IPAC2017 - List of Keywords (HOM)

Paper	Title	Other Keywords	Page
MOPVA051	Design of the High Power 1.5 GHz Input Couplers for BESSY VSR	coupling, cavity, operation, simulation	978
	E. Sharples, M. Dirsat, J. Knobloch, A.V. Vélez HZB, Berlin, Germany
	The Variable pulse length Storage Ring (BESSY VSR) upgrade to BESSY II at Helmholtz-Zentrum Berlin (HZB) requires an upgrade on the RF systems in the form of high-voltage longitudinally focusing super conducting RF cavities of 1.5 GHz ad 1.75 GHz. For operation, coaxial RF power couplers capable of handling 13 kW peak power at standing wave operation are required for both the 1.5 GHz and 1.75 GHz cavities. The coupler is based on a design by Cornell University with modifications to suit frequency and coupling requirements. The coupler is intended to provide variable coupling with a range of Qext from 6x10⁶ to 6x10⁷ to allow flexibility to adjust to operating conditions of BESSY VSR. Here we present the RF design of the high-power coaxial coupler for BESSY VSR along with the design of the test stand for conditioning a pair of couplers.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA051
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MOPVA052	Study on HOM Power Levels in the BESSY VSR Module	cavity, SRF, operation, resonance	982
	A.V. Tsakanian, H.-W. Glock, 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 of long (ca. 15ps) and short (ca. 1.5ps) bunches in the storage ring with the 'standard' user optics. This challenging goal requires installation of four new SRF cavities (2x1.5GHz and 2x1.75GHz) in a single module to minimize space requirements. These cavities are equipped with strong waveguide and beam tube HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete module. This study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. In the module different cavity arrangements are analyzed to reach the optimal operation conditions with equally distributed power portions in warm HOM loads and tolerable beam coupling impedance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA052
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MOPVA053	The SRF Module Developments for BESSY VSR	cavity, synchrotron, damping, SRF	986
	A.V. Vélez, H.-W. Glock, F. Glöckner, B.D.S. Hall, J. Knobloch, A. Neumann, P. Schnizer, E. Sharples, A.V. Tsakanian HZB, Berlin, Germany
	Helmholtz-Zentrum Berlin is developing BESSY VSR, a novel upgrade of the BESSY II facility to provide highly flexible pulse lengths while maintaining the flux and brilliance. The project goal is to simultaneously circulate both standard (some 10 ps long) and short (ps and sub-ps long) pulses offering the BESSY user community picosecond dynamics and high-resolution experiments. The concept relies on the installation of high-voltage SRF cavities operating at the 3rd and 3.5th harmonic whereby the beating of the two frequencies provides RF buckets for long and short bunches. Since these cavities will operate in CW and with high beam current (Ib=300 mA), the cavity design represents a challenging goal. In addition the need to avoid coupled bunch instabilities (CBI's), the installation of the VSR Cryomodule must fit in one of the available 4-m long low beta straights. To address the technological and engineering challenges techniques such as waveguide-damped cavities have been developed. First prototypes have been produced. In this paper, the present SRF developments are presented, including the cavities, high power couplers, higher-order mode absorbers and the cryomodule design.
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MOPVA079	A 166.6 MHz Superconducting RF System for the HEPS Storage Ring	cavity, LLRF, SRF, injection	1049
	P. Zhang, H.X. Hao, T.M. Huang, Z.Q. Li, H.Y. Lin, F. Meng, Z.H. Mi, Y. Sun, G.W. Wang, Q.Y. Wang, X.Y. Zhang IHEP, Beijing, People's Republic of China
	Funding: This work has been supported by HEPS-TF project and partly by Pioneer 'Hundred Talents Program' of Chinese Academy of Science. A superconducting 166.6 MHz quarter-wave β=1 cavity was recently proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. Four 166.6 MHz cavities will be used for main acceleration in the newly planned on-axis beam injection scheme realized by a double-frequency RF system. The fundamental frequency, 166.6 MHz, was dictated by the fast injection kicker technology and the preference of using 499.8 MHz SC RF cavity as the third harmonic. Each 166.6 MHz cavity will be operated at 4.2 K providing 1.2 MV accelerating voltage and 150 kW of power to the electron beam. The input coupler will use single-window coaxial type graded up to 200 kW CW power. Each cavity will be equipped with a 200 kW solid-state amplifier and digital low-level RF system. This paper will describe the 166.6 MHz RF system with a focus on the design and optimization of the RF cavity and its ancillaries, the LLRF system and the status of the solid-state amplifiers.
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MOPVA080	HOM Simulations and Damping Scheme for CEPC Cavities	cavity, damping, collider, impedance	1052
	H.J. Zheng, J. Gao, F. Meng, P. Sha, J.Y. Zhai IHEP, Beijing, People's Republic of China
	In this paper, it will be presented that the higher order mode (HOM) analysis of the 650 MHz cavities for the Circular Electron-Positron Collider (CEPC). The higher order modes excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. To keep the beam stable, the impedance budget and the HOM damping requirement are given. The conventional coaxial HOM coupler, which will be mounted on the beam pipe, is planned to extract the HOM power below the cut-off frequency of the beam pipe, and the propagating modes will be absorbed by the two HOM absorbers at room temperature outside the cryomodule.
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MOPVA091	Investigation of HOM Frequency Shifts Induced by Mechanical Tolerances	cavity, simulation, operation, cryogenics	1071
	S. Pirani, M. Eshraqi, M. Lindroos ESS, Lund, Sweden A. Bosotti, J.F. Chen, P. Michelato, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy T.P.Å. Åkesson Lund University, Department of Physics, Lund, Sweden
	We present Higher Order Mode (HOM) studies on ESS Medium-Beta cavity of INFN-LASA design, including both simulation and measurement results. Mechanical tolerances of the fabrication process might shift HOMs frequencies toward harmonics of the bunch frequency. Both simulation and measurements at room and cryogenic temperature show that INFN LASA cavity is fully compatible with ESS requirements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA091
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MOPVA096	The Crab Cavities Cryomodule for SPS Test	cavity, cryomodule, vacuum, monitoring	1081
	C. Zanoni, A. Amorim Carvalho, K. Artoos, S. Atieh, K. Brodzinski, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, T. Dijoud, K. Eiler, G. Favre, P. Freijedo Menendez, M. Garlaschè, L. Giordanino, S.A.E. Langeslag, R. Leuxe, H. Mainaud Durand, P. Minginette, M. Narduzzi, V. Rude, M. Sosin, J.S. Swieszek CERN, Geneva, Switzerland T.J. Jones, N. Templeton STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	RF Crab Cavities are an essential part of the HL-LHC upgrade. Two concepts of such systems are being developed: the Double Quarter Wave (DQW) and the RF Dipole (RFD). A cryomodule with two DQW cavities is in advanced fabrication stage at CERN for their tests with protons in the SPS during the 2018 run. The cavities must be operated at 2 K, without excessive heat loads, in a low magnetic environment and in compliance with CERN safety guidelines on pressure and vacuum systems. A large set of components, such as a thermal shield, a two layers magnetic shield, RF lines, helium tank and tuner is required for the successful and safe operation of the cavities. The assembly of all these components with the cavities and their couplers forms the cryomodule. An overview of the design and fabrication strategy of this cryomodule is presented. The main components are described along with the present status of cavity fabrication and processing and cryomodule assembly. The lesson learned from the prototypes, the helium tank above all, and first manufactured systems is also included.
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MOPVA113	RF Quality Control of SRF Cavities for LCLS-II Cryo-Modules	cavity, controls, cryomodule, pick-up	1108
	M.H. Awida, P. Berrutti, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: *Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE LCLS-II project is gearing up to build 36 cryo-modules of the 1.3 GHz TESLA style cavities. Half of those cryomodules are being built at Fermilab, while JLAB is carrying the production of the other half. In this paper, we present the process of quality controlling the RF performance of cavities until they are qualified for the final string assembly at Fermilab. The RF quality control process includes monitoring the frequency spectrum of each cavity and tuning/adjusting of the notch frequencies before testing at the Vertical Test Stand (VTS). Measured data during income QC is presented and in addition we show the notch frequencies before and after testing at the VTS. Moreover, we report some of the RF measurements taken while the cavity is cooled down to 2K temperature.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA113
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MOPVA130	Development of Waveguide HOM Loads for BERLinPro and BESSY-VSR SRF Cavities	cavity, simulation, SRF, network	1160
	J. Guo, F. Fors, J. Henry, R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA H.-W. Glock, A. Neumann, A.V. Tsakanian, A.V. Vélez HZB, Berlin, Germany
	Two ongoing accelerator projects at Helmholtz-Zentrum Berlin (HZB), BERLinPro and BESSY-VSR, need to design three different SRF cavities, a 1.3GHz cavity in BERLinPro and 1.5GHz/1.75GHz cavities in BESSY-VSR. These cavities have adopted waveguide HOM dampers in their design, with a few tens of watts HOM power in each load for BERLinPro and a few hundred watts for BESSY-VSR. JLab is collaborating with HZB prototyping these HOM loads. In this paper, we will report on the integrated RF-thermal-mechanical design of the loads, as well as the fabrication and testing results.
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MOPVA135	Fabrication, Processing and RF Test of RF-Dipole Prototype Crabbing Cavity for LHC High Luminosity Upgrade	cavity, dipole, luminosity, cryogenics	1174
	S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA H. Park JLab, Newport News, Virginia, USA
	The superconducting rf-dipole crabbing cavity is one of two crabbing cavity designs proposed for the LHC high luminosity upgrade. The proof-of-principle rf-dipole cavity operating at 400 MHz has demonstrated excellent performance exceeding the design specifications. The prototype cavity for SPS beam test has been designed to include the fundamental power coupler, HOM couplers, and all the ancillary components intended to meet the design requirements. A crabbing cavity system is expected to be installed in the SPS beam line and tested prior to the installation in LHC; this will be the first crabbing cavity operation on a proton beam. The fabrication of two prototype rf-dipole cavities is currently being completed at Jefferson Lab. This paper presents the details on cavity processing and cryogenic test results of the rf-dipole cavities.
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TUPVA008	Assessment of Thermal Loads in the CERN SPS Crab Cavities Cryomodule	cavity, cryomodule, radiation, pick-up	2047
	F. Carra, J. Apeland, R. Calaga, O. Capatina, T. Capelli, C. Zanoni CERN, Geneva, Switzerland S. Verdú-Andrés BNL, Upton, Long Island, New York, USA
	Funding: Work supported by the European Union HL-LHC Project and by US DOE through Brookhaven Science Associates LLC under contract No. DE-AC02-98CH10886 and the US LHC Accelerator Research Program (LARP). Research supported by the HL-LHC project. As a part of the HL-LHC upgrade, a cryomodule is designed to host two crab cavities for a first test with protons in the SPS machine. The evaluation of the cryomodule heat loads is essential to dimension the cryogenic infrastructure of the system. The current design features two cryogenic circuits. The first circuit adopts superfluid helium at 2 K to maintain the cavities in the superconducting state. The second circuit, based on helium gas at a temperature between 50 K and 70 K, is connected to the thermal screen, also serving as heat intercept for all the interfaces between the cold mass and the external environment. An overview of the heat loads to both circuits, and the combined numerical and analytical estimations, is presented. The heat load of each element is detailed for the static and dynamic scenarios, with considerations on the design choices for the thermal optimization of the most critical components. #Federico.carra@cern.ch*
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WEPAB115	Normal Conducting CW Transverse Crab Cavity For Producing Short Pulses In SPEAR3	cavity, impedance, damping, photon	2840
	Z. Li, V.A. Dolgashev, M. Dunham, K.J. Gaffney, R.O. Hettel, X. Huang, N. Kurita, J.A. Safranek, J.J. Sebek, K. Tian SLAC, Menlo Park, California, USA
	Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515. The ability to produce short pulse X-rays on the scale of 1-10 ps fwhm in the SPEAR3 storage ring light source would enable enhanced timing mode studies of dynamic processes in materials as they occur. The crab cavity approach appears to be optimal for SPEAR3 to produce short pulse X-rays. Furthermore, by using a two-frequency crabbing scheme, SPEAR3 would be able to produce short-pulse bunches while supplying the high average flux needed for regular users. While supercon-ducting RF (SCRF) technology could be a natural choice for the CW crab cavity, the deflecting voltage for SPEAR3 crabbing appears to be within reach of more affordable normal conducting RF (NCRF). In this paper, we present a preliminary NCRF CW crab cavity design for SPEAR3.
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WEPIK009	Collimators for SuperKEKB Main Ring	impedance, background, factory, positron	2929
	T. Ishibashi, Y. Suetsugu, S. Terui KEK, Ibaraki, Japan
	SuperKEKB, which is an upgrade project of KEKB, is an electron-positron collider with extremely high luminosity. Collimators (movable masks) for SuperKEKB have been designed to fit an antechamber scheme of the vacuum system and will be operated to improve backgrounds in the particle detector named Belle II. We are developing two types of collimators; a horizontal and vertical collimator. The collimator has a pair of horizontally or vertically opposed movable jaws with RF fingers. Each jaw travels independently through 5-25 mm horizontally or 2-12 mm vertically in a distance between the beam axis and the tip of the jaw. SuperKEKB will operate with high currents of short bunch lengths, therefore it is important to estimate and decrease the impedance of the collimators. Two horizontal collimators were already installed in the positron ring and operated during Phase-1 commissioning for approximately 5 months, from February to June 2016. In this presentation, the latest design, and the results in the Phase-1 commissioning are presented.
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WEPIK054	Evaluation and Attenuation of Sirius Components Impedance	impedance, dipole, storage-ring, vacuum	3048
	H.O.C. Duarte, L. Liu, S.R. Marques LNLS, Campinas, Brazil
	The Sirius in-vacuum components have their design improvements, possibilities and choices presented, where wake heating, single-bunch and multi-bunch effects and mechanical aspects were taken into account. The results were finally evaluated and added to the Sirius impedance budget.
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WEPIK055	Analysis and Countermeasures of Wakefield Heat Losses for Sirius	impedance, simulation, vacuum, storage-ring	3052
	H.O.C. Duarte, L. Liu, S.R. Marques, T.M. da Rocha, F.H. de Sá LNLS, Campinas, Brazil
	Design evaluation and possible solutions for several in-vacuum components of Sirius are presented, having their impedance analysis focused on mitigating the wake heating impact. Thermal and/or structural simulation of the models are carried out by considering the heat load directly obtained from wakefield simulations with resistive wall boundary conditions.
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WEPVA058	Development of HOM Absorber for SuperKEKB	electron, vacuum, photon, plasma	3394
	S. Terui, T. Ishibashi, Y. Suetsugu, Y. Takeuchi, K. Watanabe KEK, Ibaraki, Japan H. Ishizaki, A. Kimura, T. Sawhata Metal Technology Co. Ltd., Ibaraki, Japan
	Higher-order modes (HOM) absorbers are necessary components for recent high-power accelerators in order to prevent beam instabilities (e.g. HOM- Beam Break Up instabilities) or the overheating of vacuum components. Several kinds of absorber materials, such as SiC, ferrite and Kanthal, have been investigated and applied in accelerators. Among these materials, ferrite has been found to be superior to others because of its higher HOM absorbing efficiency. However, because of its low tensile strength and small thermal expansion rate, it cannot be easily bonded to other metals thus limiting its use as a HOM absorber. We reported the success of the fabrication of ferrite-copper-blocks using the spark plasma sintering (SPS)-technique last year. This year we report testing with a high-power RF source and measuring gas desorption rate after baking and secondary electron yield.
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THPAB047	New Features of the 2017 SixTrack Release	simulation, electron, collimation, coupling	3815
	K.N. Sjobak, J. Barranco García, R. De Maria, E. McIntosh, A. Mereghetti CERN, Geneva, Switzerland M. Fitterer Fermilab, Batavia, Illinois, USA V. Gupta IIT, Guwahati, Assam, India J. Molson LAL, Orsay, France
	The SixTrack particle tracking code is routinely used to simulate particle trajectories in high energy circular machines like the LHC and FCC, and is deployed for massive simulation campaigns on CERN clusters and on the BOINC platform within the LHC@Home volunteering computing project. The 2017 release brings many upgrades that improve flexibility, performance, and accuracy. This paper describes the new modules for wire- and electron lenses (WIRE and ELEN), the expert interface for beam-beam element (BEAM/EXPERT), the extension of the number of simultaneously tracked particles, the new Frequency Map Analysis (FMA) postprocessing option, the generation of a single zip of selected output files (ZIPF) in order to extend the coverage of the studies in LHC@HOME (e.g. FMA and on-line aperture checks), coupling to external codes (DYNK-PIPE and BDEX), a new CMAKE based build- and test mechanism, and internal restructuring.
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THPAB099	Challenges of a Stable ERL Operation Concerning the Digital RF Control System of the S-DALINAC	controls, operation, beam-loading, linac	3951
	M. Steinhorst, M. Arnold, U. Bonnes, C. Burandt, N. Pietralla TU Darmstadt, Darmstadt, Germany T. Kürzeder HIM, Mainz, Germany
	Funding: Supported by the DFG through RTG 2128. The superconducting recirculating electron linear accelerator S-DALINAC is the central large-scale research device of the institute for nuclear physics at the TU Darmstadt in Germany. In 2015/2016 the S-DALINAC received an upgrade to three recirculations. The new beam line enables in addition to higher maximum energies the possibility to operate the S-DALINAC as an Energy Recovery Linac (ERL). Therefore the current rf control system encounters new requirements for ERL operation. Since 2010 a digital rf control system is successfully used for the control of the superconducting cavities. This system was not built and optimized for the control of an ERL. This contribution is discussing the expected challenges of an ERL operation regarding the existing digital rf control system.
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THPIK013	Renewal of Bessy Ii Rf System - Solid State Amplifiers and Hom Damped Cavities	cavity, klystron, storage-ring, synchrotron	4127
	W. Anders, P. Goslawski, A. Heugel, H.-G. Hoberg, H. Hoffmann, A. Jankowiak, J. Knobloch, G. Mielczarek, M. Ries, M. Ruprecht, A. Schälicke, B. Schriefer, H. Stein HZB, Berlin, Germany M. Haucke Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany K. Ludwig BESSY GmbH, Berlin, Germany
	Due to the fact that the klystrons run out of production and due to the aging of the old cavities, a renewal of the RF system was necessary. Solid state based transmitters and HOM damped nc single cell cavities have been installed at the BESSY II storage ring. The parameters of the components, the installation phase and the results to the beam will be presented.
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THPIK029	THE RF CAVITY FOR THE INDUS-2 STORAGE RING	cavity, vacuum, dipole, operation	4154
	C. P. Pasotti, M. Bocciai, P. Pittana, M. Rinaldi Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	A new Elettra-type cavity has been delivered to the Raja Ramanna Centre for Advanced Technology (RRCAT) Indus-2 facility. This cavity is the very same of those already installed several years ago with some optimization of the cooling channels. It is the Elettra-type cavity, normal conducting copper single cell but resonating at 505.8 MHz. The cavity description, the full characterization of the accelerating mode (L0) and high order modes (HOM) and the acceptance tests are presented in this paper.
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THPIK036	Design Study of Damped Accelerating Cavity Based on the TM020-Mode and HOM Couplers for the KEK Light Source Project	cavity, damping, target, simulation	4172
	T. Takahashi, S. Sakanaka, N. Yamamoto KEK, Ibaraki, Japan
	A novel damped-cavity scheme was recently proposed by Ego et al.. In this design, TM020 resonant mode is used for beam acceleration. Power of higher-order (or lower-order) modes are extracted through cylindrical slots which are placed at the position where the magnetic fields of HOMs are strong while that of TM020 mode is zero. Extracted powers are absorbed by lossy ferrites. In this scheme, excellent HOM damping is possible while occupying less space of the straight section in storage rings. We propose in this paper an alternative design which is based on the same TM020 mode but with rod-type HOM couplers. The rod-type HOM couplers are placed where the electric fields of HOMs are strong while that of TM020 mode is zero. In this scheme, openings needed for HOM extraction can be made smaller, which is desirable for stiffening the mechanical structure of the cavity. Potential use of lossy dielectric materials is another merit. We present external Q-values of HOMs that can be achieved in this scheme, as well as an effect of HOM couplers on the TM020 mode. Our current study is directed to a 1.5 GHz higher-harmonic cavity for the proposed KEK Light Source project. H. Ego et al., in Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese]. ** K. Harada et al., IPAC2016, THPMB012.
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THPIK078	1.5 GHz Cavity Design for the CLIC Damping Ring and as Active Third Harmonic Cavity for ALBA	cavity, damping, impedance, simulation	4263
	B. Bravo, J.M. Alvarez, F. Pérez, A. Salom ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	In a collaboration framework between CERN and ALBA, we are designing a normal conducting active 1.5 GHz cavity which could serve as main RF system for the Damping Ring of CLIC and as an active third harmonic cavity for the ALBA Storage Ring. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. The main advantage of an active third harmonic cavity is that optimum conditions can be reached for any beam current. This paper presents the preliminary design of this cavity: an active, normal conducting cavity tuned at 1.5 GHz based on the 500 MHz European Higher Order Mode (HOM) damped normal conducting with nose cones using ridged circular waveguides for HOM damping. Electromagnetic simulations, mechanical and thermal stress analysis will be presented together with the calculations on beam stability improvement due to the third harmonic system.
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THPIK112	Progress With the Diamond Light Source RF Upgrade	cavity, operation, storage-ring, superconducting-cavity	4358
	C. Christou, A.G. Day, M.J. Duignan, P. Gu, N.P. Hammond, P.J. Marten, S.A. Pande, D. Spink DLS, Oxfordshire, United Kingdom
	Failure of a superconducting cavity in the Diamond storage ring can lead to extended down-time because of the time required to remove the module from the ring, the inability to access the cavity without removal from the cryostat and the long time to repair of the module. To reduce the risk to storage ring operation, normal conducting cavities are being installed to support operation of the superconducting cavities. Two cavities will be introduced in 2017 and work is progressing with RF amplifiers, transmission lines and low-level RF as well as storage ring engineering and controls. A summary of progress so far is presented and the plan for installation and further RF upgrades is outlined.
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THPIK118	Final Assembly and Testing of MICE RF Modules at LBNL	vacuum, cavity, coupling, low-level-rf	4377
	T.H. Luo, A.R. Lambert, D. Li, S.P. Virostek, J.G. Wallig LBNL, Berkeley, California, USA T.G. Anderson, A.D. Bross, D.W. Peterson Fermilab, Batavia, Illinois, USA M.A. Palmer BNL, Upton, Long Island, New York, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	Funding: Work supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC02-05CH11231 The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of a muon beam by ionization interaction with absorbers and re-acceleration in RF cavities. The final MICE cooling channel configuration has two RF modules, each housing a 201 MHz RF cavity to compensate the longitudinal energy loss in the absorbers. Two RF modules have been assembled and tested at LBNL. This paper reports the final assembly work, as well as the vacuum test and low level RF measurements.
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THPVA143	Beam-Breakup Studies for the 4-Pass Cornell-Brookhaven Energy Recovery LINAC Test Accelerator	simulation, lattice, cavity, dipole	4801
	W. Lou, J.A. Crittenden, G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cornell University and Brookhaven National Laboratory are currently designing the Cornell-BNL ERL Test Accelerator (CBETA). To be built at Cornell's Wilson Lab, CBETA utilizes the existing ERL injector and main linac cryomodule (MLC). As the electron bunches pass through the MLC cavities, higher order modes (HOMs) are excited. The recirculating bunches interact with the HOMs, which can give rise to beam-breakup instability (BBU). Here we present simulation results on how BBU limits the maximum achievable current, and potential ways to improve the threshold current.
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Paper

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Other Keywords

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MOPVA051

Design of the High Power 1.5 GHz Input Couplers for BESSY VSR

coupling, cavity, operation, simulation

978

E. Sharples, M. Dirsat, J. Knobloch, A.V. Vélez
HZB, Berlin, Germany

The Variable pulse length Storage Ring (BESSY VSR) upgrade to BESSY II at Helmholtz-Zentrum Berlin (HZB) requires an upgrade on the RF systems in the form of high-voltage longitudinally focusing super conducting RF cavities of 1.5 GHz ad 1.75 GHz. For operation, coaxial RF power couplers capable of handling 13 kW peak power at standing wave operation are required for both the 1.5 GHz and 1.75 GHz cavities. The coupler is based on a design by Cornell University with modifications to suit frequency and coupling requirements. The coupler is intended to provide variable coupling with a range of Qext from 6x10⁶ to 6x10⁷ to allow flexibility to adjust to operating conditions of BESSY VSR. Here we present the RF design of the high-power coaxial coupler for BESSY VSR along with the design of the test stand for conditioning a pair of couplers.

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MOPVA052

Study on HOM Power Levels in the BESSY VSR Module

cavity, SRF, operation, resonance

982

A.V. Tsakanian, H.-W. Glock, 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 of long (ca. 15ps) and short (ca. 1.5ps) bunches in the storage ring with the 'standard' user optics. This challenging goal requires installation of four new SRF cavities (2x1.5GHz and 2x1.75GHz) in a single module to minimize space requirements. These cavities are equipped with strong waveguide and beam tube HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete module. This study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. In the module different cavity arrangements are analyzed to reach the optimal operation conditions with equally distributed power portions in warm HOM loads and tolerable beam coupling impedance.

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MOPVA053

The SRF Module Developments for BESSY VSR

cavity, synchrotron, damping, SRF

986

A.V. Vélez, H.-W. Glock, F. Glöckner, B.D.S. Hall, J. Knobloch, A. Neumann, P. Schnizer, E. Sharples, A.V. Tsakanian
HZB, Berlin, Germany

Helmholtz-Zentrum Berlin is developing BESSY VSR, a novel upgrade of the BESSY II facility to provide highly flexible pulse lengths while maintaining the flux and brilliance. The project goal is to simultaneously circulate both standard (some 10 ps long) and short (ps and sub-ps long) pulses offering the BESSY user community picosecond dynamics and high-resolution experiments. The concept relies on the installation of high-voltage SRF cavities operating at the 3rd and 3.5th harmonic whereby the beating of the two frequencies provides RF buckets for long and short bunches. Since these cavities will operate in CW and with high beam current (Ib=300 mA), the cavity design represents a challenging goal. In addition the need to avoid coupled bunch instabilities (CBI's), the installation of the VSR Cryomodule must fit in one of the available 4-m long low beta straights. To address the technological and engineering challenges techniques such as waveguide-damped cavities have been developed. First prototypes have been produced. In this paper, the present SRF developments are presented, including the cavities, high power couplers, higher-order mode absorbers and the cryomodule design.

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MOPVA079

A 166.6 MHz Superconducting RF System for the HEPS Storage Ring

cavity, LLRF, SRF, injection

1049

P. Zhang, H.X. Hao, T.M. Huang, Z.Q. Li, H.Y. Lin, F. Meng, Z.H. Mi, Y. Sun, G.W. Wang, Q.Y. Wang, X.Y. Zhang
IHEP, Beijing, People's Republic of China

Funding: This work has been supported by HEPS-TF project and partly by Pioneer 'Hundred Talents Program' of Chinese Academy of Science.
A superconducting 166.6 MHz quarter-wave β=1 cavity was recently proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. Four 166.6 MHz cavities will be used for main acceleration in the newly planned on-axis beam injection scheme realized by a double-frequency RF system. The fundamental frequency, 166.6 MHz, was dictated by the fast injection kicker technology and the preference of using 499.8 MHz SC RF cavity as the third harmonic. Each 166.6 MHz cavity will be operated at 4.2 K providing 1.2 MV accelerating voltage and 150 kW of power to the electron beam. The input coupler will use single-window coaxial type graded up to 200 kW CW power. Each cavity will be equipped with a 200 kW solid-state amplifier and digital low-level RF system. This paper will describe the 166.6 MHz RF system with a focus on the design and optimization of the RF cavity and its ancillaries, the LLRF system and the status of the solid-state amplifiers.

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MOPVA080

HOM Simulations and Damping Scheme for CEPC Cavities

cavity, damping, collider, impedance

1052

H.J. Zheng, J. Gao, F. Meng, P. Sha, J.Y. Zhai
IHEP, Beijing, People's Republic of China

In this paper, it will be presented that the higher order mode (HOM) analysis of the 650 MHz cavities for the Circular Electron-Positron Collider (CEPC). The higher order modes excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. To keep the beam stable, the impedance budget and the HOM damping requirement are given. The conventional coaxial HOM coupler, which will be mounted on the beam pipe, is planned to extract the HOM power below the cut-off frequency of the beam pipe, and the propagating modes will be absorbed by the two HOM absorbers at room temperature outside the cryomodule.

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MOPVA091

Investigation of HOM Frequency Shifts Induced by Mechanical Tolerances

cavity, simulation, operation, cryogenics

1071

S. Pirani, M. Eshraqi, M. Lindroos
ESS, Lund, Sweden
A. Bosotti, J.F. Chen, P. Michelato, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
T.P.Å. Åkesson
Lund University, Department of Physics, Lund, Sweden

We present Higher Order Mode (HOM) studies on ESS Medium-Beta cavity of INFN-LASA design, including both simulation and measurement results. Mechanical tolerances of the fabrication process might shift HOMs frequencies toward harmonics of the bunch frequency. Both simulation and measurements at room and cryogenic temperature show that INFN LASA cavity is fully compatible with ESS requirements.

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MOPVA096

The Crab Cavities Cryomodule for SPS Test

cavity, cryomodule, vacuum, monitoring

1081

C. Zanoni, A. Amorim Carvalho, K. Artoos, S. Atieh, K. Brodzinski, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, T. Dijoud, K. Eiler, G. Favre, P. Freijedo Menendez, M. Garlaschè, L. Giordanino, S.A.E. Langeslag, R. Leuxe, H. Mainaud Durand, P. Minginette, M. Narduzzi, V. Rude, M. Sosin, J.S. Swieszek
CERN, Geneva, Switzerland
T.J. Jones, N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

RF Crab Cavities are an essential part of the HL-LHC upgrade. Two concepts of such systems are being developed: the Double Quarter Wave (DQW) and the RF Dipole (RFD). A cryomodule with two DQW cavities is in advanced fabrication stage at CERN for their tests with protons in the SPS during the 2018 run. The cavities must be operated at 2 K, without excessive heat loads, in a low magnetic environment and in compliance with CERN safety guidelines on pressure and vacuum systems. A large set of components, such as a thermal shield, a two layers magnetic shield, RF lines, helium tank and tuner is required for the successful and safe operation of the cavities. The assembly of all these components with the cavities and their couplers forms the cryomodule. An overview of the design and fabrication strategy of this cryomodule is presented. The main components are described along with the present status of cavity fabrication and processing and cryomodule assembly. The lesson learned from the prototypes, the helium tank above all, and first manufactured systems is also included.

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MOPVA113

RF Quality Control of SRF Cavities for LCLS-II Cryo-Modules

cavity, controls, cryomodule, pick-up

1108

M.H. Awida, P. Berrutti, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: *Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
LCLS-II project is gearing up to build 36 cryo-modules of the 1.3 GHz TESLA style cavities. Half of those cryomodules are being built at Fermilab, while JLAB is carrying the production of the other half. In this paper, we present the process of quality controlling the RF performance of cavities until they are qualified for the final string assembly at Fermilab. The RF quality control process includes monitoring the frequency spectrum of each cavity and tuning/adjusting of the notch frequencies before testing at the Vertical Test Stand (VTS). Measured data during income QC is presented and in addition we show the notch frequencies before and after testing at the VTS. Moreover, we report some of the RF measurements taken while the cavity is cooled down to 2K temperature.

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MOPVA130

Development of Waveguide HOM Loads for BERLinPro and BESSY-VSR SRF Cavities

cavity, simulation, SRF, network

1160

J. Guo, F. Fors, J. Henry, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA
H.-W. Glock, A. Neumann, A.V. Tsakanian, A.V. Vélez
HZB, Berlin, Germany

Two ongoing accelerator projects at Helmholtz-Zentrum Berlin (HZB), BERLinPro and BESSY-VSR, need to design three different SRF cavities, a 1.3GHz cavity in BERLinPro and 1.5GHz/1.75GHz cavities in BESSY-VSR. These cavities have adopted waveguide HOM dampers in their design, with a few tens of watts HOM power in each load for BERLinPro and a few hundred watts for BESSY-VSR. JLab is collaborating with HZB prototyping these HOM loads. In this paper, we will report on the integrated RF-thermal-mechanical design of the loads, as well as the fabrication and testing results.

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MOPVA135

Fabrication, Processing and RF Test of RF-Dipole Prototype Crabbing Cavity for LHC High Luminosity Upgrade

cavity, dipole, luminosity, cryogenics

1174

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
H. Park
JLab, Newport News, Virginia, USA

The superconducting rf-dipole crabbing cavity is one of two crabbing cavity designs proposed for the LHC high luminosity upgrade. The proof-of-principle rf-dipole cavity operating at 400 MHz has demonstrated excellent performance exceeding the design specifications. The prototype cavity for SPS beam test has been designed to include the fundamental power coupler, HOM couplers, and all the ancillary components intended to meet the design requirements. A crabbing cavity system is expected to be installed in the SPS beam line and tested prior to the installation in LHC; this will be the first crabbing cavity operation on a proton beam. The fabrication of two prototype rf-dipole cavities is currently being completed at Jefferson Lab. This paper presents the details on cavity processing and cryogenic test results of the rf-dipole cavities.

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TUPVA008

Assessment of Thermal Loads in the CERN SPS Crab Cavities Cryomodule

cavity, cryomodule, radiation, pick-up

2047

F. Carra, J. Apeland, R. Calaga, O. Capatina, T. Capelli, C. Zanoni
CERN, Geneva, Switzerland
S. Verdú-Andrés
BNL, Upton, Long Island, New York, USA

Funding: *Work supported by the European Union HL-LHC Project and by US DOE through Brookhaven Science Associates LLC under contract No. DE-AC02-98CH10886 and the US LHC Accelerator Research Program (LARP). Research supported by the HL-LHC project.
As a part of the HL-LHC upgrade, a cryomodule is designed to host two crab cavities for a first test with protons in the SPS machine. The evaluation of the cryomodule heat loads is essential to dimension the cryogenic infrastructure of the system. The current design features two cryogenic circuits. The first circuit adopts superfluid helium at 2 K to maintain the cavities in the superconducting state. The second circuit, based on helium gas at a temperature between 50 K and 70 K, is connected to the thermal screen, also serving as heat intercept for all the interfaces between the cold mass and the external environment. An overview of the heat loads to both circuits, and the combined numerical and analytical estimations, is presented. The heat load of each element is detailed for the static and dynamic scenarios, with considerations on the design choices for the thermal optimization of the most critical components.
#Federico.carra@cern.ch

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WEPAB115

Normal Conducting CW Transverse Crab Cavity For Producing Short Pulses In SPEAR3

cavity, impedance, damping, photon

2840

Z. Li, V.A. Dolgashev, M. Dunham, K.J. Gaffney, R.O. Hettel, X. Huang, N. Kurita, J.A. Safranek, J.J. Sebek, K. Tian
SLAC, Menlo Park, California, USA

Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515.
The ability to produce short pulse X-rays on the scale of 1-10 ps fwhm in the SPEAR3 storage ring light source would enable enhanced timing mode studies of dynamic processes in materials as they occur. The crab cavity approach appears to be optimal for SPEAR3 to produce short pulse X-rays. Furthermore, by using a two-frequency crabbing scheme, SPEAR3 would be able to produce short-pulse bunches while supplying the high average flux needed for regular users. While supercon-ducting RF (SCRF) technology could be a natural choice for the CW crab cavity, the deflecting voltage for SPEAR3 crabbing appears to be within reach of more affordable normal conducting RF (NCRF). In this paper, we present a preliminary NCRF CW crab cavity design for SPEAR3.

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WEPIK009

Collimators for SuperKEKB Main Ring

impedance, background, factory, positron

2929

T. Ishibashi, Y. Suetsugu, S. Terui
KEK, Ibaraki, Japan

SuperKEKB, which is an upgrade project of KEKB, is an electron-positron collider with extremely high luminosity. Collimators (movable masks) for SuperKEKB have been designed to fit an antechamber scheme of the vacuum system and will be operated to improve backgrounds in the particle detector named Belle II. We are developing two types of collimators; a horizontal and vertical collimator. The collimator has a pair of horizontally or vertically opposed movable jaws with RF fingers. Each jaw travels independently through 5-25 mm horizontally or 2-12 mm vertically in a distance between the beam axis and the tip of the jaw. SuperKEKB will operate with high currents of short bunch lengths, therefore it is important to estimate and decrease the impedance of the collimators. Two horizontal collimators were already installed in the positron ring and operated during Phase-1 commissioning for approximately 5 months, from February to June 2016. In this presentation, the latest design, and the results in the Phase-1 commissioning are presented.

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WEPIK054

Evaluation and Attenuation of Sirius Components Impedance

impedance, dipole, storage-ring, vacuum

3048

H.O.C. Duarte, L. Liu, S.R. Marques
LNLS, Campinas, Brazil

The Sirius in-vacuum components have their design improvements, possibilities and choices presented, where wake heating, single-bunch and multi-bunch effects and mechanical aspects were taken into account. The results were finally evaluated and added to the Sirius impedance budget.

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WEPIK055

Analysis and Countermeasures of Wakefield Heat Losses for Sirius

impedance, simulation, vacuum, storage-ring

3052

H.O.C. Duarte, L. Liu, S.R. Marques, T.M. da Rocha, F.H. de Sá
LNLS, Campinas, Brazil

Design evaluation and possible solutions for several in-vacuum components of Sirius are presented, having their impedance analysis focused on mitigating the wake heating impact. Thermal and/or structural simulation of the models are carried out by considering the heat load directly obtained from wakefield simulations with resistive wall boundary conditions.

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WEPVA058

Development of HOM Absorber for SuperKEKB

electron, vacuum, photon, plasma

3394

S. Terui, T. Ishibashi, Y. Suetsugu, Y. Takeuchi, K. Watanabe
KEK, Ibaraki, Japan
H. Ishizaki, A. Kimura, T. Sawhata
Metal Technology Co. Ltd., Ibaraki, Japan

Higher-order modes (HOM) absorbers are necessary components for recent high-power accelerators in order to prevent beam instabilities (e.g. HOM- Beam Break Up instabilities) or the overheating of vacuum components. Several kinds of absorber materials, such as SiC, ferrite and Kanthal, have been investigated and applied in accelerators. Among these materials, ferrite has been found to be superior to others because of its higher HOM absorbing efficiency. However, because of its low tensile strength and small thermal expansion rate, it cannot be easily bonded to other metals thus limiting its use as a HOM absorber. We reported the success of the fabrication of ferrite-copper-blocks using the spark plasma sintering (SPS)-technique last year. This year we report testing with a high-power RF source and measuring gas desorption rate after baking and secondary electron yield.

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THPAB047

New Features of the 2017 SixTrack Release

simulation, electron, collimation, coupling

3815

K.N. Sjobak, J. Barranco García, R. De Maria, E. McIntosh, A. Mereghetti
CERN, Geneva, Switzerland
M. Fitterer
Fermilab, Batavia, Illinois, USA
V. Gupta
IIT, Guwahati, Assam, India
J. Molson
LAL, Orsay, France

The SixTrack particle tracking code is routinely used to simulate particle trajectories in high energy circular machines like the LHC and FCC, and is deployed for massive simulation campaigns on CERN clusters and on the BOINC platform within the LHC@Home volunteering computing project. The 2017 release brings many upgrades that improve flexibility, performance, and accuracy. This paper describes the new modules for wire- and electron lenses (WIRE and ELEN), the expert interface for beam-beam element (BEAM/EXPERT), the extension of the number of simultaneously tracked particles, the new Frequency Map Analysis (FMA) postprocessing option, the generation of a single zip of selected output files (ZIPF) in order to extend the coverage of the studies in LHC@HOME (e.g. FMA and on-line aperture checks), coupling to external codes (DYNK-PIPE and BDEX), a new CMAKE based build- and test mechanism, and internal restructuring.

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THPAB099

Challenges of a Stable ERL Operation Concerning the Digital RF Control System of the S-DALINAC

controls, operation, beam-loading, linac

3951

M. Steinhorst, M. Arnold, U. Bonnes, C. Burandt, N. Pietralla
TU Darmstadt, Darmstadt, Germany
T. Kürzeder
HIM, Mainz, Germany

Funding: Supported by the DFG through RTG 2128.
The superconducting recirculating electron linear accelerator S-DALINAC is the central large-scale research device of the institute for nuclear physics at the TU Darmstadt in Germany. In 2015/2016 the S-DALINAC received an upgrade to three recirculations. The new beam line enables in addition to higher maximum energies the possibility to operate the S-DALINAC as an Energy Recovery Linac (ERL). Therefore the current rf control system encounters new requirements for ERL operation. Since 2010 a digital rf control system is successfully used for the control of the superconducting cavities. This system was not built and optimized for the control of an ERL. This contribution is discussing the expected challenges of an ERL operation regarding the existing digital rf control system.

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THPIK013

Renewal of Bessy Ii Rf System - Solid State Amplifiers and Hom Damped Cavities

cavity, klystron, storage-ring, synchrotron

4127

W. Anders, P. Goslawski, A. Heugel, H.-G. Hoberg, H. Hoffmann, A. Jankowiak, J. Knobloch, G. Mielczarek, M. Ries, M. Ruprecht, A. Schälicke, B. Schriefer, H. Stein
HZB, Berlin, Germany
M. Haucke
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
K. Ludwig
BESSY GmbH, Berlin, Germany

Due to the fact that the klystrons run out of production and due to the aging of the old cavities, a renewal of the RF system was necessary. Solid state based transmitters and HOM damped nc single cell cavities have been installed at the BESSY II storage ring. The parameters of the components, the installation phase and the results to the beam will be presented.

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THPIK029

THE RF CAVITY FOR THE INDUS-2 STORAGE RING

cavity, vacuum, dipole, operation

4154

C. P. Pasotti, M. Bocciai, P. Pittana, M. Rinaldi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

A new Elettra-type cavity has been delivered to the Raja Ramanna Centre for Advanced Technology (RRCAT) Indus-2 facility. This cavity is the very same of those already installed several years ago with some optimization of the cooling channels. It is the Elettra-type cavity, normal conducting copper single cell but resonating at 505.8 MHz. The cavity description, the full characterization of the accelerating mode (L0) and high order modes (HOM) and the acceptance tests are presented in this paper.

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THPIK036

Design Study of Damped Accelerating Cavity Based on the TM020-Mode and HOM Couplers for the KEK Light Source Project

cavity, damping, target, simulation

4172

T. Takahashi, S. Sakanaka, N. Yamamoto
KEK, Ibaraki, Japan

A novel damped-cavity scheme was recently proposed by Ego et al.*. In this design, TM020 resonant mode is used for beam acceleration. Power of higher-order (or lower-order) modes are extracted through cylindrical slots which are placed at the position where the magnetic fields of HOMs are strong while that of TM020 mode is zero. Extracted powers are absorbed by lossy ferrites. In this scheme, excellent HOM damping is possible while occupying less space of the straight section in storage rings. We propose in this paper an alternative design which is based on the same TM020 mode but with rod-type HOM couplers. The rod-type HOM couplers are placed where the electric fields of HOMs are strong while that of TM020 mode is zero. In this scheme, openings needed for HOM extraction can be made smaller, which is desirable for stiffening the mechanical structure of the cavity. Potential use of lossy dielectric materials is another merit. We present external Q-values of HOMs that can be achieved in this scheme, as well as an effect of HOM couplers on the TM020 mode. Our current study is directed to a 1.5 GHz higher-harmonic cavity for the proposed KEK Light Source project**.
* H. Ego et al., in Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese].
** K. Harada et al., IPAC2016, THPMB012.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK036

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THPIK078

1.5 GHz Cavity Design for the CLIC Damping Ring and as Active Third Harmonic Cavity for ALBA

cavity, damping, impedance, simulation

4263

B. Bravo, J.M. Alvarez, F. Pérez, A. Salom
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

In a collaboration framework between CERN and ALBA, we are designing a normal conducting active 1.5 GHz cavity which could serve as main RF system for the Damping Ring of CLIC and as an active third harmonic cavity for the ALBA Storage Ring. The third harmonic cavity at ALBA will be used to increase the bunch length in order to improve the beam lifetime and increase the beam stability thresholds. The main advantage of an active third harmonic cavity is that optimum conditions can be reached for any beam current. This paper presents the preliminary design of this cavity: an active, normal conducting cavity tuned at 1.5 GHz based on the 500 MHz European Higher Order Mode (HOM) damped normal conducting with nose cones using ridged circular waveguides for HOM damping. Electromagnetic simulations, mechanical and thermal stress analysis will be presented together with the calculations on beam stability improvement due to the third harmonic system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK078

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THPIK112

Progress With the Diamond Light Source RF Upgrade

cavity, operation, storage-ring, superconducting-cavity

4358

C. Christou, A.G. Day, M.J. Duignan, P. Gu, N.P. Hammond, P.J. Marten, S.A. Pande, D. Spink
DLS, Oxfordshire, United Kingdom

Failure of a superconducting cavity in the Diamond storage ring can lead to extended down-time because of the time required to remove the module from the ring, the inability to access the cavity without removal from the cryostat and the long time to repair of the module. To reduce the risk to storage ring operation, normal conducting cavities are being installed to support operation of the superconducting cavities. Two cavities will be introduced in 2017 and work is progressing with RF amplifiers, transmission lines and low-level RF as well as storage ring engineering and controls. A summary of progress so far is presented and the plan for installation and further RF upgrades is outlined.

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THPIK118

Final Assembly and Testing of MICE RF Modules at LBNL

vacuum, cavity, coupling, low-level-rf

4377

T.H. Luo, A.R. Lambert, D. Li, S.P. Virostek, J.G. Wallig
LBNL, Berkeley, California, USA
T.G. Anderson, A.D. Bross, D.W. Peterson
Fermilab, Batavia, Illinois, USA
M.A. Palmer
BNL, Upton, Long Island, New York, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: Work supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC02-05CH11231
The international Muon Ionization Cooling Experiment aims to demonstrate the transverse cooling of a muon beam by ionization interaction with absorbers and re-acceleration in RF cavities. The final MICE cooling channel configuration has two RF modules, each housing a 201 MHz RF cavity to compensate the longitudinal energy loss in the absorbers. Two RF modules have been assembled and tested at LBNL. This paper reports the final assembly work, as well as the vacuum test and low level RF measurements.

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THPVA143

Beam-Breakup Studies for the 4-Pass Cornell-Brookhaven Energy Recovery LINAC Test Accelerator

simulation, lattice, cavity, dipole

4801

W. Lou, J.A. Crittenden, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell University and Brookhaven National Laboratory are currently designing the Cornell-BNL ERL Test Accelerator (CBETA). To be built at Cornell's Wilson Lab, CBETA utilizes the existing ERL injector and main linac cryomodule (MLC). As the electron bunches pass through the MLC cavities, higher order modes (HOMs) are excited. The recirculating bunches interact with the HOMs, which can give rise to beam-breakup instability (BBU). Here we present simulation results on how BBU limits the maximum achievable current, and potential ways to improve the threshold current.

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