<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 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 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 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 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>
<br>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</blockquote>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</blockquote>
<br>
</div></div></div>
</blockquote></div><br></div>