[Halld-tracking-hw] Tracking Meting Tomorrow

[Naomi Jarvis]

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/
>>>
>>>
>>>
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>>>
>>>
>>>
>>
>>
>