[Halld-tracking-hw] HVB - FINAL VERSION - and fADC

[Fernando J. Barbosa]

Hi Curtis,

My understanding was that your previous results were obtained with the 
fADC125. The Struck ADC does not have any shaping to speak of (other 
than the resulting convolution of the input pulse with its response) so 
it does not provide for a direct comparison of results.

The fADC125's dynamic range or "gain" cannot be adjusted via firmware to 
make full use of its dynamic range but requires changing a number of 
resistors and capacitors per channel (I believe a total of 2 of each). 
Is this correct, Gerard?

Changing these components is time consuming (72 channels) but should be 
done for testing the full readout chain prior to committing to the final 
assembly version. My concern is that this change may be incompatible 
with the FDC requirements, necessitating two assembly versions (OK), and 
will impact the procurement schedules. I believe that the FDC can 
accommodate a change in the dynamic range but perhaps not to the 
magnitude needed by the CDC. Correct, Lubomir?

We need to discuss these issues at an upcoming tracking meeting with the 
CDC and the FDC groups and Gerard.

Another topic that Gerard mentioned to me recently and that needs 
checking is the buffer size.

Best regards,
Fernando




Curtis A. Meyer wrote:
> Hi Fernando
>
>    the Struck FADC with the modified HVB is fine. It appears that the 
> FADC125
> has a factor of two lower gain than the Struck. Perhaps there is a way 
> to adjust this
> in the firmware. Our original conclusions based on the data that we 
> collected
> with the old struck are still valid, the factor of two is between the 
> two FADCs
> which has caught us a little by surprise.
>
>   Curtis
> On 4/11/11 5:43 PM, Fernando J. Barbosa wrote:
>> Hi Naomi,
>>
>> The gain was halved from the original on the modified HVB to fit the 
>> amplitudes within the fADC range. From your histograms, it seems that 
>> you need to double the range of the fADC with the original HVB. Correct?
>>
>> What caused the dramatic change? Gas? Leaks?
>>
>> Certainly we need to discuss this as there will most likely be an 
>> impact on the FDC, if we are to have one fADC for both the CDC and 
>> the FDC.
>>
>> Best regards,
>> Fernando
>>
>>
>>
>>
>> Naomi Jarvis wrote:
>>> Hi Fernando and Gerard,
>>>
>>> I have some results with cosmics and the new fADC online here: 
>>> http://www.jlab.org/Hall-D/software/wiki/index.php/New_fADC_with_cosmics 
>>>
>>>
>>> This is still a work in progress, we can see (top row of histograms) 
>>> that the gain in the new fADC is about 1/2 of that of the Struck 
>>> fADC (&shaper).
>>>
>>> Is it possible to change the full scale range of the new fADC?
>>>
>>> >From previous work with the Struck fADCs, we know that the preamp 
>>> output saturates at approx 0.5V (measured after the shaper), so we 
>>> would only be using half the range of the ADC if we use the 
>>> unmodified HVB.
>>>
>>> We would like to put this on the agenda for the tracking meeting on 
>>> Wednesday.
>>>
>>> Naomi and Curtis.
>>>
>>>
>>>
>>> On Apr 8, 2011, at 1:38 PM, Fernando J. Barbosa wrote:
>>>
>>>> Hello,
>>>>
>>>> I have attached a few drawings of the final HVB. Changes from the 
>>>> first version are as follows:
>>>>
>>>> - signal attenuation network added to each signal (back of the PCB)
>>>> - location and footprint of brackets
>>>> - channel numbering order to agree with fADC125 (0 through 23) (top 
>>>> carries the preamp card - see HVB_FINAL_TOP_SILK.PDF).
>>>> - a few minor dimensional and cosmetic improvements.
>>>>
>>>> I have reviewed these changes with Slava but please take a look and 
>>>> let me know if you have any questions as I plan to start 
>>>> procurements next week.
>>>>
>>>> Thanks and best regards,
>>>> Fernando
>>>> <HVB_FINAL_TOP_SILK.pdf><HVB_FINAL.pdf><HVB_FINAL_BOT_SILK.pdf><barbosa.vcf> 
>>>>
>>>
>
>
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