Star-fst-l mailing list

["Ye, Zhenyu" <yezhenyu AT uic.edu>]

Hi Gerard,

Page 12 https://drupal.star.bnl.gov/STAR/system/files/FstReviewAug2020_v10.pdf
shows the test stand setup.

The plate with many holes is made from Aluminum. The FST module is placed 
inside a plastic storage box, which is placed on top of the Al plate. 
Underneath the plate are the IST staves.

We found that grounding the plate makes a large difference to the FST CMN 
(i.e., the CMN is much smaller by electrically connecting the Al plate to the 
grey cable shield than no connection), but not so much difference in IST. 
What Xu shows in his slides are with grounding the Al plate. 

Zhenyu

> On Aug 12, 2020, at 10:55 PM, Gerard Visser <gvisser AT indiana.edu> wrote:
> 
> hi Xu, Zhenyu,
>       So it is the two smallest radius (farthest from readout) rings of the 
> sensors which are extra noisy in both the inner and outer sensor case. That 
> is curious indeed.
>       Capacitances through the bulk of the sensor should be smaller there. 
> I thought that sort of capacitance would be the worst for CMN.
>       Routing line capacitance and resistance is of course largest there. 
> What is the routing line resistance, is there any estimae from Hamamatsu? 
> That resistance adds noise voltage, I think with basically the same effect 
> as noise voltage of the frontend amplifier. I guess one would want 1-2 
> nV/sqrt(Hz) at most (though the number is really a guess; for sure we want 
> "not more than about the voltage noise of the APV frontend" whatever that 
> is). 2 nV/sqrt(Hz) would be 240 Ohms -- how does it compare w/ the sensor 
> design?
>       I don't understand though how any noise from the routing line 
> resistance would appear as CMN.
>       A different theory is that these rings are farther from the bypass 
> capacitors on the nybrid (inevitably). The bias voltage there might be 
> picking up some external noise more than it is closer to these capacitors. 
> (If so, it could maybe be improved in our design.)
>       Sincerely,
> 
>               Gerard
> 
> On 8/12/2020 11:35 PM, Xu Sun wrote:
>> Hi Gerard,
>> 0-3 is for the inner sector from smallest radius to largest radius. And 
>> 4-7 is for the outer sector from smallest radius to largest radius.
>> Hope this helps.
>> Best,
>> Xu
>> On Wed, Aug 12, 2020 at 10:29 PM Gerard Visser <gvisser AT indiana.edu 
>> <mailto:gvisser AT indiana.edu>> wrote:
>>    hi Xu,
>>             Thanks, that is very good to see these plots including also the
>>    case from
>>    unbonded APV on the IST hybrids (+IST cable and T-board). I am glad to 
>> see that
>>    the case of FST and IST unbonded chips is about the same. We do have to
>>    decipher
>>    still if the difference between FST and IST with detector indicates a
>>    problem or
>>    merely the normal effect of different detector capacitances. I don't 
>> think
>>    it is
>>    clear; but of course it _could_ be a problem.
>>             I don't know the definition for R strip number 0-7, but your 
>> plots
>>    show that
>>    for R-strips 2, 3, 6, and 7 the CMN is about the same as the unbonded 
>> case. So,
>>    which strips are those?
>>             Sincerely,
>>                     Gerard
>>    On 8/12/2020 10:44 PM, Xu Sun wrote:
>>     > Hi Gerard,
>>     >
>>     > We just had a quick look at 2013 IST data before and after sensor
>>    mounting and
>>     > compared it with current FST data. You could find a summary slides 
>> in the
>>     > attached file.
>>     > The total noise and random noise of IST increased significantly 
>> after sensor
>>     > mounting, but the CMN from IST data didn't. This suggests that CMN 
>> is only
>>     > weakly dependent on detector capacitance in the case of IST.
>>     >
>>     > For FST, total noise, CMN and random noise increased after sensor 
>> mounting.
>>     >
>>     > Best,
>>     >
>>     > Xu
>>     >
>>     > On Tue, Aug 11, 2020 at 6:27 PM Visser, Gerard <gvisser AT indiana.edu
>>    <mailto:gvisser AT indiana.edu>
>>     > <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>>> wrote:
>>     >
>>     >     hi Zhenyu,
>>     >          All I am saying is that these plots do not indicate to me
>>    evidence of a
>>     >     problem. If the IST capacitance is "negligible enough" for 
>> instance
>>    it would
>>     >     look similar to FST unbonded. I wish we had such plots for an
>>    unbonded IST
>>     >     chip...
>>     >          The pattern of higher noise every four timebins for sure 
>> looks like
>>     >     something we don't want to see, but I think explanation for 
>> _that_
>>    ties into
>>     >     some internal details of the APV chip that we have no choice but 
>> to
>>    live with.
>>     >         Anyway, I think we need to keep investigating, we agree. At 
>> the
>>    moment I
>>     >     would say I believe the FST noise looks a bit worse than IST 
>> simply
>>    because
>>     >     the capacitances are worse, but if we think the S/N ratio is 
>> still
>>    adequate
>>     >     I don't see a clear worry. Of course we should check everything 
>> that
>>    we can
>>     >     though.
>>     >
>>     >             Gerard
>>     >
>>     >
>>     >     p.s. At least the capacitance of IST to the backside contact / 
>> bias
>>    supply
>>     >     is << than that of FST. This could be the capacitance that 
>> matters
>>    most for
>>     >     CMN. (I'd naively expect that capacitance to at least adjacent
>>    channels of
>>     >     same chip, does not generate CMN, or not significantly.)
>>     >
>>     >     ________________________________________
>>     >     From: Zhenyu Ye <yezhenyu2003 AT gmail.com
>>    <mailto:yezhenyu2003 AT gmail.com> <mailto:yezhenyu2003 AT gmail.com
>>    <mailto:yezhenyu2003 AT gmail.com>>>
>>     >     Sent: Tuesday, August 11, 2020 7:14 PM
>>     >     To: Visser, Gerard
>>     >     Cc: Xu Sun; star-fst-l AT lists.bnl.gov
>>    <mailto:star-fst-l AT lists.bnl.gov> <mailto:star-fst-l AT lists.bnl.gov
>>    <mailto:star-fst-l AT lists.bnl.gov>>
>>     >     Subject: Re: [Star-fst-l] noise vs bias for worst channel and
>>    typical   channel?
>>     >
>>     >     Hi Gerard,
>>     >
>>     >     In the other email, you argued that the CMN increases with input
>>    capacitance
>>     >     (I agree). But the argument you are making here, which is based 
>> on
>>    "CMN: IST
>>     >     with sensor ~ FST w/o sensor" and concluding there is no issue 
>> with FST,
>>     >     seems to neglect the fact that the input capacitance is 
>> different between
>>     >     IST with sensor and FST w/o sensor.
>>     >
>>     >     CMN:
>>     >     FST with sensor >> FST w/o sensor ~ IST with sensor
>>     >
>>     >     CMN/Total
>>     >     FST with sensor ~ FST w/o sensor >> IST with sensor
>>     >
>>     >     Zhenyu
>>     >
>>     >
>>     >      > On Aug 11, 2020, at 5:59 PM, Gerard Visser 
>> <gvisser AT indiana.edu
>>    <mailto:gvisser AT indiana.edu>
>>     >     <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>>> wrote:
>>     >      >
>>     >      > hi Xu, Zhenyu,
>>     >      >       I put the plot from IST that Xu sent the other day on a 
>> slide
>>     >     (attached) together with the plot from FST03 with no detector 
>> that he
>>    sent
>>     >     today, at the same scale. I think it looks fairly comparable, 
>> there is no
>>     >     obvious reason I can see that these results indicate a problem.
>>     >      >       I wish we had some understanding why the noise would be 
>> larger
>>     >     every 4th timebin. I have no clue about that. It is especially 
>> odd since
>>     >     things (readout, in particular) happen in the APV chip in groups 
>> of three
>>     >     timebins, but I don't know of anything except some "black-box" 
>> internal
>>     >     feature that happens in groups of four.
>>     >      >       It is very likely related to some internal feature of 
>> the
>>    APV. That
>>     >     doesn't mean we can conclude that it is not affected by some 
>> factor under
>>     >     our control though, of course.
>>     >      >       Sincerely,
>>     >      >
>>     >      >               Gerard
>>     >      >
>>     >      >
>>     >      > On 8/11/2020 5:56 PM, Xu Sun wrote:
>>     >      >> Hi Gerard,
>>     >      >> As Zhenyu mentioned, please find the plot of noise before 
>> sensor
>>     >     mounting (APV chips only) of FST03 attached. Please ignore the 
>> APV 7
>>    which
>>     >     shows an abnormal behavior, it is from the cable we used to take 
>> the
>>    noise run.
>>     >      >> We see the large CMN with strong time-bin dependence with the
>>    noise from
>>     >     APV chips only. This time bin dependence is the same as noise 
>> with sensor
>>     >     mounted, therefore it is very likely from APV chips on FST.
>>     >      >> Best,
>>     >      >> Xu
>>     >      >> On Tue, Aug 11, 2020 at 4:28 PM Zhenyu Ye 
>> <yezhenyu2003 AT gmail.com
>>    <mailto:yezhenyu2003 AT gmail.com>
>>     >     <mailto:yezhenyu2003 AT gmail.com <mailto:yezhenyu2003 AT gmail.com>>
>>    <mailto:yezhenyu2003 AT gmail.com <mailto:yezhenyu2003 AT gmail.com>
>>     >     <mailto:yezhenyu2003 AT gmail.com 
>> <mailto:yezhenyu2003 AT gmail.com>>>> wrote:
>>     >      >>    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 <mailto:gvisser AT indiana.edu>
>>     >     <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>>
>>     >      >>    <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>
>>    <mailto:gvisser AT indiana.edu <mailto: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>
>>     >     <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>>
>>     >      >>    <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>
>>    <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>>>
>>     >     <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>
>>    <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>>
>>     >      >>    <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>
>>    <mailto: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>
>>    <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>>
>>     >      >>    <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>
>>    <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>>>
>>     >      >>     >>    <mailto:gvisser AT indiana.edu
>>    <mailto:gvisser AT indiana.edu> <mailto:gvisser AT indiana.edu
>>    <mailto:gvisser AT indiana.edu>>
>>     >     <mailto:gvisser AT indiana.edu <mailto:gvisser AT indiana.edu>
>>    <mailto: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
>>     >      >>     >>    _______________________________________________
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