Re: Gluex doc 1131: response function

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

Hall D Electronics:

Hi Fernando,

Thanks for the information. The step function goes over a 
capacitor into the preAmp, so one could consider it a delta function. I 
would not concider it urgent at all, it would be nice to compare to 
see if the rise time of that step function plays a big role.

Cheers,
 	Yves

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On Tue, 21 Oct 2008, Fernando J. Barbosa wrote:

> 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
>>
>>                           /--------------------------------
>>                          /   Yves Van Haarlem
>>        _--~~--_         /
>>      /~/_|  |_\~\      /      Carnegie Mellon University
>>     |____________|    /        Department of Physics
>>     |[][][][][][]|:= /          Wean Hall room 8404
>>   __| __         |__ \            Pittsburgh, PA 15213
>>  |  ||. |   ==   |  | \           USA
>> (|  ||__|   ==   |  |) \
>>  |  |[] []  ==   |  |   \           Tel.:   +1 412 268-6949
>>  |  |____________|  |    \                  +1 412 641-9252
>>  /__\            /__\     \          Fax.: +1 412 681-0648
>>   ~~              ~~       \-----------------------------------
>