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<div>Hi Whit,</div>
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<div>Since Marc is out I’ll try to answer these as best as I can, which is why it’s also CC'd to our group’s gas mailing list in case I got anything grossly wrong.</div>
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That particular ambient pressure (and temperature) sensor is located on the Forward Carriage Level 1, at the top of rack C2-10, which is roughly at beam height at one of the most beam left racks.
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<div>I thought there was a document describing the system; maybe Bob has something he can share? Roughly pressure in the DC is controlled by PID based on the pressure in the buffer tank. There are two pressure sensors (both 0-5 psig) that can be selected from
as the process variable, the PID in turn controls the flow set point to the exhaust MFC. When more pressure is needed flow through the exhaust is reduced, when less pressure is needed flow through the exhaust is raised.</div>
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<div>One thing to keep in mind if you’re not getting enough pressure is that the supply flow to the DC must be high enough to account for any possible leaks/losses. If that isn’t high enough the PID will set the exhaust to 0 but the pressure won’t get to the
set point.</div>
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<div>Hope that helps.</div>
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<div>On Jan 15, 2025, at 4:11 PM, Marc Mcmullen <mcmullen@jlab.org> wrote:</div>
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<font face="Calibri, sans-serif" style="font-size: 11pt;"><b>From:</b><span class="Apple-converted-space"> </span>Armstrong, Whitney R. <<a href="mailto:warmstrong@anl.gov">warmstrong@anl.gov</a>><br>
<b>Sent:</b><span class="Apple-converted-space"> </span>Wednesday, January 15, 2025 3:02:29 PM<br>
<b>To:</b><span class="Apple-converted-space"> </span>Bob Miller <<a href="mailto:rmiller@jlab.org">rmiller@jlab.org</a>>; Marc Mcmullen <<a href="mailto:mcmullen@jlab.org">mcmullen@jlab.org</a>><br>
<b>Subject:</b><span class="Apple-converted-space"> </span>[EXTERNAL] Re: AHDC gas control</font>
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<div dir="auto">Hi Marc,</div>
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<div dir="auto">I see the ambient pressure is now reading values consistent with the weather. Where is this transducer located?</div>
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<div dir="auto">Could you please describe the pressure measurements and how they are used to maintain the gas pressure in the drift chamber?</div>
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<div dir="auto">Thanks,</div>
<div dir="auto">Whit</div>
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<div dir="auto">Whitney Armstrong</div>
<div dir="auto">Assistant Physicist</div>
<div dir="auto">Physics Division</div>
<div dir="auto">Building 203</div>
<div dir="auto"><br>
</div>
<div dir="auto">Argonne National Laboratory </div>
<div dir="auto">9700 S. Cass Ave. | Argonne, IL 60439</div>
<div dir="auto">630-252-5112 | 717-341-1080 mobile</div>
<div dir="auto"><a href="mailto:warmstrong@anl.gov">warmstrong@anl.gov</a> </div>
</div>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size: 11pt;"><b>From:</b><span class="Apple-converted-space"> </span>Bob Miller <<a href="mailto:rmiller@jlab.org">rmiller@jlab.org</a>><br>
<b>Sent:</b><span class="Apple-converted-space"> </span>Wednesday, January 15, 2025 11:20:34 AM<br>
<b>To:</b><span class="Apple-converted-space"> </span>Armstrong, Whitney R. <<a href="mailto:warmstrong@anl.gov">warmstrong@anl.gov</a>>; Marc Mcmullen <<a href="mailto:mcmullen@jlab.org">mcmullen@jlab.org</a>><br>
<b>Subject:</b><span class="Apple-converted-space"> </span>Re: AHDC gas control</font>
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Hi Whitney,</div>
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I will refer this question to Marc, as he wrote the controls.</div>
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Bob Miller</div>
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Hall B Lead Engineer</div>
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(757) 822-9586</div>
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<div id="x_x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size: 11pt;"><b>From:</b><span class="Apple-converted-space"> </span>Armstrong, Whitney R. <<a href="mailto:warmstrong@anl.gov">warmstrong@anl.gov</a>><br>
<b>Sent:</b><span class="Apple-converted-space"> </span>Wednesday, January 15, 2025 10:44 AM<br>
<b>To:</b><span class="Apple-converted-space"> </span>Bob Miller <<a href="mailto:rmiller@jlab.org">rmiller@jlab.org</a>><br>
<b>Subject:</b><span class="Apple-converted-space"> </span>[EXTERNAL] AHDC gas control</font>
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<div dir="auto">Hi Bob,</div>
<div dir="auto"><br>
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<div dir="auto">I have a question about the gas control system. When the alert gas set point is set to 90 mbar, what is that relative to in order to provide stable absolute pressure?</div>
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<div dir="auto">Also, the ambient pressure readout appears to not change and is at a value of 1017.54.</div>
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<div dir="auto">Thanks,</div>
<div dir="auto">Whit</div>
<div id="x_x_x_ms-outlook-mobile-signature" dir="auto">
<div><br>
</div>
<div dir="auto">Whitney Armstrong</div>
<div dir="auto">Assistant Physicist</div>
<div dir="auto">Physics Division</div>
<div dir="auto">Building 203</div>
<div dir="auto"><br>
</div>
<div dir="auto">Argonne National Laboratory </div>
<div dir="auto">9700 S. Cass Ave. | Argonne, IL 60439</div>
<div dir="auto">630-252-5112 | 717-341-1080 mobile</div>
<div dir="auto"><a href="mailto:warmstrong@anl.gov">warmstrong@anl.gov</a> </div>
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