HETG Line Response Function Analysis

HETG Line Response Function Analysis

Go to HETG at XRCF

XRCF HETG LRF-Relevant Measurements

Out of the 500+ HETG XRCF measurements, the following sets are of particular relevance to characterizing the HETG line response function:
HRMA-only LRFs
HRMA "Y-projections" are available from MST (Diab et al.)

HSI, Al-K : Shutter Focus and Focus Checks ( meas. summary)

These tests involve in-focus HSI observations of zero-order and diffracted orders of the gratings; in most of these tests the quadrant shutters are scanned. This data set can be analyzed for several purposes as given here.

Looking for Zero-order Effects

The zero-order PSF when a grating is inserted is expected to be the same as the non-grating, HRMA-only PSF The tests identified in the table below allow the grating zero order image to be assembled from the four quadrant images and the relevant no-grating image to be assembled from the appropriate HRMA shell images. The plots show the projections of the images along the Y and Z axes; the HRMA projection is overlaid on the grating zero-order projection, shifted so that the peaks coincide.

There is a slight indication that the LEG zero-order is a little broader than the HRMA-only image - as would be expected from the coarse support diffraction. The fine support diffracted images are at about 290 um, outside of this field of view.
OpticTRW_IDDaterunid(s) comparison
LEGD-LXH-SF-1.001970103107296,7,9,300 plots.ps
MEGD-HXH-SF-1.002970103107301,2,3,4 plots.ps
HEGD-HXH-SF-1.003970103107310,11,12,13 plots.ps
Shell 1D-IXH-PI-3.004970104107546 .
Shell 3D-IXH-PI-3.005970104107547 .
Shell 4D-IXH-PI-3.006970104107548 .
Shell 6D-IXH-PI-3.007970104107549 .
combined '3.004-7-- HRMA-HSI LRF at Al-K
( hist at 10 um bins .rdb )
*-IXF-P2-*Phase 1several HRMA-FPCpinhole LRFs from Diab
(plots above created with zero_order_effect.pro)

Detecting and Measuring Mis-aligned Gratings

Many in-focus and often shutter scanned measurements were made leading to the detection and quantization of the MEG mis-aligned gratings. Measurements also set limits on any HEG mis-aligned gratings.
Grating OrderShuttersTRW_IDDaterunid(s) notes, etc.
MEG +3MEG,SCAND-HXH-FC-1.010970104107463-6 to hlm,dsd links
HEG +2HEG,SCAND-HXH-FC-1.011970104107467-70.
MEG +31,SCAND-HXH-FC-28.001970109108026-29***
MEG +33,SCAND-HXH-FC-28.002970109108030-33***
MEG +3ALL,ALL,D-HXH-FC-28.003970109108034.
MEG -3ALL,ALL,D-HXH-FC-28.004970109108035.
MEG +31,SCANE-HXH-FC-28.001970205111316-9***
MEG +33,SCANE-HXH-FC-28.002970208111488-91***
HEG +24,SCANE-HXH-FC-28.005970208111492,4,5,6.
HEG +26,SCANE-HXH-FC-28.006970208111497-500.
*** The shell-quadrant images of Al-K +3 order were analyzed with hsi_alk_misaligned.pro to determine the angular offset of each mis-aligned grating, see the output plots (700K .ps). These plots show the 1D projection along the cross-dispersion axis (log-counts vs position) and the fits to these by up to three gaussians. The plots are for quadrants T, N, B, S from top to bottom on the page; one page for each line "***"ed above. The resulting mis-alignment angles are tabulated below; a systematic error estimated at 0.6 arc minutes applies.
HESS LocationQuadrantmis-alignment
(arc minutes)
1E4B~ +3Not seen in SCAN data,
value inferred from ring image.

MEG mis-aligned gratings in Flight
Effects of the mis-aligned gratings in Flight are demonstrated in the following MARX simulations for different modeled roll properties of the MEGs:

Rowland Geometry and Virtual Detector

The set of Al-K FC measurements can be used to i) check the HSI focus and ii) by comparing the relative focus of various orders verify the Rowland Geometry: the translation of the HSI creating a kind of virtual detector on the Rowland circle. This is similar to the same kind of check carried out with the ACIS-S to check its Rowland conformance, see Mike Stage's SPIE paper.

For this analysis the SF and FC tests in orders 0, HEG+2, MEG+3 (above) are supplemented with the 1st order FC tests:
Grating OrderShuttersTRW_IDDaterunid(s) notes, etc.
MEG -1MEG,SCAND-HXH-FC-1.006970103107NNN.
MEG +1MEG,SCAND-HXH-FC-1.007970103107NNN.
HEG -1HEG,SCAND-HXH-FC-1.008970103107NNN.
HEG +1HEG,SCAND-HXH-FC-1.009970103107NNN.

HSI, Mg-K : Defocus Tests ( meas. summary)

HSI images of the Mg-K line in high order were taken on 970116 for each of the three Chandra gratings. The HSI was positioned at 6 defocus locations with respect to the optimal Rowland circle focus: -1000 um, -500 um, 0 um, +500 um, +1000 um, and +2000 um. A HRMA-only shutter focus set provides a reference for the Mg-K HRMA image without gratings in place.

In focus images ('i2) for LEG+5, MEG+3, and HEG+2: (image height = 2000 um)
See all the images (i0 at top, made with mgk_images.pro).

Mg-K Grating Defocus Images
Grating OrderTRW_IDrunid-1000-500focus+500+1000+2000
MEG +3D-HXH-dF-16.002109002i0i1i2i3i4i5
HEG +2D-HXH-dF-16.003109003i0i1i2i3i4i5
LEG +5D-LXH-dF-16.001109001i0i1i2i3i4i5

Mg-K HRMA-only Quadrant Images

FPC, Mg-K : PSF/1D Slit scans ( meas. summary)

These measurements should provide very useful information on the LRF in the core and near wings... Comparison of the 0, +1, and higher order (HEG 2nd or MEG 3rd) allows grating-induced effects to be untangled from HRMA PSF effects.

18 HETG measurements = 3 scans X 2 gratings X 3 orders
= [10um dispersion, 80um dispersion, 10um cross-disp] * [ HEG | MEG ] * [0, +1, +2/+3]
D-HXF-P1-19.0XX, 970116 and 970117, 109056-63, '64-70, '72-80,
see 2nd floor log and tables below.

Dispersion direction scans: runid's and plots
gratingaperture m=0m=+1m=+2,3,5.
HEG10x200v+5 109056 109057 109058 plots: .ps
"80x500v 109064 109065 109066 plots: .ps
MEG10x200v-5 109061 109062 109063 plots: .ps
"80x500v 109068 109069 109070 plots: .ps
LEG10x200v 109082 109083 109084 plots: .ps
"80x500v 109085 109086 109087 plots: .ps
Cross-dispersion direction scans: runid's and plots
gratingaperture m=0m=+1m=+2,3,5XRCF MARX
HEG10x200h 109078 109079 109080 plots: .ps
note double
peak structure
plots: .ps
MARX hegdTheta =
1.5 arc min rms
MEG10x200h 109072 109076 109075 plots: .ps plots: .ps
MARX megdTheta =
1.8 arc min rms,
plus mis-aligned
LEG10x200h 109088 109089 109090 plots: .ps plots: .ps
MARX legdTheta =
1.5 arc min rms
(plots made with p1d_web_plots.pro using p1d_anal.pro; simulations and simulated plots created by meg_misalign_sim.pro.)

HSI, Mg-K : Offaxis images ( meas. summary)

HSI images were taken at orders +1, 0, and -1 for three different optic pitch angles in order to compare data and model. Each runid has three iterations corresponding to the 3 orders. (For LEG the orders are +5, 0, 5.) The data were taken on 970116.

Grating Off-axis Images: runid's and TRW_ID's
grating Yaw = -2Yaw = -5 Yaw = -15
HEG 109038
MEG 109037
LEG 109043

'2C, Mg-K : A bunch of images
Phase F and G PSF/Inner, Phase G focus checks, Phase F dFocus set

ACIS, Al-K, Si-K : quadrant scans, off-axis ( meas. summary)

This web page is: http://space.mit.edu/HETG/LRF/LRF.html.

Please send any comments and updates to Dan Dewey at dd@space.mit.edu.