Star-fst-l mailing list

[Gerard Visser <gvisser AT indiana.edu>]

Hi Xu, Zhenyu,
	I have a question about the signal size vs. bias. On slide 13 in the latest, we 
see as before from the noise vs. bias plot that the detector reaches full 
depletion around 100 V. And we see from the "Cluster Signal vs. HV" that the 
signal is pretty constant above 100 V, at least for inner detector (outer ??). 
The inner case shows less than 2% increase in signal from 100 to 150 V, which 
seems quite reasonable (AFAIK; I could be wrong). Whereas the old plot that you 
showed, in 
https://indico.bnl.gov/event/8967/contributions/39814/attachments/29461/45813/FstModuleAssemblyandTest_BNLF2F_Jul2020.pdf 
slide 10, showed again a full depletion at 100 V from the capacitance (noise) 
plot, but at least 15-20% extra signal when raising the bias above 100 V. I 
never understood that result, and it seemed rather worrisome (if correct). Is 
there any reason to think there might have been a problem with that old 
measurement and we should discount it? And from the new results, would you agree 
the bias can be set around 130 V or so both for inner and outer and it should be 
good?
        Sincerely,

                Gerard


On 7/30/2020 9:14 PM, Xu Sun wrote:
> Hi Flemming,
>
> I have made some updates and you could find the updated slides in the following 
> link:
>
> https://drupal.star.bnl.gov/STAR/system/files/FstReviewAug2020_v9.pdf
>
> Best,
>
> Xu