IPAC2018 - Table of Session: WEPMK (MC7 Poster Session)

Paper	Title	Page
WEPMK001	Preliminary Design of a Cooling System for the LHC Injection Kicker Magnets	2624
SUSPL086	use link to see paper's listing under its alternate paper code
	L. Vega Cid, M.J. Barnes, L. Ducimetière, M.T. Moester, V. Vlachodimitropoulos, W.J.M. Weterings CERN, Geneva, Switzerland A. Abánades ETSII UPM, Madrid, Spain
	The CERN Large Hadron Collider (LHC) is equipped with two fast pulsed magnet systems (MKIs) that inject particle beams from the injector chain. Future operation for High Luminosity LHC (HL-LHC) with high intensity beams will cause heating of the ferrite yokes of the MKIs beyond their Curie temperature, preventing injection until the yokes cool down. Beam coupling impedance studies show that it is possible to move a substantial portion of the beam induced power deposition from the upstream ferrite yokes, which are the yokes with the highest power deposition, to ferrite rings located at the upstream end of the magnet. Thermal predictions show that this power redistribution, combined with the installation of a cooling system around the rings, will maintain the temperatures of all the yokes and ferrite rings below their Curie point. Since the rings are not pulsed to high voltage, whereas the ferrite yokes are, the installation of a cooling system is feasible around the rings. The proposed design of the cooling system will be tested to ensure good performance before its installation on the MKIs. The details of the simulations and the design process are reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK001
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WEPMK002	Longitudinal Impedance Analysis of an Upgraded LHC Injection Kicker Magnet	2628
	V. Vlachodimitropoulos, M.J. Barnes, L. Vega Cid, W.J.M. Weterings CERN, Geneva, Switzerland
	Prior to Long Shutdown 1 (LS1) one of the LHC injection kickers (MKIs) occasionally exhibited high temperatures leading to significant turnaround times. After a successful impedance mitigation campaign during LS1, the MKI ferrite yokes have remained below their Curie point and have not limited LHC's availability. However, for HL-LHC operation the MKI yokes are expected to exceed their Curie temperatures after long physics runs. To ensure uninterrupted future HL-LHC operation, a modified beam screen design, relocating some of the heat load to more easily cooled parts, and a suitable cooling system are under development as the current baseline for the HL-LHC upgrade of the MKIs. An upgraded beam screen providing such relocation has been designed, simulated and compared to the existing model. To validate simulations, two longitudinal beam coupling impedance measurement techniques have been used and the results are compared to predictions. The modified beam screen was implemented in an upgraded MKI installed in the LHC during the Year End Technical Stop (YETS) 2017/18.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK002
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WEPMK003	An Upgraded LHC Injection Kicker Magnet	2632
	M.J. Barnes, C. Bracco, G. Bregliozzi, A. Chmielinska, L. Ducimetière, B. Goddard, T. Kramer, H. Neupert, L. Vega Cid, V. Vlachodimitropoulospresenter, W.J.M. Weterings, C. Yin Vallgren CERN, Geneva, Switzerland A. Chmielinska EPFL, Lausanne, Switzerland
	Funding: Work supported by the HL-LHC project. An upgrade of the LHC injection kickers is necessary for HL-LHC to avoid excessive beam induced heating of these magnets: the intensity of the HL-LHC beam will be twice that of LHC. In addition, in the event that it is necessary to exchange an injection kicker magnet, the newly installed kicker magnet would limit HL-LHC operation for a few hundred hours due to dynamic vacuum activity. Extensive studies have been carried out to identify practical solutions to these problems: these include redistributing a significant portion of the beam induced power deposition to ferrite parts of the kicker magnet which are not at pulsed high voltage and water cooling of these parts. Furthermore a surface coating, to mitigate dynamic vacuum activity, has been selected. The results of these studies, except for water cooling, have been implemented on an upgraded LHC injection kicker magnet: this magnet was installed in the LHC during the 2017-18 Year End Technical Stop. This paper presents the upgrades, including some test and measurement results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK003
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WEPMK005	Preliminary Results from Validation Measurements of the Longitudinal Power Deposition Model for the LHC Injection Kicker Magnet	2636
	V. Vlachodimitropoulos, M.J. Barnes, A. Chmielinska CERN, Geneva, Switzerland A. Chmielinska EPFL, Lausanne, Switzerland
	During Run 1 of the LHC, one of the injection kicker magnets (MKIs) exhibited an excessively high ferrite temperature, caused by coupling of the high intensity beam to the real impedance of the magnet. Beam-screen upgrades, implemented during Long Shutdown 1 (LS1), have been very effective in reducing beam coupling impedance and since then the MKIs have not limited LHC's availability. However, temperature measurements during operation have shown that one end of the MKI's ferrite yoke is consistently hotter than the other. Detailed simulation models and data post-processing algorithms have been developed to understand and mitigate the observed behaviour. In the present paper, the model used to obtain the power loss distribution along the magnet is presented. The model is subsequently applied to two MKI design configurations under study: (i) the one currently in operation and (ii) an upgraded magnet that was installed in the LHC tunnel during the Year End Technical Stop (YETS) 2017/18. In order to validate the expected behaviour a novel measurement technique was developed, applied in both configurations and compared to predictions. The results obtained are reported and conclusions regarding the effectiveness of the design are drawn.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK005
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WEPMK007	INFN-LASA Design and Prototyping Activity for PIP-II	2640
	A. Bignami, M. Bertucci, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy C. Paganipresenter Università degli Studi di Milano & INFN, Segrate, Italy S. Pirani ESS, Lund, Sweden
	The design of the PIP-II medium-β, 5-cell, 650 MHz SRF elliptical cavity and the first steps of its prototyping activity are here presented. A design based on a three dies fabrication model has been chosen and fully characterized in terms of electromagnetic and mechanical parameters. Goal of the optimization has been to realize a highly performant cavity for CW operation with reasonably good performances when pulsed. A prototyping phase started with the production of three single-cell cavities used to validate the LASA model and to develop an optimal recipe for RF surface treatment according to the state-of-the-art of the high-Q frontier.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK007
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WEPMK008	In-Depth Analysis of the Vertical Test Results of the Third-Harmonic Cavities for the E-XFEL Injector	2644
	M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore INFN/LASA, Segrate (MI), Italy C.G. Maiano, P. Pierini ESS, Lund, Sweden C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	The results of the vertical tests performed at LASA on the 3.9 GHz third-harmonic cavities for the E-XFEL injector are here discussed. Analysis of experimental data allows to confirm that such high frequency cavity, prepared with standard BCP treatment and 800°C annealing treatment, suffers an intrinsic performance limitation at around 22 MV/m (@ 2 K) due to a global thermal dissipation mechanism. A quantitative interpretation of the high field Q slope is also presented according to the latest theoretical models of field-dependent surface resistance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK008
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WEPMK009	Status of the ESRF-EBS Magnets	2648
	C. Benabderrahmane, J.C. Biasci, J-F. B. Bouteille, J. Chavanne, L. Eybert, L. Goirand, G. Le Bec, L. Lefebvre, S.M. Liuzzo, D. Martin, C. Penel, P. Raimondi, J.-L. Revol, F. Villar, S.M. White ESRF, Grenoble, France
	The ESRF-EBS (Extremely Brilliant Source) is an upgrade project planned at the European Synchrotron Radiation Facility (ESRF) in the period 2015-2022. A new storage ring will be built, aiming to decrease the horizontal emittance and to improve the brilliance and coherence of the X-ray beams. The lattice of the new storage ring relies on magnets with demanding specifications: dipoles with longitudinal gradient (field ranging from 0.17 T up to 0.67 T), strong quadrupoles (up to 90 T/m), combined function dipole-quadrupoles with high gradient (0.57 T and 37 T/m), strong sextupoles and octupoles. The design of these magnets is based on innovative solutions; in particular, the longitudinal gradient dipoles are permanent magnets and the combined dipole-quadrupoles are single-sided devices. The longitudinal gradient dipoles have been assembled and measured in house. The design of the magnets, production status and magnetic measurement results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK009
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WEPMK010	LCLS-II Cryomodules Production at Fermilab	2652
	T.T. Arkan, J.N. Blowers, C.M. Ginsburg, C.J. Grimm, J.A. Kaluzny, A. Lunin, Y.O. Orlov, K.S. Premo, R.P. Stanek, G. Wu Fermilab, Batavia, Illinois, USA
	Funding: DOE LCLS-II is a planned upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLS-II linac will consist of thirty-five 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab are currently producing in collaboration with SLAC. The LCLS-II 1.3 GHz cryomodule design is based on the European XFEL pulsed-mode cryomodule design with modifications needed for CW operation. Two prototype cryomodules had been assembled and tested. After prototype cryomodule tests, both laboratories have increased cryomodule production rate to meet the challenging LCLS-II project installation schedule requirements of approximately one cryomodule per month per laboratory. Fermilab is at half point for the production, meaning that 6 cryomodules are fully assembled and tested. This paper presents Fermilab Cryomodule Assembly Facility (CAF) infrastructure for the LCLS-II cryomodules assembly, production experience at the half point emphasizing the challenges and mitigations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK010
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WEPMK012	Update on Plasma Processing R&D for LCLS-II	2656
	P. Berrutti, A. Grassellino, T.N. Khabiboulline, M. Martinello Fermilab, Batavia, Illinois, USA M. Doleans, S.-H. Kim, K.E. Tippey ORNL, Oak Ridge, Tennessee, USA D. Gonnella, G. Lanza, M.C. Ross SLAC, Menlo Park, California, USA
	Funding: Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE SRF cavities performance preservation is crucial, from vertical test to accelerator operation. Field emission is still one of the main problems to overcome and plasma cleaning has been proven successful by SNS, in cleaning field emitters and increasing the work function of Nb. A collaboration has been established between FNAL, SLAC and ORNL with the purpose of applying plasma processing to LCLS-II cavities, in order to minimize and overcome field emission without affecting the high Q of N-doped cavities. The recipe will follow the neon-oxygen active plasma adopted at SNS, allowing in-situ processing of cavities and cryomodules from hydrocarbon contaminants. A novel method for plasma ignition has been developed at FNAL: a plasma glow discharge is ignited using high order modes to overcome limitations imposed by the fundamental power coupler. The results of experiments on 9-cell LCLS-II cavity are presented, along with plasma ignition studies. In addition the RF system is shown and N-doped Nb samples studies are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK012
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WEPMK014	A New Design for the Hilumi Radio-Frequency Dipole Bare Cavity	2659
	M. Parise, P. Berruttipresenter, L. Ristori Fermilab, Batavia, Illinois, USA
	Crabbing cavities are one of the technological landmark that will allow the LHC to optimize its per-formance and maximize its integrated luminosity by allowing a head-on collision between the bunches despite the non-zero crossing angle. A total of 8 crab cavities will be installed in the interaction region of each of the two experiments, ATLAS and CMS. In the last years, the two types of crab cavities were de-signed, built and tested under the US-LARP R&D pro-gram. Horizontal crabbing is obtained with a radio-frequency dipole cavity (RFD) designed by Old Do-minion University (ODU), SLAC and Fermilab (FNAL). In this paper a new mechanical design, that uses passive stiffeners, is presented. This design leads to a decrease of the Lorentz Force Detuning frequency shift, satisfy the requirements on pressure sensitivity, validate the structural integrity and increase the tuner sensitivity and the maximum elastic tuning range. Furthermore, it will be possible to greatly simplify the shape of the magnetic shield and Helium vessel with respect to the current design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK014
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WEPMK015	Optimization of Vertical Electro-Polishing Process: Experiments with Updated Cathode on Single-Cell Cavity and Performance Achieved in Vertical Test	2662
	F. Éozénou, L. Maurice CEA/DSM/IRFU, France P. Carbonnier, C. Madec, Th. Proslier, C. Servouin CEA/DRF/IRFU, Gif-sur-Yvette, France V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saekipresenter, M. Sawabe KEK, Ibaraki, Japan
	Marui Galvanizing Co.Ltd., and CEA have been studying Vertical Electro-Polishing (VEP) on Nb single-cell accelerating superconducting accelerator cavity with the goal of mass-production and cost-reduction, in collaboration with KEK within TYL-FJPPL Particle Physics Laboratory. Marui has invented and patented a rotative cathode called ‘i-Ninja'. The version 5 has been tested for the first time in Europe at CEA Saclay. The four wings of the cathode remove efficiently, bubbles of hydrogen, and the chosen parameters make it possible to achieve better surface and uniform material removal compared to VEP with a fixed cathode. The effect of the temperature of the cavity walls on current oscillations has been precisely studied. Two single-cell cavities have been electro-polished and tested at 2 K in vertical cryostat and the results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK015
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WEPMK016	New Insight on Nitrogen Infusion Revealed by Successive Nanometric Material Removal	2665
	M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	In this study we present new insight on low temperature nitrogen infusion on bulk niobium superconducting radio-frequency (SRF) cavities. Nitrogen infusion is a thermal treatment recently discovered at Fermilab that allows to reach high accelerating gradients, of the order of 45MV/m, with high Q-factors, of the order of 2 · 10¹⁰. Detailed depth dependent RF studies (by means of subsequent HF rinses) and comparisonwith SIMS results pinpointed interstitial nitrogen as the responsible for the improved performance and uncovered the extension of its profile inside the material.
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Paper

Title

Page

WEPMK001

Preliminary Design of a Cooling System for the LHC Injection Kicker Magnets

2624

SUSPL086

use link to see paper's listing under its alternate paper code

L. Vega Cid, M.J. Barnes, L. Ducimetière, M.T. Moester, V. Vlachodimitropoulos, W.J.M. Weterings
CERN, Geneva, Switzerland
A. Abánades
ETSII UPM, Madrid, Spain

The CERN Large Hadron Collider (LHC) is equipped with two fast pulsed magnet systems (MKIs) that inject particle beams from the injector chain. Future operation for High Luminosity LHC (HL-LHC) with high intensity beams will cause heating of the ferrite yokes of the MKIs beyond their Curie temperature, preventing injection until the yokes cool down. Beam coupling impedance studies show that it is possible to move a substantial portion of the beam induced power deposition from the upstream ferrite yokes, which are the yokes with the highest power deposition, to ferrite rings located at the upstream end of the magnet. Thermal predictions show that this power redistribution, combined with the installation of a cooling system around the rings, will maintain the temperatures of all the yokes and ferrite rings below their Curie point. Since the rings are not pulsed to high voltage, whereas the ferrite yokes are, the installation of a cooling system is feasible around the rings. The proposed design of the cooling system will be tested to ensure good performance before its installation on the MKIs. The details of the simulations and the design process are reported.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK001

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WEPMK002

Longitudinal Impedance Analysis of an Upgraded LHC Injection Kicker Magnet

2628

V. Vlachodimitropoulos, M.J. Barnes, L. Vega Cid, W.J.M. Weterings
CERN, Geneva, Switzerland

Prior to Long Shutdown 1 (LS1) one of the LHC injection kickers (MKIs) occasionally exhibited high temperatures leading to significant turnaround times. After a successful impedance mitigation campaign during LS1, the MKI ferrite yokes have remained below their Curie point and have not limited LHC's availability. However, for HL-LHC operation the MKI yokes are expected to exceed their Curie temperatures after long physics runs. To ensure uninterrupted future HL-LHC operation, a modified beam screen design, relocating some of the heat load to more easily cooled parts, and a suitable cooling system are under development as the current baseline for the HL-LHC upgrade of the MKIs. An upgraded beam screen providing such relocation has been designed, simulated and compared to the existing model. To validate simulations, two longitudinal beam coupling impedance measurement techniques have been used and the results are compared to predictions. The modified beam screen was implemented in an upgraded MKI installed in the LHC during the Year End Technical Stop (YETS) 2017/18.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK002

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WEPMK003

An Upgraded LHC Injection Kicker Magnet

2632

M.J. Barnes, C. Bracco, G. Bregliozzi, A. Chmielinska, L. Ducimetière, B. Goddard, T. Kramer, H. Neupert, L. Vega Cid, V. Vlachodimitropoulospresenter, W.J.M. Weterings, C. Yin Vallgren
CERN, Geneva, Switzerland
A. Chmielinska
EPFL, Lausanne, Switzerland

Funding: Work supported by the HL-LHC project.
An upgrade of the LHC injection kickers is necessary for HL-LHC to avoid excessive beam induced heating of these magnets: the intensity of the HL-LHC beam will be twice that of LHC. In addition, in the event that it is necessary to exchange an injection kicker magnet, the newly installed kicker magnet would limit HL-LHC operation for a few hundred hours due to dynamic vacuum activity. Extensive studies have been carried out to identify practical solutions to these problems: these include redistributing a significant portion of the beam induced power deposition to ferrite parts of the kicker magnet which are not at pulsed high voltage and water cooling of these parts. Furthermore a surface coating, to mitigate dynamic vacuum activity, has been selected. The results of these studies, except for water cooling, have been implemented on an upgraded LHC injection kicker magnet: this magnet was installed in the LHC during the 2017-18 Year End Technical Stop. This paper presents the upgrades, including some test and measurement results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK003

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WEPMK005

Preliminary Results from Validation Measurements of the Longitudinal Power Deposition Model for the LHC Injection Kicker Magnet

2636

V. Vlachodimitropoulos, M.J. Barnes, A. Chmielinska
CERN, Geneva, Switzerland
A. Chmielinska
EPFL, Lausanne, Switzerland

During Run 1 of the LHC, one of the injection kicker magnets (MKIs) exhibited an excessively high ferrite temperature, caused by coupling of the high intensity beam to the real impedance of the magnet. Beam-screen upgrades, implemented during Long Shutdown 1 (LS1), have been very effective in reducing beam coupling impedance and since then the MKIs have not limited LHC's availability. However, temperature measurements during operation have shown that one end of the MKI's ferrite yoke is consistently hotter than the other. Detailed simulation models and data post-processing algorithms have been developed to understand and mitigate the observed behaviour. In the present paper, the model used to obtain the power loss distribution along the magnet is presented. The model is subsequently applied to two MKI design configurations under study: (i) the one currently in operation and (ii) an upgraded magnet that was installed in the LHC tunnel during the Year End Technical Stop (YETS) 2017/18. In order to validate the expected behaviour a novel measurement technique was developed, applied in both configurations and compared to predictions. The results obtained are reported and conclusions regarding the effectiveness of the design are drawn.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK005

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WEPMK007

INFN-LASA Design and Prototyping Activity for PIP-II

2640

A. Bignami, M. Bertucci, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Paganipresenter
Università degli Studi di Milano & INFN, Segrate, Italy
S. Pirani
ESS, Lund, Sweden

The design of the PIP-II medium-β, 5-cell, 650 MHz SRF elliptical cavity and the first steps of its prototyping activity are here presented. A design based on a three dies fabrication model has been chosen and fully characterized in terms of electromagnetic and mechanical parameters. Goal of the optimization has been to realize a highly performant cavity for CW operation with reasonably good performances when pulsed. A prototyping phase started with the production of three single-cell cavities used to validate the LASA model and to develop an optimal recipe for RF surface treatment according to the state-of-the-art of the high-Q frontier.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK007

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WEPMK008

In-Depth Analysis of the Vertical Test Results of the Third-Harmonic Cavities for the E-XFEL Injector

2644

M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore
INFN/LASA, Segrate (MI), Italy
C.G. Maiano, P. Pierini
ESS, Lund, Sweden
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

The results of the vertical tests performed at LASA on the 3.9 GHz third-harmonic cavities for the E-XFEL injector are here discussed. Analysis of experimental data allows to confirm that such high frequency cavity, prepared with standard BCP treatment and 800°C annealing treatment, suffers an intrinsic performance limitation at around 22 MV/m (@ 2 K) due to a global thermal dissipation mechanism. A quantitative interpretation of the high field Q slope is also presented according to the latest theoretical models of field-dependent surface resistance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK008

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WEPMK009

Status of the ESRF-EBS Magnets

2648

C. Benabderrahmane, J.C. Biasci, J-F. B. Bouteille, J. Chavanne, L. Eybert, L. Goirand, G. Le Bec, L. Lefebvre, S.M. Liuzzo, D. Martin, C. Penel, P. Raimondi, J.-L. Revol, F. Villar, S.M. White
ESRF, Grenoble, France

The ESRF-EBS (Extremely Brilliant Source) is an upgrade project planned at the European Synchrotron Radiation Facility (ESRF) in the period 2015-2022. A new storage ring will be built, aiming to decrease the horizontal emittance and to improve the brilliance and coherence of the X-ray beams. The lattice of the new storage ring relies on magnets with demanding specifications: dipoles with longitudinal gradient (field ranging from 0.17 T up to 0.67 T), strong quadrupoles (up to 90 T/m), combined function dipole-quadrupoles with high gradient (0.57 T and 37 T/m), strong sextupoles and octupoles. The design of these magnets is based on innovative solutions; in particular, the longitudinal gradient dipoles are permanent magnets and the combined dipole-quadrupoles are single-sided devices. The longitudinal gradient dipoles have been assembled and measured in house. The design of the magnets, production status and magnetic measurement results will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK009

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WEPMK010

LCLS-II Cryomodules Production at Fermilab

2652

T.T. Arkan, J.N. Blowers, C.M. Ginsburg, C.J. Grimm, J.A. Kaluzny, A. Lunin, Y.O. Orlov, K.S. Premo, R.P. Stanek, G. Wu
Fermilab, Batavia, Illinois, USA

Funding: DOE
LCLS-II is a planned upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLS-II linac will consist of thirty-five 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab are currently producing in collaboration with SLAC. The LCLS-II 1.3 GHz cryomodule design is based on the European XFEL pulsed-mode cryomodule design with modifications needed for CW operation. Two prototype cryomodules had been assembled and tested. After prototype cryomodule tests, both laboratories have increased cryomodule production rate to meet the challenging LCLS-II project installation schedule requirements of approximately one cryomodule per month per laboratory. Fermilab is at half point for the production, meaning that 6 cryomodules are fully assembled and tested. This paper presents Fermilab Cryomodule Assembly Facility (CAF) infrastructure for the LCLS-II cryomodules assembly, production experience at the half point emphasizing the challenges and mitigations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK010

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WEPMK012

Update on Plasma Processing R&D for LCLS-II

2656

P. Berrutti, A. Grassellino, T.N. Khabiboulline, M. Martinello
Fermilab, Batavia, Illinois, USA
M. Doleans, S.-H. Kim, K.E. Tippey
ORNL, Oak Ridge, Tennessee, USA
D. Gonnella, G. Lanza, M.C. Ross
SLAC, Menlo Park, California, USA

Funding: Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
SRF cavities performance preservation is crucial, from vertical test to accelerator operation. Field emission is still one of the main problems to overcome and plasma cleaning has been proven successful by SNS, in cleaning field emitters and increasing the work function of Nb. A collaboration has been established between FNAL, SLAC and ORNL with the purpose of applying plasma processing to LCLS-II cavities, in order to minimize and overcome field emission without affecting the high Q of N-doped cavities. The recipe will follow the neon-oxygen active plasma adopted at SNS, allowing in-situ processing of cavities and cryomodules from hydrocarbon contaminants. A novel method for plasma ignition has been developed at FNAL: a plasma glow discharge is ignited using high order modes to overcome limitations imposed by the fundamental power coupler. The results of experiments on 9-cell LCLS-II cavity are presented, along with plasma ignition studies. In addition the RF system is shown and N-doped Nb samples studies are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK012

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WEPMK014

A New Design for the Hilumi Radio-Frequency Dipole Bare Cavity

2659

M. Parise, P. Berruttipresenter, L. Ristori
Fermilab, Batavia, Illinois, USA

Crabbing cavities are one of the technological landmark that will allow the LHC to optimize its per-formance and maximize its integrated luminosity by allowing a head-on collision between the bunches despite the non-zero crossing angle. A total of 8 crab cavities will be installed in the interaction region of each of the two experiments, ATLAS and CMS. In the last years, the two types of crab cavities were de-signed, built and tested under the US-LARP R&D pro-gram. Horizontal crabbing is obtained with a radio-frequency dipole cavity (RFD) designed by Old Do-minion University (ODU), SLAC and Fermilab (FNAL). In this paper a new mechanical design, that uses passive stiffeners, is presented. This design leads to a decrease of the Lorentz Force Detuning frequency shift, satisfy the requirements on pressure sensitivity, validate the structural integrity and increase the tuner sensitivity and the maximum elastic tuning range. Furthermore, it will be possible to greatly simplify the shape of the magnetic shield and Helium vessel with respect to the current design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK014

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WEPMK015

Optimization of Vertical Electro-Polishing Process: Experiments with Updated Cathode on Single-Cell Cavity and Performance Achieved in Vertical Test

2662

F. Éozénou, L. Maurice
CEA/DSM/IRFU, France
P. Carbonnier, C. Madec, Th. Proslier, C. Servouin
CEA/DRF/IRFU, Gif-sur-Yvette, France
V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saekipresenter, M. Sawabe
KEK, Ibaraki, Japan

Marui Galvanizing Co.Ltd., and CEA have been studying Vertical Electro-Polishing (VEP) on Nb single-cell accelerating superconducting accelerator cavity with the goal of mass-production and cost-reduction, in collaboration with KEK within TYL-FJPPL Particle Physics Laboratory. Marui has invented and patented a rotative cathode called ‘i-Ninja'. The version 5 has been tested for the first time in Europe at CEA Saclay. The four wings of the cathode remove efficiently, bubbles of hydrogen, and the chosen parameters make it possible to achieve better surface and uniform material removal compared to VEP with a fixed cathode. The effect of the temperature of the cavity walls on current oscillations has been precisely studied. Two single-cell cavities have been electro-polished and tested at 2 K in vertical cryostat and the results will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK015

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WEPMK016

New Insight on Nitrogen Infusion Revealed by Successive Nanometric Material Removal

2665

M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

In this study we present new insight on low temperature nitrogen infusion on bulk niobium superconducting radio-frequency (SRF) cavities. Nitrogen infusion is a thermal treatment recently discovered at Fermilab that allows to reach high accelerating gradients, of the order of 45MV/m, with high Q-factors, of the order of 2 · 10¹⁰. Detailed depth dependent RF studies (by means of subsequent HF rinses) and comparisonwith SIMS results pinpointed interstitial nitrogen as the responsible for the improved performance and uncovered the extension of its profile inside the material.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMK016

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