[Halld-tracking-hw] [CDC] preAmp follow up on todays meeting

[Fernando J. Barbosa]

Hi Yves,

It sounds like you made quite some progress. You should keep the preamps 
and perform some tests with the pre-mixed gas you already have. You can 
send the preamps later if necessary.

I also suggest you try to minimize any noise you see on the scope to a 
few mVpp.

Best regards,
Fernando




Yves Van Haarlem wrote:
> Hi All,
>
> This is to follow up on the discussion we had on todays meeting.
>
> After watching Germany lose I locked myself up the lab and noticed that:
>
> 1/ That weird noise peak, mentioned in the meeting, is caused by the 
> thermo-couple. If I switch off the T-controller that peak disappears.  
> It makes sense because after we fixed a gas leak the thermocouple must 
> have moved closer to the straws, it is around this time this noise 
> appeared. -- problem solved at the moment by switching off the T 
> monitoring. Also, the noise is higher in amplitude on straws close to 
> the T-couple.
>
> 2/ By comparing drift time spectra of the old preamp (as in the 
> published paper) with the new preAMp at 2100V and 50-50 gas. It can be 
> seen:
>
> http://www.jlab.org/Hall-D/software/wiki/index.php/Drift_time_comparison_(gas_check) 
>
>
> that the new preAmp shows that the longest drift times are 100~ns 
> shorter compared to the old measurement, this means that the gas 
> mixtures are different. L'histoire se répète: mysteries with the old 
> pre-amp were explained by wrong settings of the gas flow controllers. 
> Now the mystery of the new preAmp has again something to do with the 
> gas mixture. Indeed Beni, it looks like a 60/40 Ar/CO2 gas: both 
> drift-time as efficiency-curve wise. Back then the problem with the 
> gas mixer was easily fixed because some settings were wrong, now it 
> has to be something else.
>
> Personally I do NOT think it is worth to send the preAmps back before 
> we solve this gas problem. If you still want me to send them to J-lab 
> please ask me to do so.
>
> The way we can solve/avoid the gas problem is to compare with 
> pre-mixed gas: we have 90-10 Ar-CO2 premixed. This will take time... 
> Or we can order 50-50 premixed and repeat our studies, or we just put 
> the 90-10 premixed in and compare with the measurements done for the 
> paper and track down problems with the gas mixer later. Personally I 
> would go with the last options because this produces results 
> concerning the new preAmp faster.
>
>
> 3/ The plots requested by Lubomir with Energy/amplitude as a function 
> of energy (using cosmics) can be found here:
>
> http://www.jlab.org/Hall-D/software/wiki/index.php/Energy/Amplitude_as_a_function_of_drift_time 
>
>
> Expected behavior can be seen, this data is not tracked (to save 
> time), so some noise hits are present. Let me know if you want the 
> tracked version too.
>
> Cheers,
>     Yves
>
>
>
>                           /--------------------------------
>                          /   Yves Van Haarlem
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