SRF2013 - List of Authors (McNeal, S.R.)

Paper	Title	Page
TUP072	Quality Factor Measurements of the Ultramet 3 GHz Cavity Constructed Using Chemical Vapour Deposition	607
	D.L. Hall, D. Gonnella, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V.M. Arrieta, S.R. McNeal Ultramet, California, USA
	Funding: US Department of Energy Phase 1 Small Business Innovation Research award to Ultramet A seamless 3 GHz bulk niobium cavity constructed by Ultramet using rapid chemical vapor deposition (CVD) techniques has been tested on the vertical SRF test stand at Cornell. The cavity received a 25 um buffered chemical polish (BCP) and 700 C heat treatment for 4 days. First test results gave an intrinsic quality factor of Q0 = (1.55 ± 0.12) x 10⁷ and (2.00 ± 0.15) x 10⁷ at 4.2 K and 1.5 K, respectively. A second BCP removed 100 um of material, after which test results improved to Q0 = (7.59 ± 1.52) x 10⁷ and (4.16 ± 0.31) x 10⁸ at 4.2 K and 1.5 K. During the ﬁrst test poor coupling to the input ampliﬁer impeded tests at accelerating ﬁelds >0.2 MV/m, while during the second test the cavity quenched at 1.3 MV/m when operating at 1.5 K. An optical inspection of the cavity after the second test revealed the presence of at least 4 pits on the upper hemisphere suggesting an area of higher than average surface resistance that may have contributed to the low ﬁeld quench via thermal runaway. The potential of CVD as a construction method for SRF cavities is discussed.

Paper

Title

Page

Quality Factor Measurements of the Ultramet 3 GHz Cavity Constructed Using Chemical Vapour Deposition

607

D.L. Hall, D. Gonnella, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V.M. Arrieta, S.R. McNeal
Ultramet, California, USA

Funding: US Department of Energy Phase 1 Small Business Innovation Research award to Ultramet
A seamless 3 GHz bulk niobium cavity constructed by Ultramet using rapid chemical vapor deposition (CVD) techniques has been tested on the vertical SRF test stand at Cornell. The cavity received a 25 um buffered chemical polish (BCP) and 700 C heat treatment for 4 days. First test results gave an intrinsic quality factor of Q0 = (1.55 ± 0.12) x 10⁷ and (2.00 ± 0.15) x 10⁷ at 4.2 K and 1.5 K, respectively. A second BCP removed 100 um of material, after which test results improved to Q0 = (7.59 ± 1.52) x 10⁷ and (4.16 ± 0.31) x 10⁸ at 4.2 K and 1.5 K. During the ﬁrst test poor coupling to the input ampliﬁer impeded tests at accelerating ﬁelds >0.2 MV/m, while during the second test the cavity quenched at 1.3 MV/m when operating at 1.5 K. An optical inspection of the cavity after the second test revealed the presence of at least 4 pits on the upper hemisphere suggesting an area of higher than average surface resistance that may have contributed to the low ﬁeld quench via thermal runaway. The potential of CVD as a construction method for SRF cavities is discussed.