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<p class="MsoNormal">Scott,<o:p></o:p></p>
<p class="MsoNormal"> Over the years, I have had great results with MRL external torches. The main advantage is being able to see the combustion and whether or not the torch depth is correct. The other big advantage is being able to use a flame detector that
will shut off the H2 flow in a couple of seconds (adjustable) to avoid injecting gas continuously into a cold torch. You may be seeing uniformity issues with the coaxial if you have tiny air leaks being pulled into the tube from the ground glass joints. Are
you using Teflon seals? In any event, please ensure that you are running the H2/O2 mix Oxygen rich to prevent accumulating H2 downstream.<o:p></o:p></p>
<p class="MsoNormal"> Equipment Dood<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:14.0pt">Steve Paolini<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">Principal Equipment Engineer<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">Harvard University Center for Nanoscale Systems<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">11 Oxford St.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">Cambridge, MA 02138<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">617- 496- 9816<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">spaolini@cns.fas.harvard.edu<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">www.cns.fas.harvard.edu</span><span style="font-size:14.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> labnetwork <labnetwork-bounces@mtl.mit.edu> <b>
On Behalf Of </b>Scott Blondell<br>
<b>Sent:</b> Tuesday, August 03, 2021 3:50 PM<br>
<b>To:</b> labnetwork@mtl.mit.edu<br>
<b>Subject:</b> [labnetwork] Pyrogenic internal torch<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Greetings Labnetters,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We’re in the process of tweaking our wet ox process. Hardware changes provided an opportunity to consider
<o:p></o:p></p>
<p class="MsoNormal">alternatives to our current internal “candy cane” torch arrangement employed in several tubes. Currently running 6” silicon<o:p></o:p></p>
<p class="MsoNormal">in 205/211mm quartz w/candy cane torch. This doesn’t give us the luxury of a simple visual inspection without pulling the tube.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A straight coaxial torch is being qualified now, and it’s presenting some challenges. Growth rates are lower than predicted and
<o:p></o:p></p>
<p class="MsoNormal">across boat uniform is >6%. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Polling the audience: what are your preferences – cane v straight?; straight torch design details/vendors?; gas flows?<o:p></o:p></p>
<p class="MsoNormal">There’s a lot of knobs to turn – at 2/runs per day it’s slow to fine tune.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We do have an MRL external torch that served us well for lower temp processes. Space and budget precludes using it in<o:p></o:p></p>
<p class="MsoNormal">multiple tubes.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Appreciate any feedback, tips or outright opinions.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Scott P. Blondell<o:p></o:p></p>
<p class="MsoNormal">Fac. Mgr.<o:p></o:p></p>
<p class="MsoNormal">RIT SMFL<o:p></o:p></p>
<p class="MsoNormal">315.738.4073<o:p></o:p></p>
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