LINAC2014 - List of Authors (Gonnella, D.)

Paper	Title	Page
MOPP017	Cool Down and Flux Trapping Studies on SRF Cavities	84
MOPOL07	use link to see paper's listing under its alternate paper code
	D. Gonnella, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Recent results from Cornell and FNAL have shown that cool down rate can have a strong impact on the residual resistance of a superconducting RF cavity during operation. We have studied the effect of cool down rate, gradient, and external magnetic field during cool down on the residual resistance of an EP, EP+120C baked, and nitrogen-doped cavities. For each cavity, faster cool down and large gradient resulted in lower residual resistance in vertical test. The nitrogen-doped cavities showed the largest improvement with fast cool down, while the EP+120C cavity showed the smallest. The cavities were also placed in a uniform external magnetic field and residual resistance was measured as a function of applied field and cool down rate. We show that the nitrogen-doped cavity was the most susceptible to losses from trapped flux and the EP+120C cavity was least susceptible. These measurements provide new insights into understanding the physics behind the observed impact of cool down rates and gradients on the performance of cavities with differing preparations.

MOPP018	Nitrogen-Doped 9-Cell Cavity Performance in the Cornell Horizontal Test Cryomodule	88
	D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, D.L. Hall, Y. He, G.H. Hoffstaetter, M. Liepe, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A. Grassellino, A. Romanenko Fermilab, Batavia, Illinois, USA
	Funding: U.S. Department of Energy Cornell has recently completed construction and qualification of a horizontal cryomodule capable of holding a 9-cell ILC cavity. A nitrogen-doped niobium 9-cell cavity was assembled into the Horizontal Test Cryomodule (HTC) with a high Q input coupler and tested. We report on results from this test of a nitrogen-doped cavity in cryomodule and discuss the effects of cool down rate and thermal cycling on the residual resistance of the cavity.

THPP016	Nitrogen-Treated Cavity Testing at Cornell	866
	D. Gonnella, F. Furuta, G.M. Ge, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: U.S. Department of Energy Recent results from Cornell, FNAL, and TJNAF have shown that superconducting RF cavities given a heat treatment in a nitrogen atmosphere show higher Q₀ at operating gradients at 2.0 K than standard SRF cavities. Here we present on recent results at Cornell in which five single cell cavities and three 9-cell cavities were tested after receiving various nitrogen-doping treatments. Cavity performance was correlated with treatment, and samples treated with the cavities were analyzed with SIMS. These results provide new insights into the science behind the excellent performance that is observed in these cavities.

Paper

Title

Page

MOPP017

Cool Down and Flux Trapping Studies on SRF Cavities

84

MOPOL07

use link to see paper's listing under its alternate paper code

D. Gonnella, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Recent results from Cornell and FNAL have shown that cool down rate can have a strong impact on the residual resistance of a superconducting RF cavity during operation. We have studied the effect of cool down rate, gradient, and external magnetic field during cool down on the residual resistance of an EP, EP+120C baked, and nitrogen-doped cavities. For each cavity, faster cool down and large gradient resulted in lower residual resistance in vertical test. The nitrogen-doped cavities showed the largest improvement with fast cool down, while the EP+120C cavity showed the smallest. The cavities were also placed in a uniform external magnetic field and residual resistance was measured as a function of applied field and cool down rate. We show that the nitrogen-doped cavity was the most susceptible to losses from trapped flux and the EP+120C cavity was least susceptible. These measurements provide new insights into understanding the physics behind the observed impact of cool down rates and gradients on the performance of cavities with differing preparations.

MOPP018

Nitrogen-Doped 9-Cell Cavity Performance in the Cornell Horizontal Test Cryomodule

88

D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, D.L. Hall, Y. He, G.H. Hoffstaetter, M. Liepe, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Grassellino, A. Romanenko
Fermilab, Batavia, Illinois, USA

Funding: U.S. Department of Energy
Cornell has recently completed construction and qualification of a horizontal cryomodule capable of holding a 9-cell ILC cavity. A nitrogen-doped niobium 9-cell cavity was assembled into the Horizontal Test Cryomodule (HTC) with a high Q input coupler and tested. We report on results from this test of a nitrogen-doped cavity in cryomodule and discuss the effects of cool down rate and thermal cycling on the residual resistance of the cavity.

THPP016

Nitrogen-Treated Cavity Testing at Cornell

866

D. Gonnella, F. Furuta, G.M. Ge, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: U.S. Department of Energy
Recent results from Cornell, FNAL, and TJNAF have shown that superconducting RF cavities given a heat treatment in a nitrogen atmosphere show higher Q₀ at operating gradients at 2.0 K than standard SRF cavities. Here we present on recent results at Cornell in which five single cell cavities and three 9-cell cavities were tested after receiving various nitrogen-doping treatments. Cavity performance was correlated with treatment, and samples treated with the cavities were analyzed with SIMS. These results provide new insights into the science behind the excellent performance that is observed in these cavities.