SRF2011 - List of Authors (Liepe, M.)

Paper

Title

Page

Superconducting RF for the Cornell Energy-Recovery Linac Main Linac

90

M. Liepe, Y. He, G.H. Hoffstaetter, S. Posen, J. Sears, V.D. Shemelin, M. Tigner, N.R.A. Valles, V. Veshcherevich
CLASSE, Ithaca, New York, USA

Funding: Supported by NSF award DMR-0807731.
Cornell University is developing the superconducting RF technology required for the construction of a 100 mA hard X-ray light source driven by an Energy-Recovery Linac. Prototype components of the 5 GeV cw SRF main linac cryomodule are under development, fabrication and testing. This work includes an optimized 7-cell SRF cavity, a broadband HOM beamline absorber, and a 5 kW cw RF input coupler. In this paper we give an overview of these activities at Cornell.

MOPO019

Minimizing Microphonics Detuning by Optimization of Stiffening Rings

103

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

Maintaining a constant gradient in a superconducting cavity requires can require much more power if the cavity is not driven on resonance. Significant cost savings in both power consumption and power supplies can be realized by minimizing the detuning of the cavity away from the drive frequency. One of the largest contributions to detuning is microphonics. In this paper, simulations of microphonics detuning by LHe bath pressure fluctuations in a Cornell ERL cavity are presented, and the effect of varying stiffening ring radius is investigated. The consequences of using optimal stiffening ring radii are explored as well, including bandwidth limitations in active detuning compensation due to mechanical resonances and requirements for the frequency tuner.

MOPO042

Coupler Design for a Sample Host TE Cavity

184

Y. Xie, M. Liepe
CLASSE, Ithaca, New York, USA

Funding: Work supported by NSF and Alfred P. Sloan Foundation.
A sample host niobium superconducting cavity operating at both TE012 and TE013 modes has been developed *. The cavity features a flat 3.75'' diameter demountable bottom plate allowing RF testing of new materials such as Nb3Sn and MgB2. Since the surface resistance of the sample plates may vary a lot, an adjustable input coupler has been developed for this cavity. A hook shape coupler tip is designed and optimized to couple to the magnetic field of both transverse electric modes. The external Q factor, coupler heating considerations and 3D multipacting simulations using ACE3P will be discussed.
* Y. Xie, J. Hinnefield, M. Liepe, '' Design of a TE-type cavity for testing superconducting material samples'', SRF2009, Berlin (2009)

MOPO056

Beam Break Up Studies for Cornell's Energy Recovery Linac

229

N.R.A. Valles, D.S. Klein, M. Liepe
CLASSE, Ithaca, New York, USA

New results are presented of beam break-up (BBU) studies for the Cornell ERL main linac. Previously, a 1.3 GHz main linac 7-cell cavity was optimized to maximize the BBU current through the accelerator. This work realistically models the ERL main linac cavity shapes by taking into account small machining variations in ellipse dimensions. Cavity shapes were simulated with uniformly distributed errors, and their higher-order mode spectrum computed. The strongest higher-order modes can cause resonant excitations in the beam which can lead to beam loss. The threshold current through the accelerator is determined resulting from a linac comprised of cavities with machining variations using particle tracking and demonstrates that the threshold current is well above the 100 mA design goal for the Cornell's Energy Recovery Linac.

MOPO057

Coupler Kick Studies in Cornell's 7-Cell Superconducting Cavities

232

N.R.A. Valles, M. Liepe, V.D. Shemelin
CLASSE, Ithaca, New York, USA

Cornell is developing a 5 GeV Energy Recovery Linac operating at 100 mA with very small emittances (~30 pm-rad at 77 pC bunch charge) in the horizontal and vertical directions. We investigate the effect of the fundamental RF power couplers of the main linac SRF cavities on the beam using the ACE3P software package. The cavities in the ERL main linac will be operated at very high loaded quality factors of up to 6.5·10⁷, corresponding to a full bandwidth of only 20 Hz. Cavity microphonics will detune the cavities by more than one bandwidth during operation, thereby causing a time dependent change of the coupler kick in addition to its fast oscillation at the RF frequency. In order to investigate the dependence of the coupler kick on the cavity frequency, we calculate the coupler kick given to the beam for the case of a detuned RF cavity. We show that a compensation stub geometry located opposite to the input coupler port can be optimized to reduce the overall kick given to the beam and the emittace growth caused by its time dependence.

MOPO061

Effects of Elliptically Deformed Cell Shape in the Cornell ERL Cavity

244

L. Xiao, K. Ko, K.H. Lee, C.-K. Ng
SLAC, Menlo Park, California, USA
M. Liepe, N.R.A. Valles
CLASSE, Ithaca, New York, USA

The Cornell ERL cavity is optimized to minimize the dipole mode BBU parameters to achieve the required high beam current (100mA). Deformations due to errors in fabrication and tuning of the accelerating mode can result in a cavity shape different from the ideal. In elliptically deformed cells, this can cause dipole mode frequency spread and splitting of the mode polarizations leading to an x-y mode coupling. To investigate these effects, we use a mesh distortion technique to generate an elliptically deformed cell cavity model as a base for studying random imperfections. Simulation results from the eigensolver Omega3P of one hundred randomly elliptically deformed cell cavities covering the first three dipole bands will be presented. The results will be used as input to the beam tracking code BMAD to calculate the impact of such imperfections on the dipole mode BBU parameters.

MOPO063

HOM Measurements with Beam at the Cornell Injector Cryomodule

251

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

The Cornell ERL injector prototype is undergoing commissioning and testing for running unprecedented currents in an electron cw injector. This paper discusses preliminary measurements of HOMs in the injector prototype’s superconducting RF cryomodule. These include HOM spectra up to 30 GHz measured via small antennae located at the HOM beam line absorbers between the SRF cavities. The spectra are compared at different beam currents and repetition rates. The shape of the spectra are compared to ABCI simulations of the loss factor spectrum of the cryomodule beam line. The total HOM power dissipated in the HOM loads was also measured with beam on, which allowed for an estimate of the loss factor. This measurement was accomplished via temperature sensors on the loads, calibrated to input power by heaters on the loads.

Poster MOPO063 [5.567 MB]

MOPO067

CW Measurements of Cornell LLRF System at HoBiCaT

262

A. Neumann, W. Anders, R. Görgen, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA
J. Dobbins, R.P.K. Kaplan, M. Liepe, C.R. Strohman
CLASSE, Ithaca, New York, USA

Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin.
In Energy Recovery Linacs, such as the Cornell ERL or BERLinPro, the main linac cavities are operated in CW at low beam-loading. The choice of the external Q is given by two competing factors: The achievable field stability and the maximum provided RF power. To determine the optimum external Q, LLRF measurements with the Cornell system were performed at HoBiCaT to study the field stability at given microphonics detuning of a TESLA cavity for different gain settings and external Q values. Stable operation at external Q up to 2·10⁸ was demonstrated with field's phase stability of 0.02 degrees.

TUIOA05

The Superheating Field of Niobium: Theory and Experiment

293

N.R.A. Valles, M. Liepe
CLASSE, Ithaca, New York, USA

This study discusses the superheating field of Niobium, a metastable state, which sets the upper limit of sustainable magnetic fields on the surface of a superconductors before it transitions into the normal conducting state. Current models for the superheating field are discussed, and experimental results are presented for niobium obtained through pulsed, high power measurements performed at Cornell. Material preparation is also shown to be an important parameter in exploring other regions of the superheating field, and fundamental limits are presented based upon these experimental and theoretical results.

Slides TUIOA05 [2.247 MB]

TUPO013

Assembly of the International ERL Cryomodule at Daresbury Laboratory

382

P.A. McIntosh, R. Bate, P. Goudket, J.F. Orrett, S.M. Pattalwar
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.A. Belomestnykh, M. Liepe, H. Padamsee, P. Quigley, J. Sears, V.D. Shemelin, V. Veshcherevich
CLASSE, Ithaca, New York, USA
A. Büchner, F.G. Gabriel, P. Michel
HZDR, Dresden, Germany
M.A. Cordwell, T.J. Jones, J. Strachan
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
J.N. Corlett, D. Li, S.M. Lidia
LBNL, Berkeley, California, USA
T. Kimura, T.I. Smith
Stanford University, Stanford, California, USA
R.E. Laxdal
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
D. Proch, J.K. Sekutowicz
DESY, Hamburg, Germany

The collaborative development of an optimised cavity/cryomodule solution for application on ERL facilities is nearing completion. This paper outlines the progress of the module assembly and details the processes used for final cavity string integration. The preparation and installation of the high power couplers will be described, as will that of the HOM loads. The testing and integration of the various sub-components of the cryomodule are also detailed in this paper.

THPO001

Quench Simulation Using a Ring-Type Defect Model

687

Y. Xie, M. Liepe, H. Padamsee
CLASSE, Ithaca, New York, USA

Funding: Work supported by NSF and Alfred P. Sloan Foundation.
A 2 dimensional ring-type defect thermal feedback model has been improved by including magnetic field enhancement at the pit edge. Latest simulation results show that there is a thermally stable state below the quench field with part of edge becoming normal conducting, which can explain pre-heating phenomenon observed in thermometry measurements. 3D magnetic field enhancement calculations of pit structures using Omega3P shows angular non-uniform field enhancement around the edge. Those findings will be incorporated into a 3D finite ring-type defect thermal codes.

THPO009

Quench Studies in Large and Fine Grain Nb Cavities

714

S. Posen, M. Liepe, N.R.A. Valles
CLASSE, Ithaca, New York, USA

Quenches without radiation are sometimes observed at accelerating fields between 25 and 40 MV/m in niobium SRF cavities. The cause for this limitation is not well understood. This work presents results from vertical tests of seven 1.3 GHz single-cell cavities performing above 25 MV/m. Studies were carried out on both fine grain and large grain cavities in ILC and Cornell Reentrant shape geometries. The quenches were located by triangulation using Cornell oscillating superleak transducers and then cavities were optically inspected to determine the surface conditions of the cavity at the quench location. Optical inspection images are presented as well as 3D recreations of quench spots generated using a surface mold and a confocal microscope.

Poster THPO009 [2.013 MB]

THPO050

TE Sample Host Cavities Development at Cornell

841

Y. Xie, M. Liepe
CLASSE, Ithaca, New York, USA

Funding: Work supported by NSF and Alfred P. Sloan Foundation
In order to measure surface resistance of new materials other than niobium such as Nb3Sn and MgB2, two sample host niobium cavities operating at TE modes have been developed at Cornell University. The first one is a 6GHz pillbox TE011 cavity modified from an older vision enabling testing 2.75'' diameter flat sample plates *. The second one is an optimized mushroom-shape niobium cavity operating at both 4GHz TE012 and 6GHz TE013 modes for 3.75'' diameter flat sample plates **. First results from the commissioning of the two TE cavities will be reported.
* D. Rubin et al., Phys. Rev. B 38, 6538(1988)
** Y. Xie, J. Hinnefield, M. Liepe, '' Design of a TE-type cavity for testing superconducting material samples'', SRF2009, Berlin (2009)

THPO066

Stoichiometric Nb3Sn in First Samples Coated at Cornell

886

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

A cavity coated with the superconductor Nb3Sn theoretically will be able to reach more than twice the maximum accelerating field of Nb in a cavity under the same operating conditions and will have a much lower BCS surface resistance at a given temperature. The SRF group at Cornell has recently developed facilities to fabricate Nb3Sn on Nb. The first samples have been coated, and several tests have been performed to characterize them. Results presented include SEM images of the surface, anodization tests, a critical temperature measurement, a test for RRR degradation, and stoichiometry measurements using EDX and XPS.

Poster THPO066 [36.490 MB]

FRIOA03

Recent Progress in HOM Damping from Around The World

946

M. Liepe
CLASSE, Ithaca, New York, USA

Continuous progress in SRF technology is pushing the beam parameter envelope for SRF linacs towards higher currents and shorter bunch lengths. Therefore, the demands on the HOM dampers used in these SRF linacs are increasing continuously, and Higher-Order-Mode (HOM) damping remains a very active field of research and development. Different HOM damping concepts have been developed and improved over the last years to support high power handling and broadband HOM damping. In this paper we give an overview of recent progress on antenna, waveguide, and beamline HOM dampers.

Paper	Title	Page
MOPO016	Superconducting RF for the Cornell Energy-Recovery Linac Main Linac	90
	M. Liepe, Y. He, G.H. Hoffstaetter, S. Posen, J. Sears, V.D. Shemelin, M. Tigner, N.R.A. Valles, V. Veshcherevich CLASSE, Ithaca, New York, USA
	Funding: Supported by NSF award DMR-0807731. Cornell University is developing the superconducting RF technology required for the construction of a 100 mA hard X-ray light source driven by an Energy-Recovery Linac. Prototype components of the 5 GeV cw SRF main linac cryomodule are under development, fabrication and testing. This work includes an optimized 7-cell SRF cavity, a broadband HOM beamline absorber, and a 5 kW cw RF input coupler. In this paper we give an overview of these activities at Cornell.

MOPO019	Minimizing Microphonics Detuning by Optimization of Stiffening Rings	103
	S. Posen, M. Liepe CLASSE, Ithaca, New York, USA
	Maintaining a constant gradient in a superconducting cavity requires can require much more power if the cavity is not driven on resonance. Significant cost savings in both power consumption and power supplies can be realized by minimizing the detuning of the cavity away from the drive frequency. One of the largest contributions to detuning is microphonics. In this paper, simulations of microphonics detuning by LHe bath pressure fluctuations in a Cornell ERL cavity are presented, and the effect of varying stiffening ring radius is investigated. The consequences of using optimal stiffening ring radii are explored as well, including bandwidth limitations in active detuning compensation due to mechanical resonances and requirements for the frequency tuner.

MOPO042	Coupler Design for a Sample Host TE Cavity	184
	Y. Xie, M. Liepe CLASSE, Ithaca, New York, USA
	Funding: Work supported by NSF and Alfred P. Sloan Foundation. A sample host niobium superconducting cavity operating at both TE012 and TE013 modes has been developed . The cavity features a flat 3.75'' diameter demountable bottom plate allowing RF testing of new materials such as Nb3Sn and MgB2. Since the surface resistance of the sample plates may vary a lot, an adjustable input coupler has been developed for this cavity. A hook shape coupler tip is designed and optimized to couple to the magnetic field of both transverse electric modes. The external Q factor, coupler heating considerations and 3D multipacting simulations using ACE3P will be discussed. Y. Xie, J. Hinnefield, M. Liepe, '' Design of a TE-type cavity for testing superconducting material samples'', SRF2009, Berlin (2009)

MOPO056	Beam Break Up Studies for Cornell's Energy Recovery Linac	229
	N.R.A. Valles, D.S. Klein, M. Liepe CLASSE, Ithaca, New York, USA
	New results are presented of beam break-up (BBU) studies for the Cornell ERL main linac. Previously, a 1.3 GHz main linac 7-cell cavity was optimized to maximize the BBU current through the accelerator. This work realistically models the ERL main linac cavity shapes by taking into account small machining variations in ellipse dimensions. Cavity shapes were simulated with uniformly distributed errors, and their higher-order mode spectrum computed. The strongest higher-order modes can cause resonant excitations in the beam which can lead to beam loss. The threshold current through the accelerator is determined resulting from a linac comprised of cavities with machining variations using particle tracking and demonstrates that the threshold current is well above the 100 mA design goal for the Cornell's Energy Recovery Linac.

MOPO057	Coupler Kick Studies in Cornell's 7-Cell Superconducting Cavities	232
	N.R.A. Valles, M. Liepe, V.D. Shemelin CLASSE, Ithaca, New York, USA
	Cornell is developing a 5 GeV Energy Recovery Linac operating at 100 mA with very small emittances (~30 pm-rad at 77 pC bunch charge) in the horizontal and vertical directions. We investigate the effect of the fundamental RF power couplers of the main linac SRF cavities on the beam using the ACE3P software package. The cavities in the ERL main linac will be operated at very high loaded quality factors of up to 6.5·10⁷, corresponding to a full bandwidth of only 20 Hz. Cavity microphonics will detune the cavities by more than one bandwidth during operation, thereby causing a time dependent change of the coupler kick in addition to its fast oscillation at the RF frequency. In order to investigate the dependence of the coupler kick on the cavity frequency, we calculate the coupler kick given to the beam for the case of a detuned RF cavity. We show that a compensation stub geometry located opposite to the input coupler port can be optimized to reduce the overall kick given to the beam and the emittace growth caused by its time dependence.

MOPO061	Effects of Elliptically Deformed Cell Shape in the Cornell ERL Cavity	244
	L. Xiao, K. Ko, K.H. Lee, C.-K. Ng SLAC, Menlo Park, California, USA M. Liepe, N.R.A. Valles CLASSE, Ithaca, New York, USA
	The Cornell ERL cavity is optimized to minimize the dipole mode BBU parameters to achieve the required high beam current (100mA). Deformations due to errors in fabrication and tuning of the accelerating mode can result in a cavity shape different from the ideal. In elliptically deformed cells, this can cause dipole mode frequency spread and splitting of the mode polarizations leading to an x-y mode coupling. To investigate these effects, we use a mesh distortion technique to generate an elliptically deformed cell cavity model as a base for studying random imperfections. Simulation results from the eigensolver Omega3P of one hundred randomly elliptically deformed cell cavities covering the first three dipole bands will be presented. The results will be used as input to the beam tracking code BMAD to calculate the impact of such imperfections on the dipole mode BBU parameters.

MOPO063	HOM Measurements with Beam at the Cornell Injector Cryomodule	251
	S. Posen, M. Liepe CLASSE, Ithaca, New York, USA
	The Cornell ERL injector prototype is undergoing commissioning and testing for running unprecedented currents in an electron cw injector. This paper discusses preliminary measurements of HOMs in the injector prototype’s superconducting RF cryomodule. These include HOM spectra up to 30 GHz measured via small antennae located at the HOM beam line absorbers between the SRF cavities. The spectra are compared at different beam currents and repetition rates. The shape of the spectra are compared to ABCI simulations of the loss factor spectrum of the cryomodule beam line. The total HOM power dissipated in the HOM loads was also measured with beam on, which allowed for an estimate of the loss factor. This measurement was accomplished via temperature sensors on the loads, calibrated to input power by heaters on the loads.
	Poster MOPO063 [5.567 MB]

MOPO067	CW Measurements of Cornell LLRF System at HoBiCaT	262
	A. Neumann, W. Anders, R. Görgen, J. Knobloch, O. Kugeler HZB, Berlin, Germany S.A. Belomestnykh BNL, Upton, Long Island, New York, USA J. Dobbins, R.P.K. Kaplan, M. Liepe, C.R. Strohman CLASSE, Ithaca, New York, USA
	Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin. In Energy Recovery Linacs, such as the Cornell ERL or BERLinPro, the main linac cavities are operated in CW at low beam-loading. The choice of the external Q is given by two competing factors: The achievable field stability and the maximum provided RF power. To determine the optimum external Q, LLRF measurements with the Cornell system were performed at HoBiCaT to study the field stability at given microphonics detuning of a TESLA cavity for different gain settings and external Q values. Stable operation at external Q up to 2·10⁸ was demonstrated with field's phase stability of 0.02 degrees.

TUIOA05	The Superheating Field of Niobium: Theory and Experiment	293
	N.R.A. Valles, M. Liepe CLASSE, Ithaca, New York, USA
	This study discusses the superheating field of Niobium, a metastable state, which sets the upper limit of sustainable magnetic fields on the surface of a superconductors before it transitions into the normal conducting state. Current models for the superheating field are discussed, and experimental results are presented for niobium obtained through pulsed, high power measurements performed at Cornell. Material preparation is also shown to be an important parameter in exploring other regions of the superheating field, and fundamental limits are presented based upon these experimental and theoretical results.
	Slides TUIOA05 [2.247 MB]

TUPO013	Assembly of the International ERL Cryomodule at Daresbury Laboratory	382
	P.A. McIntosh, R. Bate, P. Goudket, J.F. Orrett, S.M. Pattalwar STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S.A. Belomestnykh, M. Liepe, H. Padamsee, P. Quigley, J. Sears, V.D. Shemelin, V. Veshcherevich CLASSE, Ithaca, New York, USA A. Büchner, F.G. Gabriel, P. Michel HZDR, Dresden, Germany M.A. Cordwell, T.J. Jones, J. Strachan STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom J.N. Corlett, D. Li, S.M. Lidia LBNL, Berkeley, California, USA T. Kimura, T.I. Smith Stanford University, Stanford, California, USA R.E. Laxdal TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada D. Proch, J.K. Sekutowicz DESY, Hamburg, Germany
	The collaborative development of an optimised cavity/cryomodule solution for application on ERL facilities is nearing completion. This paper outlines the progress of the module assembly and details the processes used for final cavity string integration. The preparation and installation of the high power couplers will be described, as will that of the HOM loads. The testing and integration of the various sub-components of the cryomodule are also detailed in this paper.

THPO001	Quench Simulation Using a Ring-Type Defect Model	687
	Y. Xie, M. Liepe, H. Padamsee CLASSE, Ithaca, New York, USA
	Funding: Work supported by NSF and Alfred P. Sloan Foundation. A 2 dimensional ring-type defect thermal feedback model has been improved by including magnetic field enhancement at the pit edge. Latest simulation results show that there is a thermally stable state below the quench field with part of edge becoming normal conducting, which can explain pre-heating phenomenon observed in thermometry measurements. 3D magnetic field enhancement calculations of pit structures using Omega3P shows angular non-uniform field enhancement around the edge. Those findings will be incorporated into a 3D finite ring-type defect thermal codes.

THPO009	Quench Studies in Large and Fine Grain Nb Cavities	714
	S. Posen, M. Liepe, N.R.A. Valles CLASSE, Ithaca, New York, USA
	Quenches without radiation are sometimes observed at accelerating fields between 25 and 40 MV/m in niobium SRF cavities. The cause for this limitation is not well understood. This work presents results from vertical tests of seven 1.3 GHz single-cell cavities performing above 25 MV/m. Studies were carried out on both fine grain and large grain cavities in ILC and Cornell Reentrant shape geometries. The quenches were located by triangulation using Cornell oscillating superleak transducers and then cavities were optically inspected to determine the surface conditions of the cavity at the quench location. Optical inspection images are presented as well as 3D recreations of quench spots generated using a surface mold and a confocal microscope.
	Poster THPO009 [2.013 MB]

THPO050	TE Sample Host Cavities Development at Cornell	841
	Y. Xie, M. Liepe CLASSE, Ithaca, New York, USA
	Funding: Work supported by NSF and Alfred P. Sloan Foundation In order to measure surface resistance of new materials other than niobium such as Nb3Sn and MgB2, two sample host niobium cavities operating at TE modes have been developed at Cornell University. The first one is a 6GHz pillbox TE011 cavity modified from an older vision enabling testing 2.75'' diameter flat sample plates . The second one is an optimized mushroom-shape niobium cavity operating at both 4GHz TE012 and 6GHz TE013 modes for 3.75'' diameter flat sample plates . First results from the commissioning of the two TE cavities will be reported. D. Rubin et al., Phys. Rev. B 38, 6538(1988) ** Y. Xie, J. Hinnefield, M. Liepe, '' Design of a TE-type cavity for testing superconducting material samples'', SRF2009, Berlin (2009)

THPO066	Stoichiometric Nb3Sn in First Samples Coated at Cornell	886
	S. Posen, M. Liepe CLASSE, Ithaca, New York, USA
	A cavity coated with the superconductor Nb3Sn theoretically will be able to reach more than twice the maximum accelerating field of Nb in a cavity under the same operating conditions and will have a much lower BCS surface resistance at a given temperature. The SRF group at Cornell has recently developed facilities to fabricate Nb3Sn on Nb. The first samples have been coated, and several tests have been performed to characterize them. Results presented include SEM images of the surface, anodization tests, a critical temperature measurement, a test for RRR degradation, and stoichiometry measurements using EDX and XPS.
	Poster THPO066 [36.490 MB]

FRIOA03	Recent Progress in HOM Damping from Around The World	946
	M. Liepe CLASSE, Ithaca, New York, USA
	Continuous progress in SRF technology is pushing the beam parameter envelope for SRF linacs towards higher currents and shorter bunch lengths. Therefore, the demands on the HOM dampers used in these SRF linacs are increasing continuously, and Higher-Order-Mode (HOM) damping remains a very active field of research and development. Different HOM damping concepts have been developed and improved over the last years to support high power handling and broadband HOM damping. In this paper we give an overview of recent progress on antenna, waveguide, and beamline HOM dampers.