Summary of May 19, 2002 work (Lange)
PMT inventory: We have exactly 96 [but
only 94 appear in the original list! DMW] Most of the serial numbers
are intact, so no need to renumber.
- Original PMT inventory 6-6-02:
Located 86 bases. Need to look harder for the rest
Should relabel the bases in some consistent manner.
Ckov patch panel seems to pass through only 1 of the 2 digital
outputs from each the base. So I need to change my hardware
requirements to use BNC instead of ribbon cables - and we will
definitely need discriminators on the digital signals. We don't
have the submillex connectors to redo the patch panel with
both digital outputs.
PMT test test setup in Lab 6 (click on image for better view):
I first ran tests with no source connected. The following plots shown
noise characteristics for two PMTS (28002 and 27084)
and several bases.
Here are plots of the digital output count rate
vs. threshold setting. Nominal HV setting in E852
was -2.5 Volts. (Click on the image for a better view)
The y-axis is presumably determined by the "darkness"
of the dark box.
- There are some differences, but these two PMTs appear
to behave in a similar manner.
- Also I looked at the count rate for a several bases.
One base that I tried did not
properly accept PMTs. One of the connector holes was
- One of the bases looks either broken or
very quiet. I did not have the time to test with
a signal input for this particular base.
- Then I added a light pulser. On the scope
we had very stable large signals. The pulse
height vs. high voltage and a rough
sketch of the signal are shown below (click on image for a
better view). A pulse height of 280 mV @2200 Volts
matches what is in Ed's documentation for the maximum
pulse height (300 mV).
These signals were much broader (in time) than the
noise signals (~1 microsec vs 50 nsec)
I did see some crosstalk between digital and analog
signals. It persisted even when I disconnected the
digital cables outside of the darkbox (leaving only
the short cables from the base to the darkbox patch
- Conclusion: I still have some work to do in order to fully
understand what I see on these PMTs/bases. Once understood
I will test all 96.