Synchrotron Optical constants, 19991215

D. Jerius

$Date: 2000/02/19 15:16:40 $

Where?

All files mentioned in this note are located on the CfA HEAD and CE LANs in /proj/axaf/Simul/databases/optconsts/synch_19991215 unless otherwise noted.

Summary

These optical constants are based upon Dale Graessle's reduction and analysis of the synchrotron reflectivity data. The main advance of this set over previous ones is the introduction of a contamination layer in the model for the witness coupons, which has lead to a dramatic improvement in the consistency in the determination of the optical constants.

The Ir optical constants are in 065o_optconsts_merged.rdb

The multi-layer surface parameters are in 065o_layers_merged_no_ol.rdb

The following plots shows the reflectivity from the surface multi-layer for the nominal grazing angles for the four HRMA shells. These are single reflections. The bumps in the high energy tail are due to the surface layers. The tabulated reflectivities are also available:

Shell Reflectivities
1 065o_layers_merged_no_ol_51.2_refl.rdb
3 065o_layers_merged_no_ol_41.2_refl.rdb
4 065o_layers_merged_no_ol_36.4_refl.rdb
6 065o_layers_merged_no_ol_27.0_refl.rdb

HRMA Multi-Layer Reflectiviy HRMA Multi-Layer Reflectiviy
HRMA Multi-Layer Reflectiviy HRMA Multi-Layer Reflectiviy

Ir Optical Constants

The file 065o_optconsts.rdb is a concatenation of all of the optical constants from Dale's directory, produced by the setup and fixup scripts. Constants for individual energy ranges are also present. The file 065o_optconsts_merged.rdb is a processed version of /data/ping3/HRMA_refl/optconsts_065/optconsts_065o.rdb (done by the fixpz script. This file is the result of merging the Synchrotron and Gullikson '95 optical constants. The Synchrotron data were taken in multiple overlapping energy ranges. The data in the overlaps were averaged together. The Gullikson data between 0.940 keV and 1.03229 keV were interpolated onto the Synchrotron energy grid and were averaged with them.

065o_optconsts_merged.rdb is the official set of Ir optical constants.

See Ping's email on his comparison of the results for flats 065 and 127 with overlayers.

Overlayer Optical Constants

There's some confusion over the optical constants used for the overlayer. Dale used what's in ch2.rdb (see the script setup for its origin).

Ping originally generated what's in polyethylene_1.out (taken from /data/ping1/idl/refl/opt_con ).

pelf% ls -l poly* 

-rw-r--r--   1 dj         117456 Jan 26  1999 polyethylene_1.out
-rw-r--r--   1 dj          18186 Jan 27  1999 polyethylene_1.rdb

From this he created an RDB table which he gave to Dale, who renamed it to ch2.atcon. However, the RDB table has slightly different optical constants from the atcon ASCII output (polyethylene_1.out), due to differences in physical constants between Ping's code and atcon (this has since been corrected). Ping's output uses more recent constants, so ch2.rdb should be considered the official CH2 results.

(The CH2.* files are my attempt at recreating the CH2 optical constants. They agree with the polyethylene_1.out. )

The differences between the atcon output and Ping's are rather small, resulting in less than ~ 6x10-7 in absolute reflectance. The script cmp_ch2CH2 generates a pretty plot illustrating this. The key point here is that one can use atcon's ASCII output without worrying about this problem.

Comparison of ch2.rdb and CH2.rdb

Multi-Layer Specification Files

multilayer_reflect compatible specification files are available:

file overlayer?
065o_layers_merged.rdb yes
065o_layers_merged_no_ol.rdb no
The surface parameters are averages of those for the different energy ranges, which are available here.

To have an overlayer or not

For grins and giggles, it's interesting to look at the effect of an overlayer on the HRMA reflectivity. We're hoping there isn't one, but...

The script cmp_ol2no_ol generates a set of comparison plots of the reflectivity, with and without the overlayer that Dale determined, at the grazing angles for the four mirror shells. For each optic an absolute and relative difference in reflectivity is determined. Note the difference around the Ir edges; this is a fairly small overlayer (only 12 Angstroms thick) and it can yield up to a 5% difference near the Ir edges.

Ping's Analysis of the Ir Optical constants

From zhao@head-cfa.harvard.edu Mon Dec 20 15:45 EST 1999 To: dj
cc: graessle, gaetz, edgar, lvs, mtibbetts, zhao Subject: New optical constant tables
Date: Mon, 20 Dec 1999 15:45:02 -0500
From: Ping Zhao <zhao@head-cfa.harvard.edu>

Diab,

I made four OC tables: 

/data/ping3/HRMA_refl/optconsts_065/optconsts_065.rdb        sample 065 w/o overlayer
/data/ping3/HRMA_refl/optconsts_065/optconsts_065o.rdb       sample 065 w overlayer
/data/ping3/HRMA_refl/optconsts_127/optconsts_127.rdb        sample 127 w/o overlayer
/ping3/HRMA_refl/optconsts_127/optconsts_127o.rdb            sample 127 w overlayer

You can also find all the PS files in the same directory if you want to see how I merged them, and how these OC comparing with the synchrotron data.

I recommend that we use /data/ping3/HRMA_refl/optconsts_065/optconsts_065o.rdb, which is the smoothest one. Also it's joint with the Henke OC at 940eV is very smooth.

The comparison of these four table and with the Henke value can be viewed at /data/ping3/HRMA_refl/synch_henke_oc_comp.ps.

Cheers,

Ping

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