[Halld-tracking-hw] New preamp

[Naomi Jarvis]

Hello,

You are absolutely correct, I did upload the wrong pic for Fe55 at 
2000V, sorry, the right one is there now (it looks better).

I started taking data at 50/50 Ar/CO2 to find the plateau for the new 
preamp and this will take a while to do.

Yes please, could you send me the preamp from doc-1364 Table 2 row 2?  

Also the pdf looks fine.

Thankyou,

Naomi.



Fernando J. Barbosa wrote:
> Hi Naomi (and Yves),
>
> Naomi Jarvis wrote:
>> Hi Fernando,
>>
>> I have put some more preamp output (after the shaper) pictures online 
>> at http://www.jlab.org/Hall-D/software/wiki/index.php/Preamp_3
>
> The pictures for the new preamp, at 2000V for Fe-55 and cosmics are 
> exactly the same - maybe cosmics?
>
>>
>> For the gas mixture 50/50 Ar/CO2 with the 55Fe source, the preamp 
>> output is saturating before the working voltage of the chamber is 
>> reached. At 1900V it looks fine but there is some saturation shown at 
>> 2000V and a lot at 2100V. I also looked at this using the old preamp, 
>> which did not show any saturation. Yves's earlier work (using the old 
>> preamp) determined that the working voltage for that gas mix should 
>> be around 2000 to 2100V, so this is causing some anxiety. It looks 
>> like the gain of the new preamp is approximately 1/3 of that of the 
>> old preamp. The signals are no longer bipolar. (Also I think the 
>> later signals after 500 ns are probably due to a delayed avalanche 
>> from the cathode following Ar+ recombination.)
>
> The old preamp had a gain of 1.5 mV/fC and a dynamic range of 400 fC; 
> the new one is 0.75 mV/fC. The attenuation of 18m of cable is 0.57 and 
> the shaper gain is 2.16. Looking at the first set of pictures (1900V), 
> the middle picture shows an amplitude of 500 mV or 270fC of input 
> charge on the old preamp; the picture on the right shows an amplitude 
> of 300 mV or 325 fC of input charge on the new preamp - this is beyond 
> the linear dynamic range of the preamp with the nominal settings. If 
> you look at GlueX-doc-1364, table 2 shows a linear range of 260 fC for 
> the nominal settings (first row). In this case, the preamp is not 
> saturating but it is not linear. This may explain, in part, the shape 
> of the pulse.
>
> At 2000V, the new preamp shows a markedly saturated behavior at an 
> amplitude of 500 mV (~flat top) or >540 fC of input charge. This is 
> way beyond the dynamic range of the preamp. The best dynamic range 
> configuration is shown on table 2, second row, with a gain of 0.57 and 
> a dynamic range of 380 fC. I can send you another preamp with this 
> configuration but it will be saturated at 2000 V also. I suggest you 
> determine the plateau with the new preamp for confirmation. You may 
> need to change the gas mixture, maybe to 40Ar/60CO2, and get the 
> detector within the operating range of the preamp.
>
>>
>> When going over the draft of the cable assembly two points caught 
>> attention:
>> - page 2/6: no color is specified or it is not readable on page 6 for 
>> the 5 different cable types. We do not care as long as the CDC is 
>> green or pink :-)
>> - page 6: on the right side the orientation of cable and connector is 
>> indicated and clear but on the left side it is not clear where the 
>> conductors need to be soldered to - maybe it is mentioned but on the 
>> copy we have all text on page 6 is unreadable.
>
> I have attached another copy of the cable specs and you should be able 
> to read the pdf in very fine detail.
>
> Section 3, page 6/17 shows the colors of the labels. Sorry, the CDC 
> has no color specified for the label, green is already assigned and I 
> am not aware of pink heat shrink. If you insist, I can assign you the 
> green.;-)
>
> On this same page, the connector on the left (3M) has the wire numbers 
> shown; the connector on the right (ERNI) only needs the red stripe for 
> orientation as this is an IDC connector.
>
> Thanks for the feedback and let me know if you want me to send you 
> another preamp configured for wider dynamic range as stated above.
>
> Best regards,
> Fernando
>
>>
>> Best regards,
>>
>> Naomi (and Yves).
>>