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Hi Saba,</div>
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I checked with my MBE guy, and he offered the following:</div>
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"I've used barium quite a bit. I definitely recommend purchasing dendritic barium sealed in a glass ampoule instead of packed with oil and then minimize exposure to oxygen and water. We would try to load it right before pumping down. Some suppliers can even
load the Ba into a customer supplied crucible for you under argon. I've seen some reports of pre-melting the Ba source in a crucible under inert atmosphere to provide a uniform surface but that takes a bit more effort."
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I'll forward you his e-ddress in a PM.</div>
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Mac</div>
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Harvard CNS<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> labnetwork-bounces@mtl.mit.edu <labnetwork-bounces@mtl.mit.edu> on behalf of Saba Sadeghi <saba.sadeghi@uwaterloo.ca><br>
<b>Sent:</b> Thursday, November 21, 2019 12:45 PM<br>
<b>To:</b> labnetwork@mtl.mit.edu <labnetwork@mtl.mit.edu><br>
<b>Subject:</b> [labnetwork] Outgassing and evaporation of Barium source in MBE</font>
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<p>Hello everyone,</p>
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<p><span style="font-size:12pt">I </span><span style="font-size:12pt">was wondering if anyone has worked with </span><span style="font-size:12pt">evaporation of </span><span style="font-size:12pt">Barium using effusion cell in a </span><span style="font-size:12pt">MBE
chamber and I was hoping to get some insight from this experienced community. </span><br>
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<p>I have issues with outgassing of the Ba source; since it is very reactive with air outgassing to get rid of H2 and H2O would take time. I tried to limit the time that the Ba source was exposed to air after cleaning with hexane (it's shipped in mineral oil),
but for me it's taking more than two weeks now to reach pressure of below 1.00 E-7 mbar while keeping the source temperature at 400
<sup>o</sup>C. The base pressure of the chamber is 2 E-10mbar. I was wondering if anyone has experienced this problem and what's the best way to degas Ba before evaporation?</p>
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<p>Thanks in advance,</p>
<p>Saba</p>
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<p>--</p>
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<i>Saba Sadeghi, PhD</i></p>
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<i>Quantum Devices Fabrication Scientist</i></p>
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<i>Institute for Quantum Computing, University of Waterloo</i></p>
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<i>Phone: 519-888-4567 ext. 31111</i></p>
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<i>Email: saba.sadeghi@uwaterloo.ca</i></p>
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