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<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">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<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); 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"><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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</blockquote>
</div>
<br>
<br>
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