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<span style="font-size:12pt;font-family:Times New Roman,Times,serif,serif,EmojiFont;"></span><span style="font-size:12pt;font-family:Times New Roman,Times,serif,serif,EmojiFont;"> Wednesday, June 12, 2019</span><br>
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<span style="font-size:12pt;font-family:Times New Roman,Times,serif,serif,EmojiFont;"> ***L102***</span><br>
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<span style="font-size:12pt;font-family:Times New Roman,Times,serif,serif,EmojiFont;"> 12:00-1:00 pm</span></span></font></p>
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<p style="margin-top:0;margin-bottom:0;">"Growth and properties of vapor diffused Nb3Sn coatings for SRF applications"
<br>
</p>
<p style="margin-top:0;margin-bottom:0;"><br>
</p>
<p style="margin-top:0;margin-bottom:0;"> Uttar Pudasaini
<br>
</p>
<p style="margin-top:0;margin-bottom:0;"><br>
</p>
<p style="margin-top:0;margin-bottom:0;"><br>
</p>
<p style="margin-top:0;margin-bottom:0;"> The College of William & Mary
<br>
</p>
<p style="margin-top:0;margin-bottom:0;"><br>
</p>
<p style="margin-top:0;margin-bottom:0;">Abstract:<br>
</p>
<p style="margin-top:0;margin-bottom:0;">The critical temperature (¡Ö 18 K) and superheating field (¡Ö 425 mT) of Nb3Sn are almost
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">twice that of niobium, thereby promising the higher quality factor and accelerating
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">gradient at any given temperature compared to traditional SRF cavities made of niobium.
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">It can enable higher temperature for cavity operation (4 K Vs 2 K), resulting in significant
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">reduction in both capital and operating cost for SRF accelerators. The most promising path
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">toward deployment is by tin vapor diffusion coating of niobium cavity interiors via a two
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">steps nucleation-then-growth sequence. Understanding of Nb3Sn nucleation and growth is
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">essential to the progress with Nb3Sn vapor diffusion coatings of SRF cavities. Samples
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">representing different stages of Nb3Sn formation have been produced and examined to elicit
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">the effects of nucleation, growth, process conditions, and impurities. Broadly, nucleation
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">deposits ultra-thin tin film and near-micron sized particles as well, resembling Stranski-Krastanov
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">growth. Tin diffuses via grain boundaries to the Nb3Sn-Nb interface, where the formation of
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">Nb3Sn into the niobium bulk takes place during the growth stage. RF measurements of coated
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">cavities combined with material studies of samples were continuously employed to update the
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">coating process to coat SRF cavities. Following an updated coating process, we were able to
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">produce Nb3Sn single-cell cavity with quality factor 2¡Á1010 for accelerating gradient up to
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">15 MV/m at 4 K, without any significant Q-slope. In this presentation, the genesis of the Nb3Sn
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">coating in a typical tin vapor diffusion process, effect of different coating parameter variation on
<br>
</p>
<p style="margin-top:0;margin-bottom:0;">material properties of Nb3Sn, and their consequences to the coating of SRF cavities will be discussed.</p>
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