May 2001 anneal report for program 8841.

There was an anneal of the CCD on May 1, 2001, 24 days after the previous
anneal on April 7, 2001.  A homogeneous set of data was obtained from
proposal 8841:  The CCD Hot Pixel Annealing.

Previous trends continue.  The growth rate of hot pixels continues within the
range seen for previous months.  The anneal worked very well to get rid of all
new hot pixels, as well as removing some old ones.

1) The number of post-anneal hot pixels has decreased or remained constant at
   all three levels.

   > 0.1 e/s: 17012 pixels on May 1, 2001
   > 1.0 e/s:  3455
   > 10. e/s:   389

   > 0.1 e/s: 17042 pixels on Apr 7, 2001
   > 1.0 e/s:  3473
   > 10. e/s:   389

   > 0.1 e/s: 17151 pixels on Mar 11, 2001
   > 1.0 e/s:  3452
   > 10. e/s:   397

   > 0.1 e/s: 16565 pixels on Feb 10, 2001
   > 1.0 e/s:  3372
   > 10. e/s:   382


2) The *raw* post-anneal dark countrate for this anneal is 0.02608 cts/pixel.
   This compares with 0.02618 cts/pixel on Apr 7, 2001, and 0.02271 cts/pixel 
   a year ago in May 2000. 
   
3) The iterated median count rate (after iterating up to 30 times by
   eliminating pixels +/- 5*sigma) is 0.00414, down from last month.

4) The creation rates for hot pixels over this period were within the normal
   range of fluctuations.

   > 0.1 e/s:  37.3 pixels/day in May 2001 
   > 1.0 e/s:   6.9
   > 10  e/s:   0.2

   > 0.1 e/s:  12.8 pixels/day in Apr 2001 
   > 1.0 e/s:   0.2
   > 10  e/s:  -0.9

   > 0.1 e/s:  53.0 pixels/day in Mar 2001 
   > 1.0 e/s:  10.2
   > 10  e/s:   1.1


   > 0.1 e/s:  61.8 pixels/day in May 2000 
   > 1.0 e/s:   6.9
   > 10  e/s:   0.9


5) The rate at which new hot pixels annealed out was within the normal range of
   fluctuations.

   > 0.1 e/s: 103.5% annealed away in the May 1, 2001 anneal.
   > 1.0 e/s: 111.4%
   > 10  e/s: 100.0%

   > 0.1 e/s: 132.8% annealed away in the Apr 7, 2001 anneal.
   > 1.0 e/s: -425.%
   > 10  e/s:  65.0%

   > 0.1 e/s:  60.5% annealed away in the Mar 11, 2001 anneal.
   > 1.0 e/s:  71.9%
   > 10  e/s:  50.0%


   The usual plots are attached.