HETG Gratings

Go to HETG at XRCF

Introduction

General Columns

• entry

  This integer is a unique number assigned to each grating or sample received by the NE80 test lab.

• frame

  This string is the set of characters inscribed on the grating frame to uniquely identify the grating. The initial letter (M/H) indicates an HEG or MEG grating. The remaining 4 or 5 characters have no specific meaning.

• ne80

  This string gives the [M]M/[D]D/YY date when the grating was received in NE80.

• wafer

  This string identifies the fabrication wafer ("device") of the grating. The first 3 characters are the fabrication lot, e.g., F12 is "flight lot 12". The next H or M indicates HEG or MEG gratings. Finally, the last three characters are the wafer number within the lot.

• type

  This single-character string indicates the grating-line orientation w.r.t. the frame ("gluing angle".) An "A" type grating can only be mounted in HESS sectors A or AA, etc.

• errsml

  This number is the measured error in degrees between the as-glued grating line angle and the designed value. Taken at face value, these "errors" would be compensated for during the grating-to-HESS alignment process and result in the grating frame being rolled from the design value.

• acoustic

  This value is the resonant frequency in Hz of the grating membrane.

• thermal

  This string is the date on which the grating was thermal cycled.

• xgef

  This string is a combination of the execution date code and X-GEF test procedure of the most recent (usually only) X-GEF test on this grating.

Installation Columns

• hessloc

  This string is the HESS location code "shell-sector-number".

• hessdate

  This string is the date on which the grating was installed onto the HESS, generally by Bob Laliberte.

• hessangle

  This value in arc minutes is the PEM-alignement-system measured roll-error of the grating line angle; these small values are due to Dick Elder's finesse.

• comment

  This string is a catch-all field for terse test comments.

• whichhess

  This string is "Flight" for gratings installed on the flight HETG.

• nofly

  This string was used to indicate conditions of the grating that prohibited its use as a flight grating.

LR Summary Columns

• lrpave

  This value is the average period of the grating in "NIST-absolute Angstroms". The average is over an "active region" roughly representative of the region illuminated by the HRMA: a 13.45 mm wide region for the MEGs and a 10.03 mm wide region for the HEGs (~dd/idl/lr/gs_lr_pspec.pro).

• lrdpop

  This value is the rms fractional variation of the grating period over the "active region" (see lrpave above). It is in units of ppm, i.e., x10-6.

• lrvalidfrac

  This value (between 0. and 1.) gives the fraction of the LR data points (over the whole LR-tested area) which have valid measurements.

• lrmacver

  This string (e.g., "LR3.23") gives the version of the LR measurement system for this most recent LR test of the grating.

• lrrollrms

  This value is the facet rms grating-line roll variation in arc seconds, averaged over the full LR-tested area.

X-GEF Summary Columns

• xgef (this appears earlier in the column order)

  This string is a combination of the execution date code and X-GEF test procedure of the most recent (usually only) X-GEF test on this grating.

• xgefdir

  This string is the MIT-local directory where the X-GEF data were analyzed and results produced for the facet-test. A prefix of "/nfs/" yields the original full path name.

• xgefthk

  This value is an approximate thickness (height) of the roughly trapezoidal grating bar shape - averaged over the several X-GEF tested regions of the facet. It is in Angstroms.

• xgefline

  This value is an approximate bar-width (FWHM) of the roughly trapezoidal grating bar shape - averaged over the several X-GEF tested regions of the facet. It is in Angstroms.

• xgef1kev, xgef4kev, xgef8kev

  These three values are the average, modeled, combined +/- first-orders facet diffraction efficiency at the three energies 1, 4, and 8 keV.