Dan, Fil

We've modified the QPD transimpedance board for the ASC-AS_C QPD so that the SUM output that's used for the fast shutter triggering no longer saturates when the DRMI is locked at 10W.  We swapped R23 from a 20k ohm resistor to 1.24k ohm; this change reduces the amplification of the SUM output by 16x and brings the board (S1301506) into agreement with version 6 of the schematic (D1001974).  [NB: with the DRMI locked at 10W we observed ~3.3mW on ASC-AS_C, or ~130mW into HAM6; this is dominated by the 45MHz sidebands and it roughly aligns with what's expected at 10W (65% transmission of 45MHz sidebands to the AS port, Gamma2=0.28 gives 112mW into HAM6 -- probably we are getting some extra light from higher order modes).] 

We also modified the controller box for the HAM6 shutters to have the correct output polarity.  The output from the box (S1203609) was previously +5V on a trigger condition (shutter CLOSED) and 0V on a nominal condition (shutter OPEN).  We implemented the version 2 modifications to the board (D1102312), namely connecting pin1 of U8A (the OUTN signal) to the front-panel OUT connector, and connected P2 pin1 (the OUT signal, opposite polarity from OUTN) to the J1 pin10 slot on the D880C card.  Note that we only modified channel1 in this box, we left channel2 as we found it.

Now, the SUM output from ASC-AS_C should not exceed 1V when the DRMI is locked (unless we mode hop?), and the controller output will be logic-low upon a trigger condition.  The trigger output has been connected to the OMC PZT driver board, we'll commission the PZT shutter function soon.  (Zach's results from L1 are here.)

I've verified that the trigger function works from the control room via the Beckhoff interface.  The code for this function may need to be modified to accomodate the toaster shutter, which has its own Beckhoff interface and will record a fault condition if the input from the shutter controller is logic-low for too long.  Currently the shutter controller will not reset the trigger logic without user intervention; it might be a good idea for the logic signal to reset itself after the PD input has passed below threshold, and have the fast shutter state remain closed (i.e., toast up) until a user/guardian/script opens it.