SRF2015 - List of Keywords (resonance)

Paper	Title	Other Keywords	Page
MOPB015	Trapped Flux Surface Resistance Analysis for Different Surface Treatments	cavity, niobium, superconductivity, instrumentation	115
	M. Martinello, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA M. Checchin Illinois Institute of Technology, Chicago, Illlinois, USA J. Zasadzinski IIT, Chicago, Illinois, USA
	Funding: Work supported by the US Department of Energy, Office of High Energy Physics The trapped flux surface resistance is one of the main contributions on cavity losses which appears when cavities are cooled in presence of external magnetic field. The study is focused on the understanding of the different parameters which determine the trapped flux surface resistance, and how this change as a function of different surface treatments. The study is performed on 1.3 GHz niobium cavities processed with different surface treatments after the 800 C bake: electro-polishing (EP), 120 C baking, and N-doping varying the time of the Nitrogen exposure. The trapped flux surface resistance normalized for the trapped magnetic flux is then analyzed as a function of the mean free path in order to find the surface treatment which minimized the trapped flux sensitivity.
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MOPB087	Integrated High-Power Tests of Dressed N-doped 1.3 GHz SRF Cavities for LCLS-II	cavity, HOM, cryomodule, vacuum	342
	N. Solyak, T.T. Arkan, B.E. Chase, A.C. Crawford, E. Cullerton, I.V. Gonin, A. Grassellino, C.J. Grimm, A. Hocker, J.P. Holzbauer, T.N. Khabiboulline, O.S. Melnychuk, J.P. Ozelis, T.J. Peterson, Y.M. Pischalnikov, K.S. Premo, A. Romanenko, A.M. Rowe, W. Schappert, D.A. Sergatskov, R.P. Stanek, G. Wu Fermilab, Batavia, Illinois, USA
	New auxiliary components have been designed and fabricated for the 1.3 GHz SRF cavities comprising the LCLS-II linac. In particular, the LCLS-II cavity’s helium vessel, high-power input coupler, higher-order mode (HOM) feedthroughs, magnetic shielding, and cavity tuning system were all designed to meet LCLS-II specifications. Integrated tests of the cavity and these components were done at Fermilab’s Horizontal Test Stand (HTS) using several kilowatts of continuous-wave (CW) RF power. The results of the tests are summarized here.
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TUPB064	Superconducting Thin Film Test Cavity Commissioning	cavity, vacuum, niobium, cryogenics	731
	P. Goudket, K.D. Dumbell, L. Gurran, O.B. Malyshev, N. Pattalwar, S.M. Pattalwar, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt, L. Gurran Cockcroft Institute, Lancaster University, Lancaster, United Kingdom G. Burt, L. Gurran Lancaster University, Lancaster, United Kingdom P. Goudket, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh Cockcroft Institute, Warrington, Cheshire, United Kingdom T.J. Jones, E.S. Jordan STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	A radiofrequency (RF) cavity and cryostat dedicated to the measurement of superconducting coatings at GHz frequencies was designed to evaluate surface resistive losses on a flat sample. The test cavity consists of two parts: a cylindrical half-cell made of bulk niobium (Nb) and a flat Nb disc. The two parts can be thermally and electrically isolated via a vacuum gap, whereas the electromagnetic fields are constrained through the use of RF chokes. Both parts are conduction cooled hence the cavity halves are suspended in vacuum during operation. The flat disc can be replaced with a sample, such as a Cu disc coated with a film of niobium or any other superconducting material. The RF test provides simple cavity Q-factor measurements as well as calorimetric measurements of the losses on the sample. The advantage of this method is the combination of a compact cavity with a simple planar sample. The paper describes the RF, mechanical and cryogenic design, and initial commissioning of the system with notes on how any issues arising are to be addressed.
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TUPB075	Measurements on the Superconducting 217 MHz CH Cavity During the Manufacturing Phase	cavity, simulation, operation, linac	757
	F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech IAP, Frankfurt am Main, Germany M. Amberg, K. Aulenbacher, W.A. Barth, S. Mickat HIM, Mainz, Germany K. Aulenbacher IKP, Mainz, Germany W.A. Barth, S. Mickat GSI, Darmstadt, Germany
	Funding: GSI, HIM, BMBF Contr. No. 05P12RFRBL Since in future the existing UNILAC (Universal Linear Accelerator) will be used as an injector for the FAIR (Facility for Antiproton and Ion Research) project, a new superconducting (sc) continuous wave (cw) linac at GSI is proposed to keep the Super Heavy Element (SHE) program at a competitive high level. In this context, a sc 217 MHz crossbar-H-mode (CH) cavity has been designed at the Institute for Applied Physics (IAP), Frankfurt University, and was built at Research Instruments (RI) GmbH, Germany. The cavity serves as a first prototype to demonstrate the reliable operability under a realistic accelerator environment and its successful beam operation will be a milestone on the way to the new linac. In this contribution measurements during the production process of the cavity as well as corresponding simulations will be presented.
	Poster TUPB075 [2.476 MB]
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TUPB091	Systematic Uncertainties in RF-Based Measurement of Superconducting Cavity Quality Factors	cavity, coupling, factory, superconducting-cavity	814
	W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	Measurements of cavity quality factor measurements are subject to at least three potentially large sources of systematic error that have not been previously recognized. Imperfect coupler directivity (cross-talk) can lead to large errors in the cavity coupling factor when the cavity coupling factor is significantly different than unity. Energy re-reflected from the circulator can systematically bias the measured cavity decay time which is used to determine the loaded quality factor. Use of the peak probe power or the minimum of the reflected power to determine the cavity resonance frequency rather than the peak of the probe/forward transfer function may lead to errors in the resonance frequency that can also affect quality factors. Each effect is illustrated with measurements in the Fermilab VTS, simulations and analytic calculations. If the magnitude and phase of the cavity RF signals are measured, these effects can be measured and corrected for. If only signal magnitudes are recorded or these effects are not measured, they must be treated as sources of systematic uncertainty.
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TUPB095	Resonance Control for Narrow-Bandwidth, Superconducting RF Applications	cavity, feedback, SRF, operation	828
	W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov Fermilab, Batavia, Illinois, USA D. Gonnella Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA M. Liepe Cornell University, Ithaca, New York, USA
	Optimal control techniques have been employed in a variety of applications since they were first developed more than 60 years ago but until now they have been used in few if any accelerator-related applications. The next generation of superconducting accelerators will require both precise control of the gradient and active stabilization of the resonance frequency. Optimal control techniques provide a self-consistent framework within which to construct a combined electro-mechanical controller. Results from recent cold cavity tests at Fermilab are presented.
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TUPB096	Mechanical Damper Study for ISAC-II Quarter Wave Resonators	damping, ISAC, cavity, simulation	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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THPB001	Propagation of the High Frequency Fields in the Chain of the Superconducting Cavities	cavity, wakefield, electromagnetic-fields, accelerating-gradient	1049
	A. Novokhatski SLAC, Menlo Park, California, USA
	Funding: Work supported by the Department of Energy. Contract no.DOE-AC03-76SF00515. Combination with the very high repetion rate requires to use the superconducting cavities to accelerate very short bunches for the FEL operation.. In the cavities these bunches excite very high frequency electromagnetic fields. There are severe concerns, that these fields will remain inside the structure for a long time, bring additional heating or even break up the Cooper pairs. We present results of the simulation of the transient dynamics of wake fields of very short bunches. We show how much of the energy is vanishing through the beam pipes immediately and how much energy is staying in the cavity for a long time.
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THPB007	A Study of Resonant Excitation of Longitudinal HOMs in the Cryomodules of LCLS-II	HOM, cavity, factory, impedance	1073
	K.L.F. Bane, C. Adolphsen, A. Chao, Z. Li SLAC, Menlo Park, California, USA
	Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 The Linac Coherent Light Source (LCLS) at SLAC, the world's first hard X-ray FEL, is being upgraded to the LCLS-II. The major new feature will be the installation of 35 cryomodules (CMs) of TESLA-type, superconducting accelerating structures. It is envisioned that LCLS-II will eventually be able to deliver 300 pC, 1 kA pulses of beam at a rate of 1 MHz. At a cavity temperature of 2K, any heat generated (even on the level of a few watts) is expensive to remove. In the last linac of LCLS-II, L3–-where the peak current is highest–-the power radiated by the bunch in the CMs is estimated at 14 W (charge 300 pC option, rep rate 1 MHz). But this calculation ignores resonances that can be excited between the bunch frequency and higher order mode (HOM) frequencies in the CMs, which in principle can greatly increase this number. In this report we develop a theory of resonant build up. Then, using 500 numerically obtained modes over the frequency range 3–5 GHz, we estimate the probability of significant resonant build up in L3 of LCLS-II. The effects of small random bunch phase and charge errors will also be addressed.
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THPB014	Mechanical Optimization of High Beta 650 MHz Cavity for Pulse and CW Operation of PIP-II Project	cavity, operation, simulation, cryomodule	1093
	T.N. Khabiboulline, I.V. Gonin, C.J. Grimm, A. Lunin, T.H. Nicol, V.P. Yakovlev Fermilab, Batavia, Illinois, USA P. Kumar RRCAT, Indore (M.P.), India
	The proposed design of the 0.8 GeV PIP-II SC Linac employs two families of 650 MHz 5-cell elliptical cavities with 2 different beta. The β=0.61 will cover the 185-500 MeV range and the β=0.92 will cover the 500-800 MeV range. In this paper we will present update of RF and mechanical design of dressed high beta cavity (β=0.92) for pulse regime of operation at 2 mA beam current. In previous CW version of PIP-II project the mechanical design was concentrated on minimization of frequency shift due to helium pressure fluctuation. In current case of pulse regime operation the main goal was Lorentz force detuning minimization. We present the scope of coupled RF-Mechanical issues and their resolution. Also detailed stress analysis of dresses cavity will be presented.
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THPB019	Bead-Pull Measurements of the Main Deflecting Mode of the Double-Quarter-Wave Cavity for the HL-LHC	cavity, simulation, luminosity, factory	1105
	M. Navarro-Tapia, R. Calaga CERN, Geneva, Switzerland
	Funding: This research has received funding from the European Commission under the FP7 project HiLumi LHC (Grant agreement no. 284404), and under a Marie Curie action (Grant agreement PCOFUND-GA-2010-267194). A full-scale model of the double-quarter-wave (DQW) cavity towards the High-Luminosity Large Hadron Collider (HL-LHC) upgrade was built in aluminum to characterize the deflecting mode. Field strength measurements have been carried out for both the transverse and longitudinal electromagnetic fields, by using the bead-pull technique. Perturbation objects of different shapes and material were used to separate the electric and magnetic field components. A reasonably good agreement was found between numerical simulation and measurements, which confirm the reliability and accuracy of the measurements done.
	Poster THPB019 [0.237 MB]
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THPB021	Balloon Variant of Single Spoke Resonator	electron, simulation, cavity, superconductivity	1110
	Z.Y. Yao, R.E. Laxdal, V. Zvyagintsev TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	Spoke resonators have been widely proposed and optimized for various applications. Good performance has been demonstrated by many cavity tests. Accompanying the great progress, the adverse impact of strong multipacting (MP) is also noted by recent test reports, consistent with modern 3D simulations. This paper will discuss MP behaviors in the single spoke resonator. In particular a phenomenological theory is developed to highlight the details of the geometry that affect MP. The analysis leads to an optimized geometry of a single spoke resonator defined here as the ‘balloon geometry’. A 325MHz β=0.3 single spoke resonator based on 'balloon' concept is under development by the RISP-TRIUMF Collaboration. The RF and mechanical design of this cavity will also be reported.
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THPB061	Performance of the Tuner Mechanism for SSR1 Resonators During Fully Integrated Tests at Fermilab	cavity, controls, niobium, linac	1252
	D. Passarelli, J.P. Holzbauer, L. Ristori Fermilab, Batavia, Illinois, USA
	In the framework of the Proton Improvement Plan-II (PIPII) at Fermilab, a cavity tuner was developed to control the frequency of 325 MHz spoke resonators (SSR1). The behavior of the tuner mechanism and compliance with technical specifications were investigated through a campaign of experimental tests in operating conditions in the spoke test cryostat (STC) and at room temperature. Figures of merit for the tuner such as tuning range, stiffness, components hysteresis and overall performance were measured and are reported in this paper.
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THPB067	HOM Coupler Notch Filter Tuning for the European XFEL Cavities	HOM, cavity, controls, database	1274
	A.A. Sulimov DESY, Hamburg, Germany
	The notch filter (NF) tuning prevents the extraction of fundamental mode (1.3 GHz) RF power through Higher Order Modes (HOM) couplers. The procedure of NF tuning was optimized at the beginning of serial European XFEL cavities production. It allows keeping the filter more stable against temperature and pressure changes during cavity cool down. Some statistics of NF condition during cavities and modules cold tests is presented.
	Poster THPB067 [0.404 MB]
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THPB098	Testing of 325 MHz Couplers at Test Stand in Resonance Mode	cavity, multipactoring, rf-amplifier, monitoring	1376
	S. Kazakov, B.M. Hanna, O.V. Pronitchev Fermilab, Batavia, Illinois, USA
	The linear accelerator for the PIP-II program utilizes two types of 325 MHz Single Spoke resonator cavities: SSR-I and SSR-II. Operating power of SSR-II is about 17 kW and requires input couplers which can reliably work at power levels > 20 kW with full reflection at any reflected phase. Currently only one 10 kW RF amp is available for coupler testing. To increase testing power, a special resonance configuration were used. This configuration allows us to raise RF power approximately 3 times. The testing scheme and results are discussed in the paper.
	Poster THPB098 [1.600 MB]
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Paper

Title

Other Keywords

Page

MOPB015

Trapped Flux Surface Resistance Analysis for Different Surface Treatments

cavity, niobium, superconductivity, instrumentation

115

M. Martinello, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
M. Checchin
Illinois Institute of Technology, Chicago, Illlinois, USA
J. Zasadzinski
IIT, Chicago, Illinois, USA

Funding: Work supported by the US Department of Energy, Office of High Energy Physics
The trapped flux surface resistance is one of the main contributions on cavity losses which appears when cavities are cooled in presence of external magnetic field. The study is focused on the understanding of the different parameters which determine the trapped flux surface resistance, and how this change as a function of different surface treatments. The study is performed on 1.3 GHz niobium cavities processed with different surface treatments after the 800 C bake: electro-polishing (EP), 120 C baking, and N-doping varying the time of the Nitrogen exposure. The trapped flux surface resistance normalized for the trapped magnetic flux is then analyzed as a function of the mean free path in order to find the surface treatment which minimized the trapped flux sensitivity.

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MOPB087

Integrated High-Power Tests of Dressed N-doped 1.3 GHz SRF Cavities for LCLS-II

cavity, HOM, cryomodule, vacuum

342

N. Solyak, T.T. Arkan, B.E. Chase, A.C. Crawford, E. Cullerton, I.V. Gonin, A. Grassellino, C.J. Grimm, A. Hocker, J.P. Holzbauer, T.N. Khabiboulline, O.S. Melnychuk, J.P. Ozelis, T.J. Peterson, Y.M. Pischalnikov, K.S. Premo, A. Romanenko, A.M. Rowe, W. Schappert, D.A. Sergatskov, R.P. Stanek, G. Wu
Fermilab, Batavia, Illinois, USA

New auxiliary components have been designed and fabricated for the 1.3 GHz SRF cavities comprising the LCLS-II linac. In particular, the LCLS-II cavity’s helium vessel, high-power input coupler, higher-order mode (HOM) feedthroughs, magnetic shielding, and cavity tuning system were all designed to meet LCLS-II specifications. Integrated tests of the cavity and these components were done at Fermilab’s Horizontal Test Stand (HTS) using several kilowatts of continuous-wave (CW) RF power. The results of the tests are summarized here.

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TUPB064

Superconducting Thin Film Test Cavity Commissioning

cavity, vacuum, niobium, cryogenics

731

P. Goudket, K.D. Dumbell, L. Gurran, O.B. Malyshev, N. Pattalwar, S.M. Pattalwar, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt, L. Gurran
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G. Burt, L. Gurran
Lancaster University, Lancaster, United Kingdom
P. Goudket, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom
T.J. Jones, E.S. Jordan
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

A radiofrequency (RF) cavity and cryostat dedicated to the measurement of superconducting coatings at GHz frequencies was designed to evaluate surface resistive losses on a flat sample. The test cavity consists of two parts: a cylindrical half-cell made of bulk niobium (Nb) and a flat Nb disc. The two parts can be thermally and electrically isolated via a vacuum gap, whereas the electromagnetic fields are constrained through the use of RF chokes. Both parts are conduction cooled hence the cavity halves are suspended in vacuum during operation. The flat disc can be replaced with a sample, such as a Cu disc coated with a film of niobium or any other superconducting material. The RF test provides simple cavity Q-factor measurements as well as calorimetric measurements of the losses on the sample. The advantage of this method is the combination of a compact cavity with a simple planar sample. The paper describes the RF, mechanical and cryogenic design, and initial commissioning of the system with notes on how any issues arising are to be addressed.

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TUPB075

Measurements on the Superconducting 217 MHz CH Cavity During the Manufacturing Phase

cavity, simulation, operation, linac

757

F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher, W.A. Barth, S. Mickat
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: GSI, HIM, BMBF Contr. No. 05P12RFRBL
Since in future the existing UNILAC (Universal Linear Accelerator) will be used as an injector for the FAIR (Facility for Antiproton and Ion Research) project, a new superconducting (sc) continuous wave (cw) linac at GSI is proposed to keep the Super Heavy Element (SHE) program at a competitive high level. In this context, a sc 217 MHz crossbar-H-mode (CH) cavity has been designed at the Institute for Applied Physics (IAP), Frankfurt University, and was built at Research Instruments (RI) GmbH, Germany. The cavity serves as a first prototype to demonstrate the reliable operability under a realistic accelerator environment and its successful beam operation will be a milestone on the way to the new linac. In this contribution measurements during the production process of the cavity as well as corresponding simulations will be presented.

Poster TUPB075 [2.476 MB]

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TUPB091

Systematic Uncertainties in RF-Based Measurement of Superconducting Cavity Quality Factors

cavity, coupling, factory, superconducting-cavity

814

W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

Measurements of cavity quality factor measurements are subject to at least three potentially large sources of systematic error that have not been previously recognized. Imperfect coupler directivity (cross-talk) can lead to large errors in the cavity coupling factor when the cavity coupling factor is significantly different than unity. Energy re-reflected from the circulator can systematically bias the measured cavity decay time which is used to determine the loaded quality factor. Use of the peak probe power or the minimum of the reflected power to determine the cavity resonance frequency rather than the peak of the probe/forward transfer function may lead to errors in the resonance frequency that can also affect quality factors. Each effect is illustrated with measurements in the Fermilab VTS, simulations and analytic calculations. If the magnitude and phase of the cavity RF signals are measured, these effects can be measured and corrected for. If only signal magnitudes are recorded or these effects are not measured, they must be treated as sources of systematic uncertainty.

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TUPB095

Resonance Control for Narrow-Bandwidth, Superconducting RF Applications

cavity, feedback, SRF, operation

828

W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA
D. Gonnella
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
M. Liepe
Cornell University, Ithaca, New York, USA

Optimal control techniques have been employed in a variety of applications since they were first developed more than 60 years ago but until now they have been used in few if any accelerator-related applications. The next generation of superconducting accelerators will require both precise control of the gradient and active stabilization of the resonance frequency. Optimal control techniques provide a self-consistent framework within which to construct a combined electro-mechanical controller. Results from recent cold cavity tests at Fermilab are presented.

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TUPB096

Mechanical Damper Study for ISAC-II Quarter Wave Resonators

damping, ISAC, cavity, simulation

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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THPB001

Propagation of the High Frequency Fields in the Chain of the Superconducting Cavities

cavity, wakefield, electromagnetic-fields, accelerating-gradient

1049

A. Novokhatski
SLAC, Menlo Park, California, USA

Funding: Work supported by the Department of Energy. Contract no.DOE-AC03-76SF00515.
Combination with the very high repetion rate requires to use the superconducting cavities to accelerate very short bunches for the FEL operation.. In the cavities these bunches excite very high frequency electromagnetic fields. There are severe concerns, that these fields will remain inside the structure for a long time, bring additional heating or even break up the Cooper pairs. We present results of the simulation of the transient dynamics of wake fields of very short bunches. We show how much of the energy is vanishing through the beam pipes immediately and how much energy is staying in the cavity for a long time.

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THPB007

A Study of Resonant Excitation of Longitudinal HOMs in the Cryomodules of LCLS-II

HOM, cavity, factory, impedance

1073

K.L.F. Bane, C. Adolphsen, A. Chao, Z. Li
SLAC, Menlo Park, California, USA

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515
The Linac Coherent Light Source (LCLS) at SLAC, the world's first hard X-ray FEL, is being upgraded to the LCLS-II. The major new feature will be the installation of 35 cryomodules (CMs) of TESLA-type, superconducting accelerating structures. It is envisioned that LCLS-II will eventually be able to deliver 300 pC, 1 kA pulses of beam at a rate of 1 MHz. At a cavity temperature of 2K, any heat generated (even on the level of a few watts) is expensive to remove. In the last linac of LCLS-II, L3–-where the peak current is highest–-the power radiated by the bunch in the CMs is estimated at 14 W (charge 300 pC option, rep rate 1 MHz). But this calculation ignores resonances that can be excited between the bunch frequency and higher order mode (HOM) frequencies in the CMs, which in principle can greatly increase this number. In this report we develop a theory of resonant build up. Then, using 500 numerically obtained modes over the frequency range 3–5 GHz, we estimate the probability of significant resonant build up in L3 of LCLS-II. The effects of small random bunch phase and charge errors will also be addressed.

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THPB014

Mechanical Optimization of High Beta 650 MHz Cavity for Pulse and CW Operation of PIP-II Project

cavity, operation, simulation, cryomodule

1093

T.N. Khabiboulline, I.V. Gonin, C.J. Grimm, A. Lunin, T.H. Nicol, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
P. Kumar
RRCAT, Indore (M.P.), India

The proposed design of the 0.8 GeV PIP-II SC Linac employs two families of 650 MHz 5-cell elliptical cavities with 2 different beta. The β=0.61 will cover the 185-500 MeV range and the β=0.92 will cover the 500-800 MeV range. In this paper we will present update of RF and mechanical design of dressed high beta cavity (β=0.92) for pulse regime of operation at 2 mA beam current. In previous CW version of PIP-II project the mechanical design was concentrated on minimization of frequency shift due to helium pressure fluctuation. In current case of pulse regime operation the main goal was Lorentz force detuning minimization. We present the scope of coupled RF-Mechanical issues and their resolution. Also detailed stress analysis of dresses cavity will be presented.

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THPB019

Bead-Pull Measurements of the Main Deflecting Mode of the Double-Quarter-Wave Cavity for the HL-LHC

cavity, simulation, luminosity, factory

1105

M. Navarro-Tapia, R. Calaga
CERN, Geneva, Switzerland

Funding: This research has received funding from the European Commission under the FP7 project HiLumi LHC (Grant agreement no. 284404), and under a Marie Curie action (Grant agreement PCOFUND-GA-2010-267194).
A full-scale model of the double-quarter-wave (DQW) cavity towards the High-Luminosity Large Hadron Collider (HL-LHC) upgrade was built in aluminum to characterize the deflecting mode. Field strength measurements have been carried out for both the transverse and longitudinal electromagnetic fields, by using the bead-pull technique. Perturbation objects of different shapes and material were used to separate the electric and magnetic field components. A reasonably good agreement was found between numerical simulation and measurements, which confirm the reliability and accuracy of the measurements done.

Poster THPB019 [0.237 MB]

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THPB021

Balloon Variant of Single Spoke Resonator

electron, simulation, cavity, superconductivity

1110

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

Spoke resonators have been widely proposed and optimized for various applications. Good performance has been demonstrated by many cavity tests. Accompanying the great progress, the adverse impact of strong multipacting (MP) is also noted by recent test reports, consistent with modern 3D simulations. This paper will discuss MP behaviors in the single spoke resonator. In particular a phenomenological theory is developed to highlight the details of the geometry that affect MP. The analysis leads to an optimized geometry of a single spoke resonator defined here as the ‘balloon geometry’. A 325MHz β=0.3 single spoke resonator based on 'balloon' concept is under development by the RISP-TRIUMF Collaboration. The RF and mechanical design of this cavity will also be reported.

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THPB061

Performance of the Tuner Mechanism for SSR1 Resonators During Fully Integrated Tests at Fermilab

cavity, controls, niobium, linac

1252

D. Passarelli, J.P. Holzbauer, L. Ristori
Fermilab, Batavia, Illinois, USA

In the framework of the Proton Improvement Plan-II (PIPII) at Fermilab, a cavity tuner was developed to control the frequency of 325 MHz spoke resonators (SSR1). The behavior of the tuner mechanism and compliance with technical specifications were investigated through a campaign of experimental tests in operating conditions in the spoke test cryostat (STC) and at room temperature. Figures of merit for the tuner such as tuning range, stiffness, components hysteresis and overall performance were measured and are reported in this paper.

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THPB067

HOM Coupler Notch Filter Tuning for the European XFEL Cavities

HOM, cavity, controls, database

1274

A.A. Sulimov
DESY, Hamburg, Germany

The notch filter (NF) tuning prevents the extraction of fundamental mode (1.3 GHz) RF power through Higher Order Modes (HOM) couplers. The procedure of NF tuning was optimized at the beginning of serial European XFEL cavities production. It allows keeping the filter more stable against temperature and pressure changes during cavity cool down. Some statistics of NF condition during cavities and modules cold tests is presented.

Poster THPB067 [0.404 MB]

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THPB098

Testing of 325 MHz Couplers at Test Stand in Resonance Mode

cavity, multipactoring, rf-amplifier, monitoring

1376

S. Kazakov, B.M. Hanna, O.V. Pronitchev
Fermilab, Batavia, Illinois, USA

The linear accelerator for the PIP-II program utilizes two types of 325 MHz Single Spoke resonator cavities: SSR-I and SSR-II. Operating power of SSR-II is about 17 kW and requires input couplers which can reliably work at power levels > 20 kW with full reflection at any reflected phase. Currently only one 10 kW RF amp is available for coupler testing. To increase testing power, a special resonance configuration were used. This configuration allows us to raise RF power approximately 3 times. The testing scheme and results are discussed in the paper.

Poster THPB098 [1.600 MB]

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