NAPAC2016 - List of Authors (Gonnella, D.)

Paper	Title	Page
MOPOB60	Performance of the Cornell Main Linac Prototype Cryomodule for the CBETA Project	204
	F. Furuta, N. Banerjee, J. Dobbins, R.G. Eichhorn, M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The main linac prototype cryomodule (MLC) is a key component for the Cornell-BNL ERL Test Accelerator (CBETA), which is a 4-turn FFAG ERL under construction at Cornell University. The MLC has been designed for high current and efficient continuous wave (CW) SRF cavity operation, and houses six high Q0 7-cell SRF cavities with individual beamline higher order-modes (HOMs) absorbers for strong HOM suppression in high beam current operation. Cavities have achieved specification values of 16.2MV/m with high Q0 of 2.0·10¹⁰ at 1.8K in CW operation after cooldown optimizations and RF processing. Damping of the HOMs has been measured in detail, indicating that the loaded quality-factors of all critical modes are low enough to avoid BBU in high current, multi-turn ERL operation. Microphonics measurements have been carried out as well, and vibration sources have been determined and eliminated. Here we report on these cryomodule performance studies.
	Poster MOPOB60 [3.321 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB60
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MOPOB65	Investigation of the Origin of the Anti-Q-Slope	218
	J.T. Maniscalco, M. Ge, D. Gonnella, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The surface resistance of a superconductor, a property very relevant to SRF accelerators, has long been known to depend on the strength of the surface magnetic field. A recent discovery showed that, for certain surface treatments, microwave cavities can be shown to have an inverse field dependence, dubbed the ‘‘anti-Q-slope'', in which the surface resistance decreases over an increasing field. Here we present an investigation into what causes the anti-Q-slope in nitrogen-doped niobium cavities, drawing a direct connection between the electron mean free path of the SRF material and the magnitude of the anti-Q-slope. Further, we incorporate residual resistance due to flux trapping to calculate an optimal mean free path for a given trapped flux.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB65
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Performance of the Cornell Main Linac Prototype Cryomodule for the CBETA Project

204

F. Furuta, N. Banerjee, J. Dobbins, R.G. Eichhorn, M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The main linac prototype cryomodule (MLC) is a key component for the Cornell-BNL ERL Test Accelerator (CBETA), which is a 4-turn FFAG ERL under construction at Cornell University. The MLC has been designed for high current and efficient continuous wave (CW) SRF cavity operation, and houses six high Q0 7-cell SRF cavities with individual beamline higher order-modes (HOMs) absorbers for strong HOM suppression in high beam current operation. Cavities have achieved specification values of 16.2MV/m with high Q0 of 2.0·10¹⁰ at 1.8K in CW operation after cooldown optimizations and RF processing. Damping of the HOMs has been measured in detail, indicating that the loaded quality-factors of all critical modes are low enough to avoid BBU in high current, multi-turn ERL operation. Microphonics measurements have been carried out as well, and vibration sources have been determined and eliminated. Here we report on these cryomodule performance studies.

Poster MOPOB60 [3.321 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB60

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPOB65

Investigation of the Origin of the Anti-Q-Slope

218

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

The surface resistance of a superconductor, a property very relevant to SRF accelerators, has long been known to depend on the strength of the surface magnetic field. A recent discovery showed that, for certain surface treatments, microwave cavities can be shown to have an inverse field dependence, dubbed the ‘‘anti-Q-slope'', in which the surface resistance decreases over an increasing field. Here we present an investigation into what causes the anti-Q-slope in nitrogen-doped niobium cavities, drawing a direct connection between the electron mean free path of the SRF material and the magnitude of the anti-Q-slope. Further, we incorporate residual resistance due to flux trapping to calculate an optimal mean free path for a given trapped flux.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB65

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)