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[Gerard Visser <gvisser AT indiana.edu>]

hi Zhenyu,
	I think this would be an excellent strategy. Of course we still have to modify 
the patchpanel board in such a scheme, but it is much simpler to cut one (two?) 
traces and wire over to pins on the same connector locally, than to cut at both 
connectors and wire across the board as will be needed I think to carry two bias 
through external cables.
	If we'll reuse IST inner cable there are extra lines (from four no-longer-used 
APV signals). If we have new cable, of course we can have anything we want.

        Gerard


p.s. I don't, however, understand what this may have to do with current draw due 
to radiation damage. Please explain... I think the motivation for splitting bias 
is if there is a real hard problem (short circuit) on the bias on (or to) one of 
the sensors. If it is simply drawing higher current due to radiation damage but 
still working fine, then so is the other sensor (group) in that wedge and no 
reason they can't share a common bias, no?


On 2/18/2019 12:52 PM, Zhenyu Ye wrote:
> Hi Li,
>
> Regarding the first question, my proposal would be to
>
> use shared bias for inner/outer sensors as the default running scheme
> but keep the option of using separate biases (the motivation is that if the 
> leakage current for the inner sensor is too high due to larger radiation does)
>
> This means that we
>
> 1) make no modification to the existing IST back of crate boards, 
> outer-signal cables and patch panel boards
> 2) have separate bias lines on inner signal cables and T-board
>
> Steve probably has already mentioned it but I forgot the answer: is it 
> already the case that inner signal cable has separate bias lines for the 
> inner/outer sensors?
>
> Zhenyu
>
> > On Feb 15, 2019, at 8:34 AM, LI YI <li.yi AT sdu.edu.cn> wrote:
> >
> > Dear All,
> >
> > Here is a follow-up to yesterday's meeting.
> >
> > 1. Two biases for inner and outer hybrids:
> > The current T-board has two separate biases for inner and outer
> > hybrids. If we want to share bias between two hybrids, we can add a
> > jumper.
> >
> > 2. Two connectors (for inner and outer hybrids) on the same side of T-board:
> > During yesterday's meeting, it is suggested that it will be easier to
> > assemble T-board and hybrids if two connectors are on the same side.
> > Could anyone elaborate more why it is easier to assemble with the same
> > side connectors? It would be nice to evaluate the pros and cons
> > carefully before the final decision is made (due to 1. time constrains
> > see below, 2.the possibility of more layers, six layers instead of
> > current four, which may increase the complexity for manufacturing)
> >
> > 3. Production time:
> > T-board ~ 10 days
> > Hybrid ~ 2-3 weeks
> > Usually it takes more than one round to get it right by the vendor.
> > One round means that vendor produces it and we test and give feedback
> > to vendor. That means, it is likely to take at least 2 times 2-3weeks
> > = 4-6 weeks to give hybrid right and 2 times 10 days  = 20 days to get
> > T-board right.
> >
> > Best,
> > Li
> >
> > On Thu, Feb 14, 2019 at 7:06 AM Ye, Zhenyu <yezhenyu AT uic.edu> wrote:
> > > Dear all,
> > >
> > > We will have a meeting to discuss Forward Silicon Tracker tomorrow at 9am BNL 
> > > time. The meeting agenda and bluejeans info can be found at
> > >
> > > https://drupal.star.bnl.gov/STAR/blog/yezhenyu/forward-silicon-tracker-weekly-meeting
> > >
> > > Best,
> > > Zhenyu
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