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    User name D. Parno

    Log entry time 12:43:55 on August 21, 2009

    Entry number 285135

    This entry is a followup to: 285129

    keyword=VtoF Card #3 in Compton DAQ

    Yesterday, we took some measurements of the VtoF card output channels in the Compton DAQ. Over the years it has become unclear which channel corresponds to which signal. During these short runs, there was no beam in the hall, but we were flipping the cavity. Thus signals relating to beam characteristics will be junk, but signals relating to the cavity will not be.

    Here's a summary of what we found for the eight output channels of VtoF Card #3 (the rightmost one in the crate), with time traces below. The channels are numbered here as they are on the face of the card; that is, 1-indexed.

    Channel 1: A very small amount of scatter around a line. The scatter is so small that you can see structure due to the fact that the number of counts in the scaler must be an integer.

    Channel 2: Cavity signal, with spikes correlated to cavity on/off changes.

    Channel 3-5 (not shown): Identically zero, no scatter. Unplugged at other end?

    Channel 6 (shown alone and with Channel 2): Cavity signal, probably quad sum position monitor before cavity entrance.

    Channel 7: We believe this is the cavity power signal, probably from the transmission photodiode since it appears to work for both laser polarization states. However, the known cavity power difference (~10%) between right and left polarization states is not reflected here (it's more of a 1% drop). This may be due to photodiode saturation. However, even if we can't quite trust the power measurements at the top of the scale, we *can* use this to determine in real-time whether the cavity is on or off, which is exactly what we need.

    Channel 8 (shown full-scale and zoomed-in): Strange structure on a scale of about 100 MPS, or 3.3 seconds, for the beginning of the run.

    A copy of this log entry has been emailed to: gbfranklin@cmu.edu, nanda, bquinn@cmu.edu, mfriend@andrew.cmu.edu

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