SRF2013 - List of Authors (Valles, N.R.A.)

Paper	Title	Page
MOP071	Record Quality Factor Performance of the Prototype Cornell ERL Main Linac Cavity in the Horizontal Test Cryomodule	300
	N.R.A. Valles, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, D.L. Hall, Y. He, K.M.V. Ho, 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
	Funding: Supported by NSF grant DMR-0807731 Future SRF linac driven accelerators operated in CW mode will require very efficient SRF cavities with high intrinsic quality factors Q at medium accelerating fields. Cornell has recently ﬁnished testing the fully equipped 1.3 GHz, 7-cell main linac cavity for the Cornell Energy Recovery Linac in a horizontal test cryomodule (HTC). Measurements characterizing the fundamental mode’s quality factor have been completed, showing record Q performance. In this paper, we present detailed quality factor vs gradient results for three HTC assembly stages. We show that the performance of an SRF cavity can be maintained when installed into a cryomodule, and that thermal cycling reduces residual surface resistance. We present world record results for a fully equipped multicell cavity in a cryomodule, reaching intrinsic quality factors at operating accelerating field of Q(E =16.2 MV/m, 1.8K) > 6·10¹⁰ and Q(E =16.2 MV/m, 1.6K) > 1.0·10¹¹, corresponding to a very low residual surface resistance of 1.1 nOhm.

TUP104	Temperature Waves in SRF Research	719
	A. Ganshin, R.G. Eichhorn, D.L. Hartill, G.H. Hoffstaetter, E.N. Smith, N.R.A. Valles Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA X. Mi Cornell University, Ithaca, New York, USA
	Funding: This work has been supported by NSF award PHY-0969959 and DOE award DOE/SC00008431 Previously Cornell University developed Oscillating Superleak Transducers (OST) to locate quench spots on superconducting cavities in superfluid helium. This work builds upon this research and presents a technique to automatically visualize quench locations from OST data (1). This system is now fully automated. The current system consists of between 8 and 16 OSTs, a high gain low noise preamplifier, and a data acquisition card that can log up to 16 simultaneously recorded inputs. The developed software allows computing quench locations on various cavity geometries, adjustment of the location of each OST and a choice between several quench finding algorithms. Observed results are in excellent agreement with optical inspection and temperature map data. 1. http://newsline.linearcollider.org/2011/04/21/the-sound-of-accelerator-cavitie

THP038	Development and Performance of a High Field TE-Mode Sample Host Cavity	985
	D.L. Hall, M. Liepe, I.S. Madjarov, K.P. McDermott, N.R.A. Valles Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: US National Science Foundation Career award PHY-0841213 A TE-mode 4 GHz sample host cavity has been designed and constructed at Cornell for the purpose of testing wafers of niobium and other candidates for the construction of SRF cavities. Simulations made using CLANS and ACE3P indicate that the peak magnetic field on the sample plate will reach approximately 120 mT before a quench occurs on the surface of the cavity due to thermal runaway. This quench field can be further increased using a 1400 C treatment to improve the thermal conductivity of the niobium bulk and a 120 C treatment to minimise the BCS surface resistance of the cavity walls. Such an improvement would put peak fields of 170 mT within reach of this cavity. Results of the cavity design, fabrication and first vertical test are presented and discussed. *Development of Superconducting RF Sample Host Cavities and study of Pit-Induced Cavity Quench, Yie Xie, PhD Thesis, Cornell University, Jan 2013

THP052	Cornell’s Beam Line Higher Order Mode Absorbers	1027
	R.G. Eichhorn, J.V. Conway, Y. He, Y. Li, T.I. O'Connel, P. Quigley, J. Sears, N.R.A. Valles Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V.D. Shemelin Cornell University, Ithaca, New York, USA
	Efficient damping of the higher-order modes (HOMs) of the superconducting cavities is essential for the proposed energy recovery linac at Cornell that aims for high beam currents and short bunches. Designing these HOM beamline absorbers has been a long endeavor, sometimes including disappointing results. We will review the design, the findings on the prototype and the final choices made for the 7 HOM absorbers being built for the main linac cryomodule (MLC) prototype.

THP071	HOM Studies of the Cornell ERL Main Linac Cavity in the Horizontal Test Cryomodule	1090
	N.R.A. Valles, R.G. Eichhorn, D.A. Goldman, G.H. Hoffstaetter, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Supported by NSF grant DMR-0807731 The Cornell energy recovery linac will accelerate a 100 mA beam to 5 GeV, while maintaining very low emittance (30 pm at 77 pC bunch charge). A major challenge to running such a large current continuously through the machine is the effect of strong higher-order modes (HOMs) in the SRF cavities that can lead to beam breakup. This paper presents the results of HOM studies for the prototype 7-cell cavity installed in a horizontal test cryomodule (HTC). HOM measurements were done for three HTC assembly stages, from initial measurements on the bare cavity to being fully outﬁtted with side-mounted RF input coupler and beam line HOM absorbers. We compare the simulated results of the optimized cavity geometry with measurements from all three HTC experiments, demonstrating excellent damping of all dipole higher order modes.

Paper

Title

Page

Record Quality Factor Performance of the Prototype Cornell ERL Main Linac Cavity in the Horizontal Test Cryomodule

300

N.R.A. Valles, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, D.L. Hall, Y. He, K.M.V. Ho, 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

Funding: Supported by NSF grant DMR-0807731
Future SRF linac driven accelerators operated in CW mode will require very efficient SRF cavities with high intrinsic quality factors Q at medium accelerating fields. Cornell has recently ﬁnished testing the fully equipped 1.3 GHz, 7-cell main linac cavity for the Cornell Energy Recovery Linac in a horizontal test cryomodule (HTC). Measurements characterizing the fundamental mode’s quality factor have been completed, showing record Q performance. In this paper, we present detailed quality factor vs gradient results for three HTC assembly stages. We show that the performance of an SRF cavity can be maintained when installed into a cryomodule, and that thermal cycling reduces residual surface resistance. We present world record results for a fully equipped multicell cavity in a cryomodule, reaching intrinsic quality factors at operating accelerating field of Q(E =16.2 MV/m, 1.8K) > 6·10¹⁰ and Q(E =16.2 MV/m, 1.6K) > 1.0·10¹¹, corresponding to a very low residual surface resistance of 1.1 nOhm.

TUP104

Temperature Waves in SRF Research

719

A. Ganshin, R.G. Eichhorn, D.L. Hartill, G.H. Hoffstaetter, E.N. Smith, N.R.A. Valles
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
X. Mi
Cornell University, Ithaca, New York, USA

Funding: This work has been supported by NSF award PHY-0969959 and DOE award DOE/SC00008431
Previously Cornell University developed Oscillating Superleak Transducers (OST) to locate quench spots on superconducting cavities in superfluid helium. This work builds upon this research and presents a technique to automatically visualize quench locations from OST data (1). This system is now fully automated. The current system consists of between 8 and 16 OSTs, a high gain low noise preamplifier, and a data acquisition card that can log up to 16 simultaneously recorded inputs. The developed software allows computing quench locations on various cavity geometries, adjustment of the location of each OST and a choice between several quench finding algorithms. Observed results are in excellent agreement with optical inspection and temperature map data.
1. http://newsline.linearcollider.org/2011/04/21/the-sound-of-accelerator-cavitie

THP038

Development and Performance of a High Field TE-Mode Sample Host Cavity

985

D.L. Hall, M. Liepe, I.S. Madjarov, K.P. McDermott, N.R.A. Valles
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: US National Science Foundation Career award PHY-0841213
A TE-mode 4 GHz sample host cavity has been designed and constructed at Cornell for the purpose of testing wafers of niobium and other candidates for the construction of SRF cavities. Simulations made using CLANS and ACE3P indicate that the peak magnetic field on the sample plate will reach approximately 120 mT before a quench occurs on the surface of the cavity due to thermal runaway. This quench field can be further increased using a 1400 C treatment to improve the thermal conductivity of the niobium bulk and a 120 C treatment to minimise the BCS surface resistance of the cavity walls. Such an improvement would put peak fields of 170 mT within reach of this cavity. Results of the cavity design, fabrication and first vertical test are presented and discussed.
*Development of Superconducting RF Sample Host Cavities and study of Pit-Induced Cavity Quench, Yie Xie, PhD Thesis, Cornell University, Jan 2013

THP052

Cornell’s Beam Line Higher Order Mode Absorbers

1027

R.G. Eichhorn, J.V. Conway, Y. He, Y. Li, T.I. O'Connel, P. Quigley, J. Sears, N.R.A. Valles
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V.D. Shemelin
Cornell University, Ithaca, New York, USA

Efficient damping of the higher-order modes (HOMs) of the superconducting cavities is essential for the proposed energy recovery linac at Cornell that aims for high beam currents and short bunches. Designing these HOM beamline absorbers has been a long endeavor, sometimes including disappointing results. We will review the design, the findings on the prototype and the final choices made for the 7 HOM absorbers being built for the main linac cryomodule (MLC) prototype.

THP071

HOM Studies of the Cornell ERL Main Linac Cavity in the Horizontal Test Cryomodule

1090

N.R.A. Valles, R.G. Eichhorn, D.A. Goldman, G.H. Hoffstaetter, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Supported by NSF grant DMR-0807731
The Cornell energy recovery linac will accelerate a 100 mA beam to 5 GeV, while maintaining very low emittance (30 pm at 77 pC bunch charge). A major challenge to running such a large current continuously through the machine is the effect of strong higher-order modes (HOMs) in the SRF cavities that can lead to beam breakup. This paper presents the results of HOM studies for the prototype 7-cell cavity installed in a horizontal test cryomodule (HTC). HOM measurements were done for three HTC assembly stages, from initial measurements on the bare cavity to being fully outﬁtted with side-mounted RF input coupler and beam line HOM absorbers. We compare the simulated results of the optimized cavity geometry with measurements from all three HTC experiments, demonstrating excellent damping of all dipole higher order modes.