Good report. I'm just commenting/questioning/remarking on selected parts.
> Finally, Chris convinced me to throw in Ioannis' suggestion for a
> fix: Ioannis suggested to get rid of the zero-suppresion and use all
> memory (currently split between ADC and TDC words) for ADC
> words. This will double the avaiable time window for digitization,
> in which case a common stop at ~160usec(?) will cover most of our
> acceptance for slow particles. Ed, would something like that be
> doable?
Sorry- the WFD is not a computer. Half the memory is reserved for
timeword/discriminator and half the memory is reserved for FADC data.
Even with zero-suppression off, the timeword/discriminator is written.
This is hardwired.
> That's all for now. Please send your comments/questions/remarks as soon
> as possible.
>
> --Erik
>
> Capacitor in the Fanouts
> ========================
> Work-bench tests we've performed during the last two weeks have
> indicated strange behaviour of the fanout channel that was
> modified with the 1mF cap. This involves reduced pulse amplitude
> and 2mv p-p oscillations; none of them were observed before. We
> believe both have to do with the soldering of the cap and not
> with a systematic effect. As a cross check we plan to check ASAP
This is scary and important. It was hard enough getting the ground
noise down with the ferrite donuts. If uncabling, removing the
fanouts, modifying them and plugging them in is going change the noise
environment, then we have to know ASAP and see if we can correct it.
> the modified channels currently in MACRO. People looking at WFD
> data: notice that channels 3B01-0,3B02-0,3B03-0,3B04-0 have
> already been modified with the 1mF cap on the fanout. In
> addressing the issue of variable WFD stopping scheme, Chris and
> Ioannis looked quite extensively in the maximum pulse output of
> our PMTs. Their measurements show that our PMT bases are not
> capable of providing pulses at the level of ~4V and above for
> more than ~5usecs. This is due to the capacitors at the last
> dynode stages which can not supply the necessary charge in order
> to meet the peak anode current. The PMT output at that level is
> consistent with loss of gain (effectively you lose the last few
> dynodes stages). They've doubled the capacitor value in the last
> dynode chain and they thus managed to see the maximum charge
> delivered by the PMT almost doubled.
Am I to infer you are considering a base change?
Thanks for the update and all the hard work,
Ed