Improvements to the WFC Loral CCDs
From: Derek Ives
Date: 8 Nov 1997
suffered from horrible vertical streaking in one half of the CCD. This is a function of upper V levels - reducing V+ fixes the problem but also reduces the full well significantly. Have compromise in voltages to give low streaking levels (flat field out).
Higher full well for CCD2 is is now approximately 45kADU in T-speed.
not touched but the QE nows seems to be corrected and flat across the CCD. This was not only a problem in the UV but also in the red, implying that it was probably contamination (hydrogen outgassing). The warm bake -out and dry air fill and long pump down seems to cure this.
This originally suffered from smearing from the CCD centre up to the top at signal levels of approx 25kADU in T-speed. This was probably due to inadequate upper clock levels. I remember when I was commissioning that this CCD suffered from horrendous charge injection, thus I lowered the levels. I am now running tri-level clocking which ensures that the CI is only a few ADU but that the smearing problem is now much less of a problem.
CCD4 is now useable up to 55kADU at least in T_speed.