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

Paper	Title	Page
WEPML001	Passive Microphonics Mitigation during LCLS-II Cryomodule Testing at Fermilab	2668
	J.P. Holzbauer, B.E. Chase, J. Einstein-Curtis, B.J. Hansen, E.R. Harms, J.A. Kaluzny, A.L. Klebaner, M.W. McGee, Y.O. Orlov, T.J. Peterson, Y.M. Pischalnikov, W. Schappert, R.P. Stanek, J. Theilacker, M.J. White, G. Wu Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The LCLS-II project calls for cryomodule production and testing at both Fermilab and JLab. Due to low beam loading and high cavity quality factor, the designed peak detuning specification is 10 Hz. Initial testing showed peak detuning up to 150 Hz with a complex and varying time-structure, showing both fast (1-2 second) and slow (1-2 hour) drifts in amplitude and spectrum. Extensive warm and cold testing showed Thermoacoustic Oscillations in the cryogenic valves were the primary source of the microphonics. This was mitigated by valve wipers and valve re-plumbing, resulting in a greatly improved cavity detuning environment. Additional modifications were made to the cavity mechanical supports and Fermilab test stand to improve detuning performance. These modifications and testing results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML001
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WEPML002	Design of 650 MHz Tuner for PIP-II Project	2671
	Y.M. Pischalnikov, S. Cheban, J.C. Yun Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The Proton Improvement Plan (PIP) II project at Fermilab is a proton driver linac which will use of five different cavity geometries including a 650 MHz 5-cell elliptical cavities that will operate in RF-pulse mode. Detuning of these cavities by Lorentz Forces will be large and strongly depend of the stiffness of the cavity's tuner. First prototype tuner built and tested warm [1,2]. Measured stiffness of the prototype tuner was below 30kN/mm instead of expected from simulation 70kN/mm [2]. Significant effort has been invested into understanding discrepancy between simulation and experimental data that led to newest tuner design. Updated 'dressed cavity-helium vessel-tuner' model provided consistent results between ANSYS simulations and experiment results. Modified tuner design and analysis in limitations for overall 'cavity/tuner system' stiffness will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML002
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WEPML003	Precision Q0 Measurement of an SRF Cavity with a Digital RF Techniques	2674
	J.P. Holzbauer, B.M. Hanna, Y.M. Pischalnikov, W. Schappert, D.A. Sergatskov, A.I. Sukhanov Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Direct measurement of the quality factor of SRF cavity using traditional RF techniques is essential for cavity production and development. Systematic effects of the measurement can contribute significant amounts of error to these measurements if not accounted for. This paper will present measurements taken at Fermilab using a digital RF system to characterize and correct for these systematic effects and directly measure the quality factor versus gradient curve for a single spoke resonator in the Spoke Test Cryostat at Fermilab. These measurements will be compared to traditional calorimetric measurements, and a discussion of improving/extending these techniques to other testing situations will be included.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML003
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WEPML004	Production Tuner Testing for LCLS-II Cryomodule Production	2678
	J.P. Holzbauer, Y.M. Pischalnikov, W. Schappert, J.C. Yun Fermilab, Batavia, Illinois, USA C. Contreras-Martinez FRIB, East Lansing, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. LCLS-II 1.3 GHz cryomodule production is well underway at Fermilab. Several dozen cavity/tuner systems have been tested, including tuning to 1.3 GHz, cold landing frequency, range/sensitivity of the slow tuner, and range/sensitivity of the fast tuner. All this testing information as well as lessons learned from tuner installation will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML004
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WEPML005	Testing of SSR1 Production Tuner for PIP-II	2681
	J.P. Holzbauer, D. Passarelli, Y.M. Pischalnikov Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The PIP-II project at Fermilab is a proton driver linac calling for the use of five different, novel cavity geometries. Prototyping at Fermilab is in the advanced stages for the low-beta single-spoke resonator (SSR1) and associated technologies. A production tuner design has been fabricated and tested, both warm and cold in the Spoke Test Cryostat (STC). This paper will present the detailed studies on this tuner, including slow motor/piezoelectric tuner range and hysteresis as well as dynamic mechanical system characterization.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML005
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WEPML006	Modified Slow Tuner Design for Cavity 1 Inside LCLS II Cryomodules	2684
	Y.M. Pischalnikov, T.T. Arkan, S. Cheban, J.P. Holzbauerpresenter, J.A. Kaluzny, Y.O. Orlov, J.C. Yun Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Initial LCLS-II cryomodule testing at Fermilab showed microphonics on the furthest upstream cavity (number 1) at least factor 2 larger than on the rest of the cavities. Testing indicated that this was a difference in the mechanical support of cavity 1, not a local acoustic source. Further investigation pointed to the upstream beam-pipe of the cavity 1. The upstream cavity flange has a solid spool piece connection to the beamline gate valve unlike the other cavities, which all connect through bellows. The gate valve's weight is supported by sliding system (free in z-axis) connected to large diameter Helium gas return pipe. The tuner design was modified to transform interface between cavity#1 and gate valve. Arms of the tuner for cavity 1 were extended and became the support structure for gate valve, eliminating the connection to the helium return pipe. Modification of the tuner design and results in microphonics mitigations will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML006
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WEPML007	Active Microphonics Compensation for LCLS-II	2687
	J.P. Holzbauer, B.E. Chase, J. Einstein-Curtis, Y.M. Pischalnikov, W. Schappert Fermilab, Batavia, Illinois, USA L.R. Doolittle, C. Serrano LBNL, Berkeley, California, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Testing of early LCLS-II cryomodules showed microphonics-induced detuning levels well above specification. As part of a risk-mitigation effort, a collaboration was formed between SLAC, LBNL, and Fermilab to develop and implement active microphonics compensation into the LCLS-II LLRF system. Compensation was first demonstrated using a Fermilab FPGA-based development system compensating on single cavities, then with the LCLS-II LLRF system on single and multiple cavities simultaneously. The primary technique used for this effort is a bank of narrowband filter set using the piezo-to-detuning transfer function. Compensation automation, optimization, and stability studies were done. Details of the techniques used, firmware/software implementation, and results of these studies will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML007
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WEPML008	Tuner Testing of a Dressed 3.9 GHz Cavity for LCLS-II at Fermilab	2690
	J.P. Holzbauer, S. Aderhold, T.N. Khabiboulline, Y.M. Pischalnikov, W. Schappert, J.C. Yun Fermilab, Batavia, Illinois, USA C. Contreras-Martinezpresenter FRIB, East Lansing, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Fermilab is responsible for the design of the 3.9 GHz cryomodule for LCLS-II. Integrated acceptance testing of a dressed 3.9 GHz cavity for the LCLS-II project has been done at the Fermilab Horizontal Test Stand. This test included a slim blade tuner (based on INFN & XFEL designs) with integrated piezoelectric fast/fine tuner. This paper will present results of the mechanical setup, cold testing, and cold function of this tuner including fast and slow tuner range, sensitivity, and hysteresis.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML008
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WEPML009	Superconducting Magnet Performance in LCLS-II Cryomodules	2693
	V.S. Kashikhin, S. Cheban, J. DiMarco, E.R. Harms, A.V. Makarov, T. Strauss, M.A. Tartaglia Fermilab, Batavia, Illinois, USA
	Abstract' New LCLS-II Linear Superconducting Accelerator Cryomodules under construction at Fermilab. Inside each SCRF Cryomodule installed superconducting magnet package to focus and steer an electron beam. The magnet package has the iron dominated configuration with racetrack type quadrupole and dipole conductively cooled coils. For easier installation the magnet could be split in the vertical plane. Initially the magnet was tested in a liquid helium bath, and were performed high precision magnetic field measurements. Several Cryomodules with magnets inside were built and successfully tested at Fermilab test facility. In the paper presented Cryomodule magnet packages test results, discussed the magnet, and current leads conduction cooling performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML009
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WEPML010	Operation Regime Analysis of Conduction Cooled Cavities Through Multi-Physics Simulation	2697
	R.A. Kostin, R. Dhuley, M.G. Geelhoed, R.D. Kephart, T.K. Kroc, O.V. Prokofiev, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA
	Funding: Department of Energy Euclid Techlabs in collaboration with Fermilab IARC (Batavia, IL) is developing industrial superconducting 10MeV electron linac. Conduction cooling is used for cooling instead of liquid helium bath to simplify linac maintenance. The cavity linked to commercially available cryo-cooler cold head through highly conductive aluminium strips. However, this solution raises a problem of contact thermal resistance. This paper shows some results of Comsol multyphysics simulations of the cavity cooling by AL strips. Some insight was obtained on the acceptable range of contact resistance. Operation regimes were obtained at different accelerating gradients and cavity temperatures. The results of simulation are presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML010
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WEPML011	Garnet Ring Measurements for the Fermilab Booster 2nd Harmonic Cavity	2700
	R.L. Madrak, J.E. Dey, K.L. Duel, J. Kuharik, A.V. Makarov, W. Pellico, J. Reid, G.V. Romanov, M. Slabaugh, D. Sun, C.-Y. Tan, I. Terechkine Fermilab, Batavia, Illinois, USA
	A perpendicularly biased tuneable 2nd harmonic cavity is being constructed for use in the Fermilab Booster. The cavity's tuner uses National Magnetics AL800 garnet as the tuning media. For quality control, the magnetic properties of the material and the uniformity of the properties within the tuner must be assessed. We describe two tests which are performed on the rings and on their corresponding witness samples.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML011
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WEPML012	Progress on the Construction of the Perpendicularly Biased 2nd Harmonic Cavity for the Fermilab Booster	2703
	R.L. Madrak, J.E. Dey, K.L. Duel, M.R. Kufer, J. Kuharik, A.V. Makarov, R.D. Padilla, W. Pellico, J. Reid, G.V. Romanov, M. Slabaugh, D. Sun, C.-Y. Tan, I. Terechkine Fermilab, Batavia, Illinois, USA
	A perpendicularly biased tuneable 2nd harmonic cavity, designed for the Fermilab Booster, is being assembled for testing this summer (2018). The cavity will work at twice the frequency of the fundamental cavities, and will be on only during the injection and transition (or extraction) periods. The main purpose of adding this cavity is to improve beam capture and reduce losses as required by Fermilab's Proton Improvement Plan (PIP). After three years of testing and optimization, the cavity design has now been finalized and all constituent parts have been received. We report on the cavity final design and on the status of the construction.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML012
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WEPML013	Anti-Q-slope enhancement in high-frequency niobium cavities	2707
	M. Martinello, S. Aderhold, S.K. Chandrasekaran, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	N-doped 1.3 GHz niobium cavities showed for the first time the so-called anti-Q-slope, i.e. the increasing of the Q-factor as a function of the accelerating field. It was verified that the anti-Q-slope is consequence of the decreasing of the temperature-dependent component of the surface resistance as a function of the field. This trend is opposite compared to the increasing of the surface resistance previously observed in 1.3 GHz standard (EP, BCP, 120 C baked) niobium cavities. The effect of the different state-of-the-art surface treatments on the field dependence of the surface resistance is studied for 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 Ghz cavities. This proceeding shows that the field dependence of the temperature-dependent component of the surface resistance has a strong frequency dependence and that the anti-Q-slope may appear even in clean niobium cavities if the resonant frequency is high enough, suggesting new routes toward the understanding of the anti-Q-slope effect.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML013
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WEPML014	Tooling Systems for the Assembly and Integration of the SSR1 Cryomodule for PIP-II Project at Fermilab	2710
	D. Passarelli, F. Di Ciocchis, M. Parise, V. Roger Fermilab, Batavia, Illinois, USA
	In this paper we present the assembly strategy and tooling design for the SSR1 cryomodule from the cavity string to the final module. Several challenging aspects were considered to minimize undesired stresses on critical components, to preserve the alignment of cavities and solenoids during final assembly, and ultimately to meet the technical requirements of the PIP-II project at Fermilab.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML014
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WEPML015	Preparation and Qualification of Jacketed SSR1 Cavities for String Assembly at Fermilab	2714
	D. Passarelli, P. Berrutti, S.K. Chandrasekaran, J.P. Ozelis, M. Parise, L. Ristori, A.M. Rowe, A.I. Sukhanov Fermilab, Batavia, Illinois, USA
	The qualification of dressed 325 MHz Single Spoke Resonators type 1 (SSR1) to meet technical requirements is an important milestone in the development of the SSR1 cryomodule for the PIP-II Project at Fermilab. This paper reports the procedures and lessons learned in processing and preparing these cavities for horizontal cold testing prior to integration into a cavity string assembly.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML015
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WEPML016	Development of Nb3Sn Coatings for Superconducting RF Cavities at Fermilab	2718
	S. Posen, S.K. Chandrasekaran, O.S. Melnychuk, D.A. Sergatskov, B. Tennis, Y. Trenikhina Fermilab, Batavia, Illinois, USA J. Lee NU, Evanston, Illinois, USA
	Nb3Sn films are a promising alternative material for su-perconducting RF cavities, with proven high quality factors at medium fields and predictions for increased superheating field as well. In this contribution, we de-scribe the latest results from the Fermilab Nb3Sn SRF program. Early experiments have been focused on single cell 1.3 GHz cavities. We briefly review efforts to bring the parameters used in the coating process into a range where they produce uniform surfaces without regions showing signs of excess tin or thin/uncoated areas. We then present the latest cavity results, after modifications to the coating recipe based on feedback from film appear-ance and RF performance. These results show high Q0 at medium fields and a maximum field of ~18 MV/m.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML016
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WEPML019	Design Update of the SSR1 Cryomodule for PIP-II Project	2721
	V. Roger, S. Cheban, T.H. Nicol, Y.O. Orlov, D. Passarelli, P. Vecchiolla Fermilab, Batavia, Illinois, USA
	This paper reports the design update of the Single Spoke Resonator 1 (SSR1) cryomodule developed in the framework of PIP-II project at Fermilab. The most re-cent design changes and results of calculations per-formed to optimize the vacuum vessel, current leads, piping system and thermal shield are described. Then the estimated heat loads of the cryomodule leading to the sizing of the cryogenic valves will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML019
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WEPML021	First Performance Results of the PIP2IT MEBT 200 Ω Kicker Prototype	2724
	G.W. Saewert, M.H. Awida, B.E. Chase, A.Z. Chen, J. Einstein-Curtis, D. Frolov, K.S. Martin, H. Pfeffer, D. Wolff Fermilab, Batavia, Illinois, USA S. Khole BARC, Trombay, Mumbai, India D. Sharma RRCAT, Indore (M.P.), India
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics The PIP-II project is a program to upgrade the Fermilab accelerator complex. The PIP-II linac includes a 2.1 MeV Medium Energy Beam Transport (MEBT) section that incorporates a unique chopping system to perform arbi-trary, bunch-by-bunch removal of 162.5 MHz structured beam. The MEBT chopping system will consist of two identical kickers working together and a beam absorber. One design of two having been proposed has been a 200 Ω characteristic impedance traveling wave dual-helix kicker driven with custom designed high-speed switches. This paper reports on the first performance results of one prototype kicker built, installed and tested with beam at the PIP-II Injector Test (PIP2IT) facility. The helix deflector design details are discussed. The electrical performance of the high-speed switch driver operating at 500 V bias is presented. Tests performed were chopping beam at 81.25 MHz for microseconds as well as with a truly arbitrary pattern for 550 us bursts having a 45 MHz average switching rate and repeating at 20 Hz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML021
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WEPML022	3.9 GHz Power Coupler Design and Tests for LCLS-II Project	2727
	N. Solyak, I.V. Gonin, C.J. Grimm, E.R. Harms, T.N. Khabiboulline, A. Lunin, O.V. Prokofiev, G. Wu Fermilab, Batavia, Illinois, USA
	LCLS-II linac requires two 3.9 GHz cryomodules (eight cavities per CM), operating up to 16MV/m in cw regime. Fermilab has designed and built few prototypes of the cavity and auxiliaries and tested them at the vertical and horizontal cryostats. Fundamental power coupler, based on existing design (FLASH, XFEL) was redesign for 2kW average power. We built three prototypes and tested them at room temperature test stand. One coupler was assembled on the cavity and tested at horizontal cryostat as part of design verification program. Test results and comparison with simulations are discussed in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML022
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WEPML023	Design and Test Results of the 3.9 GHz Cavity for LCLS-II	2730
	N. Solyak, S. Aderhold, S.K. Chandrasekaran, C.J. Grimm, T.N. Khabiboulline, A. Lunin, O.V. Prokofiev, G. Wu Fermilab, Batavia, Illinois, USA
	The LCLS-II project uses sixteen 3.9 GHz superconduct-ing cavities to linearize energy distribution before the bunch compressor. To meet LCLS-II requirements origi-nal FNAL design used in FLASH and XFEL was signifi-cantly modified to improve performance and provide reliable operation up to 16 MV/m in cw regime [1-3]. Four prototype cavities were built and tested at vertical cryo-stat. After dressing, one cavity was assembled and tested at horizontal cryostat as part of design verification pro-gram. All auxiliaries (magnetic shielding, power and HOM couplers, tuner) were also re-designed and tested with this cavity. In this paper we will discuss cavity and coupler design and test results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML023
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WEPML025	Advantages and Challenges of Nb3Sn Superconducting Undulators	2734
	A.V. Zlobin, E.Z. Barzi, D. Turrioni Fermilab, Batavia, Illinois, USA Y. Ivanyushenkov, I. Kesgin ANL, Argonne, Illinois, USA
	Funding: This work is supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. Superconducting undulators (SCUs) employ superconducting coils, and due to high critical current density in a superconductor, outperform undulators based on permanent magnets in terms of the level of magnetic field. So far, most of the SCUs, including devices built at Advanced Photon Source (APS), use Nb-Ti superconductor. Utilization of Nb3Sn conductor offers a possibility to increase the undulator field even further but requires to overcome certain challenges that are described in this paper. Based on experience of developing Nb3Sn accelerator magnets at Fermi National Accelerator Laboratory, possible solutions are discussed. The achievable field levels for Nb3Sn version of existing APS and the future APS-Upgrade superconducting undulators are also presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML025
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WEPML026	Large-Aperture High-Field Nb3Sn Dipole Magnets	2738
	A.V. Zlobin, V.V. Kashikhin, I. Novitski Fermilab, Batavia, Illinois, USA
	Funding: Work is supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy Large-aperture high-field dipole magnets based on Nb3Sn superconductor are necessary for various accelerator systems of future hadron and muon colliders. In hadron colliders, they are used needed for beam separation before and after interaction points. In a muon collider, they are considered for both the arc and the interaction regions to provide room for internal absorbers protecting magnets from the muon decay products. These magnets can also be used in test facilities to produce a background magnetic field for testing conductor samples or insert coils. High level of magnetic field and large aperture size lead to large Lorentz forces and mechanical strains and stresses which can damage brittle Nb3Sn coils. This paper describes conceptual designs of 120-mm aperture dipoles with magnetic fields up to 15 T based on cos-theta coils. Stress management technique and magnet parameters are also presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML026
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WEPML027	Conceptual Design of a 17 T Nb3Sn Accelerator Dipole Magnet	2742
	A.V. Zlobin, J.R. Carmichael, V.V. Kashikhin, I. Novitski Fermilab, Batavia, Illinois, USA
	Funding: Work is supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy Nb3Sn dipole magnets with a nominal field of 16 T and sufficient operation margins are being considered for the LHC energy upgrade or a future Very High Energy Hadron Collider. Magnet design studies are being performed in the framework of the US Magnet Development Program to explore the limits of the Nb3Sn accelerator magnet technology and feasibility of such magnets, as well as to optimize the magnet design, performance parameters and cost. This paper describes the conceptual design of a 17 T dipole magnet with 60 mm aperture and 4-layer cos-theta coil being developed at Fermilab. The results of magnetic and mechanical analyses, including the non-linear effects in magnetic field and the possible stress management techniques, are also presented and discussed.
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WEPML028	NEG Coated Vacuum Chambers and Bake-Out-Concept for the HESR at FAIR	2745
	H. Jagdfeld, N.B. Bongers, J. Böker, P. Chaumet, F.M. Esser, F. Jordan, F. Klehr, G. Langenberg, D. Prasuhn, L. Semke, R. Tölle FZJ, Jülich, Germany A. Mauel, G. Natour, U. Pabst Forschungszentrum Jülich GmbH, Central Institute of Engineering, Electronics and Analytics, Jülich, Germany
	The High-Energy Storage Ring (HESR) is part of the international Facility for Antiproton and Ion Research (FAIR) at GSI Darmstadt. Forschungszentrum Jülich (IKP and ZEA-1) is responsible for the design and installation of the HESR. The HESR is designed for antiprotons and heavy ion experiments as well. Therefore the vacuum is required to be 10-11 mbar or better. To achieve this extreme high vacuum (XHV), NEG coated chambers will be used in combination with common vacuum pumps to reach the needed pumping speed and capacity everywhere in the accelerator ring. For activation of the NEG material a bake-out system will be developed and installed. A bake-out test bench was used for checking the achievable end pressure and developing the bake-out system for the NEG coated chambers of the HESR. The results of the tests and the bake-out concept including the layout of the control system are presented. In addition, the temperature distribution of the dedicated heater jackets inside the dipole and quadrupole magnets are shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML028
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WEPML029	Vacuum System of the HESR at FAIR, Status of Tests, Layout and Manufacturing	2748
	F.M. Esser, N.B. Bongers, J. Böker, P. Chaumet, R. Gebel, R. Greven, S. Hamzic, H. Jagdfeld, F. Klehr, B. Laatsch, G. Langenberg, D. Marschall, A. Mauel, G. Natour, D. Prasuhn, L. Reifferscheidt, M. Schmitt, L. Semke, R. Tölle FZJ, Jülich, Germany
	The Research Center Jülich is leading a consortium being responsible for the design and manufacturing of the High-Energy Storage Ring (HESR) which is part of the FAIR project in Darmstadt, Germany. The HESR is designed for antiprotons within a momentum range of 1.5-15 GeV/c but can also be used for heavy ion experiments. Therefore the vacuum quality is expected to be 10-11 mbar or better which is a great challenge on the overall vacuum layout as well as on the surface quality of the chambers and beam tubes. Whereas all bent dipole chambers are installed, the manufacturing of the pumping bodies with integrated RF meshes as well as several diagnostic chambers are in the focus of investigation. To validate the intended pumping concept of both the bake-out arc sections and the non-bakable straight sections, final tests at the operational test benches are planned. In parallel, the purchasing of valves and first pumps will be prepared. The actual layout of the HESR vacuum system and its components will be presented as well as the progress of manufacturing of several vacuum chambers. The latest experimental test results will be presented also.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML029
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WEPML030	First Tests of the Main Quadrupole and Corrector Magnets for the SIS100 Synchrotron of FAIR	2751
	E.S. Fischer, A. Bleile, V.I. Datskov, V.M. Marusov, J.P. Meier, C. Omet, P.J. Spiller, K. Sugita GSI, Darmstadt, Germany P.G. Akishin, V.V. Borisov, H.G. Khodzhibagiyan, S.A. Kostromin, D.N. Nikiforov, M.M. Shandov, A.V. Shemchuk JINR, Dubna, Moscow Region, Russia
	The heavy ion synchrotron SIS100 is the main accelerator of the FAIR complex (Facility for Antiproton and Ion Research) in Darmstadt, Germany. Currently the construction site and facility are advancing fast. The series production of the main dipoles was already started in 2017. In parallel, the first two quadrupoles, a chromaticity sextupole and a steerer were built and tested in cooperation between GSI and JINR at the cryogenic test facility in Dubna. We present the operation performance of these two first of series quadrupole units (consisting both of a corrector magnet mechanically and hydraulically combined with a quadrupole). Besides the thermal stability of the fast ramped superconducting magnets special attention is directed to their magnetic field properties. The obtained results provide the basis for starting the series production of all SIS100 quadrupole and corrector magnets in 2018.
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WEPML031	The New Broadband Accelerating System for the SIS18 Upgrade at GSI	2755
	P. Hülsmann, R. Balß, H. Klingbeil, U. Laier, K.-P. Ningel, C. Thielmann, B. Zipfel GSI, Darmstadt, Germany
	In this contribution, a new SIS18 rf accelerating system is presented whose cavities are based on magnetic alloy materials. The rf system works at harmonic number h=2 (f=0,43- to 2,8 MHz) and provides the necessary accelerating voltage (up to 50kVp) for SIS18 injector operation for FAIR with high intensity heavy ion beams in a fast operation mode with up to three cycles per second. The paper focusses on the cavity part and its cooling issues as well as the broadband characteristics. Due the lossy magnetic alloy ring core filling, which consists of high permeability Finemet FT3M ring cores (HITACHI), the cavities show a broadband behaviour and thus no cavity tuning during the acceleration ramp is necessary. To keep the bandwidth of the cavities as broad as possible they are cooled by a special mineral oil with low permittivity. Also the beam impedance and the power consumption of the rf system are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML031
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WEPML032	The FAIR-SIS100 Bunch Compressor RF Station	2759
	H.G. König, R. Balß, P. Hülsmann, H. Klingbeil, P.J. Spiller GSI, Darmstadt, Germany R. Gesche, J.H. Scherer Aurion Anlagentechnik GmbH, Seligenstadt, Germany A. Morato, C. Morri, G.T. Taddia OCEM, Valsamoggia, Italy
	In the frame of the Facility for Antiproton and Ion Research (FAIR) 9 bunch compressor RF stations were ordered for the first stage of realization of the SIS100 synchrotron. For RF gymnastics referred to as bunch rotation, one RF station has to provide a sudden rise in gap voltage of up to 40 kVp within less than 30 μs. The system is designed for a maximum RF burst of 3 ms per second. The RF frequency will be pre-selectable between 310 kHz and 560 kHz at a harmonic number of h=2 with respect to the beam. Compressed bunches with a peak current > 150 A and a width < 50 ns are the goal. For this purpose, a 1.218 m long cavity was designed using iron-based magnetic alloy cores. Variable vacuum capacitors are attached for tuning. The cavity is driven by a cross-coupled push-pull tetrode amplifier. This scheme minimizes the influence of the tetrode's DC current at the working point to the cores. The energy for the pulsed system is stored in a relatively small capacitor bank which will be charged semi-continuously and a voltage-stabilizing device is added. Cavity and power amplifier were realized by AURION Anlagentechnik GmbH ' the power supply unit is designed and built by OCEM Power Electronics.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML032
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WEPML033	The FAIR-SIS100 Accelerating RF Station	2762
	H.G. König, R. Balß, H. Klingbeil, U. Laier, D.E.M. Lens, P.J. Spiller GSI, Darmstadt, Germany G. Blokesch, F. Wieschenberg Ampegon PPT GmbH, Dortmund, Germany K. Dunkel, M. Eisengruber, J.H. Hottenbacher RI Research Instruments GmbH, Bergisch Gladbach, Germany C. Hiltbrunner Ampegon AG, Turgi, Switzerland
	For the Facility for Antiproton and Ion Research (FAIR) 14 ferrite loaded accelerating RF stations are planned for the first stage of realization of the SIS100 synchrotron. Each RF station has to provide a total peak gap voltage of up to 20 kVp in CW operation - tuneable in the range of 1.1 MHz up to 3.2 MHz to allow ion beam acceleration and beam gymnastics at different harmonic numbers and energy levels in the new facility. Each RF station consists of a tuneable ferrite cavity, a single ended tetrode amplifier and a dedicated power supply and control unit (PSU) ' including two bias current supplies for cavity- and control-grid(G1)-circuit-tuning. The ferrite cavity is based on the SIS18 cavity concept but has to provide a 1.25 times higher gap voltage of 20 kVp over a total length of 3 meters. The realization is done by a consortium consisting of RI Research Instruments GmbH as consortium leader and manufacturer of the cavity, Ampegon PPT GmbH (for the tetrode amplifier) and Ampegon AG (for the power supply unit). In this contribution, the system design is discussed, and commissioning results are presented. All main parameters are achieved with the RF station described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML033
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WEPML034	Design and Commissioning of the RF System of the Collector Ring at FAIR	2765
	U. Laier, R. Balß, A. Dolinskyy, P. Hülsmann, H. Klingbeil, T. Winnefeld GSI, Darmstadt, Germany G. Blokesch, F. Wieschenberg Ampegon PPT GmbH, Dortmund, Germany K. Dunkel, M. Eisengruber, J.H. Hottenbacher RI Research Instruments GmbH, Bergisch Gladbach, Germany C. Morri, M.P. Pretelli, G.T. Taddia OCEM, Valsamoggia, Italy
	The Collector Ring (CR), a storage ring intended to perform efficient cooling of secondary beams, is under construction at GSI in the scope of the FAIR project. The RF system of the CR has to provide a frequency range from 1.1 to 1.5 MHz and pulsed gap voltages of up to 200 kVp (0.2 to 1 Hz, max. 10-3 duty cycle) and up to 10 kVp in CW operation. Five identical RF stations will be built. Each RF station consists of an inductively loaded cavity, a tetrode based power amplifier, a semiconductor driver amplifier, a switch mode power supply and two digital feedback loops. The main components of the RF station are designed, built and commissioned in close collaboration between GSI and three companies: RI Research Instruments GmbH, Ampegon PPT GmbH and OCEM Energy Technology SRL. In 2016, the first of five RF stations has been integrated at GSI. In 2017 the system was successfully commissioned to demonstrate that all envisaged parameters have been achieved. This contribution will present the requirements imposed the system, the principal design of the overall system as well as of its key components, and the results of the commissioning of the first RF station.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML034
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WEPML035	Superconducting Dipoles for SIS100	2768
	C. Roux, P. Aguar Bartolome, A. Bleile, E.S. Fischer, G. Golluccio, F. Kaether, J. Ketter, J.P. Meier, A. Mierau, C. Omet, P.J. Spiller, K. Sugita, P.B. Szwangruber, A. Warth, H.G. Weiss GSI, Darmstadt, Germany
	The international facility for antiproton and ion research (FAIR) is currently being developed in Darmstadt, Germany, for fundamental research in various fields of modern physics. Its main accelerator, the SIS100 heavy ion synchrotron, utilizes fast-cycling superconducting magnets operated at cryogenic temperatures. An intense measurement program of first of series (FoS) module revealed excellent behaviour with respect to, e.g., quench performance and AC losses. With an optimized fabrication technique, the geometrical accuracy was improved to be sufficient to provide a highly homogeneous field. Consequently, the series production of 110 dipoles was released. First significant results on the reproducibility and the variation of physical properties along the series production gained at the test facility of GSI are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML035
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WEPML036	Truncated Cosine Theta Magnet and the Applications	2772
	K. Sugita, E.S. Fischer, P.J. Spiller GSI, Darmstadt, Germany
	Typically septum magnets are designed with a combination of a C-shape iron yoke and a copper cable. Due to leakage of a magnetic field at a circulating beam passing through a saturated iron area, high field septum magnets with this concept is not feasible. Thus, this conventional design approach is limited magnetic field strength below 2 Tesla. For high energy machines, like SIS300 at FAIR or FCC at CERN, high field septum magnets are required to shorten the injection and extraction branch lines. Recently superconducting magnets, which enable to reduce the size of a building, are being introduced to medical accelerators. However, even if bending magnets are replaced by high field magnets, long straight sections, which is partly composed by a conventional septum magnet, remain. By introducing high field septum magnets, more compact accelerator can be designed. To get over the limitation of 2 Tesla, a novel concept of a septum magnet generating high magnetic field has been developed and design studies are ongoing. By using superconducting technology, a septum magnet can be designed to generate more than 2 Tesla. We present the concept and various application for the accelerators.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML036
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WEPML038	Plasma Window as a Pressure Valve for FAIR	2776
	B. F. Bohlender, M. Iberler, J. Jacoby IAP, Frankfurt am Main, Germany A. Michel Goethe Universität Frankfurt, Frankfurt am Main, Germany
	Funding: Funded by BMBF, Ref. No: 05P15 RFRBA and HIC for FAIR This contribution shows the progress in the development of a plasma window at the institute for applied physics at Goethe University Frankfurt. A plasma window* is a membrane free transition between two regions of different pressure, enabling beam transmission from a rough vacuum area (~1 mbar) to a higher pressure (up to 1 bar) region on short length scales. In comparison to differential pumping stages a length reduction by a factor of up to 100 is achievable, while the absence of a solid membrane yields prolonged operation time. The sealing effect is based on the high temperature arc discharge sustained in a cooled copper channel between the pressure regimes. Due to a bulk temperature around 10,000K** the viscosity of the gas is dramatically increased, leading to a slower gas flow, enabling a higher pressure gradient. This contribution will present first results regarding the pressure gradient in dependence of the discharge current and the aperture. Until now, a pressure factor around 100 has been established for well over 50 min. This contribution goes along with the one from Mr. A. Michel, he focuses on the spectroscopic analysis of the arc plasma. *A. Hershcovitch, J. Appl. Phys., AIP Publishing (1995) 78, 5283 **Y.E. Krasik et al., "Plasma Window Characterization", J. Appl. Phys., AIP Publishing (2007) 101, 053305.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML038
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WEPML039	Design of the Two-Gap Superconducting Re-Buncher	2779
	M. Gusarova, W.A. Barth, S. Yaramyshev MEPhI, Moscow, Russia W.A. Barth, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth, M. Miski-Oglu HIM, Mainz, Germany M. Basten, M. Buschpresenter IAP, Frankfurt am Main, Germany M. Gusarova JINR, Dubna, Moscow Region, Russia
	A new design of a spoke cavity for low relative velocities of heavy ions has been elaborated. Simulation results for a 2-gap spoke cavity with a resonance frequency of 216.816 MHz and a relative velocity of 0.07с are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML039
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WEPML040	Further Tests on the Final State of the SC 325 MHz CH-Cavity and Coupler Test Bench Update	2783
	M. Busch, M. Basten, J. List, P. Müller, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany W.A. Barth, J. List GSI, Darmstadt, Germany W.A. Barth HIM, Mainz, Germany W.A. Barth MEPhI, Moscow, Russia
	Funding: Work supported by BMBF Contr. No. 05P15RFBA At the Institute for Applied Physics, Goethe-University Frankfurt, a sc 325 MHz CH-cavity has been developed and successfully tested up to 14.1 mV/m and has now reached the final production stage with the helium vessel welded to the frontal joints of the cavity and final processing steps have been performed. Further tests in a vertical and horizontal environment are being prepared for intensive studies. This cavity is a prototype for envisaged beam tests with a pulsed ion beam at 11.4 AMeV. In this contribution the results of the performed RF tests are being presented. Furthermore, first measurements of the recently installed 217 MHz coupler test bench are shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML040
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WEPML041	Comparative Study of Low Beta Multi-Gap Superconducting Bunchers	2786
	K.V. Taletskiy, W.A. Barth, M. Gusarova, S. Yaramyshev MEPhI, Moscow, Russia W.A. Barth, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth, M. Miski-Oglu HIM, Mainz, Germany M. Basten, M. Buschpresenter IAP, Frankfurt am Main, Germany M. Gusarova JINR, Dubna, Moscow Region, Russia
	The results of a comparative study of low beta multi-gap superconducting bunchers for 216.816 MHz and a relative velocity of 0.07с with dedicated limitations of the overall geometrical dimensions are presented. A comparison of electrodynamic, mechanical and thermal properties of 3-gap and 2-gap cavities is shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML041
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WEPML043	RF Simulations of the Injector Section from CH8 to CH15 for MYRRHA	2790
	P. Müller, M. Busch, H. Hähnelpresenter, K. Kümpel, D. Mäder, N.F. Petry, H. Podlech IAP, Frankfurt am Main, Germany
	Funding: Work supported by the EU Framework Programme H2020 662186 (MYRTE) and HIC for FAIR MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) is the first prototype of an accelerator driven nuclear reactor dealing with the transmutation of long-living nuclear waste. Beam quality and reliability are crucial for the reactor. The injector design is done by IAP, Goethe-University, and has been adapted to the final magnet design and voltage distributions. The energy section from 5.87 MeV up to 16.6 MeV has been changed to normal conducting CH cavities as in the lower energy part of the injector. For beam adjustment a 5-gap CH cavity rebuncher at 5.87 MeV as well as two doublet magnets forming the new MEBT-2 section between CH7 and CH8 have been added. Starting parameters for the RF simulations have been given by beam dynamics results calculated with LORASR. RF simulations of these structures consisting of flatness and tuning optimizations will be presented within this contribution.
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WEPML044	Design of HOM Couplers for Superconducting 400 MHz RF Cavities	2793
	N.F. Petry, M. Busch, K. Kümpel, O. Meusel, H. Podlech IAP, Frankfurt am Main, Germany
	The Future Circular Collider (FCC) is one possible future successor of the Large Hadron Collider (LHC). The proton-proton collider center-of-mass collision energy is set to 100 TeV with a beam current of 0.5 A. To reach this goal a stable acceleration is critical and therefore higher order modes (HOM) need to be damped. To avoid a high power level in the HOM dampers, further described as couplers, the loaded Q-factor should be below 1000 for the cavity with mounted HOM couplers. Besides a low Q-factor the R/Q value should also be in the range of 1 Ω or below. Two different types of couplers are used to achieve a high damping. The two types are a narrowband Hook-type HOM coupler and a broadband Probe-type HOM coupler. The recent results of the design of the HOM couplers attached to a superconducting 400 MHz RF cavity will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML044
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WEPML045	Infrastructure for Superconducting CH-Cavity Preparation at HIM	2796
	T. Kürzeder, K. Aulenbacher, W.A. Barth, F.D. Dziuba, V. Gettmann, M. Miski-Oglu, E. Riehn HIM, Mainz, Germany K. Aulenbacher, R.G. Heine, T. Stengler IKP, Mainz, Germany W.A. Barth, S. Yaramyshev GSI, Darmstadt, Germany F. Hug KPH, Mainz, Germany
	A superconducting cw LINAC for heavy ions is currently under development at GSI in Darmstadt and HIM in Mainz. This Linac is based on 217 MHz multigap bulk niobium Crossbar H-mode RF-cavities. In order to treat and prepare RF-cavities with such a complex geometry a new cleanroom facility has been already built at the Helmholtz-Institut in Mainz. All tools and machines inside the cleanroom can handle cavities with up to 800 mm in diameter and with up to 1300 mm in length. In its ISO-class 6 and 4 zones, respectively it features a large ultrasonic and conductance rinsing bath, a high pressure rinsing (HPR) cabinet and a vacuum oven. The HPR cabinet has an inside clearance of 1.4 m. The large cavities sit on a rotating table, while the rising wand moves vertically up and down. Due to the crossbar structure of the RF-cavities the HPR device allows for off axis-rinsing in their quadrants. For RF testing a 52 m² (4 m x 13 m) concrete shielded area with sufficient liquid helium and nitrogen supply is located next to the cleanroom and the cryo-module assembly area. We will report on the new SRF infrastructure in Mainz and the commissioning of the new high pressure rinsing cabinet.
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WEPML046	Multipactor Discharge in Superconducting Accelerating CH Cavities	2800
	M. Gusarova, D. I. Kiselev MEPhI, Moscow, Russia F.D. Dziuba, T. Kuerzederpresenter, M. Miski-Oglu HIM, Mainz, Germany M. Gusarova JINR, Dubna, Moscow Region, Russia
	The results of numerical simulations of multipacting discharge in a superconducting accelerating CH cavity are presented in this paper. The localization of multipactor trajectories in the 15-gap 217 MHz superconducting (sc) CH cavity at various levels of accelerating voltage is considered.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML046
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WEPML047	Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module	2804
	A.V. Tsakanian, T. Mertens Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany H.-W. Glockpresenter, J. Knobloch, M. Ries, A.V. Vélez HZB, Berlin, Germany
	The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring with the standard user optics. This challenging goal requires installation of four new SRF multi-cell cavities (2x1.5GHz and 2x1.75GHz) equipped with strong waveguide HOM dampers ensuring tolerable beam coupling impedance, necessary for stable operation. These cavities will operate at high 20MV/m in CW mode and at the zero-crossing phase according to the accelerating voltage. Consequently the transverse voltages will be maximum and can impact the transverse beam dynamics. The asymmetric character of those transverse kicks are caused by cavity fundamental power couplers (FPC) with strong monopole terms, introducing transverse kick to on-axis particles. Different FPC orientations were analyzed to optimize the net coupler kick from the four cavity chain. The coupler kick strength of each cavity is estimated taking into account accelerating mode amplitudes and phases required for operation in VSR mode.
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WEPML048	HOM Power Levels in the BESSY VSR Cold String	2808
	A.V. Tsakanian, T. Flisgen Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany H.-W. Glockpresenter, J. Knobloch, A.V. Vélez HZB, Berlin, Germany
	The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring. This challenging goal requires installation of four new SRF cavities (2x1.5 GHz and 2x1.75 GHz) in one module for installation in a single straight. These cavities are equipped with strong waveguide HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete cold string. The cold string is a combination of various elements such as SRF cavities, bellows with and without shielding, warm HOM beampipe absorbers and UHV pumping domes. The presented study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. The contribution of each component to the total HOM power is presented. In addition the optimization of different cavity arrangements in the module is performed in order to reach the optimal operation conditions with equally distributed power levels along the string and tolerable beam coupling impedance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML048
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WEPML049	The Challenge to Measure nΩ Surface Resistance on SRF Samples	2812
	S. Keckert, T. Junginger, J. Knobloch, O. Kugeler HZB, Berlin, Germany T. Junginger Lancaster University, Lancaster, United Kingdom
	Systematic research on fundamental limits of superconducting materials for SRF applications and their intrinsic material properties relevant for use in an accelerator requires studies in a wide parameter space of temperature, RF field and frequency. The Quadrupole Resonator at HZB enables precision measurements on planar samples at temperatures of 1.8 K to >20 K, RF fields of up to 120 mT, and frequencies of 420 MHz, 850 MHz and 1285 MHz. In the past years the capabilities of the setup were studied intensively and developed further. Sources of systematic errors, such as microphonics or misalignment have been identified and eliminated. In this contribution the current status of the QPR and its systematic limitations are discussed.
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WEPML051	Improvement of the Chopper System for rf Deflector at the J-PARC Linac	2816
	K. Futatsukawa, Z. Fangpresenter, Y. Fukui KEK, Ibaraki, Japan Y. Sato Nippon Advanced Technology Co., Ltd., Tokai, Japan S. Shinozaki JAEA/J-PARC, Tokai-mura, Japan
	In the J-PARC linac, the RF deflector has been operated to kick the wasted beam and to shape the intermediate-pulse like the comb structure. Then about 50% of the beam current is removed by leading the scraper and the rest beam current is injected to the downstream synchrotron ring RCS. The fast rising time and falling time, the cavity with low loading Q value in the chopper system are required to decrease the incomplete kicked beam. However, there was the ringing of the RF field on the chopper cavity, and it influenced the beam rising time. The chopper controllers, which has the fast RF -switch to make the particular RF according to the intermediate-pulses, were improved for the RF falling time by outputting short pulses with inverting phase. The beam study for the new system was successfully done. In this paper, I would like to introduce this system and to show the results of the beam study.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML051
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WEPML053	Availability of the TiN Coating-Free Ceramic in the STF-type Power Coupler for ILC	2819
	Y. Yamamoto, E. Kako, T. Matsumotopresenter, S. Michizono, A. Yamamoto KEK, Ibaraki, Japan M. Irikura, M. Ishibashi, H. Yasutake Toshiba Electron Tubes & Devices Co., Ltd (TETD), Tochigi, Japan C. Julie, E. Montesinos CERN, Geneva, Switzerland
	In the Superconducting RF Test Facility (STF) in KEK, the research and development for the power coupler with the TiN coating-free ceramic has been done from 2014. In 2016, the high power test at the test bench was stopped due to the worse vacuum level by the unusual heating around the RF window with the TiN coating-free ceramic and the coaxial tapered section, which was caused by the enormous emission of the secondary electrons from the ceramic. And, the situation was never also changed by the ultrapure water rinsing for the power couplers several times. However, in 2017, the ultrasonic rinsing was done for the power couplers for the first time by the collaboration between KEK and TETD. After that, the situation was drastically improved, and the secondary electron emission almost disappeared even in the higher RF duty. This shows that the TiN coating-free ceramic is the prospective item for the cost reduction in ILC. In this report, the recent result for the power coupler with the TiN coating-free ceramic will be presented in detailed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML053
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WEPML055	Simulation Study of Parasitic-Mode Damping Methods for a 1.5-GHz TM020-Mode Harmonic Cavity	2822
	N. Yamamoto, S. Sakanaka, T. Takahashi KEK, Ibaraki, Japan
	Design study of parasitic-mode (PM) damped structures has been conducted for the purpose to realize a normal conducting 1.5 GHz harmonic cavity which is based on the TM020 resonant mode*. We have investigated the performances of two PM-damping mechanisms, that are, rod-type antennas** and annular slots. The rod-type antennas locate at the node of electric field of the TM020 mode while the annular slots locate at the node of magnetic field. As a result of 3D electromagnetic simulations, suitable performances of PMs were confirmed by employing either of the PM-damping mechanisms. It was also shown that the slot-type structure is superior in PM-damping performance and in the unloaded Q of the TM020 mode. * N. Yamamoto et al., IPAC'17, paper THOPIK037; N. Yamamoto Phys. Rev. Accel. Beams, 21, 1, 012001. ** T. Takahashi et al., IPAC'17, paper THPIK036.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML055
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WEPML057	First Commissioning of Vacuum System of Positron Damping Ring for SuperKEKB	2826
	K. Shibata, H. Hisamatsu, T. Ishibashi, K. Kanazawa, M. Shirai, Y. Suetsugupresenter, S. Terui KEK, Ibaraki, Japan
	To satisfy the requirements of high beam quality for positron injection into the SuperKEKB main ring, a new damping ring (DR) is constructed in an upgraded injector system. The DR is a racetrack-shaped storage ring with a circumference of 135.5 m, in which the 1.1 GeV positron beam is stored for 40 ms to damp the emittance. The maximum stored beam current is 70.8 mA. Required beam lifetime due to residual gas scattering is longer than 1000 s and the average pressure should be lower than 10-5 Pa. Non-evaporable getter (NEG) pumps are mainly used, and the average effective pumping speed for CO is expected to be 0.013 m3s−1m-1 immediately after NEG activation. The beam pipes are made of aluminum alloy, and have antechambers to deal with synchrotron radiation (critical energy 0.8-0.9 keV, total power 7.2 kW) in arc sections, which are effective in reducing the electron cloud and the impedance of the beam pipes. As additional countermeasures against the electron cloud effect, TiN coating and grooved surfacing are also adopted. The commissioning of the DR will commence at the beginning of 2018. The status of the vacuum system of the DR during the first commissioning will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML057
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WEPML058	Observation of Pressure Bursts in the SuperKEKB Positron Ring	2830
	S. Terui, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, Y. Suetsugupresenter KEK, Ibaraki, Japan
	The SuperKEKB is an electron-positron collider with asymmetric energies in KEK aiming an extremely high luminosity of 8x1035 cm-2 s-1 using a nano-beam scheme. In the Phase 1 commissioning from February to June, 2016, the vacuum system of the main ring worked well as a whole at stored beam currents of approximately 1 A. However, the localized pressure bursts accompanied by beam losses were observed in the positron ring. The beam loss monitors triggered beam aborts, and the phenomena has became an obstacle to the beam commissioning. These pressure bursts were frequently observed from the early stage of the commissioning. Most of the pressure bursts occurred near or inside of aluminum-alloy beam pipes in dipole magnets, which have grooved surface at the top and bottom sides. The various observations indicates that the most probable cause of this phenomenon was the collision between the dusts dropped from the grooves and the circulating positron beam. We report the properties and the probable causes of the pressure bursts, and the possible mitigation methods. Some results of the countermeasures taken prior to the ongoing Phase-2 commissioning will be also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML058
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WEPML059	Status of the SuperKEKB Vacuum System in the Phase-2 Commissioning	2833
	Y. Suetsugu, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, S. Terui KEK, Ibaraki, Japan
	The SuperKEKB is an electron-positron collider with asymmetric energies in KEK aiming an extremely high luminosity of 8.0·1035 /cm2/s. In the Phase-1 commissioning from February to June, 2016, the vacuum system of the main ring worked well as a whole at stored beam currents of approximately 1 A. However, several problems were found for the future commissioning, and various countermeasures were taken against these problems during the shutdown period before starting the Phase-2 commissioning. For example, permanent magnets were placed around the beam pipe to suppress the electron cloud effect in the positron ring. Other than these works, new beam pipes for the collision point, the super-conducting final focusing magnets and the positron beam injection region were installed in the main ring. Additional six beam collimators were installed for reducing background noise of the particle detector. Furthermore, the vacuum system for new damping ring for the positron beam was constructed. Reported here will be the present status of the vacuum system of the main ring, and major results of the countermeasures taken prior to the Phase-2 commissioning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML059
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WEPML060	Yb/Nd Doped Hybrid Solid Laser of RF Gun and Beam Commissioning for Phase-II of SuperKEKB	2836
	R. Zhang, T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou KEK, Ibaraki, Japan
	For SuperKEKB project schedule of the phase-II, low emittance 1 nC electron beams were required with good stability and reliability at end of the linac. In the injector linac, several instruments have been installed. An Nd/Yb hybrid laser system is development with two beam lines light source. The both side of quasi-traveling wave side coupled cavity S-band RF gun were injected by the two sub μJ UV picosecond laser pulses at same times. And beam commissioning with the RF gun is in progress.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML060
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WEPML064	Design of the Trim Coil for the Superconducting Cyclotron Extraction	2840
	L.G. Zhang, K. Fan, S. Hu, Z.Y. Mei, Z.J. Zeng HUST, Wuhan, People's Republic of China
	A proton therapy system is being developed at Huazhong university of science and technology (HUST). A 250 MeV superconducting cyclotron with an average magnetic filed of 3.1 T in the extraction region is selected to reduce the machine size, which creates difficulties for beam extraction because of the small turn separation of the beam orbits in the extraction region. To obtain high extraction efficiency, a carefully controlled magnetic perturbation is introduced to excite resonance when beam passes through the νr =1 resonance. The first-order perturbation in the magnetic field is generated by trim coils within confined regions. The profile of the trim coil and the resultant perturbation fields are optimized iteratively with orbit tracking. Simulation shows that sufficient turn separation can be obtained with the proper setting of trim coils.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML064
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WEPML067	Second Sound Quench Detection on Superconducting Cavities	2843
	Z.C. Liu, S. Baipresenter, J. Gao, F.S. He, H.Y. Lin, P. Zhang IHEP, Beijing, People's Republic of China
	Second sound is an effective way to detect the quench position on superconducting cavity. A second sound quench site detection system is under developing for the PAPS. High gradient is very important for superconducting cavity, however it may be limited by quench on the cavity high field region. Quench can be caused by various reasons. To locate the position is the key to reveal the mysteries of quench. Now we are developing the quench position detection system by RTD sensors such as Cernox and OST sensors.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML067
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WEPML069	Fast Kicker and Pulser R&D for the HEPS on-Axis Injection System	2846
	H. Shi, J. Chen, Z. Duanpresenter, L. Huo, P. Liu, X.L. Shi, G. Wang, L. Wang, N. Wang IHEP, Beijing, People's Republic of China
	The HEPS plans to adopt on-axis injection scheme because the dynamic aperture of machine is not large enough for off-axis injection for its baseline 7BA lattice design. A sets of super fast kicker and pulser of ±15kV amplitude, 15ns pulse bottom width are needed for bunch spacing of 10ns to minimize perturbation on adjacent bunches. To achieve these requirement, a multifaceted R&D program including the strip-line kicker and HV pulser, was initiated last 2 years. So far, the prototype development of a 750mm long strip-line kicker and a DSRD pulser was completed and the preliminary test results show they can meet the baseline requirement of the HEPS.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML069
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WEPML070	The Status of the CSNS/RCS Power Supply System	2850
	X. Qi, Z. Hao, W. Zhang IHEP, Beijing, People's Republic of China
	The 1.6GeV proton synchrotron proposed in the CSNS Project is a 25Hz rapid-cycling synchrotron (RCS) with injection energy of 80MeV. Beam power is aimed to 100kW at 1.6GeV. In this year, the neutron beam was successfully obtained for the first time. This paper will introduce the commission statues of RCS Power Supply System status in the last year.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML070
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WEPML071	Superconducting 16-Pole Wiggler for Beijing Electron-Positron Collider II	2853
	M.X. Li, X.J. Bian, F.S. Chen, W. Chen, X.J. Sun, H. Wangpresenter, J.L. Wang, N. Wang, M.F. Xu, X.C. Yang IHEP, Beijing, People's Republic of China
	A superconducting 16-pole 2.6T wiggler with period 170mm of The High-Energy Photon Source and the Test Facility Project (HEPS-TF) designed and fabricating in the Institute of High Energy Physics (IHEP) in China is described. This wiggler will be installed in Beijing Electron-Positron Collider II (BEPCII). The main parameters and structure of the wiggler are presented. Besides, some vertical testing results are involved.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML071
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WEPML072	Gas Permeability Measurement of Graphene Films	2856
	P.C. Wang, X. Sun DNSC, Dongguan, People's Republic of China Liu. S. Liu Institute of High Energy Physics (IHEP), People's Republic of China C. Meng, H. Wangpresenter, D.H. Zhu IHEP, Beijing, People's Republic of China
	Graphene has extremely high strength and thermal conductivity, which can possibly be used for high-power beam window in accelerator. In this paper, gas permeabilities of different graphene films have been measured by the permeation measurement facility. According to the results, the possibility of the graphene-made beam windows will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML072
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WEPML073	Research on Magnetic Center Measurement of Quadrupole and Sextupole Using Vibrating Wire Alignment Technique in HEPS-TF	2860
	L. Wu, C. H. Li, H. Qu, H. Wangpresenter, X.L. Wang IHEP, Beijing, People's Republic of China H.Y. Zhu Institute of High Energy Physics (IHEP), People's Republic of China
	In order to meet the extremely low emittance re-quirement, the magnets in the storage ring of High Energy Photon Source(HEPS) need to have a stable support and precise positioning. Vibrating wire align-ment technique can be used to pre-align the quadru-poles and sextupoles on one girder with high preci-sion. Research of vibrating wire alignment technique is one important project of HEPS Test Facility (HEPS-TF). In HEPS-TF, the key and difficult technologies of HEPS should be researched and developed. This paper introduces the principle of the vibrating wire align-ment technique and the measurement system in brief. The magnetic center measurement of quadrupole and sextupole using vibrating wire will be introduced in detail. It concludes the measurement procedure, mag-netic field distribution, measurement repeatability, sag correction and magnet adjustment measurement. The research of vibrating wire has get a better precision than the aim. The magnetic center measurement preci-sion reach to ±3μm and the magnet adjustment error is less than 6μm.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML073
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WEPML075	Test of Magnet Girder Prototypes for HEPS-TF	2863
	H. Wang, C. H. Li, S.J. Li, J. Liu, H. Qu, Z. Wang, L. Wu IHEP, Beijing, People's Republic of China H.Y. Zhu Institute of High Energy Physics (IHEP), People's Republic of China
	Auto-tuning magnet girder is one of the key technolo-gies to be solved for HEPS-TF (Test Facility of High Ener-gy Photon Source). The girder should have high adjusting accuracy, high stability and can be beam-based aligned, to obtain the stability requirements of beam orbit. There are two girders developed, and the tests have been done. The accuracy of girder motion is within 10 microns while the adjusting range is 1 mm and the resolution is better than 1 microns, the natural frequency is higher than 24 Hz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML075
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WEPML076	The Magnetic Measurement of Enhancer-Dipole Magnet for CEPC	2866
	Z. Zhang, H. Wangpresenter IHEP, Beijing, People's Republic of China
	The CEPC (Circular Electron Positron Collider) project is in the pre-research stage. When the beam energy of booster is 120 GeV, the magnetic field of deflection magnet is 640 Gs. In order to save funds for scientific research, we also consider the injection energy of 6 GeV, the magnetic field of deflection magnet is 32 Gs. At the different current, the magnetic field value of the enhancer-dipole magnet can reach the beam energy range of 6 Gev-120 GeV. In such a requirements of magnetic field, the stability of the magnetic field value, repeatability, magnet magnetism, has become an important data for the design parameters of enhancer-dipole magnet. The magnet is measured with the Hall-Probe measurement facility by IHEP. In this paper, first written the procedure of motor control and collection by Labview software, then hen the excitation curve（repeat the measurement six times）, transverse field distribution（repeat the measurement three times）, and integral field distribution are measured. Based on the results of the analysis of large amounts of data, the stability and repeatability of the enhance-dipole magnet in different magnetic fields has summarized and analyzed.
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WEPML078	Development of a Superconducting Double-Spoke Cavity at IMP	2869
SUSPL071	use link to see paper's listing under its alternate paper code
	T.C. Jiang, H. Guo, Y. He, C.L. Li, L.B. Liu, T. Tan, P.R. Xiong, Z.M. You, W.M. Yue, S.H. Zhang, S.X. Zhang IMP/CAS, Lanzhou, People's Republic of China
	Superconducting multi-spoke cavities are well-known optional choice for acceleration of heavy ions in medium velocity regimes. The paper describes the design, fabrication and test results of the superconducting double-spoke cavity developed at IMP. After Buffered Chemical Polishing and High pressure Rinsing, one cavity has undergone high gradient RF testing at 4 K in the Vertical Test Stand. We present measurements of the quality factor as a function of accelerating field and maximum field on the surface. Accelerating gradient of more than 15 MV/m is reached with peak electric field of 61 MV/m, and peak magnetic field of 118 mT.
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