Re: question on the CDC/ASIC doc

[Yves Van Haarlem <yvhaarle@ernest.phys.cmu.edu>]

Hi Gerard,

Some answers:

> Hi Curtis, Yves,
> 	I'm reading the freshly posted document on your CDC/ASIC studies. 
> _Now_ I understand (I think) that the sharp cutoff in for instance fig 2a/2b 
> are the trigger threshold. But then _what_ is all that stuff below threshold? 
> Are you not triggering only on the channel of interest here?
I am triggering on the straw of interest only using a discriminator. The 
sharp cut off is indeed the threshold - what the stuff below the threshold 
is: I thought it were double nim pulses coming from the discriminator but 
now that I think of it: the time distance between them is most likely too 
short to cause this -> I have to look into this.


> If you're not 
> triggering only on the channel of interest, it would probably be interesting 
> now to see the total charge (integral) spectrum when the trigger is changed 
> to be only on the channel of interest. (For some reason you've left off the 
> total charge spectrum from the document?)
The integrated signal plots exists so they could be added but as we tried 
to calculated the straw's output charge we were more interested in the 
peak-amplitude.



> 2, simply the highest sample point, or is it based on a fit to the waveform 
> around the peak? In the former case, of course it suffers from the _fact_ 
> that a sample point might be on the actual waveform peak, or the peak might 
> straddle two sample points, this could make a 10-30% random error depending 
> on the relative time of the peak and the sample clock. [This is another 
> reason why it might be better to concentrate on the total charge spectrum 
> instead of the peak voltage spectrum in figuring the gains. At least, in my 
> opinion.]
It is the highest sample point - no fit was made.


Cheers,
 	Yves