star-fst-l AT lists.bnl.gov
Subject: Star-fst-l mailing list
List archive
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?
- From: Zhenyu Ye <yezhenyu2003 AT gmail.com>
- To: Gerard Visser <gvisser AT indiana.edu>
- Cc: "star-fst-l AT lists.bnl.gov" <star-fst-l AT lists.bnl.gov>
- Subject: Re: [Star-fst-l] noise vs bias for worst channel and typical channel?
- Date: Tue, 11 Aug 2020 16:28:54 -0500
Hi Gerard,
The total capacitance of a readout strip for silicon strip detectors is given
by the sum of the strip-backplane capacitance, and the inter-strip
capacitance. The latter usually dominates.
As we know, the APV noise is linearly dependent on input capacitance, i.e.,
the total capacitance of the readout strip. For FST, we have seen that outer
(larger R, Rstrip3 for the inner sensor or Rstrip7 for the outer sensor in
Xu’s plots) strips have much smaller noises than the inner strips (Rstrip0
for the inner sensor or Rstrip4 for the outer sensor), despite the fact that
outer strips have larger area and thus large strip-backplane capacitance.
This is consistent with the above statement that the interstrip capacitance
dominates.
The CMN, by definition, affects a group of channels in a coherent way. It is
usually caused by a common electromagnetic pick-up, or noise on the supply
voltage, etc. The fact that we see large CMN in FST, suggests to me that we
should check FST inner cable/T-board/hybrid, such as grounding.
P.S. Xu will send some plots on FST prototype modules before sensors were
mounted. We see large CMN with strong time-bin dependence. I think this is
consistent with my above assessment.
Best,
Zhenyu
> On Aug 10, 2020, at 3:45 PM, Gerard Visser <gvisser AT indiana.edu> wrote:
>
> hi Xu, Zhenyu,
> Thanks; I didn't realize about this timebin dependence in the IST. By
> the way do we see any dependence of noise on the "cap id" (i.e. the
> "address" reported in the APV header)? I am assuming we are triggering at a
> low rate and asynchronous to the clock (ARC-II local clock) so we should be
> getting data in all values of capid. This could show some features (and
> perhaps can allow for some capid-dependent correction applied offline).
>
> I make some estimate of the capacitances as follows: Neglecting the
> capacitance to neighbor pads, and all the capacitance of the routing line
> on the detector, let's consider only the infinite-parallel-plate
> capacitance in bulk of the detector:
>
> IST: Pad size is 594 x 6275 um, thickness 300 um, k=11.7 ==> C=1.3 pF (I
> think this must certainly then be dominated by the other, neglected
> capacitances mentioned above).
>
> FST: worst case outer pad size is (about) 1087 x 28750 um. (Right? If you
> have more precise info please say.) Also 300 um thick. ==> C=10.8 pF. (+
> other again)
>
> If you have some info about the gap in contact/metal between adjacent
> pads in the case of IST and FST I could try to roughly estimate the
> perimeter capacitance to neighbor pads.
> If you have some measured capacitance info or real calculated
> capacitances from detector design, of course we could better think about
> those.
> Anyway, my guess is that the capacitances in FST (outer at least) are
> probably 2-3x the capacitances in IST. This is probably responsible for the
> larger common mode noise and larger noise. If so unfortunately it probably
> means there is nothing that we can do about it.
> If we have an IST stave with a defective detector and wanted to do
> further tests, we could bond some APV input pads to test capacitors of
> value similar to the FST detector and see how that looks. I think this
> could be a significant effort though.
> Really the only question that we must answer is whether the PPB,
> purple cable, T-board, and hybrids are working well together to deliver
> clean supply voltages and clock/trigger signals to the APV chips (and clean
> bias to the sensors). This is probably so, I think all your noise plots
> look reasonable, but we could try to check more directly with low noise
> probing of the supply voltages on one of the prototype hybrids. We probably
> would have done this already if it weren't for the virus situation.
> Sincerely,
>
> Gerard
>
>
> p.s. I suppose that, at least for lower trigger rates <3 kHz or so, we
> should consider to setup to read 4 timebins and ignore 0 in offline, use
> only 1-3. If 3 timebins is all that we really need, that is. What do you
> think?
>
>
> On 8/10/2020 2:29 PM, Xu Sun wrote:
>> Hi Gerard,
>> Sorry for the late reply. Please find the FST & IST noise study in the
>> attached file.
>> I see a similar behaviour for IST with a much smaller magnitude.
>> Best,
>> Xu
>> On Tue, Aug 4, 2020 at 1:12 PM Gerard Visser <gvisser AT indiana.edu
>> <mailto:gvisser AT indiana.edu>> wrote:
>> Hi Xu, Zhenyu,
>> Do we see the timebin-dependece of noise as you show here
>>
>> https://drupal.star.bnl.gov/STAR/event/2020/05/04/star-forward-silicon-tracker-meeting/prototype-module-assembly-and-test
>> in the IST data too?
>> Thanks,
>> Gerard
>> p.s. And, if possible to answer, there is also the question whether
>> this was
>> seen in the IST installed in STAR/HFT? I don't remember hearing about
>> it before.
>> On 8/4/2020 12:39 PM, Zhenyu Ye wrote:
>> > Hi Gerard,
>> >
>> >> On Aug 4, 2020, at 11:19 AM, Gerard Visser <gvisser AT indiana.edu
>> <mailto:gvisser AT indiana.edu>> wrote:
>> >>
>> >> hi Zhenyu,
>> >> That timebon dependence sounds definitely odd. Are you sure?
>> Do we
>> see that in IST too, only more mildly? I wasn't aware of this.
>> > ‘
>> > Please take a look at Xu’s presentation in FST meeting on May 4
>> (FST) and
>> 11 (FST and IST):
>> >
>> >
>>
>> https://drupal.star.bnl.gov/STAR/event/2020/05/04/star-forward-silicon-tracker-meeting/prototype-module-assembly-and-test
>> >
>>
>> https://drupal.star.bnl.gov/STAR/event/2020/05/11/star-forward-silicon-tracker-meeting/prototype-module-assembly-and-test
>> >
>> >> The capacitance of FST is much larger than IST, I think. This
>> may
>> certainly be relevant. For sure it is relevant to CMN.
>> >> Anyway, I agree we should investigate these noise issues, I do
>> not
>> like to ignore them. However on the other hand it _may_ be an inherent
>> property of APV chips.
>> >
>> >> - Gerard
>> >>
>> >>
>> >>
>> >> On 8/4/2020 12:12 PM, Zhenyu Ye wrote:
>> >>> Hi Gerard,
>> >>> From the plots that Xu sent, there is a clear pattern where the
>> channels showing enhanced noise level after mounting the sensors, also
>> show
>> enhanced noise level before mounting the sensors.
>> >>> An independent topic, we see that the CMN in FST is much higher
>> than
>> IST, and show a strong time-bin dependence, i.e., when we read in 9 time
>> bins, the 1st, 5th and 9th time bins have much higher CMN than the other
>> time bins. I don’t feel comfortable to ignore it w/o knowing the cause,
>> as
>> it may get worse in the real experiment.
>> >>> Best,
>> >>> Zhenyu
>> _______________________________________________
>> Star-fst-l mailing list
>> Star-fst-l AT lists.bnl.gov <mailto:Star-fst-l AT lists.bnl.gov>
>> https://lists.bnl.gov/mailman/listinfo/star-fst-l
> _______________________________________________
> Star-fst-l mailing list
> Star-fst-l AT lists.bnl.gov
> https://lists.bnl.gov/mailman/listinfo/star-fst-l
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Zhenyu Ye, 08/04/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Gerard Visser, 08/04/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Zhenyu Ye, 08/04/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Gerard Visser, 08/04/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Zhenyu Ye, 08/04/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Xu Sun, 08/10/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Gerard Visser, 08/10/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Zhenyu Ye, 08/11/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Xu Sun, 08/11/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Gerard Visser, 08/11/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Zhenyu Ye, 08/11/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Visser, Gerard, 08/11/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Xu Sun, 08/12/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Gerard Visser, 08/12/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Xu Sun, 08/12/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Gerard Visser, 08/12/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Ye, Zhenyu, 08/13/2020
- Re: [Star-fst-l] noise vs bias for worst channel and typical channel?, Gerard Visser, 08/13/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Zhenyu Ye, 08/11/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Gerard Visser, 08/10/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Gerard Visser, 08/04/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Zhenyu Ye, 08/04/2020
-
Re: [Star-fst-l] noise vs bias for worst channel and typical channel?,
Gerard Visser, 08/04/2020
Archive powered by MHonArc 2.6.24.