Log entry time 22:12:40 on October 6,2009

Entry number 293541

Tried to establish coincidence runs with lower background.

Electron detector position at 0mm.  


** Run #20161  100uA, ~10 minutes coincidences.  Looks good!

   http://www.jlab.org/~adaq/halog/html/0910_archive/091006183812.html

** Run #20162  100uA, ~1 hour coincidences.  Looks good.

** Run #20163  10uA.  0 coincidences found!



** Run #20164  - run failed, coda hung -  (Went to no prescale [100%] on photon 
and electron, but also raised beam current... led to fifo overfill and hang.)

** Run #20165 short run, all prescale at 100 (means... take all).

Scanned current to get a sense of this "threshold":

** Run #20166  50 uA, found coincidences. (Run 20167 same?) 

** Run #20168  30 uA, found coincidences. 

** Run #20169  20 uA, found coincidences.

** Run #20170  15 uA. Found coincidences.

** Run #20171  12-10 uA. Found coincidences at start, not after current went 
from 12-10uA.

** Run #20172  10 uA.  No coincidences after 10 uA.


Rebooted coda for no particular reason (getting ready for long run) and set 
3-plane trigger to get bump free coincidences.  Should be a factor of 10 lower 
statistics, right?

** Run #20173  15uA, 3-plane edet trigger. Rates unbelievably low, 
            much below 10x reduction in 2-plane edet runs. 

** Run #20174  15uA, 2-plane edet trigger.  Rates TOO LOW!!!!  WTF!?!

** Run #20176  same conditions, try again.  Need I say WTF?!?!

Rather than raise beam current, went to 1-plane coincidence on edet.

** Run #20177  15uA, 1-plane edet trigger.  No coincidences at all.

Tried to reboot coda, had some trouble getting back up.


** Run #20178  back to 100uA. 2 plane coincidence.  Seems fine.

** Run #20179 back to production (photon only) at 100 uA.  

We'll return to get a low-current coincidence after being sure that the DAQ is 
done acting dumb.