Re: News on the preAmp + CDC

["Fernando J. Barbosa" <barbosa@jlab.org>]

Hi Yves,

Thanks for the clarification.

Have you taken an efficiency curve for the straws? I can see the onset 
of some limited streamer pulses on fig. 1.4. Even at 1850 V, the straw 
gain seems to be too high and this may be the reason for the anomalous 
drift time spectra. Try decreasing the HV to 1800 V which should still 
keep the gain on the plateau.

Regards,
Fernando



Yves Van Haarlem wrote:
> Hi All,
>
> To clarify:
>>   I would also note that to date we have not used Gerard's shaper.
>> He was putting a connector on for it this afternoon, but I believe that
>> all of the pulses are without it.
> All the scope traces shown in section 1 ("News on the preAmp") are 
> without shaper board (fig. 1.1-1.4). Fig. 1.5 and 1.6 in that section 
> were taken with the shaper board.
>
> All the figures/plots shown in section 2 ("understanding the drift 
> time spectrum") were taken with the old preAmp without shaper board.
>
> Cheers,
>     Yves
>
>
>
>>
>>   cheers - curtis
>> On Mon January 21 2008, Fernando J. Barbosa wrote:
>>> Hall D Electronics:
>>>
>>> Hi Yves,
>>>
>>> It looks like you and Gerard are making quite a lot of progress with 
>>> the
>>> FDC. The pulses look reasonable but there is still some work left in
>>> trying to understand the source of the oscillations you observed 
>>> before.
>>>
>>> I also looked at the drift time spectra at different sampling rates 
>>> that
>>> you obtained. The time structure of the main pulse is similar and of 
>>> the
>>> order of 200 ns. There shouldn't be any aliasing as the pulse structure
>>> out of the preamp is already over 10 ns. However, there seems to be 
>>> some
>>> reflection or after pulsing, as the 200 MSPS picture clearly shows. If
>>> you are using the shaper, check if this is not an artifact from the
>>> shaper. Gerard may have chosen the shaping constants based on the CLAS
>>> preamp. I and Simon observed a similar characteristic with the anode
>>> shaper on the FDC.
>>>
>>> Regards,
>>> Fernando
>>>
>>>
>>>
>>> Yves Van Haarlem wrote:
>>>> Hi Fernando,
>>>>
>>>> Gerard is now looking at the CDC setup with the new preAmp. First
>>>> findings can be found on the CDC wiki (it looks much better now):
>>>>
>>>> http://www.jlab.org/Hall-D/software/wiki/index.php/CDC_23_01_2008
>>>>
>>>> ("news on the preAmp" part)
>>>>
>>>> Cheers,
>>>>     Yves
>>>>
>>>>
>>>>                           /--------------------------------
>>>>                          /   Yves Van Haarlem
>>>>        _--~~--_         /
>>>>      /~/_|  |_\~\      /      Carnegie Mellon University
>>>>     |____________|    /        Department of Physics
>>>>     |[][][][][][]|:= /          Wean Hall room 8404
>>>>   __| __         |__ \            Pittsburgh, PA 15213
>>>>  |  ||. |   ==   |  | \           USA
>>>> (|  ||__|   ==   |  |) \
>>>>  |  |[] []  ==   |  |   \           Tel.:   +1 412 268-6949
>>>>  |  |____________|  |    \                  +1 412 641-9252
>>>>  /__\            /__\     \          Fax.: +1 412 681-0648
>>>>   ~~              ~~       \-----------------------------------
>>>
>>
>>
>>
>> -- 
>> Professor Curtis A. Meyer        Department of Physics
>> Phone:  (412) 268-2745          Carnegie Mellon University
>> Fax:    (412) 681-0648            Pittsburgh PA 15213-3890
>> cmeyer@ernest.phys.cmu.edu  http://www.curtismeyer.com/
>>
begin:vcard
fn:Fernando J. Barbosa
n:Barbosa;Fernando J.
org:Jefferson Lab
adr:Suite #10, 12B3;;12000 Jefferson Ave.;Newport News;VA;23606;USA
tel;work:757-269-7433
version:2.1
end:vcard