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<font size="2">Hi Justin, and All,<br>
<br>
yes a "two path" approach may give us the most value. <br>
The LYSO may not be the best solution either. The advantage is
that the geometry is very well defined <br>
like the cross section of 2mm by 2mm has a very high accuracy of
0.02mm the potential disadvantages,<br>
as pointed out by Eugene, is the potential shower effects as the
radiation length of this material is 1.1cm<br>
so a 10mm long crystal may be a better choice. Secondly the signal
decay time of order 35ns which may<br>
be too long at the high rates we can expect in GlueX III.<br>
<br>
cheers,<br>
Beni<br>
<br>
<br>
</font><br>
<div class="moz-cite-prefix">On 10/10/25 15:40, Justin Stevens
wrote:<br>
</div>
<blockquote type="cite" cite="mid:187540C8-B42F-43CF-9287-CF98C440E1A3@jlab.org">
Hi Beni, All,
<div><br>
</div>
<div>Thanks for the information about the crystals. I like the
idea to replace some of the scintillators directly in the
“production” microscope for the experiment if we’re convinced it
will produce usable signals so that we don’t create a loss of
acceptance in some region of the tagger. We would learn more
about the radiation hardness there than we would in the PS area.</div>
<div><br>
</div>
<div>A test setup in the PS area would have the advantage that it
could be more flexible to evaluate different couplings
procedures or other scintillator options which are more
speculative, with easier access to adjust the geometry or setup
without moving the full microscope. If we have any spare
material from the original scintillator from Saint-Gobain, we
could also have a control sample to compare with (before
radiation). </div>
<div><br>
</div>
<div>Maybe we want to do both of these tests in 2026?</div>
<div><br>
</div>
<div>-Justin<br id="lineBreakAtBeginningOfMessage">
<div><br>
<blockquote type="cite">
<div>On Oct 10, 2025, at 10:15 AM, zihlmann via Halld-tagger
<a class="moz-txt-link-rfc2396E" href="mailto:halld-tagger@jlab.org"><halld-tagger@jlab.org></a> wrote:</div>
<br class="Apple-interchange-newline">
<div>
<div><font size="4" face="monospace">Hi All,<br>
<br>
regarding scintillator alternatives (proposed by
Malte, Arshak, ...) I am investigating several paths
to obtain LYSO crystals <br>
with 2mm by 2mm cross section and a length of 20mm or
thereabouts. I think the length is not that important
but the cross section <br>
is to fit the current geometry. I contacted two
companies in the US and waiting responses. There is a
company in China where one <br>
could buy online such crystals right away with a cost
of 39$ per piece (excluding taxes and tarifs). So my
hope is that we could <br>
get our hands on some such crystals on a rather short
time scale.<br>
<br>
My basic idea is to equip the last "bundle" (most
downstream), 3 columns with 5 scintillators each, with
such crystals<br>
(the coupling has not yet been evaluated) till
February and run with that in the next run period. If
that is possible we would learn<br>
likely quite a lot about the usefulness of such
crystals and hopefully a path forward to "upgrade" the
full microscope.<br>
<br>
cheers,<br>
Beni <br>
</font><br>
<div class="moz-cite-prefix">On 10/10/25 08:36, Justin
Stevens via Halld-tagger wrote:<br>
</div>
<blockquote type="cite" cite="mid:0840C242-5EDD-4244-8875-74F803C24016@jlab.org">
<div>Hi Richard, All,</div>
<div><br>
</div>
<div>Thanks for the summary of yesterday’s discussion
and sorry I had to leave a bit early for the DNP
practice talks. While we continue to investigate
the exact reason for the loss of light yield, I
suggest we begin planning a test that can be
performed in 2026 to evaluate the options for
potential replacement of the scintillating fibers
before GlueX-III. </div>
<div><br>
</div>
<div>One possibility would be a small test setup on
one of the PS arms with candidates for the 2x2 mm
scintillators that can be tested with real signals
from <span style="caret-color: rgb(0, 0, 0);">energy-tagged
electrons. We would need </span>an equivalent
readout to the existing TAGM bundles, but most of
the electronics infrastructure: f250 and f1TDC
boards, crates, LV, etc. should already be available
in that area for the PS/ST/TPOL readout. So, I
believe we would need the TAGM preamp boards with
SiPMs and light guide fibers to couple to the
candidate scintillators we want to evaluate. Do we
have spares of those items that could be used for
such a test starting in early 2026?</div>
<div><br>
</div>
<div>There is also the potentially more important
question of what are the options for replacement
scintillators with the appropriate shape that may be
more radiation resistant and how can we test that
radiation hardness? I understood from Malte that
there may be some LYSO crystals with an appropriate
profile and Eljen <a href="https://eljentechnology.com/products/fibers" moz-do-not-send="true" class="moz-txt-link-freetext">https://eljentechnology.com/products/fibers</a> may
have some appropriate fibers, but we should consider
procuring these and other options soon if we aim to
test them next year.</div>
<div><br>
</div>
<div>More thoughts, suggestions, corrections are
welcome. I just think we need to keep brainstorming
on this to keep up the momentum towards finding a
solution for GlueX-III.</div>
<div><br>
</div>
<div>-Justin</div>
<div><br>
<blockquote type="cite">
<div>On Oct 9, 2025, at 2:20 PM, Richard T. Jones
via Halld-tagger <a class="moz-txt-link-rfc2396E" href="mailto:halld-tagger@jlab.org" moz-do-not-send="true">
<halld-tagger@jlab.org></a> wrote:</div>
<br class="Apple-interchange-newline">
<div>
<div dir="ltr">Hello all,
<div><br>
</div>
<div>We had a special meeting this morning at
10:00 devoted to a review of everything we
know regarding the degrading response of the
tagger microscope over the last few run
periods. A new logbook entry has been added
containing a historical record of the photon
yield and other calibration constants for
the TAGM which presents clear evidence of
significant loss of scintillation photon
yields over the past 5 years, with most of
the loss occurring in the rows that saw the
greatest flux of electrons.</div>
<div>
<ul>
<li><a href="https://logbooks.jlab.org/entry/4459304" class="gmail-logtitle" style="color:rgb(143,106,175);font-family:"Trebuchet MS","Helvetica Neue",Arial,Helvetica,sans-serif;font-size:14px;background-color:rgb(245,245,245)" moz-do-not-send="true">gain and photon
yield history of the tagger microscope</a></li>
</ul>
<div>Ideas to further investigate the exact
reasons for the decrease, as well as ideas
for recovering and sustaining good
performance during Phase 3 running are
still in process, with follow-up to happen
in the next Photon Beam working group mtg
next week.</div>
</div>
<div><br>
</div>
<div>-Richard Jones</div>
</div>
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