RE: receiver/shaper board on the way; my travel

["Visser, Gerard" <gvisser@indiana.edu>]

Hi Simon,
  I saw your logbook posting #283, looks reasonable. Seems the tail cancellation is about right, and the amplitude distribution also turned out ok...
  Regarding that, can you confirm or correct, is it still +1650, -300 V that you used for this? (Maybe add a note about it in that log entry...) And also, that the channel of my board you used for these measurements is not channel 8, the one with the yellow tape on the lemo connector? That channel is (temporarily) wired for 5X more gain which is presumably about right for the cathodes. [Please try the board on cathodes and report how it looks for ch8 and for some other channel, when you get a chance.]
  Would be good to hear how it looks for timing, you now have about ~20-25 ns risetime on the signals. We can make it longer - but there are tradeoffs (effect of later ionization clusters, i.e., no longer "leading edge" timing; rate & pileup issues).
  I have been reviewing some earlier log entries and have two questions: First, I see in a picture (old one, log #110), plain round flat cable connected to the preamp outputs... You really really should be using twisted pair cable, i.e., twist-n-flat. Preferably loose pair (laminated at the flats only) shielded round twist-n-flat. Non-twisted pair cable might result in crosstalk & feedback. I am concerned by the wacky ringing in the ADC trace seen at the bottom of your log entry 283. Certainly can be eliminated, also certainly must be eliminated for reasonable results at high rate. We can investigate that when I'm there - but for now please first find or procure the appropriate twist-n-flat cable, if you're presently still using the non-twisted-pair version. Second question is, you are running the SIS3320 at a 210 MHz sample rate? Unfortunately I don't have the manual here at hand, but I thought it went up to 200 only? Anyway, it would probably be best to back off the sample rate to 200 MHz (or even a bit lower). There may be performance issues if the sample rate is maxxed out, and anyway this is well beyond what we can afford for the real ADC, I think. Are you sampling from the board's internal clock or is there an external sample clock source connected?
  Anyway, thanks for getting the receiver/shaper in there so quickly. I look forward to seeing you in a little over a week.
 
  Gerard
 
p.s. Opinions about whether the second board should be set up for anodes or cathodes gain? Probably cathodes, I guess - but please let me know soon.

________________________________

From: Simon Taylor [mailto:staylor@jlab.org]
Sent: Fri 1/19/2007 2:29 PM
To: Visser, Gerard
Subject: Re: receiver/shaper board on the way; my travel



Hi, Gerard.

I have the board and have installed it in my VME crate. I have started
looking at signals on the scope and with the DAQ -- so far so good.

Simon