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A picture of the IOC screens when the camera is working in full-frame mode:

Single-Photon Mode Thoughts

From an email thread with RIX scientists on July 9, 2021:

Executive summary: now that you’ve set the preamp gain to 4 (we think you did that today, following Matt’s advice) we think you’re running with the same settings we used for sxrx30416 run 83, as best we can tell.  Note that the manual describes an EM (electron-multiplying) gain setting that is useful for single photon counting that we never used in LCLS1.
Details: Dan and I looked at the settings from sxrx30416 run 83 vs. the current running.  These are the settings we had:

In [2]: andorconfig.highCapacity()
Out[2]: 0

(This is Alex’s question in his most recent message) This is not settable in the IOC, but Dan looked and it defaults to 0 now, which we think is right (highCapacity=1 corresponds to large dynamic range, which you don’t want for single-photon regime)

In [3]: andorconfig.readoutSpeedIndex()
Out[3]: 0

This corresponds to 3MHz which is what you are running now, and it is correct: this increases the readout speed so we can run at 120Hz, but also increases noise.

In [4]: andorconfig.gainIndex()
Out[4]: 2

This “gain enum index” corresponds to the factor 4 you have just set (today) for the highest preamp gain, as Matt suggested.

The only other feature you can consider trying in the future is the EM (electron-multiplying) gain.  This feels to us like it comes before the preamp and creates an electron-avalanche controlled by a voltage.  It was never used in LCLS1, but the manual talks quite a bit about using it for single-photon counting.  We don’t have experience with it, so there may be a learning curve, but it looks like it is intended specifically for low signals.  A warning:  the manual talks about “premature aging” of the camera if the signals get too large in EM Gain mode.