SRF2013 - List of Authors (Zvyagintsev, V.)

Paper	Title	Page
THP004	Design Progress of SSR1 Single Spoke Resonator for RAON	899
	H.J. Cha, D. Jeon, H.C. Jung, H.J. Kim, G.-T. Park IBS, Daejeon, Republic of Korea R.E. Laxdal, Z.Y. Yao, V. Zvyagintsev TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	Funding: The Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of the Republic of Korea under Contract 2011-032011 An advanced heavy ion accelerator for basic sciences and multiple applications, called “RAON”, is under construction in Daejeon, South Korea. The fabrication of prototypes for four different types of superconducting cavities, QWR, HWR, SSR1 and SSR2, is scheduled based on the on-going technical designs. In this paper, we present the electromagnetic and mechanical analyses for the SSR1 cavity (β=0.3 and f=325 MHz). Several variants have been considered and compared in terms of rf parameters, multipacting sensitivity, helium pressure sensitivity and ease of fabrication. This includes an analysis of stiffening rings and helium jacket design for stable operation. The progress towards the design of the SSR1 cavity will be given.

THP019	1.3 GHz SRF Cavity Tests for ARIEL at TRIUMF	933
	P. Kolb, P.R. Harmer, D. Kishi, A. Koveshnikov, C. Laforge, D. Lang, R.E. Laxdal, Y. Ma, B.S. Waraich, Z.Y. Yao, V. Zvyagintsev TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	The 1.3 GHz cavity test program at TRIUMF for the ARIEL eLINAC progressed into its next stage: Going from single cell cavity tests to demonstrate the operating Q and gradient for ARIEL can be reached at TRIUMF to nine cell cavity tests for production cavities. Single cell cavity tests at TRIUMF showed a comparable performance to a characterization done on the same cavity at FNAL last year. These single cell tests showed that the operating point for ARIEL of Q0 > 10¹⁰ at 10 MV/m during 2 K operation can be reached and exceeded at TRIUMF. To prepare for the first ARIEL nine cell cavity, a test with a TESLA nine cell cavity was done. This included frequency and field tuning, etching via BCP, HPR and assembly in a class 10 clean environment as well as modifications to the cryo assembly and upgrades to the 2 K pumping system. The performance of this TESLA cavity and the performance of first ARIEL nine cell cavity produced by PAVAC will be shown.

THP020	Measuring the Higher Order Mode Spectrum of the TRIUMF 9-cell Cavity	936
	P. Kolb, B. Amini, R.E. Laxdal, Y. Ma, Z.Y. Yao, V. Zvyagintsev TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	The ARIEL eLINAC consists of five nine cell cavities, produced by PAVAC, and will accelerate 10 mA electrons to 50 MeV. This 500 kW beam will be used for rare isotope production. Future upgrade plans include a recirculating beam line. Recirculating the beam, for either energy doubling or energy recovery to drive a FEL, brings the risk of multi-pass beam break up (BBU). Therefore it is necessary to avoid higher order modes (HOMs) with high shunt impedance. The goal of the cavity design is to reduce the highest shunt impedance of any dipole HOM to 1 *10⁶Ω or less. Measurements on the nine cell cavity with bead pulling have been done to identify dipole modes and their geometric shunt impedance R/Q as well as measurements at 2 K to estimate the quality factor of those HOMs. Results of these measurements will be shown and compared to computer simulations done with ACE3P.

THP033	Study of Balloon Spoke Cavities	972
	Z.Y. Yao, R.E. Laxdal, B.S. Waraich, V. Zvyagintsev TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada R. Edinger PAVAC, Richmond, B.C., Canada
	A balloon geometry has been proposed to suppress multipacting for single spoke resonators. The design may find a useful application for proton and ion accelerator projects. TRIUMF has completed initial RF, mechanical, and fabrication studies on this special geometry for both low (β=0.12) and medium (β=0.3) β geometries. The RF properties are comparable with that of traditional spoke cavities but with improved RF efficiency in addition to the reduced multipacting. The results of electro-magnetic and structural design studies comparing the balloon geometry with traditional spoke geometries will be presented. We will also present optimization studies of the mechanical design, such as decreasing df/dp by EM field compensation as well as discussing tuning strategies and fabrication techniques.

THP034	Multipacting Suppression in a Single Spoke Cavity	975
	Z.Y. Yao, R.E. Laxdal, V. Zvyagintsev TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada X.Y. Lu, K. Zhao PKU, Beijing, People's Republic of China
	Spoke cavities are good candidates for the low and medium β section of a high intensity proton or ion accelerator. For many high intensity accelerators, stability and reliability are the most important properties. Currently, one of the key issues of spoke cavity performance is multipacting, which may cause instability during operation. Multipacting in a spoke cavity has a troublesome characteristic as it presents a continual barrier over a wide gradient range, usually in the range of operation from 3MV/m to 15MV/m. A good surface processing can improve the secondary electron emission yield. However, the complex 3D structure makes it not easily achievable as with the elliptical cavity variants. Suppressing multipacting in the design stage is clearly advantageous. This paper will present a multipacting study based on the PKU-I spoke cavity. A systematic correlation between geometric parameters and multipacting behaviors is obtained. Based on this study a new geometry of single spoke cavity called the ‘balloon’ variant is proposed.

THP035	Production of a 1.3 GHz Niobium 9-cell TRIUMF-PAVAC Cavity for the ARIEL Project	978
	V. Zvyagintsev, B. Amini, P.R. Harmer, P. Kolb, R.E. Laxdal, Y. Ma, B.S. Waraich, Z.Y. Yao TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada R. Edinger, M.C. Leustean, R. Singh PAVAC, Richmond, B.C., Canada
	A nine-cell 1.3 GHz superconducting niobium cavity has been fabricated for the ARIEL project at TRIUMF. The cavity is intended to accelerate a beam current of 10 mA at an accelerating gradient of 10 MV/m. The beam loaded RF power of 100 kW is supplied through two opposed fundamental power couplers. The electromagnetic design was done by TRIUMF. The cavity final design and fabrication procedure have been developed in collaboration between TRIUMF and PAVAC Industries Inc. Several innovations in the cavity fabrication process were developed at PAVAC. Since the most important weld is at the equator this weld is done first to form a ‘smart-bell’ as the basic unit as opposed to welding first at the iris to form ‘dumb-bell’ units. Each half cell is pressed with a male die into a plastic forming surface to produce half-cells with less shape distortion and material dislocations. The cavity fabrication sequence including the frequency tuning steps and RF frequency modelling methods will be discussed.

Paper

Title

Page

Design Progress of SSR1 Single Spoke Resonator for RAON

899

H.J. Cha, D. Jeon, H.C. Jung, H.J. Kim, G.-T. Park
IBS, Daejeon, Republic of Korea
R.E. Laxdal, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

Funding: The Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of the Republic of Korea under Contract 2011-032011
An advanced heavy ion accelerator for basic sciences and multiple applications, called “RAON”, is under construction in Daejeon, South Korea. The fabrication of prototypes for four different types of superconducting cavities, QWR, HWR, SSR1 and SSR2, is scheduled based on the on-going technical designs. In this paper, we present the electromagnetic and mechanical analyses for the SSR1 cavity (β=0.3 and f=325 MHz). Several variants have been considered and compared in terms of rf parameters, multipacting sensitivity, helium pressure sensitivity and ease of fabrication. This includes an analysis of stiffening rings and helium jacket design for stable operation. The progress towards the design of the SSR1 cavity will be given.

THP019

1.3 GHz SRF Cavity Tests for ARIEL at TRIUMF

933

P. Kolb, P.R. Harmer, D. Kishi, A. Koveshnikov, C. Laforge, D. Lang, R.E. Laxdal, Y. Ma, B.S. Waraich, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

The 1.3 GHz cavity test program at TRIUMF for the ARIEL eLINAC progressed into its next stage: Going from single cell cavity tests to demonstrate the operating Q and gradient for ARIEL can be reached at TRIUMF to nine cell cavity tests for production cavities. Single cell cavity tests at TRIUMF showed a comparable performance to a characterization done on the same cavity at FNAL last year. These single cell tests showed that the operating point for ARIEL of Q0 > 10¹⁰ at 10 MV/m during 2 K operation can be reached and exceeded at TRIUMF. To prepare for the first ARIEL nine cell cavity, a test with a TESLA nine cell cavity was done. This included frequency and field tuning, etching via BCP, HPR and assembly in a class 10 clean environment as well as modifications to the cryo assembly and upgrades to the 2 K pumping system. The performance of this TESLA cavity and the performance of first ARIEL nine cell cavity produced by PAVAC will be shown.

THP020

Measuring the Higher Order Mode Spectrum of the TRIUMF 9-cell Cavity

936

P. Kolb, B. Amini, R.E. Laxdal, Y. Ma, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

The ARIEL eLINAC consists of five nine cell cavities, produced by PAVAC, and will accelerate 10 mA electrons to 50 MeV. This 500 kW beam will be used for rare isotope production. Future upgrade plans include a recirculating beam line. Recirculating the beam, for either energy doubling or energy recovery to drive a FEL, brings the risk of multi-pass beam break up (BBU). Therefore it is necessary to avoid higher order modes (HOMs) with high shunt impedance. The goal of the cavity design is to reduce the highest shunt impedance of any dipole HOM to 1 *10⁶Ω or less. Measurements on the nine cell cavity with bead pulling have been done to identify dipole modes and their geometric shunt impedance R/Q as well as measurements at 2 K to estimate the quality factor of those HOMs. Results of these measurements will be shown and compared to computer simulations done with ACE3P.

THP033

Study of Balloon Spoke Cavities

972

Z.Y. Yao, R.E. Laxdal, B.S. Waraich, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
R. Edinger
PAVAC, Richmond, B.C., Canada

A balloon geometry has been proposed to suppress multipacting for single spoke resonators. The design may find a useful application for proton and ion accelerator projects. TRIUMF has completed initial RF, mechanical, and fabrication studies on this special geometry for both low (β=0.12) and medium (β=0.3) β geometries. The RF properties are comparable with that of traditional spoke cavities but with improved RF efficiency in addition to the reduced multipacting. The results of electro-magnetic and structural design studies comparing the balloon geometry with traditional spoke geometries will be presented. We will also present optimization studies of the mechanical design, such as decreasing df/dp by EM field compensation as well as discussing tuning strategies and fabrication techniques.

THP034

Multipacting Suppression in a Single Spoke Cavity

975

Z.Y. Yao, R.E. Laxdal, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
X.Y. Lu, K. Zhao
PKU, Beijing, People's Republic of China

Spoke cavities are good candidates for the low and medium β section of a high intensity proton or ion accelerator. For many high intensity accelerators, stability and reliability are the most important properties. Currently, one of the key issues of spoke cavity performance is multipacting, which may cause instability during operation. Multipacting in a spoke cavity has a troublesome characteristic as it presents a continual barrier over a wide gradient range, usually in the range of operation from 3MV/m to 15MV/m. A good surface processing can improve the secondary electron emission yield. However, the complex 3D structure makes it not easily achievable as with the elliptical cavity variants. Suppressing multipacting in the design stage is clearly advantageous. This paper will present a multipacting study based on the PKU-I spoke cavity. A systematic correlation between geometric parameters and multipacting behaviors is obtained. Based on this study a new geometry of single spoke cavity called the ‘balloon’ variant is proposed.

THP035

Production of a 1.3 GHz Niobium 9-cell TRIUMF-PAVAC Cavity for the ARIEL Project

978

V. Zvyagintsev, B. Amini, P.R. Harmer, P. Kolb, R.E. Laxdal, Y. Ma, B.S. Waraich, Z.Y. Yao
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
R. Edinger, M.C. Leustean, R. Singh
PAVAC, Richmond, B.C., Canada

A nine-cell 1.3 GHz superconducting niobium cavity has been fabricated for the ARIEL project at TRIUMF. The cavity is intended to accelerate a beam current of 10 mA at an accelerating gradient of 10 MV/m. The beam loaded RF power of 100 kW is supplied through two opposed fundamental power couplers. The electromagnetic design was done by TRIUMF. The cavity final design and fabrication procedure have been developed in collaboration between TRIUMF and PAVAC Industries Inc. Several innovations in the cavity fabrication process were developed at PAVAC. Since the most important weld is at the equator this weld is done first to form a ‘smart-bell’ as the basic unit as opposed to welding first at the iris to form ‘dumb-bell’ units. Each half cell is pressed with a male die into a plastic forming surface to produce half-cells with less shape distortion and material dislocations. The cavity fabrication sequence including the frequency tuning steps and RF frequency modelling methods will be discussed.