[Halld-tracking-hw] Tracking Meting Tomorrow
Fernando J. Barbosa
barbosa at jlab.org
Mon Apr 18 09:19:37 EDT 2011
Hi Naomi, Gerard,
I have attached a brief doc on the impulse response of the preamp. I
think it should work well with the CDC setup.
Best regards,
Fernando
Fernando J. Barbosa wrote:
> Hi Naomi, Gerard,
>
> I have configured and tested the preamps as I described earlier
> (should have a short doc later) and they are shipping to each of you
> today via FedEx. You should have them on Monday.
>
> Best regards,
> Fernando
>
>
>
>
> Naomi Jarvis wrote:
>> Great! That should work nicely.
>>
>>
>> Thanks,
>>
>> Naomi.
>>
>>
>> On Thu, April 14, 2011 9:29 am, Fernando J. Barbosa wrote:
>>
>>> Hi Naomi,
>>>
>>>
>>> Yes, the changes (removing terminating resistors at the output of the
>>> preamp) will be on the preamp. We still need the modified HVB to
>>> attenuate
>>> the charge into the ASIC. So, the CDC will have the preamp
>>> configured with
>>> low gain (~0.6 mV/fC - the setting you have now), no terminating
>>> resistors
>>> on the preamp output, modified HVB and fADC125. One fADC125 will be
>>> used
>>> with both the CDC and the FDC and as it is now.
>>>
>>> 14-bit ADCs are not on the plans.
>>>
>>>
>>> Best regards,
>>> Fernando
>>>
>>>
>>>
>>>
>>> Naomi Jarvis wrote:
>>>
>>>
>>>> Hi Fernando,
>>>>
>>>>
>>>> you do mean the preamp and not the HVB, right? I already collected
>>>> cosmics with the unmodified HVB (without the attenuators) to see if
>>>> the
>>>> resolution would be any different, it does look better (pics on the
>>>> wiki, tracking mtg agenda) but we do still need to use the modified
>>>> HVB
>>>> to fit the dynamic range we want into the preamp.
>>>>
>>>> What about using 14-bit ADCs ?
>>>>
>>>>
>>>> Naomi.
>>>>
>>>>
>>>>
>>>> On Apr 13, 2011, at 7:47 PM, Curtis A. Meyer wrote:
>>>>
>>>>
>>>>
>>>>
>>>>> Hi Fernando -
>>>>>
>>>>>
>>>>> please do send us one of these preamp cards -- thanks .. curtis On
>>>>> 4/13/11 5:22 PM, Fernando J. Barbosa wrote:
>>>>>
>>>>>
>>>>>
>>>>>> Hi Gerard,
>>>>>>
>>>>>>
>>>>>> OK, I will send you two preamps (CDC and FDC).
>>>>>>
>>>>>>
>>>>>> There is an easy way to double the pulse amplitude at the input of
>>>>>> the ADC which is to remove the back-terminating resistors on the
>>>>>> preamp card. This would not change the preamp response . This change
>>>>>> would not require any changes to the fADC125 and one version would
>>>>>> still fit both detectors as this is already the consensus at JLab. I
>>>>>> can send a preamp to Naomi in this configuration for tests.
>>>>>>
>>>>>> Best regards,
>>>>>> Fernando
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Gerard Visser wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>> Hi Fernando,
>>>>>>> Thanks, I will change the gain setting as you say.
>>>>>>> Could you please still send me another board in CDC
>>>>>>> configuration? First of all this one is set for cathodes and I
>>>>>>> might not have enough 0402 jumpers to convert to anodes operation,
>>>>>>> and secondly this board has apparently all channels dead on the
>>>>>>> middle ASIC and I worry perhaps could have an abnormal response on
>>>>>>> the others (I don't know what the cause of the trouble is). In any
>>>>>>> case, having two boards to be able to confirm the measurements on
>>>>>>> the second unit, I think will be a good idea. If you have 'plenty'
>>>>>>> then please also send one in FDC cathode configuration (same
>>>>>>> reasons). I have updated my slide with a 2nd one showing the
>>>>>>> waveforms at the ADC output terminals. With the caveat this is as
>>>>>>> you say for quite the wrong gain selection on the ASIC, the
>>>>>>> results of this test look to me to indicate the linearity is
>>>>>>> really worse than it looks on the ADC125 view, the maximum
>>>>>>> reasonably linear pulse height is about 43% of full scale on the
>>>>>>> ADC. We'll have to see how this looks with
>>>>>>> the correct gain setting on the ASIC. My updated slides are here
>>>>>>> http://npvm.ceem.indiana.edu/~gvisser/GlueX/ADC_scale.pdf
>>>>>>> Sincerely,
>>>>>>>
>>>>>>>
>>>>>>> Gerard
>>>>>>>
>>>>>>>
>>>>>>> p.s. And the answer to Curtis' question from the other day "Does
>>>>>>> the input of the FADC-125 match the 0V to 0.5V output of the ASIC,
>>>>>>> or is it something else?": For pulses of this shape, the input of
>>>>>>> the ADC125 matches to an amplitude of 990mV, which is indeed
>>>>>>> probably higher than intended (sorry). HOWEVER care is certainly
>>>>>>> needed - for _wider_ pulses the ADC125 full scale will be _lower_
>>>>>>> in amplitude (it is a shaper...). [And I presume the CDC can get
>>>>>>> some pretty wide pulses when tracks pass at an angle.]
>>>>>>>
>>>>>>>
>>>>>>> On 4/13/2011 2:54 PM, Fernando J. Barbosa wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Hi Gerard,
>>>>>>>>
>>>>>>>>
>>>>>>>> The preamp you have is set for a gain of 3.2 mV/fC and a
>>>>>>>> dynamic range of 110 fC (@ 5% linearity), quite different from
>>>>>>>> the CDC. This is the fifth row in the Table 2 of GlueX-doc-1364
>>>>>>>> (the CDC is set as per the second row -
>>>>>>>> 0.57 mV/fC,
>>>>>>>> DR=380 fC).
>>>>>>>>
>>>>>>>>
>>>>>>>> I attach the preamp configuration settings showing where the
>>>>>>>> resistors are to be installed. To set your preamp to the CDC
>>>>>>>> configuration, move the resistor to the left of the RC label to
>>>>>>>> the pads on the right (5.1 Ohm resistor sets RC to logic
>>>>>>>> 1) and move the resistor to the left of the HG label to the pads
>>>>>>>> on the left (5.1 Ohm resistor sets HG to logic 0).
>>>>>>>>
>>>>>>>>
>>>>>>>> The FDC cathode setting is the sixth row in Table 2 (2.6 mV/fC
>>>>>>>> gain). Let me know if this works for you as this changes are easy
>>>>>>>> to make with a soldering iron. If not, I will send you another
>>>>>>>> preamp(s).
>>>>>>>>
>>>>>>>> There is GlueX-doc-1570 showing the dynamic range with the HVB
>>>>>>>> and shows good linearity.
>>>>>>>>
>>>>>>>> Best regards,
>>>>>>>> Fernando
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Gerard Visser wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> the preamp strapping picture (for current discussion)
>>>>>>>>> http://npvm.ceem.indiana.edu/~gvisser/GlueX/straps.jpg
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>> --
>>>>> Prof. Curtis A. Meyer Department of Physics
>>>>> Phone: (412) 268-2745 Carnegie Mellon University
>>>>> Fax: (412) 681-0648 Pittsburgh PA 15213-3890
>>>>> cmeyer at ernest.phys.cmu.edu http://www.curtismeyer.com/
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Halld-tracking-hw mailing list
>>>>> Halld-tracking-hw at jlab.org
>>>>> https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>
>>
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