SRF2015 - List of Keywords (damping)

Paper	Title	Other Keywords	Page
TUAA03	BESSY VSR: A Novel Application of SRF for Synchrotron Light Sources	cavity, SRF, HOM, storage-ring	462
	A.V. Vélez, H.-W. Glock, P. Goslawski, A. Jankowiak, J. Knobloch, A. Neumann, M. Ries, G. Wüstefeld HZB, Berlin, Germany
	CW SRF Cavities have been used very successfully in the past in synchrotron light sources to provide high power acceleration. Here we present a novel application of higher harmonic systems of two frequencies (1.5 GHz and 1.75 GHz) to generate a beating of accelerating voltage. With such a system it is possible to store "standard" (some 10 ps long) and "short" (ps and sub-ps long) pulses simultaneously in the light source. This opens up brand new possibilities for light source users to perform dynamic and high-resolution experiments at the same facility. The demands on the SRF system and RF control are substantial and a new design, based on waveguide damping, is currently being developed. This system will be used for a major upgrade of the BESSY-II facility to the BESSY Variable Pulse Storage Ring (BESSY-VSR) for a next-generation storage-ring light source. We will discuss the concept, challenges and designs for BESSY-VSR.
	Slides TUAA03 [2.103 MB]
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TUPB096	Mechanical Damper Study for ISAC-II Quarter Wave Resonators	ISAC, cavity, simulation, resonance	832
	L. Yang, R.E. Laxdal, V. Zvyagintsev TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	ISAC-II superconducting quarter wave resonators are equipped with mechanical dampers to supress mechanical oscillations of the cavity structure. The study has been carried out to optimize the damper efficiency.
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WEBA07	Beam Commissioning of the 56 MHz QW Cavity in RHIC	cavity, HOM, operation, SRF	982
	Q. Wu, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, T. Hayes, K. Mernick, F. Severino, K.S. Smith, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA
	Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. A 56 MHz superconducting RF cavity has been designed, fabricated and installed in the Relativistic Heavy Ion Collider (RHIC). The cavity operates at 4.4 K with a “quiet helium source” to isolate the cavity from environmental acoustic noise. The cavity is a beam driven quarter wave resonator. It is detuned and damped during injection and acceleration cycles and is brought to operation only at store energy. We have observed clear luminosity increase and bunch length reduction in the first operation of the cavity with Au + Au and Au + He3 collisions. The cavity voltage was limited by quenching in the Higher Order Mode coupler. This paper also discusses the cavity beam experiments with no higher order mode coupler in p + p and p + Au RHIC operation.
	Slides WEBA07 [2.522 MB]
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THBA04	Overview of Recent HOM Coupler Development	HOM, cavity, SRF, operation	1031
	B. P. Xiao BNL, Upton, Long Island, New York, USA
	Funding: Work partly supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE， by the US LARP, and by EU FP7 HiLumi LHC - Grant Agreement 284404. HOM damping is important for SRF applications, especially for high intensity machines. A good HOM damping design will help to reduce power load to the cryogenic system and to reduce the risk of beam breakup. The design of HOM damping, including antenna/loop HOM couplers, beam pipe HOM absorbers and waveguide HOM couplers, is to solve a multi-physics problem that involves RF, thermal, mechanical, and beam-cavity interaction issues. In this talk, the author provides an overview on the latest advances of the HOM couplers for high intensity SRF applications.
	Slides THBA04 [2.619 MB]
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THPB003	Calculations for RF Cavities with Dissipative Material	HOM, cavity, SRF, dipole	1056
	F. Marhauser JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 3D simulations have been performed for a variety of SRF cavities which incorporate Higher Order Mode dampers, either in form of coaxial couplers or waveguide dampers. Instead of utilizing the rather standard approach of matching the output port of the dampers with a broadband coaxial or waveguide port, dissipative materials are modelled for RF field absorption. This for instance not only avoids the otherwise required definition of the number of modes considered for damping, which has an impact on the computational time, but also allows tailoring the load material to conform with experimental data of e.g. non-perfect absorbers. The new calculation scheme is presented. Findings are partially compared with those achieved with the standard waveguide port approach by means of external quality factors. CPU speeds are briefly discussed for both approaches.
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THPB008	RF Simulations for an LCLS-II 3rd Harmonic Cavity Cyromodule	cavity, HOM, cryomodule, dipole	1078
	L. Xiao, C. Adolphsen, Z. Li, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	The FNAL designed 3.9 GHz third harmonic cavity for XFEL will be used in LCLS-II for linearizing the longitudinal beam profile. The 3.9 GHz SRF cavity is scaled down from the 1.3 GHz TESLA cavity shape, but has a disproportionately large beampipe radius for better higher-order mode (HOM) damping. The HOM and fundamental power (FPC) couplers will generate asymmetric field in the beam region, and thereby dilute the beam emittance. Meanwhile, due to the large beampipe, all but a few of the HOMs are above the beampipe cutoff. Thus the HOM damping analyses need to be performed in a full cryomodule, rather than in an individual cavity. The HOM damping in a 4-cavity cryomodule was investigated to determine possible trapped modes using the parallel electromagnetic code suite ACE3P developed at SLAC. The coupler RF kicks induced by the HOM and FPC couplers in the 3.9 GHz cavity were evaluated. A possible cavity-to-cavity arrangement is proposed which could provide effective cancellation of these RF kicks. In this paper we present and discuss the RF simulation results in the 3.9 GHz third harmonic cavity cryomodule. Work supported by Department of Energy under contract Number DE-AC02-76SF00515.
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THPB068	Practical Aspects of HOM Suppression Improvement for TM011	HOM, cavity, simulation, dipole	1277
	A.A. Sulimov, A. Ermakov, J.H. Thie DESY, Hamburg, Germany A. Gresele Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
	Some Higher Order Modes (HOM) pass bands were controlled during cryo-tests at DESY for the European XFEL cavities. The second monopole mode (TM011) showed most instabilities and suppression degradation. The authors will explain this phenomenon on the example of cavity CAV00553 and present the practical method of TM011 damping improvement.
	Poster THPB068 [0.182 MB]
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THPB074	High Current eRHIC Cavity Design and HOM Damping Scheme	cavity, HOM, linac, impedance	1297
	W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn BNL, Upton, Long Island, New York, USA
	Funding: This work is supported by LDRD program of Brookhaven Science Associates. A 422 MHz cavity was designed for high current FFAG lattice ERLs for high luminosity eRHIC. The cavity was optimized to be able to propagate all the HOMs out of the cavity for high BBU threshold current and low HOM power (loss factor). Coupling the full spectrum (up to 30 GHz) HOMs out of the cavity and delivering the HOM power (up to 8 kW) out of the cryomodule is a challenge. A damping scheme with 6 coaxial line HOM couplers for low frequency HOMs and 3 waveguide HOM dampers for high frequency (so that the waveguide is small) is proposed to damp the full spectrum and high power HOMs. This paper will present the cavity design and HOM damping scheme.
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THPB104	Higher Order Modes Simulation and Measurements for 2400 MHz Cavity	HOM, cavity, simulation, higher-order-mode	1394
	Ya.V. Shashkov, D.S. Bazyl, R.V. Donetskiy, M.V. Lalayan, N.P. Sobenin MEPhI, Moscow, Russia R. Calaga CERN, Geneva, Switzerland A.A. Zavadtsev Nano, Moscow, Russia M. Zobov INFN/LNF, Frascati (Roma), Italy
	Funding: Work supported by Ministry of Education and Science grant 3.245.2014/r and the EU FP7 HiLumi LHC – Grant Agreement 284404 In the frameworks of the High Luminosity LHC upgrade program an application of additional harmonic cavities operating at multiples of the main RF system frequency of 400 MHz is currently under discussion. The 800 MHz superconducting cavities with grooved beam pipes were suggested for implementation. A scaled aluminum prototype with a frequency of the operational mode of 2400 MHz was manufactured for testing the results of simulations. The load reflection coefficient measurements were performed as well as the Qload measurements for cavities with the load. Here we discuss the prototype design and report the obtained measurement results. Higher order modes, superconducting cavities, srf*
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Paper

Title

Other Keywords

Page

TUAA03

BESSY VSR: A Novel Application of SRF for Synchrotron Light Sources

cavity, SRF, HOM, storage-ring

462

A.V. Vélez, H.-W. Glock, P. Goslawski, A. Jankowiak, J. Knobloch, A. Neumann, M. Ries, G. Wüstefeld
HZB, Berlin, Germany

CW SRF Cavities have been used very successfully in the past in synchrotron light sources to provide high power acceleration. Here we present a novel application of higher harmonic systems of two frequencies (1.5 GHz and 1.75 GHz) to generate a beating of accelerating voltage. With such a system it is possible to store "standard" (some 10 ps long) and "short" (ps and sub-ps long) pulses simultaneously in the light source. This opens up brand new possibilities for light source users to perform dynamic and high-resolution experiments at the same facility. The demands on the SRF system and RF control are substantial and a new design, based on waveguide damping, is currently being developed. This system will be used for a major upgrade of the BESSY-II facility to the BESSY Variable Pulse Storage Ring (BESSY-VSR) for a next-generation storage-ring light source. We will discuss the concept, challenges and designs for BESSY-VSR.

Slides TUAA03 [2.103 MB]

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

TUPB096

Mechanical Damper Study for ISAC-II Quarter Wave Resonators

ISAC, cavity, simulation, resonance

832

L. Yang, R.E. Laxdal, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

ISAC-II superconducting quarter wave resonators are equipped with mechanical dampers to supress mechanical oscillations of the cavity structure. The study has been carried out to optimize the damper efficiency.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

WEBA07

Beam Commissioning of the 56 MHz QW Cavity in RHIC

cavity, HOM, operation, SRF

982

Q. Wu, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, T. Hayes, K. Mernick, F. Severino, K.S. Smith, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
A 56 MHz superconducting RF cavity has been designed, fabricated and installed in the Relativistic Heavy Ion Collider (RHIC). The cavity operates at 4.4 K with a “quiet helium source” to isolate the cavity from environmental acoustic noise. The cavity is a beam driven quarter wave resonator. It is detuned and damped during injection and acceleration cycles and is brought to operation only at store energy. We have observed clear luminosity increase and bunch length reduction in the first operation of the cavity with Au + Au and Au + He3 collisions. The cavity voltage was limited by quenching in the Higher Order Mode coupler. This paper also discusses the cavity beam experiments with no higher order mode coupler in p + p and p + Au RHIC operation.

Slides WEBA07 [2.522 MB]

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THBA04

Overview of Recent HOM Coupler Development

HOM, cavity, SRF, operation

1031

B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: Work partly supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE， by the US LARP, and by EU FP7 HiLumi LHC - Grant Agreement 284404.
HOM damping is important for SRF applications, especially for high intensity machines. A good HOM damping design will help to reduce power load to the cryogenic system and to reduce the risk of beam breakup. The design of HOM damping, including antenna/loop HOM couplers, beam pipe HOM absorbers and waveguide HOM couplers, is to solve a multi-physics problem that involves RF, thermal, mechanical, and beam-cavity interaction issues. In this talk, the author provides an overview on the latest advances of the HOM couplers for high intensity SRF applications.

Slides THBA04 [2.619 MB]

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB003

Calculations for RF Cavities with Dissipative Material

HOM, cavity, SRF, dipole

1056

F. Marhauser
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
3D simulations have been performed for a variety of SRF cavities which incorporate Higher Order Mode dampers, either in form of coaxial couplers or waveguide dampers. Instead of utilizing the rather standard approach of matching the output port of the dampers with a broadband coaxial or waveguide port, dissipative materials are modelled for RF field absorption. This for instance not only avoids the otherwise required definition of the number of modes considered for damping, which has an impact on the computational time, but also allows tailoring the load material to conform with experimental data of e.g. non-perfect absorbers. The new calculation scheme is presented. Findings are partially compared with those achieved with the standard waveguide port approach by means of external quality factors. CPU speeds are briefly discussed for both approaches.

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB008

RF Simulations for an LCLS-II 3rd Harmonic Cavity Cyromodule

cavity, HOM, cryomodule, dipole

1078

L. Xiao, C. Adolphsen, Z. Li, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

The FNAL designed 3.9 GHz third harmonic cavity for XFEL will be used in LCLS-II for linearizing the longitudinal beam profile. The 3.9 GHz SRF cavity is scaled down from the 1.3 GHz TESLA cavity shape, but has a disproportionately large beampipe radius for better higher-order mode (HOM) damping. The HOM and fundamental power (FPC) couplers will generate asymmetric field in the beam region, and thereby dilute the beam emittance. Meanwhile, due to the large beampipe, all but a few of the HOMs are above the beampipe cutoff. Thus the HOM damping analyses need to be performed in a full cryomodule, rather than in an individual cavity. The HOM damping in a 4-cavity cryomodule was investigated to determine possible trapped modes using the parallel electromagnetic code suite ACE3P developed at SLAC. The coupler RF kicks induced by the HOM and FPC couplers in the 3.9 GHz cavity were evaluated. A possible cavity-to-cavity arrangement is proposed which could provide effective cancellation of these RF kicks. In this paper we present and discuss the RF simulation results in the 3.9 GHz third harmonic cavity cryomodule.
Work supported by Department of Energy under contract Number DE-AC02-76SF00515.

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB068

Practical Aspects of HOM Suppression Improvement for TM011

HOM, cavity, simulation, dipole

1277

A.A. Sulimov, A. Ermakov, J.H. Thie
DESY, Hamburg, Germany
A. Gresele
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy

Some Higher Order Modes (HOM) pass bands were controlled during cryo-tests at DESY for the European XFEL cavities. The second monopole mode (TM011) showed most instabilities and suppression degradation. The authors will explain this phenomenon on the example of cavity CAV00553 and present the practical method of TM011 damping improvement.

Poster THPB068 [0.182 MB]

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB074

High Current eRHIC Cavity Design and HOM Damping Scheme

cavity, HOM, linac, impedance

1297

W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn
BNL, Upton, Long Island, New York, USA

Funding: This work is supported by LDRD program of Brookhaven Science Associates.
A 422 MHz cavity was designed for high current FFAG lattice ERLs for high luminosity eRHIC. The cavity was optimized to be able to propagate all the HOMs out of the cavity for high BBU threshold current and low HOM power (loss factor). Coupling the full spectrum (up to 30 GHz) HOMs out of the cavity and delivering the HOM power (up to 8 kW) out of the cryomodule is a challenge. A damping scheme with 6 coaxial line HOM couplers for low frequency HOMs and 3 waveguide HOM dampers for high frequency (so that the waveguide is small) is proposed to damp the full spectrum and high power HOMs. This paper will present the cavity design and HOM damping scheme.

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB104

Higher Order Modes Simulation and Measurements for 2400 MHz Cavity

HOM, cavity, simulation, higher-order-mode

1394

Ya.V. Shashkov, D.S. Bazyl, R.V. Donetskiy, M.V. Lalayan, N.P. Sobenin
MEPhI, Moscow, Russia
R. Calaga
CERN, Geneva, Switzerland
A.A. Zavadtsev
Nano, Moscow, Russia
M. Zobov
INFN/LNF, Frascati (Roma), Italy

Funding: *Work supported by Ministry of Education and Science grant 3.245.2014/r and the EU FP7 HiLumi LHC – Grant Agreement 284404
In the frameworks of the High Luminosity LHC upgrade program an application of additional harmonic cavities operating at multiples of the main RF system frequency of 400 MHz is currently under discussion. The 800 MHz superconducting cavities with grooved beam pipes were suggested for implementation. A scaled aluminum prototype with a frequency of the operational mode of 2400 MHz was manufactured for testing the results of simulations. The load reflection coefficient measurements were performed as well as the Qload measurements for cavities with the load. Here we discuss the prototype design and report the obtained measurement results.
Higher order modes, superconducting cavities, srf

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