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Re: News on CDC noise



Hall D Electronics:

Nice description of your progress. I often  ask people how long their FM 
radio antenna is when describing straw pickup issues and relate that to 
the length of
a straw wire/tube. The preamp (highest BW block) has ~100MHz BW, within 
the FM band. To operate a in proportional mode sensitivity to a small 
number of primaries we want high input sensitivity ~100uV like an FM 
radio.  The shaping stages help but add  gain while reducing the BW to 
~30MHz.   So it is quite important to encase the  straw antennae and 
preamp inputs in a  Faraday shield. Not sure what the sweep time was on 
your scope plots but the HF resonance must have been ~50MHz.    
In the ATLAS TRT barrel, the front end board is perpendicular to the 
direction of the wires and forms part of an RF tight Faraday shield.  We 
use edge plating
on the boards to connect our analog gnd to the detector frame.  
Compression fit copper beryllium RF fingers connect the board to the 
detector support frame on all sides, completing the shield.   In the 
end, the 40MHz digital readout on the other side of the 14 layer board 
causes a +/-1500e threshold shift synchronous
with the 40MHz clock.    
-- Mitch 


Yves Van Haarlem wrote:
> Hall D Electronics:
>
> Hi All,
>
> Today, inspired by Gerard and equipped with his differential probe I 
> continued the noise studies on the CDC and I believe progress in the 
> form of an improvement was made. I put my findings on the CDC-wiki:
>
> http://www.jlab.org/Hall-D/software/wiki/index.php/CDC_06_02_2008#1_News_on_the_noise_issue 
>
>
>
> Cheers,
>     Yves
>
>
>
>
>                       /--------------------------------
>                          /   Yves Van Haarlem
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