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<div id="content">Below are my notes from today's meeting on obtaining
a clean compton tune. We will pick this discussion up and finalize the
plan after the 8am meeting. Thanks for attending and I'll see everyone
tomorrow morning.<br>
<h1 class="title">Arne's Journal</h1>
<div id="outline-container-1" class="outline-2">
<h2 id="sec-1"><span class="section-number-2">1</span> Hall-A Compton
Meeting <span class="tag"><span class="OPS">OPS</span> <span
class="SELECT">SELECT</span> <span class="Bteam">Bteam</span> <span
class="AHLA">AHLA</span></span></h2>
<div class="outline-text-2" id="text-1">
<p><span class="timestamp-wrapper"> <span class="timestamp">2009-11-09
Mon 14:24</span></span><br>
</p>
</div>
<div id="outline-container-1.1" class="outline-3">
<h3 id="sec-1.1"><span class="section-number-3">1.1</span> Injector
Summary <span class="tag"><span class="Reza">Reza</span></span></h3>
<div class="outline-text-3" id="text-1.1">
<p>Roughly same setup as for Happex-III. This setup results in a large
compton rate. </p>
<ul>
<li>pre-buncher is at 0.95
</li>
<li>capture phase
</li>
<li>laser phase
</li>
<li>small adjustment of lens in front of the 1/4 cryo unit.
</li>
<li>BLM in chicane trip as current approaches 200 μ A
</li>
<li>The 1kHz/μ A rate drops at high current due to pile up.
</li>
</ul>
</div>
</div>
<div id="outline-container-1.2" class="outline-3">
<h3 id="sec-1.2"><span class="section-number-3">1.2</span> Hall-A
transport <span class="tag"><span class="Yan">Yan</span></span></h3>
<div class="outline-text-3" id="text-1.2">
<ul>
<li>Dog4 was railed and has been fixed today.
</li>
<li>small dispersion in Arc8 and Arc9.
</li>
<li>Orbits look reasonable in the machine.
</li>
<li>Horizontal orbit in A line is not nominal. Horizontal position at
target is -2.4mm. </li>
<li>Upstream of compton chicane appear to the same as for Happex-III
</li>
<li>Steering up/down left/right shows no changes.
</li>
<li>BLM activity is low
</li>
<li>Compton ion chamber shows some counts with high current, normally
the ion chamber reads zero at all currents.
</li>
</ul>
</div>
</div>
<div id="outline-container-1.3" class="outline-3">
<h3 id="sec-1.3"><span class="section-number-3">1.3</span> Matching
summary <span class="tag"><span class="Michele">Michele</span></span></h3>
<div class="outline-text-3" id="text-1.3">
<ul>
<li>ε and TWISS measurements on Thursday were successful and
showed that the horizontal match was the most problematic.
</li>
<li>Match was loaded
</li>
<li>Beam size measurements after match was loaded on Friday, showed
that
the beam was no longer matched.
</li>
<li>ε and TWISS measurements on Monday show that the
horizontal β and α values have changed. </li>
<li>Using the Monday input measurements, the predicted size for the
beam
agrees with the Friday harp measurements, so it appears that the
machine has been stable since Friday.
</li>
<li>What is the dispersion leakage in the matching region?
.05/.8=η<sub>1C05</sub>/η<sub>1c12</sub> if η<sub>1C12</sub> = 4m, then
η<sub>1C05</sub> = 25cm. Is this significant?
</li>
</ul>
</div>
<div id="outline-container-1.3.1" class="outline-4">
<h4 id="sec-1.3.1"><span class="section-number-4">1.3.1</span> Post
meeting information </h4>
<div class="outline-text-4" id="text-1.3.1">
<p>Addition match data was taken after the meeting. Again horizontal
plane shows some changes, whereas the vertical plane is reasonable
constant. Some of the differences between the data set is the
excitation of the Hall-A dipole string. Is this causing a fringe
field upstream of 1C05?
</p>
</div>
</div>
</div>
<div id="outline-container-1.4" class="outline-3">
<h3 id="sec-1.4"><span class="section-number-3">1.4</span> Raytrace
summary <span class="tag"><span class="Tief">Tief</span></span></h3>
<div class="outline-text-3" id="text-1.4">
<ul>
<li>No significant distortion in horizontal and vertical. </li>
<li>But some distortion is introduced in the compton region.
</li>
<li>emittance reasonably conserved.
</li>
</ul>
</div>
</div>
<div id="outline-container-1.5" class="outline-3">
<h3 id="sec-1.5"><span class="section-number-3">1.5</span> Suggestions </h3>
<div class="outline-text-3" id="text-1.5">
<ul>
<li>Requirements from Hall-A are that the photon count rate should be
below 100 cnt/μ A. </li>
<li>Can OPS have access to the "real" rate so that we can see how
close
the rate is to the maximum rate at which the photon counter
saturates? Alex says yes, see action item.
</li>
<li>Waveform and FFT of the compton counts to see if the MOMOD
frequencies show us anything. </li>
<li>SEE BPM FFT could be used as well to look for a source or loss of
specific frequencies.
</li>
<li>Change injector optics back to M<sub>56</sub> ≠ 0 for different
bunch
compression. </li>
<li>Look at orbits for 5.9GeV run in March 2010.
</li>
<li>null out dispersion leakage
</li>
<li>Is the 5-pass separator operating at the right point.
</li>
</ul>
</div>
<div id="outline-container-1.5.1" class="outline-4">
<h4 id="sec-1.5.1"><span class="section-number-4">1.5.1</span> Post
meeting suggestions (Tiefenback) </h4>
<div class="outline-text-4" id="text-1.5.1">
<ul>
<li>Mike Spata had expressed concern over the separator high power.
Whether this could be a source of problems can be tested by turning
the separator off and using magnetic extraction (even if only for 20
minutes) to check for HallA Compton background count sensitivity. </li>
<li>It is possible that there is some injector-sourced bleed-through
causing a diffuse background beam in the Hall A line. Shutting the B
and C slits (even for 10-20 minutes) might be a worthwhile test of
whether there is any contribution from this source. (I suspect not,
but I'm all for ruling things out cleanly.) With the beam quality
questions we have, it may behoove us to close down the Hall A slit
partially to restrict the longitudinal acceptance of the injector and
improve the quality of the beam at 10 uA-ish current levels (turning
the pre-buncher down or off). This would rule out injector-sourced
halo (along with closing the B and C slits) as a contributor to the
HallA Compton background. </li>
<li>With the HallA slit narrowed down, a laser phase scan across the
slit would help us confidently to conclude that the injector is not
fogging the beam line. </li>
<li>Reza had suggested that the Wien filter does not now have the
same
setting it had at 5.9 GeV. This is not a high-confidence problem
source for the Compton background, but it is too simple to do and the
Wien has been subject to too much ugliness in the past not to look.
I'd endorse changing the Wien filter back to the 5.9 GeV run settings
just as a test, not as a long-term configuration. The more things we
can rule out and the better we understand the parametric behavior, the
better able we will be to identify and correct this nagging issue. </li>
</ul>
</div>
</div>
</div>
<div id="outline-container-1.6" class="outline-3">
<h3 id="sec-1.6"><span class="section-number-3">1.6</span> Actions </h3>
<div class="outline-text-3" id="text-1.6">
</div>
<div id="outline-container-1.6.1" class="outline-4">
<h4 id="sec-1.6.1"><span class="section-number-4">1.6.1</span> <span
class="todo TODO"> TODO</span> Communicate EPICS record name of the
raw photon rate <span class="tag"><span class="Alex">Alex</span></span></h4>
<div class="outline-text-4" id="text-1.6.1">
<p>The epics record name of all Compton epics records with human
readable
description should be communicated to OPS (Arne).
</p>
</div>
</div>
<div id="outline-container-1.6.2" class="outline-4">
<h4 id="sec-1.6.2"><span class="section-number-4">1.6.2</span> <span
class="todo TODO"> TODO</span> Provide independent of compton
equipment halo detector <span class="tag"><span class="Alex">Alex</span></span></h4>
<div class="outline-text-4" id="text-1.6.2">
<p>Either pick an existing detector that is tightly correlated to
Compton
detector that is robust and always on. Put it in EPICS and tell OPS
about it. This detector should be stay on all the time and have
stable configuration. </p>
</div>
</div>
<div id="outline-container-1.6.3" class="outline-4">
<h4 id="sec-1.6.3"><span class="section-number-4">1.6.3</span> <span
class="todo TODO"> TODO</span> Escort Mike Tiefenback on a tour in
Hall-A <span class="tag"><span class="Alex">Alex</span></span></h4>
<div class="outline-text-4" id="text-1.6.3">
</div>
</div>
</div>
<div id="outline-container-1.7" class="outline-3">
<h3 id="sec-1.7"><span class="section-number-3">1.7</span> Thursday </h3>
<div class="outline-text-3" id="text-1.7">
<ol>
<li>Check main machine, check/fix A orbit.
</li>
<li>Restore beam to A
</li>
<li>Check compton rates
</li>
<li>Load new Match quads
</li>
<li>Check compton rates
</li>
<li>Measure beam size will ALL accelerator harps in the A line.
</li>
<li>Go straight ahead mode (not through compton) and measure compton
background. </li>
</ol>
</div>
</div>
<div id="outline-container-1.8" class="outline-3">
<h3 id="sec-1.8"><span class="section-number-3">1.8</span> Friday </h3>
<div class="outline-text-3" id="text-1.8">
<ol>
<li>Null vertical spin component (Grames)
</li>
<li>Make A-B-C beams co-linear
</li>
<li>Look for obstruction in Injector
</li>
<li>Measure Compton
</li>
<li>Steering in 0L region vs. compton count rate.
</li>
<li>check 5 MeV dipole chamber
</li>
<li>???</li>
<li>????</li>
<li>?????</li>
<li>??????</li>
<li>???????<br>
</li>
</ol>
</div>
</div>
</div>
<div id="postamble">
<p class="author"> Author: Arne Freyberger
<a href="mailto:freyberg@jlab.org"><freyberg@jlab.org></a>
</p>
<p class="date"> Date: 2009-11-09 19:47:38 EST</p>
<p class="creator">HTML generated by org-mode 6.32trans in emacs 23</p>
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