Goal
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We discuss the evolution of CTI and its impact on spectral resolution for X-ray CCDs in different orbital environments. We specifically prepare
models of the energy scale and resolution as a function of the background, CCD type (FI vs. BI), and application of charge injection, considering
energies spanning the CCD range.
Outline
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- about the instruments
- first describe each separately (label CCDIDs)
- then similarities/differences between ACIS/XIS that impact CTI (just the instruments and operation, no environment yet) in a table and summarize in text
- initial pre-launch CTI, ACIS BI > XIS BI, XIS FI > ACIS FI
- Transfer speeds, fast transfer (image-to-framestore) serial transfer not the same
- Frame time, 3.2s vs 8s
- Focal plane temperature, -90C vs -120C
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- Measuring CTI, ACIS vs XIS (methodology)
- ACIS, fit center pixel pulseheight vs ccdy/ccdx (binning/fitting details too)
- XIS, fit good grades summed pulseheight from top cal source corners
- (should we process ACIS the same way as XIS for comparison? only use center pixels?)
- only use Mn K alpha
- include
checker-flag CTI measurement for XIS, SCI-off (Ozawa 2009)
- CTI evolution, plots of measured CTI vs time
- for ACIS, apply corrections for temperature and sacrificial charge
- not done for XIS; temperature is stable, background is integrated over 1 day = 16 orbits
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- comparison of a celestial source
- E0102
- has been observed extensively over time with ACIS and XIS
- low energy lines very different from Mn K alpha
- mostly on ACIS-S3
- Perseus, other clusters
- check ACIS time coverage, XIS and ACIS roll angles
- Fe line centroid changes with kT, location in cluster
- E0102