[Halld-tracking-hw] Tracking Meting Tomorrow

[Naomi Jarvis]

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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