Plot of CTI correction factor against Time of CCD 7
This short memo investigates whether temperature-CTI correction factor evolves with time.
Data were gathered in the following way;
The Mn K alpha data between Feb 2000 and Feb 2004 were obtained, The data were divided into 4 month period chunk (total 11 periods). Each period contains about 100 data points.
We excluded the data colder than -119.6 C. This is because there are far too many data points clustered in that range, and skewed fitting significantly. This step reduced the number of data to 2/3; for the first two periods, the number of the data were down to 1/4. This is because most calibration observations were done at or colder then -199.6 C during these two periods.
There are also many out-layers due to short integration time, and other problems.
We dropped these data by following steps.
First, a mean and a standard deviation for CTI are
computed, then the data points outside of two sigma away from the mean were
dropped.
Second, a linear fit was made for the remaining data. Drop any data points outside
of two sigma from the fitting line. Then the final fitting was done.
An example fit are shown below (DOM around 1107, CCD6 in 10**4).
All other plots
The fitting results for CCD6 and CCD7 were shown in the tables and figures. The date are in DOM, and the correction factors are in 10**4 CTI/degree C.
mn_ccd6 Date Quad 0 Quad 1 Quad 2 Quad 3 255 0.058 +/- 0.018 0.057 +/- 0.043 0.007 +/- 0.025 0.063 +/- 0.030 377 0.053 +/- 0.003 0.054 +/- 0.005 0.052 +/- 0.010 0.063 +/- 0.016 499 0.037 +/- 0.010 0.023 +/- 0.011 0.050 +/- 0.011 0.032 +/- 0.011 530 0.072 +/- 0.011 0.052 +/- 0.039 0.045 +/- 0.012 0.061 +/- 0.012 742 0.039 +/- 0.003 0.037 +/- 0.012 0.050 +/- 0.004 0.042 +/- 0.003 864 0.044 +/- 0.006 0.041 +/- 0.008 0.046 +/- 0.005 0.041 +/- 0.005 985 0.040 +/- 0.008 0.067 +/- 0.011 0.036 +/- 0.009 0.030 +/- 0.006 1107 0.047 +/- 0.004 0.044 +/- 0.008 0.059 +/- 0.005 0.048 +/- 0.005 1229 0.047 +/- 0.004 0.050 +/- 0.004 0.048 +/- 0.004 0.041 +/- 0.004 1350 0.053 +/- 0.005 0.053 +/- 0.004 0.059 +/- 0.004 0.051 +/- 0.005 1472 0.047 +/- 0.003 0.056 +/- 0.005 0.055 +/- 0.003 0.057 +/- 0.003 1592 0.037 +/- 0.004 0.033 +/- 0.006 0.042 +/- 0.005 0.043 +/- 0.006 mn_ccd7 Date Quad 0 Quad 1 Quad 2 Quad 3 255 -0.036 +/- 0.014 0.006 +/- 0.013 0.008 +/- 0.011 -0.011 +/- 0.012 377 -0.003 +/- 0.001 -0.004 +/- 0.001 -0.002 +/- 0.001 -0.004 +/- 0.002 499 0.002 +/- 0.007 0.001 +/- 0.005 -0.007 +/- 0.004 -0.006 +/- 0.005 530 -0.002 +/- 0.006 0.005 +/- 0.007 0.005 +/- 0.005 -0.002 +/- 0.006 742 -0.003 +/- 0.001 -0.003 +/- 0.002 -0.004 +/- 0.001 -0.000 +/- 0.001 864 -0.003 +/- 0.003 -0.005 +/- 0.003 0.001 +/- 0.003 0.005 +/- 0.003 985 -0.000 +/- 0.004 -0.005 +/- 0.003 -0.006 +/- 0.003 0.000 +/- 0.003 1107 0.001 +/- 0.001 -0.001 +/- 0.001 -0.000 +/- 0.001 -0.002 +/- 0.001 1229 -0.001 +/- 0.002 -0.000 +/- 0.002 -0.002 +/- 0.002 -0.002 +/- 0.002 1350 0.001 +/- 0.002 -0.001 +/- 0.002 -0.003 +/- 0.002 -0.004 +/- 0.002 1472 -0.003 +/- 0.001 -0.003 +/- 0.001 -0.002 +/- 0.001 -0.000 +/- 0.001 1592 -0.004 +/- 0.003 -0.006 +/- 0.003 -0.005 +/- 0.002 -0.007 +/- 0.002
As we can see the plots, there are no strong time dependency of the correction factors. At this stage, it seems permissible to use the current correction factor for the future observations.