IPAC2012 - List of Keywords (superconducting-cavity)

Paper	Title	Other Keywords	Page
WEPPC002	Impact of Trapped Flux and Thermal Gradients on the SRF Cavity Quality Factor	cavity, niobium, SRF, controls	2203
	O. Kugeler, J. Knobloch, J.M. Vogt HZB, Berlin, Germany S. Aull CERN, Geneva, Switzerland
	The obtained Q0 value of a superconducting niobium cavity is known to depend on various factors like the RRR of the Niobium material, crystallinity, chemical treatment history, the high-pressure rinsing process, or effectiveness of the magnetic shielding. We have observed that spatial thermal gradients over the cavity length during cool-down appear to contribute to a degradation of Q0. Measurements were performed in the Horizontal Bi-Cavity Test Facility (HoBiCaT) at HZB on TESLA type cavities as well as on disc- and rod-shaped niobium samples equipped with thermal, electrical and magnetic diagnostics. Possible explanations for the effect are discussed.

WEPPC021	Development of Superconducting Radio Frequency Cavities at SINAP	cavity, niobium, electron, HOM	2248
	J.F. Liu, H.T. Hou, C.W. Lu, C. Luo, Z.Y. Ma, D.Q. Mao, J. Shi, Zh.G. Zhang, S.J. Zhao, X. Zheng SINAP, Shanghai, People's Republic of China Z.Q. Feng, Z. Li, J.F. Liu, Y.L. Wei, K. Xu, Y.B. Zhao Shanghai KEY Laboratory of Cryogenics & Superconducting RF Technology, Shanghai, People's Republic of China H. Yu Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
	This paper presents the development of superconducting radio frequency cavities at Shanghai Institute of Applied Physics (SINAP) mainly focused on the 500MHz band. Firstly, Two KEKB type 500MHz single cell niobium cavities have been fabricated and one of them has been vertical tested successfully in 2010. The highest accelerating gradient of the fabricated cavity higher than 10MV/m was obtained while the quality factor was better than 4·10⁸ at 4.2K. Secondly, a new type of 500MHz single cell cavity has been designed which adopts the fluted beam pipe for higher order modes propagation and a coaxial type high power input coupler. Thirdly, a 500MHz 5-cell superconducting cavity with large aperture, enlarged beam pipe for HOM propagation and high r/Q value has been optimized which can be a candidate cavity for high current FEL and ERL.

WEPPC071	Quench Studies of a Superconducting RF Cavity	cavity, superconducting-RF, superconductivity, resonance	2375
	D. Gonnella, M. Liepe, S. Posen CLASSE, Ithaca, New York, USA
	In tests of superconducting RF cavities, it is important to understand the cause of high field quenches. Quenches at high field above 25 MV/m are a limiting factor in the performance of high accelerating field cavities but their causes are currently not well understood. An ILC shaped single cell cavity with quench field near 40 MV/m was tested with temperature mapping to determine the cause of its hard quench. Prior to quench, heating on the order of 25 mK was concentrated in two hot spots. After a quench, these two hot spots remain and a new one appears with much higher heating (about 40 mK). The quench location was found by the temperature mapping system to be centered at the new hot spot, not at the two hot spot locations before that dominated quench. By studying the quench location and heating on the surface of the cavity, some hints were gained as to the cause of this quench.

WEPPC083	Tunable 28 MHz Superconducting Cavity for RHIC	cavity, niobium, site, superconducting-RF	2405
	C.H. Boulware, T.L. Grimm Niowave, Inc., Lansing, Michigan, USA S.A. Belomestnykh, I. Ben-Zvi BNL, Upton, Long Island, New York, USA
	Funding: This research has been supported by a Department of Energy Small Business Innovative Research Phase II grant through the Nuclear Physics program office, contract #DE-SC0001215. Replacement of the normal conducting 28 MHz accelerating cavities in the RHIC ring with superconducting structures offers a number of advantages for the machine operation, including reduction of the number of cavities required and improved HOM performance. A prototype folded quarter wave structure is under construction at Niowave, Inc. to meet this need. This novel cavity geometry achieves the very low resonant frequency required with a relatively compact structure, and can provide the large tuning range required (~1% of the cavity frequency). Progress of the cavity fabrication will be presented along with room temperature RF measurements.

WEPPR037	First-Principle Approach for Optimization of Cavity Shape for High Gradient and Low Loss	cavity, superconductivity, wakefield, multipactoring	3015
	V.D. Shemelin, G.H. Hoffstaetter CLASSE, Ithaca, New York, USA
	Funding: Supported by NSF award DMR-0807731. Minimization of surface fields for a given accelerating rate is the subject of cavity optimization because high electric and magnetic fields lead to field emission or thermal breakdown, respectively. The ratio between peak electric and magnetic fields is a function of geometry and the desired ratio depends on application. For each application the optimal geometry may be different. The elliptic shape of the cavity have been found evolutionarily: starting from a pill-box with beam-pipes having rounded corners. No attempts up to now are known for a search of non-elliptical optimal shapes. Here we describe the search for a cavity shape that has the lowest surface fields, not restricting to the conventional elliptical cavity shapes.

Paper

Title

Other Keywords

Page

WEPPC002

Impact of Trapped Flux and Thermal Gradients on the SRF Cavity Quality Factor

cavity, niobium, SRF, controls

2203

O. Kugeler, J. Knobloch, J.M. Vogt
HZB, Berlin, Germany
S. Aull
CERN, Geneva, Switzerland

The obtained Q0 value of a superconducting niobium cavity is known to depend on various factors like the RRR of the Niobium material, crystallinity, chemical treatment history, the high-pressure rinsing process, or effectiveness of the magnetic shielding. We have observed that spatial thermal gradients over the cavity length during cool-down appear to contribute to a degradation of Q0. Measurements were performed in the Horizontal Bi-Cavity Test Facility (HoBiCaT) at HZB on TESLA type cavities as well as on disc- and rod-shaped niobium samples equipped with thermal, electrical and magnetic diagnostics. Possible explanations for the effect are discussed.

WEPPC021

Development of Superconducting Radio Frequency Cavities at SINAP

cavity, niobium, electron, HOM

2248

J.F. Liu, H.T. Hou, C.W. Lu, C. Luo, Z.Y. Ma, D.Q. Mao, J. Shi, Zh.G. Zhang, S.J. Zhao, X. Zheng
SINAP, Shanghai, People's Republic of China
Z.Q. Feng, Z. Li, J.F. Liu, Y.L. Wei, K. Xu, Y.B. Zhao
Shanghai KEY Laboratory of Cryogenics & Superconducting RF Technology, Shanghai, People's Republic of China
H. Yu
Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China

This paper presents the development of superconducting radio frequency cavities at Shanghai Institute of Applied Physics (SINAP) mainly focused on the 500MHz band. Firstly, Two KEKB type 500MHz single cell niobium cavities have been fabricated and one of them has been vertical tested successfully in 2010. The highest accelerating gradient of the fabricated cavity higher than 10MV/m was obtained while the quality factor was better than 4·10⁸ at 4.2K. Secondly, a new type of 500MHz single cell cavity has been designed which adopts the fluted beam pipe for higher order modes propagation and a coaxial type high power input coupler. Thirdly, a 500MHz 5-cell superconducting cavity with large aperture, enlarged beam pipe for HOM propagation and high r/Q value has been optimized which can be a candidate cavity for high current FEL and ERL.

WEPPC071

Quench Studies of a Superconducting RF Cavity

cavity, superconducting-RF, superconductivity, resonance

2375

D. Gonnella, M. Liepe, S. Posen
CLASSE, Ithaca, New York, USA

In tests of superconducting RF cavities, it is important to understand the cause of high field quenches. Quenches at high field above 25 MV/m are a limiting factor in the performance of high accelerating field cavities but their causes are currently not well understood. An ILC shaped single cell cavity with quench field near 40 MV/m was tested with temperature mapping to determine the cause of its hard quench. Prior to quench, heating on the order of 25 mK was concentrated in two hot spots. After a quench, these two hot spots remain and a new one appears with much higher heating (about 40 mK). The quench location was found by the temperature mapping system to be centered at the new hot spot, not at the two hot spot locations before that dominated quench. By studying the quench location and heating on the surface of the cavity, some hints were gained as to the cause of this quench.

WEPPC083

Tunable 28 MHz Superconducting Cavity for RHIC

cavity, niobium, site, superconducting-RF

2405

C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
S.A. Belomestnykh, I. Ben-Zvi
BNL, Upton, Long Island, New York, USA

Funding: This research has been supported by a Department of Energy Small Business Innovative Research Phase II grant through the Nuclear Physics program office, contract #DE-SC0001215.
Replacement of the normal conducting 28 MHz accelerating cavities in the RHIC ring with superconducting structures offers a number of advantages for the machine operation, including reduction of the number of cavities required and improved HOM performance. A prototype folded quarter wave structure is under construction at Niowave, Inc. to meet this need. This novel cavity geometry achieves the very low resonant frequency required with a relatively compact structure, and can provide the large tuning range required (~1% of the cavity frequency). Progress of the cavity fabrication will be presented along with room temperature RF measurements.

WEPPR037

First-Principle Approach for Optimization of Cavity Shape for High Gradient and Low Loss

cavity, superconductivity, wakefield, multipactoring

3015

V.D. Shemelin, G.H. Hoffstaetter
CLASSE, Ithaca, New York, USA

Funding: Supported by NSF award DMR-0807731.
Minimization of surface fields for a given accelerating rate is the subject of cavity optimization because high electric and magnetic fields lead to field emission or thermal breakdown, respectively. The ratio between peak electric and magnetic fields is a function of geometry and the desired ratio depends on application. For each application the optimal geometry may be different. The elliptic shape of the cavity have been found evolutionarily: starting from a pill-box with beam-pipes having rounded corners. No attempts up to now are known for a search of non-elliptical optimal shapes. Here we describe the search for a cavity shape that has the lowest surface fields, not restricting to the conventional elliptical cavity shapes.