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Hi Richard,<br>
<br>
OK, looks good. I will look at options for the supplies.<br>
<br>
Thanks and best regards,<br>
Fernando<br>
<br>
On 12/9/2013 10:28 AM, Richard Jones wrote:
<blockquote
cite="mid:CABfxa3QLVFh7-c4hXrerYvFccsA+mZYDqg=TgPK4+2CB54yN5g@mail.gmail.com"
type="cite">
<div dir="ltr">Fernando,
<div><br>
</div>
<div>Our background study showed that we could continue to
function for 10 years of high-rate running without annealing,
just allowing the dark rate to increase at the rate that was
measured in Hall B and allowing the supply current to
increase. Under the zero-shielding scenario, just leaving the
electronics unshielded in the tagger hall, we estimated that
we would reach the point where we would need to do something
(eg. anneal or replace the SiPM's) after 10 years of high-rate
running. The usual assumptions were applied (100 days of
running per year, standard 20 micron diamond, 12 GeV electrons
at 2.2 microAmps). With shielding, we expect to reduce this
figure by a factor of 5-10 (the simulation gave a factor
around 8), so we should be able to run for the duration of
GlueX without annealing.</div>
<div><br>
</div>
<div>I agree with you that we can segment the supplies. Each of
them can be split up to 6 ways, because there are 6 identical
backplanes in the system. The specs we posted were for the
total sum of all 6 backplanes.</div>
<div><br>
</div>
<div>-Richard J.</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Mon, Dec 9, 2013 at 9:52 AM,
Fernando J Barbosa <<a moz-do-not-send="true"
href="mailto:barbosa@jlab.org">barbosa@jlab.org</a>>
wrote:<br>
<blockquote class="gmail_quote">
<div bgcolor="#FFFFFF" text="#000000"> Hi Richard,<br>
<br>
Certainly the rates in the tagger are higher but what is
your planning for annealing the SiPMs? I am just curious
given the higher rates.<br>
<br>
Regarding the power supplies, you mentioned the
possibility of having three supplies instead of one for
the whole system. Is it possible to consider further
segmentation? One channel per backplane? Do you have a
document that shows the whole system as installed? The
issue is also related to the space available under the
magnet.<br>
<br>
Best regards,<br>
Fernando
<div>
<div class="h5"><br>
<br>
<br>
On 12/6/2013 10:09 AM, Richard Jones wrote:
<blockquote type="cite">
<div dir="ltr">Fernando,
<div><br>
</div>
<div>These estimates for the BCal do not apply to
the TAGM, where the rates are much higher. We
can set up a meeting to discuss this further if
you feel we need it. We worked out these rates
back during the design phase for the readout
electronics, and had them reviewed within the
photon beam working group. Also keep in mind
that the neutron flux is much higher in the
tagger hall than in the experimental hall. On
the other hand, the TAGM can operate efficiently
at much higher single-pixel rates than can a
calorimeter because it is not producing an
energy measurement, but only time, and the
photon statistics are high, <n> = 350-400
within a 15ns window. We are shielding these
electronics, but we only expect to cut down the
neutron flux by about a factor 10-20 in this
way. Alex Somov did the neutron rates and
shielding studies for us, and can provide more
details in this regard.</div>
<div><br>
</div>
<div>-Richard J.</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Fri, Dec 6, 2013 at
9:04 AM, Fernando J Barbosa <<a
moz-do-not-send="true"
href="mailto:barbosa@jlab.org">barbosa@jlab.org</a>>
wrote:<br>
<blockquote class="gmail_quote">
<div bgcolor="#FFFFFF" text="#000000"> Hi
Richard,<br>
<br>
In reference to the BCAL and taking Yi's
measurements in Hall A regarding radiation
damage, we settled on a maximum of 10mA for
10 arrays or 160 cells (3mm x 3mm). This
works out to 62.5uA per cell and your
estimate is higher by a factor greater than
10. What is your plan for annealing the
SiPMs? Frequency?<br>
<br>
Did you look into any supplies that might
fit your requirements? I recall that each
backplane of the TAGM has a single bias
supply input, correct? This would be
important in considering a multi-channel
supply system. Please send me your latest
drawings on the TAGM system and its
installation in the Tagger hall.<br>
<br>
Best regards,<br>
Fernando
<div>
<div><br>
<br>
<br>
On 12/5/2013 10:50 PM, Richard Jones
wrote:
<blockquote type="cite">
<div dir="ltr">Hello Fernando,
<div><br>
</div>
<div>I am spec'ing the Vbias supply
capacity at 500mA to allow for the
maximum SiPM draw current that is
permitted by the bias voltage
supply system. Initially we
expect the average current to be
around 15 mA at full intensity
(2.2 uA electrons on 20 micron
diamond) but that it will increase
gradually over time due to
radiation damage. To get the
maximum current spec, I imagine
the worst possible circumstances
under which the radiation damage
might accumulate faster than
expected, and ask how much current
could we sustain across all
channels before the resolution and
efficiency degrade significantly
due to dark current. The answer
to that is approximately 800uA per
channel, which totals about 400mA
from the supply. I rounded that
up to 500mA. </div>
<div><br>
</div>
<div>-Richard Jones</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Thu, Dec
5, 2013 at 4:51 PM, Fernando J
Barbosa <<a
moz-do-not-send="true"
href="mailto:barbosa@jlab.org">barbosa@jlab.org</a>>
wrote:<br>
<blockquote class="gmail_quote">Hi
Richard,<br>
<br>
I looked at the specs and the
bias supply current seems to be
excessive at 500mA. What's the
reason for this?<br>
<br>
Best regards,<br>
Fernando
<div>
<div><br>
<br>
<br>
On 12/5/2013 3:33 PM,
Richard Jones wrote:<br>
<blockquote
class="gmail_quote"> Hello
Alex,<br>
<br>
Here is a draft of the
specs for the microscope
readout dc power supplies.
They can be a single unit
for each of 3 levels, or a
few lower-capacity
supplies in tandem with
the same total output
capacity. Please request
justification for any of
the specs. One thing we
do not spec here, but
think would be useful, is
separate delivery and
sense terminals for each
output. We have separate
pins on the backplane
connector for this
purpose.<br>
<br>
<a moz-do-not-send="true"
href="http://zeus.phys.uconn.edu/wiki/index.php/Microscope_Electronics#Power_Supply_Requirements">http://zeus.phys.uconn.edu/wiki/index.php/Microscope_Electronics#Power_Supply_Requirements</a><br>
<br>
-Richard Jones<br>
</blockquote>
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