73
MA1022  Chi^2   fo:   0.71,   so:    1.3,   zo:    1.2
ME1409  Chi^2   fo:    1.2,   so:    2.8,   zo:   0.41

HC2214  Chi^2   fo:   0.62,   so:    3.2,   zo:    0.0
HC2259  Chi^2   fo:    1.3,   so:    1.7,   zo:    0.0
HB2104  Chi^2   fo:    2.5,   so:    4.3,   zo:    5.2
HE2426  Chi^2   fo:   0.76,   so:    3.2,   zo:   0.22
HE2412  Chi^2   fo:   0.54,   so:    1.2,   zo:    1.2
HF2517  Chi^2   fo:    1.5,   so:    1.9,   zo:    4.3

*** OLD 010328 Values *** Rad-exposed Gratings "Post- / Pre-"
MA1025  Chi^2   fo:    1.3,   so:    1.2,   zo:    21.
MA1026  Chi^2   fo:   0.95,   so:    1.0,   zo:    2.1
MB1148  Chi^2   fo:    1.4,   so:    5.5,   zo:    2.6
MB1158  Chi^2   fo:   0.66,   so:4.5E+04,   zo:   0.73
MA1022  Chi^2   fo:   0.71,   so:    1.3,   zo:    1.2
ME1409  Chi^2   fo:    1.2,   so:    2.8,   zo:   0.41

HC2214  Chi^2   fo:   0.62,   so:    3.2,   zo:    0.0
HC2259  Chi^2   fo:    1.3,   so:    1.7,   zo:    0.0
HB2104  Chi^2   fo:    2.5,   so:    4.3,   zo:    5.2
HE2426  Chi^2   fo:   0.76,   so:    3.2,   zo:   0.22
HE2412  Chi^2   fo:   0.54,   so:    1.2,   zo:    1.2
HF2517  Chi^2   fo:    1.5,   so:    1.9,   zo:    4.3

VSG "Controls"

Similar plots were made by comparing the HETG Vacuum Storage Gratings at different (sequential) epochs:

rad_allvsg1.ps and rad_allvsg1.pdf <--- Compares "Dec.00" to "July 99"
rad_allvsg2.ps and rad_allvsg2.pdf <--- Compares "July 99" to "Oct.98"

VSG Controls, "Dec.00 / July 99"

MA1019  Chi^2   fo:    1.1,   so:    1.5,   zo:   0.51
MA1040  Chi^2   fo:   0.95,   so:    1.5,   zo:    1.8
MC1212  Chi^2   fo:    2.5,   so:    2.6,   zo:    1.9
ME1408  Chi^2   fo:   0.94,   so:    2.1,   zo:    1.3
MB1165  Chi^2   fo:    1.5,   so:    1.8,   zo:    1.6
MD1367  Chi^2   fo:    1.8,   so:    1.5,   zo:    1.2

HA2003  Chi^2   fo:   0.94,   so:    2.2,   zo:   0.60
HD2334  Chi^2   fo:   0.61,   so:   0.94,   zo:    1.4
HA2045  Chi^2   fo:    3.8,   so:    12.,   zo:    10.
HC2251  Chi^2   fo:   0.71,   so:    1.3,   zo:    98.
HB2121  Chi^2   fo:   0.96,   so:    1.2,   zo:    0.0
HF2503  Chi^2   fo:    1.6,   so:    2.2,   zo:   0.71
HE2423  Chi^2   fo:    2.9,   so:    1.1,   zo:    18.
H2102   Chi^2   fo:    1.3,   so:    2.0,   zo:    0.0

VSG Controls, "July 99 / Oct.98"

MA1019  Chi^2   fo:    1.5,   so:   0.92,   zo:   0.92
MA1040  Chi^2   fo:    1.6,   so:    1.3,   zo:    1.9
MC1212  Chi^2   fo:    1.4,   so:    1.2,   zo:   0.87
ME1408  Chi^2   fo:   0.98,   so:    3.4,   zo:   0.73
MB1165  Chi^2   fo:    1.8,   so:4.8E+02,   zo:    1.2
MD1367  Chi^2   fo:   0.84,   so:    1.3,   zo:    1.6

HA2003  Chi^2   fo:   0.99,   so:    1.8,   zo:   0.37
HD2334  Chi^2   fo:    1.1,   so:    1.1,   zo:    2.9
HA2045  Chi^2   fo:    1.1,   so:    3.2,   zo:    2.5
HC2251  Chi^2   fo:   0.96,   so:    1.2,   zo:    8.4
HB2121  Chi^2   fo:    1.1,   so:    1.1,   zo:   0.79
HF2503  Chi^2   fo:   0.93,   so:   0.85,   zo:    1.2
HE2423  Chi^2   fo:   0.97,   so:    1.1,   zo:   0.49
H2102   Chi^2   fo:    1.3,   so:    1.6,   zo:   0.95

Rad Analysis Software

For reference, the tables and plots presented here were created by the IDL routines:

xgef_test/rad_compare.pro
xgef_test/rad_loop.pro

which access as input the standard X-GEF analysis result files.

MIT Accessibility

Plot of the absolute efficiencies measured by X-GEF for a specific grating and region. For each closely spaced pair of points, the left one is the "pre" value and the right one is the "post" value. The diffraction order is indicated by "1st", "2nd", and "zo". The second-order points are: MEG: m= + - + - + - + - (8) E= 1.25 1.49 2.29 4.51 HEG: m= - - - + - + - (7) E= 1.25 1.49 2.29 4.51 6.40
Plot of the Ratio of "post"/"pre" exposure values. The X-GEF date codes are given as well as the Chi-squared value for each order set. The error bars shown are plus/minus one sigma.