Re: Gluex doc 1131: response function

["Fernando J. Barbosa" <barbosa@jlab.org>]

Hi Yves,

My simulations only took the preamp into account, so I did not include 
the cable nor the shaper. The response in figure 6 is for an impulse 
source. A step function would provide the same shape as the first 
portion of your scope, or my simulation, picture but with a very long 
tail (almost flat) because of the long RC time constant (220 us) of the 
HV cap and resistor. The shaper, of course, removes this tail and gives 
you a shape like the one you show.

If this is really needed, I can add the shaper functionality to my 
simulations but it may take a while because of other priorities that I have.

Regards,
Fernando




Yves Van Haarlem wrote:
> Hi Fernando,
>
> By looking at figure 6 in your document and comparing it with the 
> response function I measured, I see that I have the same shape but in 
> my cased the response is three times as long. I checked my input 
> signal again (which is a step function and is shown in 
> http://www.jlab.org/Hall-D/software/wiki/index.php/Electronic_chain_simulation 
> )
>
> The rise time of this step is 12.5-20~ns - I think this can cause a 
> response function that is too long. This has an implication for how we 
> we determine the gas-gain and on how we simulate the CDC response.
>
> Would it be easy for you to provide me with an (eg. ascii) file 
> containing your response function when you inject a step function in 
> the CDC HV-board (a sample/ns) in your simulation? - guess you have to 
> add the HV board-circuit. Also, is (Gerard's) shaper included in the 
> circuit in figure 4 or is this just the pre-amp?
>
> Thanks a lot!
>
> Cheers,
>     Yves
>
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