Log entry time 10:54:38 on December 04, 2011

Entry number 242336

Please read the instructions for how to change the Half-wave plate properly before you request MCC to change the IHWP. Instructions can be found at Wiki, How-to-IHWP

Following these instrctions are very important and actually very simple. You only have to do,

1. Coordinate the IHWP change request with other Halls, as appropriate
2. Stop the current run in the CODA setup (Qweak, Compton, and injector).
3. Phone MCC and ask them to change the IHWP; check the control screen to confirm that the IHWP is changed to the new setting.
4. In a fresh cdaql5 terminal call the script,
   
   1. FlipPCValues
      
5. Log the output of the FlipPCValues script. (cc rakithab)
   
6. Wait about 10 min and watch the strip-charts to verify that the charge asymmetry is converging to ~0 within about 10 ppm
   
7. If the run has large charge asymmetry ( >100ppm ) in the beginning, end the run in CODA, and flag it as "bad" in the good_for_GUI. Add a comment as Transition run , and Start a new run.
   

I would appreciate if anyone can comment on any difficulties to follow these instructions and I will change them to make it more clear.

FYI

The reason I'm emphasizing the procedure is that if we don't run the script properly, the RHWP (Rotatable Half Wave Plate) setting and nominal PC (Pockels Cell) voltages get screw up and we will end up getting large position differences and charge asymmetries.

As I happened to realized that one complete slug of data were taken with the wrong RHWP and nominal PC settings due to not following these instructions.