Log entry time 08:40:35 on July 05, 2010

Entry number 195310

run 403 was the same configuration as run 402, triggered on R2 in coincidence with MD5. For run 404 the discriminator threshold was dropped from 50 mV to 20 mV. With 10 mV offset and 15 mV single photoelectron peak run 404 should have the maximum possible rate, which was about 4 Hz.

Plots show correlated ADC spectra in both channels of MD5, and ADC software sum. Both correlated spectra have a "pedestal"-like blob of events at channel (410,460). With the higher threshold there's a gap between the pedestal blob and the more obvious events. With the lower threshold the gap is not so obvious in the 2D plot, but the sum light output is well-separated from the pedestal. This was also the case while these detectors were on the test stand in EEL.

Now why there's a pedestal blob at all I don't quite understand, since the trigger requires signal from both of these tubes. Also it'd be interesting to know if there's R2 data in the file that we can correlate with.

Figure 1

Figure 2

Figure 3