WEPMF —  MC7 Poster Session   (02-May-18   16:00—17:30)

Paper	Title	Page
WEPMF001	Upgrade of the ALBA Magnetic Laboratory for Measuring LIPAc HEBT Quadrupoles and Dipole	2369
	J. Campmany, F. Becheri, L.G.O. Garcia-Orta, J. Marcospresenter, V. Massana, R. Petrocelli ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain B. Brañas, J. Castellanos CIEMAT, Madrid, Spain
	Along 2017 ALBA magnetic measurements facility has measured LIPAc HEBT quadrupoles and dipole designed by CIEMAT and built by ELYTT company. ALBA magnetic measurements laboratory has been improved through an upgrade program of its measurement benches to complete their measurements. One of the main aims of the upgrade has been to standardize both the hardware and software and therefore ensure an easy maintenance. Especially relevant has been the upgrade of the flipping coil bench, in which the DC motors and the obsolete controller have been replaced by step-motors and ICEPAP controller. Also, software has been migrated to Tango package. Hardware and software of Hall probe bench has been upgraded as well, using the last DeltaTau motion controller. Tango has been upgraded too, using Devian 8 as operative system. Next step will be the upgrade of the rotating coil hardware and software using also step-motor and ICEPAP controller. In parallel, new shafts have been build and tested, with specific designs to improve the sensitivity and minimize the noise to signal ratio. In this contribution we detail the upgrades and the results of performance tests.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF001
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WEPMF002	Operational Experience with IOTs at Alba Synchrotron	2372
	J.R. Ocampo, B. Bravo, R. Fos, F. Pérez, A. Salom, P. Solans ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain S. Bethuys, A. Beunas, M. Grezaud, P. Reynaud TED, Velizy-Villacoublay, France M. Boyle, J. Cipolla, W.F. Coyle, H. Schult L-3, Williamsport, Pennsylvania, USA
	ALBA is a 3 GeV Synchrotron light source in operation since 2012. The RF systems are based in Inductive Output Tube (IOT) transmitters. A total of 13 80 kW IOT amplifiers are used to power the Storage Ring and Booster cavities at 500 MHz. The transmitters were initially configured to operate the TH-793-1 and TH-794 IOT from THALES Electron devices. On 2015, the amplifiers have been adapted to operate also the TH-795 from THALES and the L4444-C from L3 Communications. In this paper, a brief overview of the differences between these IOT models will be presented, as well as operation results for each type of IOT from the point of view of performance, reliability and durability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF002
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WEPMF004	The Saclay Test Stand for Conditioning the ESS RFQ Power Couplers at High RF Power	2375
	N. Misiara, A.C. Chauveau, D. Chirpaz-Cerbat, P. Daniel-Thomas, M. Lacroix, L. Maurice CEA/IRFU, Gif-sur-Yvette, France M. Desmons, A. Dubois, A. Gaget, L. Napoly, M. Oublaid, G. Perreu, O. Piquet, B. Pottin, Y. Sauce CEA/DRF/IRFU, Gif-sur-Yvette, France
	The RF power coupler system for the RFQ of the ESS LINAC will feed 1.6 MW peak power through two coaxial loop couplers for a 352.21 MHz operation at the expected duty cycle. A specific test stand has been designed to condition the power couplers, and test the different auxiliary components in the nominal conditions of the RFQ. The power couplers were successfully assembled, installed and instrumented on the test cavity. This paper presents the general layout of the test stand, the installation and preparation of the power couplers for their conditioning at high RF power up to the ESS nominal conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF004
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WEPMF005	Design and Testing of a 12 kW, 352 MHz Solid State rf System at the Advanced Photon Source	2378
	D. Horan, D.J. Bromberek, A. Goel, T.J. Madden, A. Nassiri, G.J. Waldschmidt ANL, Argonne, Illinois, USA
	A 12 kW, 352 MHz rf power amplifier system was designed and constructed at the Advanced Photon Source as a research and development test bed for eventual development of a 200 kW cw rf system capable of supporting accelerator beam operation. The system utilizes six 2 kW laterally diffused metal oxide field effect transistor (MOSFET) rf amplifiers, an output cavity combiner terminated with a WR2300 waveguide output flange, and a monitoring system based on programmable logic controller technology. The combining cavity has a total capacity of 108 two-kilowatt inputs to support eventual operation up to 216kW maximum output power. Design details and operational performance of the 12 kW system will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF005
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WEPMF008	Preliminary Designs and Test Results of Bipolar Power Supplies for APS Upgrade Storage Ring	2381
	J. Wang, I.A. Abid, R.T. Keane, G.S. Sprau ANL, Argonne, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The upgrade (APS-U) of the APS storage ring requires more than 1200 bipolar power supplies. Based on the performance requirement, the power supplies can be divided into two categories: fast bipolar power supplies for fast correctors and slow bipolar power supplies for trim coils and slow correctors. The common requirement of the power supplies is a bipolar output current up to ±15 A. The main difference is that the fast corrector power supplies require a small-signal bandwidth of 10 kHz. A prototype DC/DC power converter utilizing a MOSFET H-bridge circuit with a 500 kHz PWM was successfully developed through the R&D program, achieving the required bandwidth with less than 3-dB attenuation for a signal 0.5% of ±15 A. After the successful R&D program, the preliminary designs were performed to further improve the performance and to finalize the schematics, the PCB layouts, and the power supply constructions. The two types of the power supplies share the majority of the designs and features, with minor differences for the different bandwidth requirement. This paper presents the preliminary design, the key power supply functions and features, and the test results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF008
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WEPMF009	Influence of Argon-Ion Irradiation on Field Emission from Polycrystalline Cu and Large-Grain NB Surfaces	2384
	S. Soykarci University of Wuppertal, Wuppertal, Germany D. Lützenkirchen-Hecht, V. Porshynpresenter, P. Serbun Bergische Universität Wuppertal, Wuppertal, Germany
	Funding: This work is funded by the BMBF project 05H15PXRB1. In the present work, systematic investigations of the enhanced field emission (EFE) from polycrystalline copper and large grain niobium surfaces before and after argon-ion irradiation with an energy of 5 keV were performed with a variation of the irradiation time. Results show that the suppression of the EFE might be achievable.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF009
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WEPMF010	Laser Treatment of Niobium Surface for SRF Aplications	2387
	V. Porshyn, D. Lützenkirchen-Hecht, P. Serbun Bergische Universität Wuppertal, Wuppertal, Germany H. Bürger, S. Soykarci University of Wuppertal, Wuppertal, Germany
	Funding: The research was funded by the German Federal Ministry of Education and Research (BMBF) under project number 05H15PXRB1. We report on a laser surface treatment of high purity niobium (110) single crystals. Typical surface defects like scratches, pits, sharp rims and holes were eliminated by a focused pulsed ns-laser beam. A laser fluence of about 0.68 J/cm2 and 40 - 80 pulses per spot were required to induce well detectable surface modifications. The remelted surface was sufficiently smooth, but exhibited also a number of wave structures. Thus, the surface roughness slightly increased with increasing number of pulses. Finally, boiling traces and μm-deep ablation were observed and studied as well. Local field electron emission measurements showed no emission up to 700 MV/m from a moderate remelted area below the boiling point.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF010
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WEPMF011	Design and Status of Sirius Light Source RF Systems	2391
	R.H.A. Farias, A.P.B. Lima, L. Liupresenter, F.S. Oliveira LNLS, Campinas, Brazil
	Sirius is the new synchrotron light source currently under construction at the site of the Brazilian Synchro-tron Light Laboratory (LNLS) in Campinas, Brazil. The facility comprises a 3 GeV electron storage ring, a full energy booster and a 150 MeV linac. This work provides a brief description of the RF system of the booster and storage ring, presenting their main characteristics and specification goals.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF011
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WEPMF012	Power Requirement and Preliminary Coupler Design for the eRHIC Crab Cavity System	2394
	S. Verdú-Andrés, I. Ben-Zvipresenter, D. Holmes, Q. Wu BNL, Upton, Long Island, New York, USA I. Ben-Zvipresenter Stony Brook University, Stony Brook, USA
	Funding: Work supported by Brookhaven Science Associates LLC under contract no. DE-SC0012704 with the U.S. Department of Energy. Crab cavities are deflecting cavities operated in such a way that the bunch center is in synchronism with the zero-crossing kick voltage. In that case, beam loading is zero for an on-axis beam. The crab cavity system of the future electron-ion collider eRHIC will manipulate 275 GeV proton beams. At high energies, the beam offset can be as large as 2 mm (including mechanical and electrical offset tolerances). The beam loading resulting from such offset can greatly incur in large power requirements to the RF amplifier. The choice of external Q for the Fundamental Power Coupler (FPC) is critical to limit the power requirement to practical values. The loaded Q of the eRHIC crab cavities is mainly governed by the external Q of the FPC, so the external Q will also define the cavity bandwidth and thus the tuning requirements to counteract frequency transients from external perturbations. This paper discusses the choice of external Q for the FPC of the eRHIC crab cavities and introduces the design of a preliminary FPC antenna concept that would provide the appropriate external Q.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF012
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WEPMF014	Fast Track Actively Shielded Nb3Sn IR Quadrupole R&D	2398
	B. Parker, M. Anerella, J.P. Cozzolino, R.C. Gupta, R.B. Palmer, J. Schmalzle, H. Witte BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. The Interaction Region (IR) magnets for future Electron Ion Colliders (EIC), such as eRHIC at BNL, JLEIC at JLab and LHeC at CERN, must satisfy strongly opposing requirements. EIC IR superconducting quadrupole coils must provide strong focusing gradients, leading to large peak fields, for the high momentum hadron beam while permitting the nearby electron beam to pass through a nearly field free region. An actively shielded coil geometry does this using nested, opposite polarity, quadrupoles where the combined external fields cancel while leaving a net gradient inside. In order to fabricate and test this concept in a timely and cost effective manner we propose to reuse the inner coils from an existing high gradient Nb3Sn LARP quadrupole inside a new structure with a new NbTi active shield coil. The main challenge is to design a compact structure for applying prestress to the Nb3Sn coil that fits the restricted space inside the shield coil. We first construct a 15 cm long mechanical model of this structure with coil strain gauges to verify the design concept before proceeding with the full coil. Mechanical modeling results and our preliminary design concept are reported here.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF014
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WEPMF017	Options for the Spectrometer Magnet of the eRHIC IR	2401
	H. Witte, R.B. Palmer, B. Parker BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Presently the electron-ion collider eRHIC is under design, which aims to provide a facility with a peak luminosity of 1034cm-2sec-1. This paper outlines different concepts for the so-called B0 magnet, which is the first bending magnet after the interaction region. The B0 magnet has to provide a 1.3 T dipole field to the hadron beam, while the nearby electron beam should not be exposed to any field. Several possible solutions have been evaluated, each with their specific strengths and shortcomings. This paper presents an overview of the solutions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF017
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WEPMF018	Magnet Designs for the eRHIC Rapid Cycling Synchrotron	2404
	H. Witte, I. Marneris, V.H. Ranjbar BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Presently the electron-ion collider eRHIC is under design, which aims to provide a facility with a peak luminosity of 1034cm-2sec-1. Part of the eRHIC design is a rapid cycling synchrotron, which accelerates electrons from 1-18 GeV. In this paper we present conceptual designs of the required dipole, quadrupole and sextupole magnets. The magnets meet the specifications in terms of performance and field quality with an acceptable power dissipation. The power supply requirements are also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF018
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WEPMF019	Conceptual Design of the eRHIC Storage Ring Magnets	2407
	H. Witte, J.S. Berg, S. Tepikian BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Presently the electron-ion collider eRHIC is under design, which aims to provide a facility with a peak luminosity of 1034cm-2sec-1. Part of the eRHIC accelerator is the addition of an electron storage ring to the existing tunnel. This paper describes the magnets required for this storage ring. The necessary bending is provided by a triplet of dipole magnets, which generate excess bending to create additional radiation damping to allow a larger beam-beam tune shift. Each triplet consists of two long, low field magnets and a short, high-field magnet. This paper also describes the quadrupole and sextupole magnets necessary for this machine. All magnets require a large aperture to accommodate the beam-pipe.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF019
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WEPMF020	Pulsed Systems for eRHIC Beam Injection and Extraction	2410
	W. Zhang, M. Blaskiewicz, A. Hershcovitch, C.J. Liaw, H. Lovelace III, M. Mapes, G.T. McIntyre, J.-L. Mi, C. Montag, C. Pai, V. Ptitsyn, J. Sandberg, N. Tsoupas, J.E. Tuozzolo, G.M. Wang, W.-T. Weng, F.J. Willeke, H. Witte, Q. Wu BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The electron-ion collider eRHIC requires a variety of kickers and septa for injection and extraction of beams throughout the entire collider complex. We plan to use pulsed systems for beam injection and extraction in Electron RCS, Electron Storage Ring, and Hadron ring. In this paper, we describe the pulsed systems required for beam transfer in the eRHIC Ring-Ring Pre-conceptual Design. We will outline the parameter ranges, technology choices, and opportunities for research and development in pulsed power technology.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF020
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WEPMF021	Magnet Design Considerations for an Ultralow Emittance Canadian Light Source	2413
	L.O. Dallin, D. Bertwistlepresenter CLS, Saskatoon, Saskatchewan, Canada
	The strong focusing requirements for ultralow emittance light sources result in high field magnets that are very close together. High fields are readily achieved by using small magnet gaps. This is possible due to the small beam sizes involved. Reduction in the physical aperture and the reduction in the good field region requirements results in magnets with compact transverse dimensions. The very strong focusing of the magnets results in very small drift spaces between the various magnetic elements. To keep these drift spaces clear magnets with recessed coils have been studied. In such magnets the coils do not stick out beyond the end of the magnet yoke in the longitudinal direction. By placing the coils on the outer yoke loss of efficiency can be avoided while maintaining good control of the higher order field harmonics. This is very well suited for quadrupole magnets where only two coils are required. Possible designs for gradient dipoles and sexutpoles are also considered.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF021
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WEPMF022	Coulped Multiphysics Simulation for the Water Cooling Layout of a Rhodotron Cavity	2416
	L. Yang, X. Hepresenter, H. Li, S.Q. Liao CAEP/IFP, Mainyang, Sichuan, People's Republic of China
	A Rhodotron-based electron accelerator served as micro-focused X-ray source is under development at IFP, CAEP. The RF-cavity, running in long pulse/ CW mode, will deliver 9 MeV energy to electron beams after multiple accelerations within the same field at a frequency of 107.5MHz. A substantial amount of average power loss with tens of kW will be dissipated on the RF surface of the cavity to maintain the operational field level. Efficient water cooling is critical to prevent large scale temperature rise for stable operation sake. Reasonable prediction of temperature rise becomes essential to assess a certain cooling layout in the design phase. The frequency drift and thermal stress on account of temperature variation and gradient on cavity wall respectively, could be computed accordingly. This paper presents a comprehensive coupled simulation involving electromagnetic, thermal and structural for the RF-cavity of Rhodotron.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF022
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WEPMF030	Optimization of Klystron Efficiency with MOGA	2419
	C. Meng, X. Hepresenter, S. Pei, S.C. Wang, O. Xiao, Z.S. Zhou IHEP, Beijing, People's Republic of China
	As the very important element of accelerator the klystron provide power to cavities for accelerating. Considering the accelerator cost of construction and running, the improvement of klystron efficiency is one developing hotspot of klystron research. In this paper the optimization method of klystron efficiency with MOGA based on 1D simulation program is proposed and the influences on klystron efficiency will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF030
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WEPMF031	Development of a High-Power High-Directivity Directional Coupler and Four Power Dividers for S-Band	2422
	X. He, J. Lei, J.R. Zhang IHEP, Beijing, People's Republic of China
	A novel Bethe-hole S band directional coupler has been designed based on some structural optimizations, the prototype has been tested with a Directivity of more than 30 dB. The new directional coupler can also hold higher power compared to the old type, which is more useful for the future accelerator applications. Four power dividers using different structures are studied and the best one is chosen for fabrication. The prototype with matching rod in the middle has got qualified microwave cold test results and has been used during the whole microwave commissioning of an accelerating structure, the performance is quite stable.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF031
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WEPMF032	Experimental Studies on Secondary Electron Emission Characteristics for Chamber Materials of Accelerators	2425
	Y. Jiao, Z. Duan, W.B. Liu, Y.D. Liu IHEP, Beijing, People's Republic of China Liu. S. Liu Institute of High Energy Physics (IHEP), People's Republic of China P.C. Wang DNSC, Dongguan, People's Republic of China
	Funding: National Natural Science Foundation of China (11275221) and Key Laboratory Foundation of Particle Acceleration Physics &Technology (Y5294106TD) Secondary electron emission (SEE) of surface is origin of multipacting effect which could seriously deteriorate beam quality and even perturb the normal operation of particle accelerators. Experimental measurements on secondary electron yield (SEY) on different materials and coating have been developed in many accelerator laboratory. In fact, the SEY is just one parameter of secondary electron emission characteristics which include spatial and energy distribution of emitted electrons. A novel experimental apparatus was set up in China Spallation Neutron Source (CSNS) and innovative measurement methods were applied to obtain the whole characteristics of SEE. With some traditional accelerator chamber materials such as Cu, Al, TiN, SEY dependence on primary electron energy and beam injection angle, spatial and energy distribution of emitted secondary electrons were achieved with this measurement apparatus. This contribution also tries to give all the experimental results a reasonable theoretical analysis.
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WEPMF033	RF Study And Cold Test of an S-band Spherical Cavity Pulse Compressor	2429
	J. Lei, X. Hepresenter, M. Hou, X.P. Li, G. Pei, H. Wang, J.B. Zhao IHEP, Beijing, People's Republic of China S. Shu Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
	An S-band (2856 MHz) spherical cavity pulse compressor has been designed, fabricated and tested in the Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS). The pulse compressor consists of a special 3 dB coupler and only one spherical energy storage cavity, two TE114 modes are chosen to oscillate in which for fairly high unload Q factor. The prototype was made of aluminum for studying the performance of the pulse compressor and checking the validity of the simulations. The cold test results of the aluminum cavity are also presented. The copper coating on the whole internal surface of the aluminum spherical cavity is in progress and the test results will also be presented in the future.
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WEPMF034	Development of Superconducting RF Double Spoke Cavity at IHEP	2432
SUSPL078	use link to see paper's listing under its alternate paper code
	Z.Q. Zhou, H.F.S. Feisi, W.M. Pan IHEP, Beijing, People's Republic of China
	Funding: State Key Development Program for Basic Research of China (Grant No.2014CB845500) The China Initiative Accelerator Driven System (CiADS) has been approved to transmute long-lived radi-oisotopes in used nuclear fuel into shorter-lived fission products. IHEP is developing a 325MHz double spoke cavity at β0 of 0.5 for the CiADS linac. The cavity shape was optimized to minimize Ep/Ea while keeping Bp/Ep reasonably low, while the multipacting was analyzed. Meanwhile, mechanical design was applied to check stress, Lorentz force detuning and microphonic effects, and to minimize pressure sensitivity. A new RF coupling scheme was proposed to avoid electrons hitting directly on ceramic window. The detailed design for the cavity is addressed in this paper.
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WEPMF035	Investigating the Effect of Inhomogeneous Resistivity on Bulk RRR and Heat Conductivity Using a Lattice Green's Functions Method	2436
	N.C. Shipman, A. Macpherson CERN, Geneva, Switzerland G. Burtpresenter Cockcroft Institute, Lancaster University, Lancaster, United Kingdom J.A. Mitchell Lancaster University, Lancaster, United Kingdom
	A method was developed to calculate the bulk RRR (residual resistivity ratio) which would be measured on a superconducting cavity or sample with an inhomogeneous resistivity and arbitrary geometry. The method involves modelling the object as a network of resistors and employs lattice Green's functions. A further adaptation of the method which allows the heat transport characteristics of such an object to be predicted is also described.
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WEPMF036	RF Test Result of a BNL N-Doped 500 MHz B-Cell Cavity at Cornell	2440
	F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J.T. Maniscalcopresenter, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA F. Gao, J. Rose BNL, Upton, Long Island, New York, USA
	Cornell's SRF group has collaborated with Brookhaven National Laboratory (BNL) on one 500 MHz CESR type SRF "B-cell" cavity (BNL B-cell) for the National Synchrotron Light Source II. Cornell has been responsible for RF surface preparation, vertical testing, and short cavity string assembly. As a state-of-the-art surface preparation protocol, Cornell selected Nitrogen doping for the BNL B-cell. N-doping has been well demonstrated and established to push the cavity quality factor (Q0) higher in 1.3GHz SRF cavities at many laboratories. Cornell calculated that N-doping could also be beneficial on a 500MHz SRF cavity, with a potential to increase its Q0 by a factor of two compared with the traditional chemical polishing based surface preparation protocol. Here we report on the detailed surface preparation and vertical test result of the BNL B-cell.
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WEPMF037	HF Free Bipolar Electro-Polishing Studies on Niobium SRF Cavities at Cornell With Faraday Technology	2443
	F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, P.N. Koufalispresenter, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T.D. Hall, M.E. Inman, R. Radhakrishnan, S.T. Snyder, E.J. Taylor Faraday Technology, Inc., Clayton, Ohio, USA
	Cornell's SRF group and Faraday Technology have been collaborating on two phase-II SBIR projects. One of them is the development and commissioning of a 9-cell scale HF free Bipolar Electro-Polishing (BEP) system. Faraday Technology has upgraded their 1.3 GHz single-cell BEP system for hosting 9-cell cavities. Initial commissioning of the new system was done with a three single-cell cavity string, and high a gradient of 40MV/m was demonstrated during the RF tests at Cornell. After this success with the test string, the 9-cell cavity was processed with the new system at Faraday and RF test was performed at Cornell. Here we report detailed results from these 9-cell scale HF free BEP studies.
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WEPMF038	Microphonics Suppression in the CBETA Linac Cryomodules	2447
SUSPL068	use link to see paper's listing under its alternate paper code
	N. Banerjee, J. Dobbins, F. Furuta, G.H. Hoffstaetter, R.P.K. Kaplan, M. Liepe, P. Quigley, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was performed through the support of New York State Energy Research and Development Agency. The linac cryomodules were constructed with funding from the National Science Foundation. The Cornell-BNL ERL Test Accelerator (CBETA) is a new multi-turn energy recovery linac currently under construction at Cornell University. It uses two superconducting linacs, both of which are susceptible to microphonics detuning. The high-current injector accelerates electrons to 6 MeV and the main linac accelerates and decelerates electrons by 36 MeV. In this paper, we discuss various measures taken to reduce vibrations caused by instabilities and flow transients in the cryogenic system of the main linac cryomodule. We further describe the use of a Least Mean Square algorithm in establishing a stable Active Microphonics Compensation system for operation of the main linac cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF038
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WEPMF039	Experimental Results on the Field and Frequency Dependence of the Surface Resistance of Niobium Cavities	2451
	P.N. Koufalis, M. Liepe, J.T. Maniscalco, T.E. Oseroff Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	We investigate the field and frequency dependence of the surface resistance of single-cell niobium cavities as a function of surface treatment at 1.3, 2.6, and 3.9 GHz. The surface resistance is broken down into two parts: the temperature-independent residual resistance and the temperature-dependent BCS resistance. While the low-field BCS resistance is known to vary quadratically with frequency, the exact dependence of the BCS and residual resistances on field at higher frequencies are important topics for further investigation. We offer results on a systematic experimental study of the residual and BCS resistance as a function of frequency and field for clean niobium and high-temperature nitrogen-doped niobium.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF039
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WEPMF041	Insights into the Role of C, N, and O Introduced by Low Temperature Baking on Niobium Cavity Performance	2455
SUSPL072	use link to see paper's listing under its alternate paper code
	P.N. Koufalis, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Previous experiments have shown that introducing nitrogen gas during low temperature bakes (120-160 C) of niobium cavities introduces C, N, and O impurities to the first 10-100 nm of the surface. This new treatment results in higher quality factors and even 'anti-Q-slope' in some cases. However, it is not entirely clear the role that each of these impurities plays in the performance enhancement of the cavities. It has been suggested that interstitial N within the first few nm of the surface is solely responsible for the observed enhancement, but little work has been done on the role of C and O. Because both C and O are abundant in much higher quantities than N near the surface, it is important to understand whether they are beneficial or detrimental to cavity performance. We provide further insight into the effects of C and O on cavity performance by baking in an ambient atmosphere rich in CO2 as opposed to N2.
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WEPMF042	A Computational Method for More Accurate Measurements of the Surface Resistance in SRF Cavities	2458
	J.T. Maniscalco, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The principal loss mechanism for superconducting RF cavities in normal operation is Ohmic heating due to the microwave surface resistance in the superconducting surface. The typical method for calculating this field-dependent surface resistance Rs(H) from RF measurements of quality factor Q0 implicitly returns a weighted average of Rs over the surface as a function of peak surface magnetic field H, not the true value of Rs as a function of the local magnitude of H. In this work we present a computational method to convert a measured Q0 vs. Hpeak to a more accurate Rs vs. Hlocal, given knowledge about cavity geometry and field distribution.
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WEPMF043	Frequency Tuner Development at Cornell for the RAON Half Wave Resonators	2461
	M. Ge, F. Furuta, T. Gruber, S.W. Hartman, M. Liepe, J.T. Maniscalcopresenter, T.I. O'Connell, P.J. Pamel, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin IBS, Daejeon, Republic of Korea
	The superconducting half-wave-resonators for the RAON project require a slow frequency tuner that can provide at least 80 kHz tuning range. Cornell University has designed, prototyped, and tested a tuner for these half-wave-resonators. In this paper, we present the tuner design, prototype fabrication, test insert preparation, long-term testing and tuner performance test results at cryogenic temperature. The performance of the tuner is analyzed in detail.
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WEPMF044	Updates on the DC Field Dependence Cavity	2465
	J.T. Maniscalco, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Work at Cornell has demonstrated good agreement between a theoretical model by A. Gurevich of the anti-Q-slope (a field-dependent decrease of the microwave surface resistance) and experimental results from impurity-doped niobium. As a corollary, the model predicts that a strong DC magnetic field applied parallel to the RF surface will produce a similar decrease in surface resistance. In order to explore this prediction for many materials, we have designed a new coaxial cavity with a strong, uniform DC field superimposed over a weak RF field on a removable and replaceable niobium sample. Here we present updates on the progress of this new cavity.
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WEPMF045	Performance of the Prototype SRF Half-Wave-Resonators Tested at Cornell for the RAON Project	2468
	M. Ge, F. Furuta, T. Gruber, S.W. Hartman, M. Liepe, J.T. Maniscalcopresenter, T.I. O'Connell, P.J. Pamel, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin IBS, Daejeon, Republic of Korea
	Two prototype superconducting half-wave-resonator (162.5 MHz and β=0.12) for the RAON project have been successfully tested at Cornell University. Detailed vertical performance testing included (1) test of the bare cavity without the helium tank, and (2) test of the dressed cavity with a helium tank. In this paper, we report on the development of the test infrastructure, test results, and performance data analysis, showing that the specifications for RAON were met.
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WEPMF046	Modeling of the Frequency and Field Dependence of the Surface Resistance of Impurity-Doped Niobium	2471
SUSPL073	use link to see paper's listing under its alternate paper code
	J.T. Maniscalco, P.N. Koufalis, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The anti-Q-slope, a field-dependent decrease in surface resistance observed in impurity-doped niobium, has been investigated extensively in 1.3 GHz cavities. New early research into this effect has recently been performed at higher and lower frequencies, revealing an additional dependence on frequency: the anti-Q-slope is stronger at higher frequencies and weaker at lower frequencies. Several models have been proposed to explain the anti-Q-slope, with varying success in this new frequency-dependent regime. In this work, we analyze recent experimental data from a low-temperature-doped 1.3 GHz cavity and a high-temperature nitrogen-doped 2.6 GHz cavity and discuss the implications of these results on the proposed models.
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WEPMF047	Performance of Samples With Novel SRF Materials and Growth Techniques	2475
SUSPL074	use link to see paper's listing under its alternate paper code
	T.E. Oseroff, M. Ge, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA S.R. McNeal Ultramet, Pacoima, California, USA M.J. Sowa Veeco-CNT, Medford, USA
	Novel materials are currently being studied in an attempt to push accelerating superconducting RF cavities to support higher accelerating fields and to operate with lower power loss. Growing layers of these materials of the quality necessary has proven to be difficult. In this work, we present the SRF performance of planar samples of the promising materials, NbN and Nb¬3Sn, grown using atomic layer deposition (ALD) and chemical vapor deposition (CVD) respectively. Results are promising.
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WEPMF050	Update on Nb3Sn Progress at Cornell University	2479
	R.D. Porter, J. Ding, D.L. Hall, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T.A. Arias, P. Cueva, D.A. Muller, N. Sitaraman Cornell University, Ithaca, New York, USA
	Niobium-3 Tin (Nb3Sn) is the most promising alternative material for SRF accelerator cavities. The material can achieve higher quality factors, higher temperature operation and potentially higher accelerating gradients compared to conventional niobium. Cornell University has a leading program to produce 2 - 3 micrometer thick coatings of Nb3Sn on Nb for SRF applications using vapor diffusion. This program has been the first to produce quality factors higher than achievable with conventional Nb at usable accelerating gradients. Here we present an update on progress at Cornell University, including studies of the formation of the Nb3Sn layer, density functional theory calculations of Nb3Sn growth, and designs for a sample host cavity for measuring the quench field of Nb3Sn.
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WEPMF051	Multipacting in an RF Window: Simulations and Measurements	2483
	M. Bousonville, S. Choroba DESY, Hamburg, Germany
	Electron guns are used in the accelerators of the European XFEL and FLASH. They are operated at 1.3 GHz. The RF peak power is 5 MW at 650 us pulse width and 10 Hz repetition rate. In order to understand the multipacting that occurs during conditioning, it was simulated in the RF window type that is used for the electron gun in the XFEL. The reduction in secondary emission yield associated with conditioning was taken into account. Since the RF windows are tested with high power on a test stand before their use, without the electron gun, measurement results are available which are compared with the simulation results. The main advantage of the simulation compared to the measurement is that the locations of multipacting can be determined in the RF window. This could be helpful for the development of high-power RF components in the future, in order to detect pronounced multipacting resonances even before production and to avoid them by design changes.
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WEPMF053	XFEL Modulators with Pulse Cables	2487
	H.-J. Eckoldt, S. Choroba, T. Grevsmühl, A. Hauberg, J. Havlicek, N. Heidbrook, K. Machau, N. Ngada DESY, Hamburg, Germany M. Frei, S.G. Keens, T.H. Strittmatter Ampegon AG, Turgi, Switzerland H. Leich DESY Zeuthen, Zeuthen, Germany
	The modulators of the European XFEL produce high voltage, at the 10kV level, having a power of up to 16.8 MW for 1.54 ms. The operation frequency of the super-conducting inac is 10 Hz. The series production of the 29 modulators started in 2012. The first modulator began operation in 2014 and the start of linac was beginning 2017. The R&D phase for the modulators started directly with the development of superconducting cavities. Besides the pulse generation, the modulator had to suppress the 10 Hz repetition rate in order not to disturb the grid. Another unique demand was the development of pulse cables. Since the power RF had to be generated in the tunnel, the klystrons were installed near the cavities. However, the modulators had to be installed outside of the tunnel for space, maintenance reasons and radiation concerns. This transmission of high power pulses via long cables is unique in the world and the suppression of EMI effects was mandatory. During the first year operation no EMI disturbances of other systems were detected and the modulator system works as expected.
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WEPMF054	Design and Status of the MicroTCA.4 Based LLRF System for TARLA	2490
	Gumus, C. Gumus, M. Hierholzer, K.P. Przygoda, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany A.A. Aksoy, A. Aydin Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
	The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) is constructing a 40 MeV Free Electron Laser with continuous wave (CW) RF operation. In order to control and monitor the four superconducting (SC) TESLA type cavities as well as the two normal conducting (NC) buncher cavities, a MicroTCA.4 based LLRF system is foreseen. This highly modular system is further used to control the mechanical tuning of the SC cavities by control of piezo actuators and mechanical motor tuners. This paper focuses on giving brief overview on hardware and software components of LLRF control of TARLA, as well as updates on the ongoing integration tests at DESY.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF054
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WEPMF055	The REGAE Accelerator Vacuum System	2493
	S. Lederer, K. Flöttmann, L. Lilje, N. Plambeck DESY, Hamburg, Germany
	Since 2011 the Relativistic Electron Gun for Atomic Exploration (REGAE) is operated at DESY in Hamburg. The accelerator consists mainly of a high gradient S-band RF-gun, which generates ultra-low emittance electron bunches, and an S-band RF-buncher cavity for bunch compression. In this contribution we describe the vacuum system of the REGAE accelerator. We will cover design aspects, applied cleaning and installation procedures as well as operation experience over the last years.
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WEPMF056	Cs2Te Photocathode Lifetime at Flash and European XFEL	2496
	S. Lederer, S. Schreiber DESY, Hamburg, Germany
	The photo-injectors of FLASH and the European XFEL at DESY (Hamburg, Germany) use Cs2Te photocathodes. In this contribution we give an update on the lifetime and quantum efficiency of the cathodes operated in both facilities. Cathode #680.1 was operated at the European XFEL from the injector commissioning to the first user run for over 700 days. At FLASH cathode #73.3 has been operated with a record of more than 1000 days.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF056
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WEPMF057	PETRA III Vacuum System - Experiences from the First Decade of Operation	2499
	L. Lilje, R. Bospflug, N. Plambeck DESY, Hamburg, Germany
	In 2008 the construction of the PETRA III vacuum system started. A year later the first photons were delivered to initial experiments and in 2010 the user operation started. In this paper the operation of the vacuum system will be reviewed. Some of the lessons learned in the initial phase will be presented as well as the main upgrades since then. By now the vacuum system has shown a very high reliability and shows no significant impact on the availability of the machine.
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WEPMF058	Anomaly Detection for Cavity Signals - Results from the European XFEL	2502
	A.S. Nawaz, S. Pfeiffer DESY, Hamburg, Germany G. Lichtenberg HAW, Hamburg, Germany P. Rostalski Institute for Electrical Engineering in Medicine, Lübeck, Germany
	The data throughput of the European XFEL DAQ is about 1.5 Gb/s. Data depicting the cavity signal behavior is currently only saved manually. This either happens, when cavity tests are being performed, or an operator detects a fault in the cavity system, that has to be further investigated. Those instances of interest are neither systematically nor automatically stored. It can therefore be assumed that unwanted or degraded cavity behavior is detected late or not at all. It is proposed to change the focus from detecting known faults (such as quenches) to additionally detect anomalies in the cavity system behavior. In order to detect anomalies in the cavity signals, an algorithm is proposed using a cavity model. It aims on finding those data sets, which diverge from the nominal cavity behavior, saving those instances for later analysis. The nominal behavior is defined by the cavity electromagnetic resonance model with beam loading as well as the model for the mechanical oscillations due to the Lorentz Forces. By using such an approach, the detection of anomalies, as well as faults could be automated. This contribution aims to summarize the influence of beam loading on the detection and gives examples for anomalies that were found in several cavities.
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WEPMF061	High Gradient Pulsed Quadrupoles for Novel Accelerators and Space Charge Limited Beam Transport	2505
	C. Tenholt CERN, Geneva, Switzerland G. Loischpresenter, F. Stephan DESY Zeuthen, Zeuthen, Germany B. Marchetti DESY, Hamburg, Germany
	Novel acceleration schemes like plasma wake-field based accelerators demand for high gradient focusing elements to match the Twiss parameters in the plasma to the transport lattice of the conventional accelerator beamlines, with typically much higher beta-functions. There are multiple candidates for achieving high gradient focusing fields, each one having certain drawbacks. Permanent magnets are limited in tunability, plasma lenses might degrade the transverse beam quality significantly and conventional magnets cannot reach very high gradients and often cannot be placed in direct proximity of the plasma accelerator because of their size. In this paper we present design considerations and simulations on compact, high gradient, pulsed quadrupoles, that could be used e.g. for final focusing of space charge dominated bunches into a LWFA (Laser Wake-Field Accelerator) at SINBAD or other facilities with similar demands. The target design gradient is 200 T/m at a physical aperture on the order of 10 mm.
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WEPMF062	Simulation of Cavity Conditioning for the Diamond SCRF Cavity	2509
	S.A. Pande, C. Christou, P. Gu DLS, Oxfordshire, United Kingdom
	Diamond SCRF cavities are pulse conditioned every week in order to keep them operating reliably. During conditioning, the cavities are detuned in order to sweep the standing wave through the waveguide. To match these cavities at lower voltage (typically < 1.4 MV) and at higher power, 3 stub tuners are used in the waveguide feed. Simulations with CST studio show that a strong SW field exists between the RF window and the matching posts. As the cavity is detuned the electric field maximum passes through the window causing heating of the ceramic. Temperature measurements with thermal camera reveal that the temperature of the window increases to maximum when the cavity is detuned towards higher frequency. Based on the simulation results and the measurements, it was decided to reduce the conditioning voltage. These results are summarised.
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WEPMF063	Thyratron Replacement*	2512
	I. Roth, N. Butler, M.P.J. Gaudreau, M.K. Kempkespresenter, R.E. Simpson Diversified Technologies, Inc., Bedford, Massachusetts, USA
	Funding: Funded under US DOE grant no. DE-SC0011292. Thyratrons are typically used as the switch in high power, short pulse modulators with pulse-forming networks. However, thyratrons have a lifetime of only ten to twenty thousand hours, their reservoir heater voltage needs to be adjusted periodically, and reduced overall demand has led multiple thyratron vendors to slow or cease production. In contrast, solid-state switches have a much longer lifetime, need no maintenance, and are based on widely-available commercial items. Despite these advantages, solid-state devices have not historically seen use, due to limited voltage, current, and risetime. Diversified Technologies, Inc. (DTI) has removed this barrier, having developed, built, and tested a thyratron-replacement switch for SLAC based on an array of series and parallel-connected commercial insulated-gate bipolar transistors (IGBTs). This switch has demonstrated operation at very high voltage and current, meeting the full specifications required by SLAC to completely replace (form-fit-function-interface) the L-4888 thyratron: 48 kV, 6.3 kA, and 1 μs risetime.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF063
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WEPMF064	Daresbury Laboratory Short Pulse Klystron Modulators	2515
	C. Chipman, M.P.J. Gaudreau, L. Jashari, M.K. Kempkespresenter, J. Kinross-Wright, R.E. Simpson Diversified Technologies, Inc., Bedford, Massachusetts, USA S.A. Griffiths, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom H.J. Zhang Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
	Diversified Technologies, Inc. (DTI) has developed a unique short pulse klystron modulator system for the Compact Linear Advanced Research Accelerator (CLARA) Project at Daresbury Laboratory. One unit has been delivered and three more are on contract. This system is based on the combination of a high voltage solid-state switch, with a conventional 1:7 pulse transformer, and a passive pulse corrector with automated adjustment. This unique passive circuitry delivers the extremely flat output pulse required for advanced accelerator applications. The CLARA modulators share design elements with previous DTI modulators which provides both a lower cost and easier to maintain system. The modulators are designed to pulse 80 MW-class klystrons at an avg power of 250 kW and provides adjustable high efficiency operation in the 45 kV to 450 kV range for currents up to 545 A and pulse lengths of 1.5 to 4.0 μs. One key objective of modulator development is optimization of voltage flatness (± 0.02 %), stability (± 0.05 %), and reproducibility (± 0.05 %).
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WEPMF065	High Efficiency, High Power, Resonant Cavity Amplifier For PIP-II	2518
	M.P.J. Gaudreau, N. Butler, D.B. Cope, P. H. Gordon, E.G. Johnson, M.K. Kempkes, R.E. Simpsonpresenter Diversified Technologies, Inc., Bedford, Massachusetts, USA
	Funding: Funded under US DOE grant no. DE-SC0015780 Diversified Technologies, Inc. (DTI) is developing an integrated resonant-cavity combined solid-state amplifier for the Proton Improvement Plan-II (PIP-II) at Fermilab. The prototype has demonstrated multiple-transistor combining at 71% efficiency, at 675 watts per transistor at 650 MHz. The design simplifies solid-state transmitters to create straightforward scaling to high power levels. A crucial innovation is the reliable "soft-failure" mode of operation; a failure in one or more of these myriad combined transistors has negligible performance impact. The design couples the transistor drains directly to the cavity without first transforming to 50 Ohms, avoiding the otherwise-necessary multitude of circulators, cables, and connectors. DTI's design increases the power level at which it is cost-effective to employ a solid-state transmitter. DTI is upgrading the system to accommodate more transistors in each cavity module, and then will design and build a complete 100 kW-class transmitter which will consist of four such cavity modules and a combiner.
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WEPMF066	Fabrication of Split-Section X-band Structure Using Elastic Averaging	2521
	P. Borchard, S.A. Appert, J.S. Hoh Dymenso LLC, San Francisco, USA
	Conventional accelerator structures are manufactured using axial stacks of cylindrical components which, when brazed together, form the accelerator cell structure. Splitting the accelerator structure into two sections along the beam axis allows for a significant reduction in part count and vacuum joint length. The resultant single and coplanar vacuum joint between the two split sections allows for joining techniques such as electron beam welding or brazing of the parts to form the accelerator vacuum envelope. High precision alignment of the two sections is achieved through an elastic averaging interface coupling where improved accuracy is derived from the averaging of errors over a large number of relatively compliant contacting members. The monoblock split sections allow for highly optimized cooling configurations with enhanced heat removal in high heat flux regions, reducing vacuum wall thermal stresses and enabling higher power operation. This paper describes the engineering and manufacturing of four generations of brazed and electron beam welded X-band accelerator structures at both 9.3 GHz and 11.4 GHz frequencies.
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WEPMF067	A High Gradient Solution for Increasing the Energy of the FERMI Linac	2525
	C. Serpico, I. Cudin, S. Di Mitri, N. Shafqat, M. Svandrlik Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy M. Bopp, R. Zennaro PSI, Villigen PSI, Switzerland
	FERMI is the seeded Free Electron Laser (FEL) user facility at Elettra laboratory in Trieste, operating in the VUV to soft X-rays spectral range. In order to extend the FEL spectral range to shorter wavelengths, a feasibility study for increasing the Linac energy from 1.5 GeV to 1.8 GeV is actually going on. The design of new S-band accelerating structures, intended to replace the present Backward Travelling Wave sections, is presented. Such design is tailored for high gradient operation, low breakdown rates and low wakefield contribution. In this paper, we will also present the first, short prototype that has been built in collaboration with Paul Scherrer Institute (PSI).
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WEPMF068	Inexpensive Brazeless Accelerator Prototype	2528
	S.P. Antipov, R.A. Kostin, S.V. Kuzikov Euclid TechLabs, LLC, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	Funding: DOE SBIR A simple, inexpensive way to manufacture a standard radio frequency (RF) driven particle accelerator is presented. The simplification comes from two innovations: utilization of LCLS gun type RF design to avoid an expensive brazing process and copper plating of stainless steel that further reduces manufacturing cost. This is realized by a special structure design where accelerating structure cells are made out of copper plated stainless steel with knife edges and structure irises - copper disks acts also as gaskets for vacuum and RF seal. Besides the reduced cost, brazeless assembly allows integration of effective cooling and magnet optics elements into accelerator cells. Here we report on manufacturing and testing of brazeless accelerator prototype.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF068
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WEPMF069	High Shunt Impedance Accelerating Structure with Distributed Microwave Coupling	2531
	S.P. Antipov, R.A. Kostin, S.V. Kuzikov Euclid TechLabs, LLC, Solon, Ohio, USA V.A. Dolgashev SLAC, Menlo Park, California, USA
	Funding: DOE SBIR Conventional traveling wave or pi-phase advance standing wave structures use coupling of the microwave power through the beam pipe. This feature constrains the cavity shunt impedance (efficiency) to relatively small values. As microwave power flows through the accelerating cells in such structures, the probability of breakdown in high gradient operation is greatly increased. In this paper we present results from an accelerating structure prototype with distributed microwave coupling, an approach invented at SLAC. These structures include one or more parallel waveguides which are loaded by accelerating cavities. In this configuration accelerating cavities are fed independently and completely isolated at the beam pipe. Thus there is no microwave power flow through the accelerating cavity, making this geometry favorable for high gradient operation and maximizing the shunt impedance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF069
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WEPMF071	Dynamic Testing and Characterization of Advanced Materials in a New Experiment at CERN HiRadMat Facility	2534
	A. Bertarelli, C. Accettura, E. Berthomé, L. Bianchi, F. Carra, C. Fichera, M.I. Frankl, G. Gobbi, P. Grosclaude, M. Guinchard, A. Lechner, M. Pasquali, S. Redaelli, E. Rigutto, O. Sacristan De Frutos CERN, Geneva, Switzerland Ph. Bolz, P. Simon GSI, Darmstadt, Germany T.R. Furness University of Huddersfield, Huddersfield, United Kingdom J. Guardia Valenzuela Universidad de Zaragoza, Zaragoza, Spain P. Mollicone, M. Portelli UoM, Msida, Malta
	Funding: This work has received funding from the European Union's Horizon 2020 Research and Innovation programme under Grant Agreement No 730871. An innovative and comprehensive experiment (named "Multimat") was successfully carried out at CERN HiRadMat facility on 18 different materials relevant for Collimators and Beam Intercepting Devices. Material samples, tested under high intensity proton pulses of 440 GeV/c, exceeding the energy density expected in HL-LHC, ranged from very light carbon foams to tungsten heavy alloys, including novel composites as graphite/carbides and metal/diamond without and with thin-film coatings. Experimental data were acquired relying on extensive integrated instrumentation (strain gauges, temperature sensors, radiation-hard camera) and on laser Doppler vibrometer. This allows investigating relatively unexplored and fundamental phenomena as dynamic strength, internal energy dispersion, nonlinearities due to inelasticity and inhomogeneity, strength and delamination of coatings and surfaces. By benchmarking sophisticated numerical simulations against these results, it is possible to establish or update material constitutive models, which are of paramount importance for the design of devices exposed to interaction with particle beams in high energy accelerators such as the HL-LHC or FCC-hh.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF071
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WEPMF072	Magnet Power Supplies for ALS-U	2538
	G.C. Pappas, J.-Y. Jungpresenter, C.A. Swenson LBNL, Berkeley, California, USA
	The ALS-U project is an upgrade to the existing Advanced Light Source at Lawrence Berkeley Laboratory to a diffraction limited light source. To be able to achieve the small horizontal emittance of the ALS-U, the three bend achromats in the ALS will be replaced with nine bend achromats. Because the lifetime of the ALS-U beam will be significantly reduced, the plan is to use a swap out injection scheme between the storage ring and a new accumulator ring. The present plan is to use individual power supplies for each magnet in the storage ring, and series connected magnet strings for the accumulator ring. The sheer number of supplies needed, along with the tighter stability requirements for the ALS-U, is demanding in terms of the power supply requirements for stability and reliability. This paper will discuss the ALS-U magnet power supply requirements, and possible options to meet them.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF072
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WEPMF073	Adaptation of the Cryogenic System Capacity for the LHC Dynamic Heat Load - Operational Experience	2541
	K. Brodzinski, B. Bradu, S.D. Claudet, D. Delikaris, L.P. Delprat, G. Ferlin CERN, Geneva, Switzerland
	During second LHC physics operation period (Run2), between 2015 and 2018, the accelerator operation modes and beam parameters have been adapted thus allowing significantly improved integrated luminosity production. Increased energy, intensity and adapted beam operation schemes with 25 ns of inter-bunches spacing have an essential influence on the dynamic heat load generation with direct impact on the cryogenic cooling system. In order to cope with significantly higher than expected beam induced thermal load, the cryogenic system was tuned and optimized to adapt the required refrigeration capacity to the beam operational requirements. The most challenging part of tuning was focused on the dynamic heat load compensation on the beam screens circuits. The paper will provide the overview on the main differences between the theoretical heat load values considered for initial design and the on-line measurements performed on cryogenic LHC sectors. Finally, the paper will summarize the methodology and tools implemented in the cryogenic process control system allowing the highly efficient on-line adaptation of the refrigeration power with respect to the beam induced heat load distribution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF073
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WEPMF074	High Power Conditioning of X-Band RF Components	2545
	N. Catalán Lasheras, H. Damerau, R.L. Gerard, A. Grudiev, G. McMonagle, J. Paszkiewicz, A. Solodko, I. Syratchev, B.J. Woolley, W. Wuensch, V. del Pozo Romano CERN, Geneva, Switzerland T.G. Lucas, M. Volpi The University of Melbourne, Melbourne, Victoria, Australia S. Pitman Lancaster University, Lancaster, United Kingdom A. Vnuchenko IFIC, Valencia, Spain
	As part of the effort to qualify CLIC accelerating struc-tures prototypes, new X-band test facilities have been built and commissioned at CERN in the last years. In this context, a number of RF components have been designed and manufactured aiming at stable operation above 50 MW peak power and several kW of average power. All of them have been tested now in the X-band facility at CERN either as part of the facility or in dedicated tests. Here, we describe shortly the main design and manufac-turing steps for each component, the testing and eventual conditioning as well as the final performance they achieved.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF074
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WEPMF075	Performance Measurements and Analysis of Jitter Like Events for the PS Injection Kicker System	2549
	A. Ferrero Colomo, J.C.C.M. Borburgh, L. Ducimetière, L.M.C. Feliciano, V. Forte, M.A. Fraser, T. Kramer, L. Sermeus CERN, Geneva, Switzerland
	In the framework of the LIU project, several modifications have been made to the CERN PS injection kicker system during the winter stop 2016-2017 (EYETS). Current waveform and beam-based measurements were carried out in 2017 to validate the implemented design changes by observing the magnetic field impact on the beam. During these long-term measurements, increased values for the rise and fall times were observed when compared to single shot observations of the current waveform. An unknown source of jitter-like pre-firing in the main switch has been identified, creating an additional challenge to meet the already tight system rise and fall time specifications. This paper briefly describes the efforts made to fine tune the pulse generator after the EYETS, summarises the optimised configuration and analyses the observed jitter events. A new triggering system design is briefly outlined to address the issue.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF075
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WEPMF076	First Prototype Inductive Adder for the FCC Injection	2553
	D. Woog, M.J. Barnes, A. Ferrero Colomopresenter, J. Holma, T. Kramer CERN, Geneva, Switzerland
	A highly reliable kicker system is required as part of the injection for the FCC. A significant weak point of conventional kicker systems is often the pulse generator, where a Pulse Forming Network/Line (PFN/PFL) is discharged through a thyratron switch to generate the current pulse for the kicker magnet. This design has several disadvantages: in particular the occasional erratic turn-on of the switch which cannot be accepted for the FCC. A potential replacement is the inductive adder (IA) that uses semiconductor switches and distributed capacitors as energy storage. The modular design, low maintenance and high flexibility make the IA a very interesting alternative. In addition, the ability to both turn-on and off the current also permits the replacement of PFN/PFL by the capacitors. A first FCC prototype IA, capable of generating 9 kV and 2.4 kA pulses, has been designed and built at CERN. It will be upgrade to a full-scale prototype (15 kV, 2.4 kA) in 2018. This paper presents measurement results from the 9 kV prototype and outlines the conceptual changes and expected performance of the 15 kV prototype.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF076
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WEPMF077	Demonstration of Feasibility of the CLIC Damping Ring Extraction Kicker Modulators	2557
	J. Holma, M.J. Barnes, A. Ferrero Colomopresenter CERN, Geneva, Switzerland
	The CLIC study is investigating the technical feasibility of an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. Pre-damping rings and damping rings (DRs) will produce ultra-low emittance beam with high bunch charge. The DR kicker systems must provide extremely stable field pulses to avoid beam emittance increase. The DR extraction kicker system consists of a stripline kicker and two pulse modulators. Specifications for the electromagnetic field pulses require that the modulator produce pulses of 160 or 900 ns flattop duration, ±12.5 kV and 305 A, with ripple and droop of not more than ±0.02 % (±2.5 V) with respect to an ideal waveform. Inductive adder topology has been chosen for the pulse modulators where the output waveform can be adjusted by applying analogue modulation methods. Two full-scale, 20-layer, 12.5 kV prototype inductive adders have been designed and built, and they are being tested at CERN. These modulators will be tested with a prototype stripline kicker, installed in a beamline at ALBA Synchrotron Light Source in Spain. The results of the laboratory tests and measurements are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF077
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WEPMF078	Assembly of the DQW Crab Cavity Cryomodule for SPS Test	2561
	M. Garlaschè, K. Artoos, R. Calaga, O. Capatina, T. Capelli, N. El Kbiri, D. Lombard, P.F. Marcillac, P. Minginette, M. Narduzzi, L.R.A. Renaglia, J. Roch, J.S. Swieszek CERN, Geneva, Switzerland A. Krawczyk, B. Prochal IFJ-PAN, Kraków, Poland
	RF Crab Cavities are an essential part of the High Luminosity Upgrade of the LHC accelerating complex. Two concepts of such superconducting systems are being developed: the Double Quarter Wave (DQW) and the RF Dipole (RFD). A prototype cryomodule - hosting two DQW cavities - has been fabricated and assembled for validation tests to be carried out in the Super Proton Synchrotron (SPS) at CERN. An overview of the main cryomodule components is presented, together with the system features and main fabrication requirements. The preparatory measures for cryomodule assembly, the execution and lessons learned are also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF078
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WEPMF079	Experimental Modal Analysis of Lightweight Structures used in Particle Detectors: Optical non-contact Method	2565
	M. Guinchard, M. Angeletti, F.B. Boyer, A. Catinaccio, C.G. Gargiulo, L.L. Lacny, E.L. Laudi, L.S. Scislo CERN, Geneva, Switzerland
	CERN's specialized structures such as particle detectors are built to have high rigidity and low weight, which comes at a cost of their high fragility. Shock and vibration issues are a key element for their successful transport, handling operations around the CERN infra-structure, as well as for their operation underground. The experimental modal analysis measurement technique is performed to validate the Finite Element Analysis in the case of complex structures (with cables and substructure coupling). In the case of lightweight structures, standard contact measurements based on accelerometers are not possible due to the high mass ratio between the accelerometers and the structure itself. In such a case, the vibration of the structure can be calculated based on the Doppler shift of the laser beam reflected off the vibrating surface. This paper details the functioning and application of an advanced laser-scanning vibrometry system, which utilizes the fore-mentioned non-contact method. The results of the Experimental Modal Analysis of selected lightweight structure using this instrument is also presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF079
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WEPMF080	Investigation and Estimation of the LHC Magnet Vibrations Induced by HL-LHC Civil Engineering Activities	2568
	M. Guinchard, M. Cabon, C. Charrondière, K. Develle, P. Fessia, L.L. Lacny, J.A. Osborne, L.S. Scislo, J. Wenninger CERN, Geneva, Switzerland
	HL-LHC requires the excavation of large underground infrastructures in order to host new equipment. The tunnel shall be ready for installation for LS3 (2022) and therefore its construction shall take in place in parallel with the LHC exploitation. Effect of vibrations induced by civil engineering activities need to be evaluated in order to take required corrective actions. For this purpose, several diverse measurements and experiments have been performed in order to estimate the vibration sources and determine the vibration transfer path through the floor and the structure. The transfer functions from amplitude and phase point of view were determined through molasses rock, for both horizontal and vertical vibrations, with dedicated tools and Experimental Modal Analysis was carried out on mechanical structure. The campaign of measurements have been used to confirm the effect of the surface induced vibration on the circulating beam orbit at the resonance frequencies of the structure. This paper reviews the advanced technique of measurements, results and the conclusion about the impact of operating civil engineering machines (road header, hydraulic hammer) during beam exploitation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF080
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WEPMF081	Mechanical Strain Measurements Based on Fiber Bragg Grating Down to Cryogenic Temperature - R&D Study and Applications	2572
	M. Guinchard, A. Bertarelli, L. Bianchi, F.B. Boyer, M. Cabon, M. Calviani, O. Capatina, A. Catinaccio, P. Ferracin, P. Grosclaude CERN, Geneva, Switzerland
	In recent years, optical fiber sensors have been increasingly used due to their outstanding performances. Their application is preferable in case of special requirements that exclude the application of conventional electrical sensors. The scientific background of optical fiber sensors is well developed. However, the characteristic of sensors employed in rather harsh environments is often different from the one determined in laboratory conditions or prior to their installation. In order to achieve long-term stable functioning and reliable measurement under severe working environments, such as those occurring at CERN (radiation, cryogenics, high magnetic and electrical field), a statistical measurement campaign was carried out following the international standard ISO 5725. The paper describes the ongoing study to define the accuracy of optical fiber sensors based on Fiber Bragg Grating (FBG) for strain measurements, from room temperature down to 4.2 K. It also describes some of the demanding applications for which optical fiber sensors have been deployed to perform experimental strain measurements (e.g. detectors components, high-energy beam targets and dumps, superconducting magnets).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF081
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WEPMF082	Design and Construction of the CERN PS Booster Charge Exchange Injection Chicane Bumpers	2575
	B. Balhan, C. Baud, J.C.C.M. Borburgh, M. Houricanpresenter CERN, Geneva, Switzerland
	In the framework of the LIU project and the connection from LINAC4 to PS Booster, the 160 MeV H− beam will be injected horizontally into the PSB by means of one charge-exchange injection system for each PSB ring. A set of four outside vacuum pulsed dipole magnets (BSW) creating the required injection bump has been designed and built. The dynamic requirements for the bump ramp down determine, to a large extent, the field homogeneity due to the eddy currents induced in the corrugated Inconel vacuum chamber. Magnetic simulations were performed to determine the field harmonics during bump ramp down, and the results subsequently used for the dynamic tracking of the beam during injection. The mechanical design and construction of the magnets will be briefly outlined, and the article will conclude with the magnetic measurements of the magnets. The magnetic performance of the as built magnets will be compared with the simulations and the influence of the vacuum chambers on the magnetic field will be quantified.
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WEPMF083	Comparison of Superconducting Septa Topologies and Parameter Space Exploration	2578
	M.G. Atanasov, J.C.C.M. Borburgh, M. Houricanpresenter, A. Sanz Ull CERN, Geneva, Switzerland
	The unprecedented energy scale of the FCC poses challenging requirements for its magnetic elements including the septum magnets for injection and extraction. With an ambitious target field of 4 T and an apparent septum thickness of only 25 mm, different superconducting septa topologies have been investigated to explore their limitations. This article will cover the currently feasible topologies, amongst which the truncated cosine-theta, the double truncated cosine-theta, the superconducting shield (SuShi) and the so called stealth dipole. A performance figure of merit will be proposed, taking into account the maximum achievable magnetic field, the septum thickness and the leak field magnitude.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF083
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WEPMF084	Design, Prototyping Activities and Beam Irradiation Test for the New nTOF Neutron Spallation Target	2582
	R. Esposito, M. Bergeret, J. Busom, M.E.J. Butcher, M. Calviani, R. Cimmino, T. Coiffet, J.P.C. Espadanal, L. Gentini, R. Illan Fiastrepresenter, V. Maire, F. Ogallar Ruiz, A. Perillo-Marcone, S. Sgobba, M.A. Timmins, C. Torregrosa, E. Urrutia, V. Vlachoudis CERN, Geneva, Switzerland R. Logé EPFL, Lausanne, Switzerland
	A third-generation neutron spallation target for the neutron time-of-flight facility at CERN (nTOF) is currently undergoing the design and prototyping stage. The new design aims at improving reliability, increasing beam intensity on target and avoiding issues encountered in the current generation target, in particular the contamination of the cooling system water with radioactive spallation products coming from washing out lead. After a preliminary design and an initial prototyping stage*, a baseline solution has been defined consisting in a pure lead target core contained in a Ti-6Al-4V cladding and embedded in a massive Pb block. A backup solution has also been defined, consisting in a Ta-cladded W core embedded in a Pb block. Both solutions are currently undergoing the detailed design stage. This contribution details the prototyping activity, the robustness studies for accidental scenarios and the design of a beam irradiation test on prototypes of the target core. R. Esposito et al., "Design of the new CERN nTOF neutron spallation target: R&D and prototyping activities," in Proc. of IPAC'17, Copenhagen, May 2017.
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WEPMF086	Eradication of Mercury Ignitron from the 400 kA Magnetic Horn Pulse Generator for CERN Antiproton Decelerator	2586
	V. Namora, M. Calviani, L. Ducimetière, P. Faure, L.E. Fernandez, G. Gräwer, V. Senaj CERN, Geneva, Switzerland
	The CERN Antiproton Decelerator (AD) produces low-energy antiprotons for studies of antimatter. A 26 GeV proton beam impacts the AD production target which produces secondary particles including antiprotons. A magnetic Horn (AD-Horn) in the AD target area is used to focus the diverging antiproton beam and increase the antiproton yield enormously. The horn is pulsed with a current of 400 kA, generated by capacitor discharge type generators equipped with ignitrons. These mercury-filled devices present a serious danger of environmental pollution in case of accident and safety constraints. An alternative has been developed using solid-state switches and diodes. Similar technology was already implemented at CERN for ignitron eradication in the SPS Horizontal beam dump in the early 2000s. A project was launched to design and set up a full-scale test-bench, to install and test a dedicated solid-state solution. Following the positive results obtained from the test-bench, the replacement of ignitrons by solid-state devices in the operational AD-Horn facility is currently under preparation. This paper describes the test-bench design and results obtained for this very high current pulser.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF086
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WEPMF087	LHC Injectors Upgrade Project: Outlook of the Modifications to the Super Proton Synchrotron (SPS) Vacuum System and Impact on the Operation of the Carbon-Coated Vacuum Chambers	2589
	C. Pasquino, G. Bregliozzi, P. Chiggiato, P. Cruikshank, A. Farricker, A. Harrison, J. Perez Espinos, J.A.F. Somoza, M. Taborelli, C. Vollinger CERN, Geneva, Switzerland
	Aiming at doubling the beam intensity and reducing the beam emittance, significant modifications of the LHC and its injector chain will take place during Long Shutdown 2 (LS2), starting from 2019. The LIU project (LHC Injector Upgrade), in the specific, touches Linac4, the Proton Synchrotron Booster (PSB), the Proton Synchrotron (PS), the Super Proton Synchrotron (SPS) as well as the heavy ion chain. During LS2, important changes will take place mainly in the Long Straight Sections of the SPS to host a newly conceived dumping system, upgraded RF cavities and upgraded extraction channels. Additionally, the vacuum chambers of the main bending and focusing magnets as well as vacuum drifts will be coated with amorphous carbon in order to reduce the dynamic pressure effects induced by multipacting. The modifications to the different vacuum sectors will be described in details as well as the impact on operation of amorphous carbon coated sectors that have been already deposited.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF087
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WEPMF089	Measurements of Electromagnetic Properties of Ferrites as a Function of Frequency and Temperature	2592
	A. Chmielinska, M.J. Barnes, F. Caspers, B.K. Popovicpresenter, C. Vollinger CERN, Geneva, Switzerland
	Fast kicker magnets are used to inject beam into and extract beam out of the CERN accelerator rings. These kickers are often ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. The interaction of the beam with the resistive part of the longitudinal beam coupling impedance leads to power dissipation and heating of different elements in the accelerator ring. In particular, power deposition in the kicker magnets can be a limitation: if the temperature of the ferrite yoke exceeds the Curie temperature, the beam will not be properly deflected. In addition, the imaginary portion of the beam coupling impedance contributes to beam instabilities. A good knowledge of electromagnetic properties of materials up to GHz frequency range is essential for a correct impedance evaluation. This paper presents the results of transmission line measurements of complex initial permeability and permittivity for different ferrite types. We present an approach for deriving electromagnetic properties as a function of both frequency and temperature; this information is required for simulating ferrite behaviour under realistic operating conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF089
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WEPMF090	Upgrade of the CMS Experimental Beam Vacuum During LS2	2596
	J.S. Sestak, G. Bregliozzi, P. Chiggiato, C. Di Paolo CERN, Geneva, Switzerland
	Starting from December 2018, the Large Hadron Collider (LHC) is going to interrupt its physic operations for more than two years within the period called second long shutdown (LS2). The Compact Muon Solenoid (CMS) experiment will undergo the biggest upgrade of its experimental beam vacuum system since the first operations in 2008. The new experimental vacuum layout should comply with demanding structural, vacuum, integration and physics requirements. Moreover, the new layout should be compatible with foreseen engineering changes of the detector and the machine during the upgrade phase of High-Luminosity LHC in LS3. This paper gives an overview of the CMS LS2 experimental vacuum sectors upgrades. Both design and production phase of the new vacuum layout is discussed in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF090
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