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Operation of the PMT/DAS BD
This will be some subsample of the PMT/DAS BD block diagram from D. Seim. I'mnot sure how to
simplify this and get the important details for this audience. Same problem with the Galvo Bd.
Also, I'm not sure how much of Doug's explanation to include. Therefore, I'm putting almost all of
the text in below and we can talk about how or if it needs to be simplified (rewritten).
HMB
1. The 5 PMT Tubes plug into the PMT/DAS BD itself. The HIGH VOLTAGE POWER SUPPLY feeds power to the HIGH VOLTAGE DIVIDERS. Each PMT has its
own HIGH VOLTAGE DIVIDER whose function is to send the particular high voltage levels to the structures inside the PMTs.
2. The ANODE of each PMT is connected to an individual CURRENT TO VOLTAGE AMPLIFIER, which turns the small current signal from each PMT into a
proportional voltage signal. Each of the voltage signals goes through a PMT GAIN CONTROL D/A CONVERTER. These converters act like volume controls so we
can adjust the signal level coming from each PMT in order to account for gain variances from PMT to PMT.
3. The corrected signals are added together in the SUMMING AMPLIFIER. An OFFSET ADJUSTMENT SIGNAL is added in to "tune out" any "dark current" that may
have accumulated and to compensate for any other offset error in the electronics. The offset signal comes from a pair of D/A CONVERTERS that allow coarse and
fine adjustments.
4. The summed signal is then sent through a LOW PASS FILTER for noise reduction.??do we need the sampling theory stuff here??
1234563 – 12/12/94
OPTICAL Subsystem
9–45
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