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Re: Cross talk
Hi Yves,
I looked at the plots you just posted and I have a few questions.
For crosstalk, you are plotting the peak amplitude distributions for the
whole data run, I believe. You need to compare the peak amplitudes on an
event-by-event basis, e.g., compare peak amplitude on ch1 to ch2 for
event 1, and repeat for the other events. The best way to do this is to
get a scatter plot. Applying a fit to the scatter plot, should yield a
straight horizontal line (or vertical) [meaning independence between
channels] for zero crosstalk or a line with a slope for any crosstalk.
The slope is the crosstalk, say volts in ch1 to volts in ch2. You will
need a plot for each channel adjacent to the straw with the source.
For the raw ADC data, one event per plot, it seems that the noise is
very low and that is a good thing. Now, when you take this data and plot
the amplitude distribution do you apply a threshold cut? For instance, I
see that the baseline or pedestal is at about ADC channel 650 - do you
exclude all the samples below this value? It would also be interesting
to see how the amplitude distributions change with different threshold
cuts.
For the "energy" plots, it seems that these plots follow the same trend
as those plots under "Different-HV" which is good. But I still don't
understand why the shape - it should look like a Poisson distribution or
more properly a Landau distribution. What I see is that the low level
amplitude tail gets proportionally smaller with increasing HV, as a
result of perhaps higher S/N ratio. This may be artificial, of course,
due to higher occurrence of limited streamer pulses or higher gain (more
signals above the trigger threshold).
It would be nice if you could form a trigger by using the coincidence of
two overlapping straws, as I mentioned in a previous email.
Regards,
Fernando
Yves Van Haarlem wrote:
> Hi All,
>
> As a follow up from the meeting this after noon. I posted some
> peak-amplitude spectra on the wiki concerning cross talk. One can see
> that there is some measurable electronic cross talk between adjacent
> channels on the HV-board.
>
> http://www.jlab.org/Hall-D/software/wiki/index.php/ASIC_design_optimizations#Cross_talk
>
>
>
> Cheers,
> Yves
>
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