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6 Conclusions

In order to efficiently use the limited time allotted for calibration of flight devices for the ACIS instrument, we have developed a screening protocol that measures device-level performance parameters. These measurements are then compared with the minimum acceptance criteria, allowing an informed decision to be made on whether to subject a CCD to a full calibration.

Most of the screened devices easily meet the acceptance criteria. On average a CCD will have RMS noise of 2-4 e, CTI below , and spectral resolutions within 10 % of the theoretical limits. Given the uniformly high quality of the FI CCDs, we find that noise, low-energy (525 eV) spectral resolution and cosmetics are the most useful parameters for ranking devices.