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</style><article id="node-618961" class="node node-logentry article ia-n clearfix" role="article"><header class="node-header"><h1 class="node-title">
<a href="https://logbooks.jlab.org/entry/3546081" rel="bookmark">Continued Noise Investigation</a>
</h1>
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<p class="author-datetime">
Lognumber <a href="https://logbooks.jlab.org/entry/3546081" class="lognumber" data-lognumber="3546081">3546081</a>. Submitted by <a href="https://logbooks.jlab.org/user/davidl">davidl</a> on <time datetime="2018-03-22T13:26:10-0400" pubdate="pubdate">Thu, 03/22/2018 - 13:26</time>. </p>
<table class="field-vitals"><tr><th>Logbooks: </th><td><a href="https://logbooks.jlab.org/book/hdfmwpc">HDFMWPC</a></td></tr></table></div>
<div class="logentry node-content">
<p>Some effort was made in the hall over the past few days to reduce the amount of noise in the MWPC. Several people<br />
were involved with numerous tests. One thing that seemed to reduce the amplitude of the noise was simply grabbing<br />
the chamber itself, using the capacitance of the human body. I took a few runs this morning under various conditions.<br />
These are described below. For all of these runs, the HV cable was connected to both the chamber and the CAEN<br />
supply but the HV itself was off.</p>
<p>Run 257: Attached chamber ground plane to u-metal cylinder via large copper wire with copper clamps. The<br />
cylinder was found in the hall. It was made from a sheet that was rolled up into a cylinder that was approximately<br />
1 ft in diameter and 1ft tall.</p>
<p>Run 258: Grabbed the chamber firmly to use human body as capacitor to absorb noise. Gripped at roughly center of<br />
HV side of chamber. Both upstream and downstream sides were in contact with skin.</p>
<p>Run 259: No additional capacitor/grounding attached.</p>
<p>Run 260: Attached a large metal trashcan using copper cable with clamps. The can was placed on some cloth to<br />
make sure it was electrically disconnected from platform.</p>
<p>The figure below shows the maximum sample height vs. wire number for each of the 4 runs,.<br />
[figure1]</p>
<p>The following figure is made by projecting wires 73-79 from the above plots onto the y-axis. This indicates that the human<br />
body and the trash can give similar improvements. While in the hall, the u-metal shield appeared to give an improvement<br />
when observing from the scope, but that does not seem to be the case in these plots. One difference from the u-metal and<br />
the trash can is that the trash can was placed on cloth in order to insure electrical isolation from the platform itself. The u-metal<br />
was left to sit on the platform. It is unclear if the paint on the platform gave sufficient resistance to isolate the u-metal.<br /></p><div class="image-wrapper"><img class="image-style-plentybig" src="cid:a5bfb0fa3025348ebadb3f83c379558f@logbooks.jlab.org" width="698" height="476" alt="" /></div>
<p>OBSERVATIONS:</p>
<p>1. There is still a strong dependence on wire number for the noise with wires near the center of the chamber being more affected.<br />
One possible action is to solder additional cables to the HV board grounds and connect them to the ground planes as is already done<br />
at the top and bottom of the chamber.</p>
<p>2. Several wires seem to have significantly lower noise (e.g. wires 63 and 64). It is not clear what is different about these wires.</p>
<p>3. A Number of people have commented on possible solutions. These all tend to involve installing good shielding around all of the<br />
sense boards with thick, short contacts between the sense board ground and the shielding,</p>
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