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Weekly Health Check: WFI CCD #53

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General Information

The detector system for scientific exposures is an array of 2x4 CCD44 chips by EEV which each have 2kx4k 15-micron pixels. Further details on the CCDs can be found in the WFI User Manual.

* Derivatives
* Standard CCD Test
* Long CCD Test



Time Evolution

The below plot shows the variation of the bias level, standard light-source (note that often a beta-light is used which, due to radioactive decay, will fade. It is also possible that the phosphor can be poisoned, but our data show no evidence for such an effect), gain, read-out noise, shutter error, and linearity error as a function of time. The values for the bias, gain and read-out noise are plotted along with the associated measurement error. The blue dashed line in the plots shows the mean value of all the points, while the dotted blue line shows the standard deviation of this distribution. The blue and red points in the bottom plot show the maximum deviations in a positive and negative sense wrt the least-squares fit of the linearity data. Plotted vertically on the bottom of the graph is the date (dd/mm) on which the test was made.

[Click here to download ps file]

For printing, the above plot is also available in postscript format . The raw data can also be viewed in a tabular format.




Standard CCD Test

Below we show the most recent test.



*** MIDAS logfile (05SEPpl1.3) *** Sa, 04 Apr 2009   16:30:21   Page 1
 
 
*** MIDAS logfile (vers. 05SEPpl1.3) *** Sa, 04 Apr 2009   16:30:37   Page 2
 
     ==========================================================
     SUMMARY STANDARD TEST CCD#53 TAKEN ON 090404 IN norm MODE
     ==========================================================
 
      BIAS
      ====
 
      5 biases at start test: average = 160.60 stddev =   2.82
 
      There were 0 hot pixels/columns detected
 
 
      TRANSFER FUNCTION AND LINEARITY DATA
      ====================================
 
  Table : Std_norm_53_090404 
 Sequence Exp_tim1  Med_cnt1  Med_cnt2  Variance  Frc_cnt1  Frc_cnt2  el_adu1  
 -------- --------- --------- --------- --------- --------- --------- ---------
        1      2.09     284.6     284.3     159.7      0.28      0.24      1.78
        2      3.99     546.3     546.1     295.5      0.09      0.09      1.85
        3      6.99     954.1     954.1     534.8     -0.55     -0.55      1.78
        4     13.99    1913.2    1913.4    1035.4     -0.60     -0.59      1.85
        5     27.99    3833.0    3833.5    2059.9     -0.58     -0.56      1.86
        6     41.99    5756.6    5756.1    3055.3     -0.51     -0.52      1.88
        7     62.99    8647.4    8647.1    4550.2     -0.40     -0.40      1.90
        8     83.99   11546.1   11546.8    6061.0     -0.28     -0.27      1.90
        9    104.99   14451.3   14452.8    7635.0     -0.16     -0.14      1.89
       10    139.99   19308.9   19309.3   10062.8      0.04      0.05      1.92
       11    174.99   24180.2   24178.7   12482.0      0.22      0.21      1.94
       12    219.99   30458.4   30459.2   15810.2      0.41      0.42      1.93
       13    259.99   36052.5   36053.9   18655.5      0.57      0.57      1.93
       14    299.99   41658.2   41656.7   21036.6      0.71      0.71      1.98
       15    309.99   43058.4   43055.3   21861.1      0.74      0.73      1.97
 -------- --------- --------- --------- --------- --------- --------- ---------
 
      Dynamic range explored: from 559 to 84612 e-
      Average count rate measured: 138 ADU/sec.
 
      CONV. FACTOR AND RON
      ====================
 
      C.Fact =   1.97 +/-   0.01 e-/ADU
 
      RON    =   5.53 +/-   0.03 e- RMS
 
 
      SHUTTER ERROR
      =============
 
 Average shutter error derived from fractional count rate = -0.035 sec
 
 
      LINEARITY ERROR
      ===============
 
 Average linearity error after shutter correct. = + 0.73/-0.59 %
 
 These errors represent maximum deviation in % from the average
 
*** MIDAS logfile (05SEPpl1.3) *** Sa, 04 Apr 2009   16:30:37   Page 3
 
 count rate after correction for shutter delay

In addition, the previous standard tests are available. Click in the table below to access these files.

Standard Tests 1 2 3 4 5 6