EIS Sensitivity Update

1
EIS Sensitivity Update
John Mariska NRL 3-5 Feb 2003
2
EIS Effective Areas

• First set of flight optics coated at Columbia
  University and Characterized at Brookhaven
• Effective areas computed using
• Measured M 1 reflectivities
• Measured FL 7 efficiencies (combination of
  reflectivity and groove efficiency)
• Same Al filter transmission as earlier
  calculations
• Al filter mesh transmission factor of 0.85
• Spider transmission factor of 0.80
• CCD QE of 0.80
• Mirror area of 0.588.4
• Results are near those used in all earlier EIS
  sensitivity calculations

3
EIS Effective Area Curves
4
EIS Effective Area Data

• All data files used to compute the effective area
  are in the EIS SolarSoft directory
  SSW_EIS/response
• All data files are text, with -delimited
  comments at beginning
• Read using data rd_tfile(file, /nocom, /auto,
  /conv)
• Each data file has a three digit extensionhigher
  numbers are newer, so highest number of each file
  should be considered current
• Key files are
• EIS_EffArea_A.001 and EIS_EffArea_B.001
• Procedure for reading effective area files will
  be placed in SSW_EIS/idl/cal and will default to
  taking highest version number of area files
• Procedures for using emission measure curves and
  Chianti data to generate spectra for planning
  purposes under development

5
Modeling EIS

• Using preliminary sensitivity information, have
  modeled EIS detectors
• Model uses a TRACE 195 Angstrom image to
  interpolate between quiet Sun and active region
  differential emission measure curves
• For each location in the TRACE image, model
  computes an emission measure and uses that to
  synthesize the spectrum along the EIS slit
• Thermal, nonthermal, and instrumental broadening
  included
• Includes Poisson statistics on number of arriving
  photons and converts to photoelectrons and then
  DN
• Adds a pedestalcurrently 100 electronsand a
  normal distribution of read noise with a standard
  deviation of 6 electrons
• Will be updating to include random Doppler shifts
  and other delights
• Data and detailed description at
  http//tcrb.nrl.navy.mil/mariska/eismod

6
EIS Model Sample Output
7
EIS Model Implications

• Large difference in count rates between the two
  detectors
• For active regions and a 10 s integration, the
  model predicts
• 10,000 to 14,000 DN for Fe XII
• 1,500 DN for Fe XV
• Observing strategy will need to carefully
  consider how to handle these differences