Hi Elton, I made a slide which I am attaching. Please check the numbers as I show what a MIP in the chamber corresponds to the charge into the preamp. Regards, Fernando Elton Smith wrote: > Hi Fernando, > > Yesterday during your presentation you showed the dynamic range of the > preamp to saturate at 400 fC. We are a little confused about the range > required. I know that there was quite a bit of discussion at the time the > range was decided, but simple estimates give higher numbers and we need to > know what we are missing. > > Fernando was correct in that the induced signal on the wire on the wire > coming from the electron signal is only about 20% of the avalanch charge > (in the first say 10 ns). Therefore, we obtain the following for a minimum > ionizing track: > > Simon says that the gain of the FDC is about 0.8x10^5. > > assume: 100 ions, 20% of Qtot, Gain=10^5, e=1.6x10^-19. > Signal charge (anode) = 0.2 x 100 x 10^5 x 1.6x10^-19 ~ 300 fC > Signal charge (cathode) ~ 300 fC x 1/2 x 1/4 ~ 40 fC. > > My preliminary (rough) estimate concludes that this should work for the > FDC cathodes. The FDC anodes under the nominal design do not use the > FADCs, but would likely saturate if they do. > > For the CDC, the anode signal will also be used for dE/dx, so a factor of > at least 30 is needed in dynamic range. These would clearly saturate at a > Gain of 10^5, but we might want to run them at lower gain. At G=10^4 > gain, and 30 dynamic range, we get a maximum signal of 900 fC, also > saturating the preamp. > > Comments? What am I doing wrong? > > Thanks, Elton. > > > > > > > Elton Smith > Jefferson Lab MS 12H5 > 12000 Jefferson Ave > Suite # 16 > Newport News, VA 23606 > elton@jlab.org > (757) 269-7625 >
Drift Chamber- signal development.pdf
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