Vernier scans were taken during fill 15255 (runs 12060050, 52, 53, and 54). Here are the BBC coincidence rates during that fill (vs. time in seconds from an arbitrary zero), zoomed in to just those runs, which are highlighted in blue, except for run 12060053 which is in red. The latter is the only run which shows significant decrease in coincidence rates:

Zooming in on just the run with varying BBC coincidence rates and using log10 scale, we can see that the coincidence rates drop by 2 orders of magnitude during the Vernier scan (from 1 MHz down to 10 kHz):

Here are the ratios of the following quantities divided by the BBC coincidence rate during this one run:

• top left : BBC east singles
• top right : BBC west singles
• bottom left : BBC yellow background
• bottom right : BBC blue background

It appears that all of these ratios increase by a factor of ~3-4 during these dips in coincidence rates. In the context of achieving a low luminosity operation, this could be an acceptable sacrifice for a factor of ~100 decrease in luminosity.

-Gene