IPAC2012 - List of Keywords (multipactoring)

Paper	Title	Other Keywords	Page
TUPPD064	Cathode Insert Design for SC RF Guns	cathode, gun, cavity, HOM	1548
	V. Volkov BINP SB RAS, Novosibirsk, Russia R. Barday, T. Kamps, J. Knobloch, A.N. Matveenko HZB, Berlin, Germany
	Funding: Work supported by Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Assiciation VH-NG-636 and HRJRG-214. The cathode inserts in superconducting (SC) RF guns are normal conducting devices attached to a SC RF gun cavity. They enable the photocathode replacement and, at the same time, preserve high quality factor and high fields in the RF guns. However, the insert may also limit the gun performance because of multipacting etc. The experience gathered in early designs at Wuppertal [1], and, more recently at BNL [2] and HZDR [3] is taken into account. We consider the design structure of the cathode insert worked out by BINP for 1 cell prototype of SC HZDR RF gun [4]. The detailed electric, mechanic, and thermal calculations of the initial [4] and the upgraded design are presented in this paper. * A. Michalke et al., EPAC'92, p. 1014 (1992). A. Burrill et al., PAC07, p. 2544 (2007). * D. Janssen et al., NIM A507, 314 (2003). **** D. Janssen et al., NIM A445, 408 (2000).

TUPPR049	An X-band Standing Wave Dielectric Loaded Accelerating Structure	cavity, coupling, simulation, resonance	1927
	C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow Euclid TechLabs, LLC, Solon, Ohio, USA S.H. Gold NRL, Washington, DC, USA S. Kazakov Fermilab, Batavia, USA R. Konecny ANL, Argonne, USA
	Funding: DOE SBIR Phase I grant #DE-SC0006303 An 11.4 GHz standing wave dielectric loaded accelerating structure was recently developed. We expect to achieve a 120 MV/m gradient powered by a 10 MW 200 ns rf pulse from the X-band Magnicon at the Naval Research Laboratory. The structure uses on-axis rf coupling, which helps to localize the maximum EM fields within the dielectric region. Bench testing shows excellent agreement with the simulation results. The high power rf test is scheduled for January 2012.

WEPPC032	Analysis of the Four Rod Crab Cavity for HL-LHC	cavity, simulation, niobium, luminosity	2275
	B.D.S. Hall, P.K. Ambattu, G. Burt, D. Doherty, C. Lingwood Cockcroft Institute, Lancaster University, Lancaster, United Kingdom P. Goudket STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The Hi-Lumi Upgrade to the LHC will utilise crab cavities to increase the peak luminosity and provide luminosity levelling at the increased crossing angle. A transversely compact design is required to fit within the limited space between opposing beamlines. In this paper a four rod TEM deflecting cavity (4RCC) is shown to be suitable for LHC. The variation of the deflecting voltage with radial offset has been minimised by careful design and an aluminium prototype has been constructed and beadpull measurements are compared to simulations. Multipacting simulations have been performed on the cavity geometry and it is predicted that the growth rate is less than unity for a clean surface. Pressure variations in the LHe can result in deformation of the complex shape which will alter the resonant frequency. Mechanical simulations have also been performed to assess the sensitivity of the frequency to pressure. In order to reduce the impact of these cavities on the LHC beam low impedance is required for the HOMs as well as the fundamental monopole mode. The couplers for the 4RCC cavity have been optimised to provide effective damping of these modes while rejecting the operating mode.

WEPPC051	Multipactor Simulation in SC Elliptical Shape Cavities	cavity, simulation, electron, accelerating-gradient	2327
	S. Kazakov, I.V. Gonin, V.P. Yakovlev Fermilab, Batavia, USA
	Typically multipactor exists near equator region in elliptical shape superconductive cavities. If the multipactor power zone dose not coincide with operating power, it is often the cavity has to pass through it before it reaches operating level of field. Results of multipactor simulations for several shapes of elliptical cavity are presented. New shape, which significantly suppresses multipactor, is found.

WEPPC052	High Gradient Tests of the Fermilab SSR1 Cavity	cavity, vacuum, SRF, linac	2330
	T.N. Khabiboulline, C.M. Ginsburg, I.V. Gonin, R.L. Madrak, O.S. Melnychuk, J.P. Ozelis, Y.M. Pischalnikov, L. Ristori, A.M. Rowe, D.A. Sergatskov, A.I. Sukhanov, I. Terechkine, R.L. Wagner, R.C. Webber, V.P. Yakovlev Fermilab, Batavia, USA
	In Fermilab we are build and tested several superconducting Single Spoke Resonators (SSR1, β=0.22) which can be used for acceleration of low beta ions. Fist two cavities performed very well during cold test in Vertical Test Station at FNAL. One dressed cavity was also tested successfully in Horizontal Test Station. Currently we are building 8 cavity cryomodule for PIXIE project. Additional 10 cavities were manufactured in the industry and ongoing cold test results will be presented in this poster.

WEPPR037	First-Principle Approach for Optimization of Cavity Shape for High Gradient and Low Loss	cavity, superconductivity, wakefield, superconducting-cavity	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.

THPPC040	Improved RF Design for an 805 MHz Pillbox Cavity for the US MuCool Program	cavity, coupling, simulation, ion	3371
	Z. Li, C. Adolphsen, L. Ge SLAC, Menlo Park, California, USA D.L. Bowring, D. Li LBNL, Berkeley, California, USA
	Funding: Work supported by US DOE under contract number DE-AC02-05CH11231, and DE-AC02-76SF00515. Normal conducting RF cavities are required to operate at high gradient in the presence of strong magnetic field in muon ionization cooling channels for a Muon Collider. Experimental studies using an 805 MHz pillbox cavity at MTA of Fermilab has shown significant degradation in gradient performance and damage in the regions that are correlated with high RF fields in magnetic field up to 4 Tesla. These effects are believed to be related to the dark current and/or multipacting activities in the presence of external magnetic field. To improve the performance of the cavity, a new RF cavity with significantly lower surface field enhancement was designed, and will be built and tested in the near future. Numerical analyses of multipacting and dark current were performed using the 3D parallel code Track3P for both the original and new improved cavity profiles in order to gain more insight in understanding of the gradient issues under strong external magnetic field. In this paper, we will present the improved RF design and the dark current and multipacting analyses for the 805 MHz cavity.

Paper

Title

Other Keywords

Page

TUPPD064

Cathode Insert Design for SC RF Guns

cathode, gun, cavity, HOM

1548

V. Volkov
BINP SB RAS, Novosibirsk, Russia
R. Barday, T. Kamps, J. Knobloch, A.N. Matveenko
HZB, Berlin, Germany

Funding: Work supported by Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Assiciation VH-NG-636 and HRJRG-214.
The cathode inserts in superconducting (SC) RF guns are normal conducting devices attached to a SC RF gun cavity. They enable the photocathode replacement and, at the same time, preserve high quality factor and high fields in the RF guns. However, the insert may also limit the gun performance because of multipacting etc. The experience gathered in early designs at Wuppertal [1], and, more recently at BNL [2] and HZDR [3] is taken into account. We consider the design structure of the cathode insert worked out by BINP for 1 cell prototype of SC HZDR RF gun [4]. The detailed electric, mechanic, and thermal calculations of the initial [4] and the upgraded design are presented in this paper.
* A. Michalke et al., EPAC'92, p. 1014 (1992).
** A. Burrill et al., PAC07, p. 2544 (2007).
*** D. Janssen et al., NIM A507, 314 (2003).
**** D. Janssen et al., NIM A445, 408 (2000).

TUPPR049

An X-band Standing Wave Dielectric Loaded Accelerating Structure

cavity, coupling, simulation, resonance

1927

C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
Euclid TechLabs, LLC, Solon, Ohio, USA
S.H. Gold
NRL, Washington, DC, USA
S. Kazakov
Fermilab, Batavia, USA
R. Konecny
ANL, Argonne, USA

Funding: DOE SBIR Phase I grant #DE-SC0006303
An 11.4 GHz standing wave dielectric loaded accelerating structure was recently developed. We expect to achieve a 120 MV/m gradient powered by a 10 MW 200 ns rf pulse from the X-band Magnicon at the Naval Research Laboratory. The structure uses on-axis rf coupling, which helps to localize the maximum EM fields within the dielectric region. Bench testing shows excellent agreement with the simulation results. The high power rf test is scheduled for January 2012.

WEPPC032

Analysis of the Four Rod Crab Cavity for HL-LHC

cavity, simulation, niobium, luminosity

2275

B.D.S. Hall, P.K. Ambattu, G. Burt, D. Doherty, C. Lingwood
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P. Goudket
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The Hi-Lumi Upgrade to the LHC will utilise crab cavities to increase the peak luminosity and provide luminosity levelling at the increased crossing angle. A transversely compact design is required to fit within the limited space between opposing beamlines. In this paper a four rod TEM deflecting cavity (4RCC) is shown to be suitable for LHC. The variation of the deflecting voltage with radial offset has been minimised by careful design and an aluminium prototype has been constructed and beadpull measurements are compared to simulations. Multipacting simulations have been performed on the cavity geometry and it is predicted that the growth rate is less than unity for a clean surface. Pressure variations in the LHe can result in deformation of the complex shape which will alter the resonant frequency. Mechanical simulations have also been performed to assess the sensitivity of the frequency to pressure. In order to reduce the impact of these cavities on the LHC beam low impedance is required for the HOMs as well as the fundamental monopole mode. The couplers for the 4RCC cavity have been optimised to provide effective damping of these modes while rejecting the operating mode.

WEPPC051

Multipactor Simulation in SC Elliptical Shape Cavities

cavity, simulation, electron, accelerating-gradient

2327

S. Kazakov, I.V. Gonin, V.P. Yakovlev
Fermilab, Batavia, USA

Typically multipactor exists near equator region in elliptical shape superconductive cavities. If the multipactor power zone dose not coincide with operating power, it is often the cavity has to pass through it before it reaches operating level of field. Results of multipactor simulations for several shapes of elliptical cavity are presented. New shape, which significantly suppresses multipactor, is found.

WEPPC052

High Gradient Tests of the Fermilab SSR1 Cavity

cavity, vacuum, SRF, linac

2330

T.N. Khabiboulline, C.M. Ginsburg, I.V. Gonin, R.L. Madrak, O.S. Melnychuk, J.P. Ozelis, Y.M. Pischalnikov, L. Ristori, A.M. Rowe, D.A. Sergatskov, A.I. Sukhanov, I. Terechkine, R.L. Wagner, R.C. Webber, V.P. Yakovlev
Fermilab, Batavia, USA

In Fermilab we are build and tested several superconducting Single Spoke Resonators (SSR1, β=0.22) which can be used for acceleration of low beta ions. Fist two cavities performed very well during cold test in Vertical Test Station at FNAL. One dressed cavity was also tested successfully in Horizontal Test Station. Currently we are building 8 cavity cryomodule for PIXIE project. Additional 10 cavities were manufactured in the industry and ongoing cold test results will be presented in this poster.

WEPPR037

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

cavity, superconductivity, wakefield, superconducting-cavity

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.

THPPC040

Improved RF Design for an 805 MHz Pillbox Cavity for the US MuCool Program

cavity, coupling, simulation, ion

3371

Z. Li, C. Adolphsen, L. Ge
SLAC, Menlo Park, California, USA
D.L. Bowring, D. Li
LBNL, Berkeley, California, USA

Funding: Work supported by US DOE under contract number DE-AC02-05CH11231, and DE-AC02-76SF00515.
Normal conducting RF cavities are required to operate at high gradient in the presence of strong magnetic field in muon ionization cooling channels for a Muon Collider. Experimental studies using an 805 MHz pillbox cavity at MTA of Fermilab has shown significant degradation in gradient performance and damage in the regions that are correlated with high RF fields in magnetic field up to 4 Tesla. These effects are believed to be related to the dark current and/or multipacting activities in the presence of external magnetic field. To improve the performance of the cavity, a new RF cavity with significantly lower surface field enhancement was designed, and will be built and tested in the near future. Numerical analyses of multipacting and dark current were performed using the 3D parallel code Track3P for both the original and new improved cavity profiles in order to gain more insight in understanding of the gradient issues under strong external magnetic field. In this paper, we will present the improved RF design and the dark current and multipacting analyses for the 805 MHz cavity.