<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
We have all talked and agree that we should go back to the 50
micron, including Sascha. We too want to do this ASAP.<br>
<br>
<div class="moz-cite-prefix">On 07/18/2012 07:57 AM, Elton Smith
wrote:<br>
</div>
<blockquote cite="mid:5006A493.1060503@jlab.org" type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<div class="moz-cite-prefix">HI Fernando, Mark and Werner,<br>
<br>
The order for the SiPMs is out and if a change is going to be
made, it should be done before Hamamatsu gets started. From
Fernando's tests, it seems wise to revert to the well-tested 50
um sensors for all applications, including the ST. Sasha is
planning to contact the Hamamatsu rep to find out if and when
the switch can be made. The decision should be made a soon as
possible.<br>
<br>
Cheers, Elton.<br>
<pre class="moz-signature" cols="72">Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite #16
Newport News, VA 23606
(757) 269-7625
(757) 269-6331 fax </pre>
On 7/16/12 10:34 PM, Fernando J Barbosa wrote:<br>
</div>
<blockquote cite="mid:5004CF1C.9080208@jlab.org" type="cite">Hi
Mark, Werner, <br>
<br>
I have been optimizing and testing the ST readout for the 50 um
and 100 um SiPMs. There are 4 SiPMs connected together (current
sum) to one readout channel on each of two SiPM PCBs (50 um and
100 um). The sensor capacitance is the same in both cases so one
optimization is all that is required for fast risetimes for the
group of 4 SiPMs. <br>
<br>
The prototype is fully functional but I determined that the
micro-coax ribbon cable assembly (connects the readout to the
breakout PCB) is not good enough due to cross-talk (primarily
due to the connectors on these cable assemblies - a single
micro-coax cable assembly provides the power to the electronics,
3 bias supplies, 6 outputs [3 channels w/ 3 for ADCs and 3 for
TDCs] and has a thermocouple two-wire output for readout). The
readout is temperature compensated via thermistors. The
workaround has two coax cables (ADC and TDC), in addition to the
micro-coax, which bypass the micro-coax signal connections. So,
the final design will change but the current prototype will be
useful for tests with ST detector prototype. <br>
<br>
I have attached two pics: ST50 is for the 50 um and ST100 is for
the 100 um. These were taken with a laser and a diffuser
stimulating all 4 SiPMs in the group. Some comments: <br>
<br>
1. 50 um - Fast pulses with width of 37 ns (~10%-10%) <br>
2. 100 um - Fast pulses with width of 125 ns (~10%-10%),
step/kink ~ 5 ns after peak. <br>
<br>
The leading edge slew rate is about the same for both but the
100 um has a slower recovery w/a kink (the quench resistor on
each pixel would need to be ~3x smaller for similar recovery but
there are other factors at play, i.e. Geiger current) . I will
investigate this a little further but these are definitely
characteristics of these SiPMs and I will write a GlueX note
soon. <br>
<br>
In the meantime, let me know if there is interest in pursuing
the 100 um further. Even though the rates are expected to be in
the KHz range, the long recovery time will likely lead to
pileup. <br>
<br>
Best regards, <br>
Fernando <br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Halld-pid mailing list
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:Halld-pid@jlab.org">Halld-pid@jlab.org</a>
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="https://mailman.jlab.org/mailman/listinfo/halld-pid">https://mailman.jlab.org/mailman/listinfo/halld-pid</a></pre>
</blockquote>
<br>
<br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Halld-pid mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Halld-pid@jlab.org">Halld-pid@jlab.org</a>
<a class="moz-txt-link-freetext" href="https://mailman.jlab.org/mailman/listinfo/halld-pid">https://mailman.jlab.org/mailman/listinfo/halld-pid</a></pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Mark M. Ito
Jefferson Lab (<a class="moz-txt-link-abbreviated" href="http://www.jlab.org">www.jlab.org</a>)
(757)269-5295</pre>
<br>
<br>
</body>
</html>