Charge Transfer In-efficiencies (CTIs) of ACIS CCDs are graudually changing with time, and it is essential to know how the degradation progresses. Since CTI are strongly depending on focal temperature, to see the degradation, it is better to remove the temperature dependency of CTI observations. MIT/ACIS team suggested that there is a (close to) linear relation between a focal plane temperature and CTI, and the CTI temperature dependency can be easily corrected (MIT ACIS Memo #204). Related memos and detail analysis can be found at ACIS CTI @-120C page maintained by Catherine E. Grant at MIT.
The following three plots show time trends of monthly averaged CTI of imaging CCDs, spectral CCDS, and backside illuminated CCDs computed using Mn Kα line. CTIs are averaged over four quadrants of each CCD. The CTI values used here are corrected for temperature dependency and detrended (see How CTI are computed?), except those for the backside illuminated CCDs. The latters are temeprature dependency corrected, but not detrended. To see a full size plot, please click the plot.
Imaging CCDs | Spectral CCDs |
---|---|
Back Side CCDs | |
The following table lists links to individual CCD/Quad CTI trend plots computed using Mn Kα line. Each page shows five different CTI trend plots. From the top to the bottom, they are:
The third case is the cleanest estimation, but we lose many data points, especially after year 2012. The fourth/fifth cases keep all data points, but they may introduce errors from temperature corrections. Two trending lines are fitted on each plot. The dividing point are slightly different from that of the combined data. For the imaging and the spectral CCDs, the division point is year 2011 and year 2009 for the backsdie CCDs.
CTI data are far more scattered after year 2012 and extreme data points are dropped before fitting the trending lines. These scatters were introduced because less and less time, the focal tempearture stays at or around 119.7C and fractuates widely.
CCD0 | CCD1 | CCD2 | CCD3 | CCD4 | CCD5 | CCD6 | CCD7 | CCD8 | CCD9 |
---|---|---|---|---|---|---|---|---|---|
Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 |
Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 |
Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 |
Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 |
The following table shows the links to individual CCD/Quad plots similar to above, but the data are detrended by dtracning drop amp effect. See How CTI are computed? section for details. Backside Illuminated CCDs 5 and 7 are not detrended and not included.
CCD0 | CCD1 | CCD2 | CCD3 | CCD4 | CCD5 | CCD6 | CCD7 | CCD8 | CCD9 |
---|---|---|---|---|---|---|---|---|---|
Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 |
Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 |
Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 |
Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 |
Although they are not clean as CTI computed from Mn Kα line, we also computed CTI based on Al Kα and Ti Kα.
Line | CCD0 | CCD1 | CCD2 | CCD3 | CCD4 | CCD5 | CCD6 | CCD7 | CCD8 | CCD9 | |
---|---|---|---|---|---|---|---|---|---|---|---|
Al K alpha | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | |
Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | ||
Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | ||
Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | ||
Line | CCD0 | CCD1 | CCD2 | CCD3 | CCD4 | CCD5 | CCD6 | CCD7 | CCD8 | CCD9 | |
Ti K alpha | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | |
Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | ||
Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | ||
Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 |
Line | CCD0 | CCD1 | CCD2 | CCD3 | CCD4 | CCD5 | CCD6 | CCD7 | CCD8 | CCD9 | |
---|---|---|---|---|---|---|---|---|---|---|---|
Al K alpha | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | |
Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | ||
Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | ||
Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | ||
Line | CCD0 | CCD1 | CCD2 | CCD3 | CCD4 | CCD5 | CCD6 | CCD7 | CCD8 | CCD9 | |
Ti K alpha | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | Quad0 | |
Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | Quad1 | ||
Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | Quad2 | ||
Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 | Quad3 |
The following links show CTI change rate per year of each quadrant and those of averaged cases are listed.
Al K alpha | CCD 0 | CCD 1 | CCD 2 | CCD 3 | CCD 4 | CCD 5 | CCD 6 | CCD 7 | CCD 8 | CCD 9 |
---|---|---|---|---|---|---|---|---|---|---|
Mn K alpha | CCD 0 | CCD 1 | CCD 2 | CCD 3 | CCD 4 | CCD 5 | CCD 6 | CCD 7 | CCD 8 | CCD 9 |
Ti K alpha | CCD 0 | CCD 1 | CCD 2 | CCD 3 | CCD 4 | CCD 5 | CCD 6 | CCD 7 | CCD 8 | CCD 9 |
CTIs are computed in the following steps:
If you have any questions about this page, contact swolk@cfa.harvard.edu.
Last Update: Sep 24, 2021.