ACIS Preliminary Calibration Report

Outline of MIT Contributions

The ACIS Preliminary Calibration Report will be issued in September 1997. The following outline summarizes the material MIT's ACIS group intends to contribute to the report.

A. Basic CCD model components and measurement strategy
        gate structure/channel stops
        depletion depth
        branching ratios

B. Overview of measurements CCD
        Bessy response function and QE
        CSR spectral response fucntion
        CSR relative and absolute QE
        XRCF response function and QE

C. Energy scale and spectral redistribution function
        1) energy scale linearity, T dependence,accuracy
        2) fwhm vs energy
        3) escape & fl peak amplitudes
        4) concerns/present uncertaintie(tail)

D. Pileup for diffuse source measurements
        1) Model
        2) Results: cross-sections vs E
        3) Use in spectral fitting

E. Subpixel Structure and Mesh Experiments
        1) Motive: constrain channel stops
        2) Approach: description of mesh experiment
        3) First results
        4) prospects for sub-pixel resolution

F. Absolute QE measurements
        1 Synchroton
         a) Experiment and synchrotron
         b) Analysis(ccd model assumptions)
         c) pileup effects
         d) Results/accuracy (for each ref. detector)
         e) Accuracy: normalization and amplitude
         f) Reproducibility
        2. Branching ratio technique for high-energy qe
         a) summary of technique
         b) estimated accuracy
         c) comparison to BESSY WLS
        3. XRCF flat field measurements of absolute efficiency
         a) hst measurements vs ssd in xrcf flat field
         b) telem measurements vs ssd
        4. EXAFS in CCD structure
         a) Measurement method
         b) Sample results 
         c) Effect on continuum spectral anlaysis

G. Relative Efficiency Measurements
        1) measurement technique at CSR
        2) analysis assumptions, (detector model)
        3) pileup corrections
        4) Results on raw efficiency differences
        5) Accuracy of relative measurements
        6) Relative efficiency at XRCF f-f (telemetry only!)

H.  High-speed tap vs. telemetry  

I. Effects of instrument configuration on calibration
        1) parallel clock levels:
        2) clocking modes:
                improved resolution in 100-row-subarray (?)
                reduced h.e. efficiency in cc mode
        3) Impact of Grade selection

J .Background
        1) background counting rate at mit vs split threshold (bi vs fi)
        2) results at xrcf
        3) expected rate on orbit.

K. Status of model development
        1) Ways to compare simulation and observation
        2) tail physics
        3) BI physics
        4) Trap modelling
        5) areas for future work

L. Response Function Generation

MIT ACIS Home Page MIT's ACIS CCD Group PSU ACIS Home Page