We (TB, KD) are convinced that the Analog Adders do not behave
properly.
a) their output is non linear. Sending 3 equal pulses of 300 mV each
produced about 300, 450, 550 mV output
b) They actually always send a pulse, even for large inputs ( >> 400 mV)
such as those coming from tube noise.
In this scenario is very difficult to gain match. We throw out the
adders and should hope/wait for a liner device and start in earnest next
week. Nevertherless we could start gain matching the tubes.
Unfortunately, attenuating the fiber signal by "loosening" the connection
does not really work that well. So we used 6db analog attenuators. We
triggered on the pin diode and looked at signal on the scope, changing HV
through the serial port while the wc people take data.
For RC0, we tweaked channels (cables) number 81,82,83 (corresponing to
the first 3 HV channels) such that their analog out (through the
attenuator) were all - 295 mV. The voltages are documented in the "blast
scintillator project" starting from page 100.
Today and over the weekend we should continue with the other tubes and
then with the other boxes.
The fine tuning will be done looking at the ADC spectra (for signals of
about 300 mV like the attenuated flasher) for runs trigger on the pin
diode only. I am looking into finding a sufficient number of these
attenuators (6db, white pomona type) and in getting the passive delay
boxes done.
-- t
________________________________________________________________________________
Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
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