SRF2015 - List of Keywords (ion)

Paper	Title	Other Keywords	Page
MOAA05	Status of the RISP Superconducting Heavy Ion Accelerator	cryomodule, linac, rfq, ECR	31
	D. Jeon IBS, Daejeon, Republic of Korea
	Funding: This work was supported by the the Institute for Basic Science funded by the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of Korea. Construction of the RISP heavy ion accelerator facility is in progress in Korea. The driver linac is a superconducting linac that can accelerate uranium to proton beams, delivering 400 kW beam power to various targets. Prototyping and test of the superconducting cavities and cryomodules are proceeding. Prototype superconducting cavities were fabricated through domestic vendors and their vertical tests were performed in collaboration with TRIUMF. Vertical tests showed good performance of the prototype cavities, which verified that there were no significant issues of the cavity design and fabrication. SRF Test Facility is under construction to be completed by early 2016. Progress report of the RAON accelerator systems is presented.
	Slides MOAA05 [5.587 MB]
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MOPB035	Nature and Implication of Found Actual Particulates on the Inner Surface of Cavities in a Full-Scale Cryomodule Previously Operated With Beams	cavity, cryomodule, vacuum, operation	164
	R.L. Geng, J.F. Fischer, E.A. McEwen, O. Trofimova JLab, Newport News, Virginia, USA
	Field emission in an SRF cavity is often the result of small foreign particulates lodging on the cavity inner surface. To avoid these particulate field emitters, careful cleaning and handling of individual cavities and clean room assembly of cavity strings are common practice. Despite these elaborate processes, some particulates persist to stay on the final surface of a beam-ready cavity. Moreover, as will be shown in this contribution, new particulates accumulate after a cryomodule is placed in the accelerator tunnel. The nature of these accumulated particulates on the inner surface of a beam-accelerating cavity is largely unknown for two reasons: (1) lack of access to such surfaces; (2) lack of a workable procedure for investigation without destroying the cavity. In this contribution, we report the first study on found actual particulates on the inner surface of 5-cell CEBAF cavities in a full-scale cryomodule previously operated with beam. The nature of the studied particulates is presented. The implication of the findings will be discussed in view of reliable and efficient operation of CEBAF and future large-scale SRF accelerators.
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MOPB036	TOF-SIMS Study of Nitrogen Doping Niobium Samples	niobium, experiment, cavity, vacuum	169
	Z.Q. Yang, L. Lin, X.Y. Lu, W.W. Tan, D.Y. Yang, J. Zhao PKU, Beijing, People's Republic of China
	Nitrogen doping treatment with the subsequent electropolishing (EP) of the niobium superconducting cavity can significantly increase the cavity’s quality factor up to a factor of 3. The nitrogen doping experiment has been successfully repeated and demonstrated. But the mechanism of the nitrogen doping effect remains unclear. Nitrogen doping study on niobium samples was carried out in Peking University. The niobium samples were manual processed to avoid heat generation. The experiment condition is close to that of the Fermilab. After the nitrogen doping treatment, the samples were mildly electropolished with the thickness of 1.3μm, 1.9μm, 3.3μm, 4.2μm, 5.1μm, 5.9μm and 7.0μm. The time of flight secondary ion mass spectrometry (TOF-SIMS) measurements show that the samples directly after nitrogen doping have a much higher nitrogen concentration in the depth of about 90nm. When the EP removal is larger than 1.3μm, the samples’ impurity elements is remarkably reduced and their distribution is similar to each other. Also the measured results to some extent prove that EP removal can introduce H to the niobium surface.
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MOPB065	Recent Measurements on the SC 325 MHz CH-Cavity	cavity, linac, heavy-ion, controls	255
	M. Busch, M. Amberg, M. Basten, F.D. Dziuba, H. Podlech, U. Ratzinger IAP, Frankfurt am Main, Germany M. Amberg HIM, Mainz, Germany
	Funding: Work supported by GSI, BMBF Contr. No. 06FY7102 At the Institute for Applied Physics (IAP), Frankfurt University, a sc 325 MHz CH-Cavity has been designed and fabricated. Successful tests at 4 K and 2 K with gradients up to 14.1 MV/m have been performed. The cavity is destined for a 11.4 AMeV 10 mA ion beam at the GSI UNILAC, Darmstadt. Consisting of 7 gaps and a geometrical beta of 0.16 this resonator is designed to provide a gradient of 5 MV/m. Novel features of this structure comprise a compact design, low electric peak fields, improved surface processing possibilities and power coupling. In addition a tuner system based on mechanically deformable bellow tuners attached inside the cavity and driven either by a stepping motor or a piezo actuator will keep the cavity on resonance. This contribution reports about the latest measurements on the cavity with the recently attached helium vessel and a renewed surface processing.
	Poster MOPB065 [1.270 MB]
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MOPB066	R&D Status of the New Superconducting CW Heavy Ion LINAC@GSI	cavity, linac, simulation, operation	258
	M. Basten, M. Busch, F.D. Dziuba, D. Mäder, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany M. Amberg, K. Aulenbacher, M. Miski-Oglu HIM, Mainz, Germany W.A. Barth, V. Gettmann, M. Heilmann, S. Mickat GSI, Darmstadt, Germany
	To keep the ambitious Super Heavy Element (SHE) physics program at GSI competitive a superconducting (sc) continuous wave (cw) high intensity heavy ion LINAC is currently under progress as a multi-stage R&D program of GSI, HIM and IAP. The baseline linac design consists of a high performance ion source, a new low energy beam transport line, an (cw) upgraded High Charge State Injector (HLI), and a matching line (1.4 MeV/u) which is followed by the new sc-DTL LINAC for post acceleration up to 7.3 MeV/u. In the present design the new cw-heavy ion LINAC comprises constant-beta sc Crossbar-H-mode (CH) cavities operated at 217 MHz. The advantages of the proposed beam dynamics concept applying a constant beta profile are easy manufacturing with minimized costs as well as a straightforward energy variation. An important milestone will be the full performance test of the first CH cavity (Demonstrator), in a horizontal cryo module with beam. An advanced demonstrator setup comprising a string of cavities and focussing elements is proposed to build from 10 short CH-cavities with 8 gaps. The corresponding simulations and technical layout of the new cw heavy ion LINAC will be presented. W. Barth et al., Further R&D for a new Superconducting cw Heavy Ion LINAC@GSI, IPAC2014, THPME004 **M. Schwarz et al., Beam Dynamics for the sc cw Heavy Ion Linac at GSI, IPAC2015, THPF025
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MOPB067	Steps Towards Superconducting CW-LINAC for Heavy Ions at GSI	linac, heavy-ion, quadrupole, cavity	262
	M. Miski-Oglu, M. Amberg, K. Aulenbacher, V. Gettmann HIM, Mainz, Germany W.A. Barth, M. Heilmann, S. Mickat, S. Yaramyshev GSI, Darmstadt, Germany M. Basten, D. Bänsch, F.D. Dziuba, H. Podlech, U. Ratzinger IAP, Frankfurt am Main, Germany
	Providing heavy ion beams for the ambitious experiment program at GSI, the Universal Linear Accelerator (UNILAC) serves as a powerful high duty factor (25%) accelerator. Beam time availability for SHE-research will be decreased due to the limitation of the UNILAC providing a proper beam for FAIR simultaneously. To keep the GSI-SHE program competitive on a high level, a standalone sc cw-LINAC in combination with the upgraded GSI High Charge State injector is planned to build. In preparation for this the first linac section (financed by HIM and partly by HGF-ARD-initiative) will be tested in 2015 as a demonstrator. After successful testing the construction of an extended cryomodule comprising two further, but shorter CH cavities is foreseen to test until end of 2017. In this contribution the measurement of the beam parameters at the entrance of CW-Demonstartor, the preliminary simulation of beam dynamics for the first stage of advanced demonstrator will be presented. As a final R&D step towards an entire linac an advanced cryo module comprising up to five CH cavities is envisaged for 2019 serving for first user experiments at the coulomb barrier.
	Poster MOPB067 [2.807 MB]
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MOPB068	Pulsed SC Ion Linac as an Injector to Booster of Electron Ion Collider	linac, operation, cavity, proton	265
	P.N. Ostroumov, Z.A. Conway, B. Mustapha ANL, Argonne, USA B. Erdelyi Northern Illinois University, DeKalb, Illinois, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under contract number DE-AC02-06CH11357. The electron-ion collider (EIC) being developed at JLAB requires a new ion accelerator complex (IAC). The IAC includes a new linac and a booster accelerator facility. The new facility is required for the acceleration of ions from protons to lead for colliding beam experiments with electrons in the EIC storage ring. Originally, we proposed a pulsed linac which is based upon a NC front end, < 5 MeV/u, with a SC section for energies > 5 MeV/u and capable of providing 285 MeV protons and ~100 MeV/u lead ions for injection into the IAC booster. A recent cost optimization study of the IAC suggested that lower injection energy into the booster may reduce the overall project cost with ~120 MeV protons and ~40 MeV/u lead ions. Stronger space charge effects in the booster caused by lower injection energy will be mitigated by the booster design. In this paper we discuss both linac options.
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MOPB115	Surface Studies of Plasma Processed Nb Samples	plasma, cavity, vacuum, SRF	438
	P.V. Tyagi, R. Afanador, B. DeGraff, M. Doleans, B.S. Hannah, M.P. Howell, S.-H. Kim, J.D. Mammosser, C.J. McMahan, J. Saunders, S.E. Stewart ORNL, Oak Ridge, Tennessee, USA
	Funding: This work is supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. Contaminants present at top surface of superconducting radio frequency (SRF) cavities can act as field emitters and restrict the cavity accelerating gradient. A room temperature in-situ plasma processing technology for SRF cavities aiming to clean hydrocarbons from inner surface of cavities has been recently developed at the Spallation Neutron Source (SNS). Surface studies of the plasma processed Nb samples by Secondary ion mass spectrometry (SIMS) and Scanning Kelvin Probe (SKP) showed that the NeO2 plasma processing is very effective to remove carbonaceous contaminants from top surface and improves the surface work function by 0.5 to 1.0 eV. M. Doleans et al., Proc. 2013 SRF, Paris, France. P. V. Tyagi, et al., Proc. Linac14, Geneva, Switzerland. **M. Doleans et al., These proceedings.
	Poster MOPB115 [0.524 MB]
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TUBA03	On the Understanding of Q-Slope of Niobium Thin Films	ECR, niobium, SRF, cavity	494
	S. Aull, T. Junginger, A. Sublet, W. Venturini Delsolaro, P. Zhang CERN, Geneva, Switzerland J. Knobloch HZB, Berlin, Germany J. Knobloch University of Siegen, Siegen, Germany A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	The Q-slope of niobium coated copper cavities at medium fields is still the limiting factor for the application the Nb/Cu technology in accelerators. This paper presents a dedicated study of a niobium coating with bulk-like characteristics which shows a Q-slope comparable to bulk Nb at 400 MHz and 4 K. Combining the bulk like film with recent findings of the HIE Isolde indicates that the film microstructure and the Nb/Cu interface are the key aspects to understanding the Q-slope.
	Slides TUBA03 [3.414 MB]
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TUPB015	A New Cleanroom With Facilities for Cleaning and Assembly of Superconducting Cavities at Helmholtz-Institut Mainz	cavity, linac, heavy-ion, status	575
	F. Schlander, K. Aulenbacher, R.G. Heine IKP, Mainz, Germany K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu HIM, Mainz, Germany W.A. Barth, S. Mickat GSI, Darmstadt, Germany
	The Helmholtz-Institut Mainz HIM will operate a clean room facility for the assembly and possible re-treatment of superconducting cavities. This is mandatory for several SRF accelerator projects, like the advanced demonstrator for a dedicated sc heavy ion cw-linac at HIM or other projects pursued by research facilities or universities close by. While the installation of the clean room is in progress, the procurement of the appliances is ongoing. The present equipment planned and the current status of the installation will be presented.
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TUPB016	Progress on Superconducting Linac for the RAON Heavy Ion Accelerator	cavity, linac, cryomodule, electron	578
	H.J. Kim IBS, Daejeon, Republic of Korea
	The RISP (Rare Isotope Science Project) has been proposed as a multi-purpose accelerator facility for providing beams of exotic rare isotopes of various energies. It can deliver ions from proton to uranium. Proton and uranium ions are accelerated upto 600 MeV and 200 MeV/u respectively. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. In this paper, we present the RISP linac design, the prototyping of superconducting cavity and cryomodule.
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TUPB020	Recent Status New Superconducting CW Heavy Ion LINAC@GSI	cavity, solenoid, linac, heavy-ion	589
	V. Gettmann, M. Amberg, K. Aulenbacher, W.A. Barth, M. Miski-Oglu HIM, Mainz, Germany M. Amberg, M. Basten, D. Bänsch, F.D. Dziuba, H. Podlech, U. Ratzinger IAP, Frankfurt am Main, Germany K. Aulenbacher IKP, Mainz, Germany W.A. Barth, M. Heilmann, S. Mickat, S. Yaramyshev GSI, Darmstadt, Germany
	The demonstrator is a prototype of the first section of the proposed cw-LINAC@GSI, comprising a superconducting CH-cavity embedded by two superconducting solenoids. The sc CH-structure is the key component and offers a variety of research and development. The beam focusing solenoids provide maximum fields of 9.3 T at an overall length of 380 mm and a free beam aperture of 30 mm. The magnetic induction of the fringe is minimized to 50 mT at the inner NbTi-surface of the neighboring cavity. The fabrication of the key components is still in progress and is near to completion. After cold performance testing of the RF cavity, the helium jacket will be welded on. The cryostat is partly assembled and will be finished in the next weeks. The test environment is completely prepared. Advanced emittance measurement is foreseen to prepare for best matching of the heavy ion beam from the injector. Integration of the cryostat into the beam line, the first cool down of the module and commissioning of the RF elements will be performed as next steps towards a complete testing of the demonstrator.
	Poster TUPB020 [8.595 MB]
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TUPB024	Tuning the Linac With Superconducting Resonator Used as a Phase Detector	linac, acceleration, detector, bunching	602
	N.R. Lobanov, P. Linardakis, D. Tsifakis Research School of Physics and Engineering, Australian National University, Canberra, Australian Capitol Territory, Australia
	The ANU Heavy Ion Facility is comprised of a 15 MV electrostatic accelerator and superconducting linac booster. The beam is double terminal stripped to provide high charge states at the entrance to the linac, which consists of twelve β=0.1 Split Loop Resonators (SLR). Each SLR needs to be individually tuned in phase and amplitude for optimum acceleration efficiency. The amplitude and phase of the superbuncher and time energy lens also have to be correctly set. The linac set up procedure developed at ANU utilises a beam profile monitor in the middle of a 180 degree achromat and a new technique based on a superconducting resonator operating in a beam bunch detection mode. Both techniques are used to derive a full set of phase distributions for quick and efficient setting up of the entire linac. Verification of the superconducting phase detector is accomplished during routine linac operations and is complemented by longitudinal phase space simulations. The new technique allows better resolution for setting the resonator acceleration phase and better sensitivity to accelerating current.
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TUPB025	Tuning the Superconducting Linac at Low Beam Intensities	linac, bunching, acceleration, operation	607
	N.R. Lobanov, P. Linardakis, D. Tsifakis Research School of Physics and Engineering, Australian National University, Canberra, Australian Capitol Territory, Australia
	The ANU Heavy Ion Facility comprises a 15 MV electrostatic accelerator followed by a superconducting linac booster. The beam is foil stripped in the terminal and then stripped again to provide high charge states at the entrance to the linac. Employment of double terminal stripping allows the system to accelerate beams with mass up to 70 amu. The disadvantage of double terminal stripping is low beam intensity of few particle nA delivered to the linac. The linac encompasses twelve β=0.1 lead tin plated Split Loop Resonators (SLR) housed in four module cryostats. One of the linac set up procedures that developed at ANU utilises U-bend at the end of the linac. One special wide Beam Profile Monitor (BPM) is installed after 90 degrees magnet. The technique allows to set correct phase by observing the displacement of beam profile versus phase shift of the last phase locked resonator. In this paper a simple method has been proposed to improve sensitivity of commercially available BPM for efficient operation with low beam intensities. The system demonstrated very high stability, simplicity of operation and high reliability allowing sustained operation of the LINAC facility.
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TUPB029	Material Quality & SRF Performance of Nb Films Grown on Cu via ECR Plasma Energetic Condensation	ECR, SRF, plasma, interface	622
	A-M. Valente-Feliciano, G.V. Eremeev, C.E. Reece, J.K. Spradlin JLab, Newport News, Virginia, USA S. Aull CERN, Geneva, Switzerland Th. Proslier ANL, Argonne, Illinois, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The RF performance of bulk Nb cavities has continuously improved over the years and is approaching the intrinsic limit of the material. Although some margin seems still available with processes such as N surface doping, long term solutions for SRF surfaces efficiency enhancement need to be pursued. Over the years, Nb/Cu technology, despite its shortcomings, has positioned itself as an alternative route for the future of superconducting structures used in accelerators. Significant progress has been made in recent years in the development of energetic deposition techniques such as Electron Cyclotron Resonance (ECR) plasma deposition. Nb films with very high material quality have then been produced by varying the deposition energy alluding to the promise of performing SRF films. This paper presents RF measurements, correlated with surface and material properties, for Nb films showing how, by varying the film growth conditions, the Nb film quality and surface resistance can be altered and how the Q-slope can be eventually overcome.
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TUPB034	Bulk Niobium Polishing and Electropolishing Steps for Thinfilm Coated Copper SRF Cavities	cavity, SRF, plasma, cathode	633
	M. Krishnan, S.F. Chapman, I. Irfan, K.M. Velas AASC, San Leandro, California, USA J.K. Spradlin, H. Tian JLab, Newport News, Virginia, USA
	Funding: Research supported at AASC by the US DOE via SBIR grant: DE-SC0011371. The JLab effort was provided by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Alameda Applied Sciences Corporation (AASC) grows Nb thin films via Coaxial Energetic Deposition (CED) from a cathodic arc plasma. The plasma consists of 60-120eV Nb ions (Nb+ and Nb++) [1] that penetrate a few monolayers into the substrate [2] and enable sufficient surface mobility to ensure that the lowest energy state (crystalline structure with minimal defects) is accessible to the film [3]. One limitation of CED thinfilms is the presence of Nb macroparticles (~0.1-10 microns) that could be deleterious to high field performance of the SRF cavity. One way to remove such macroparticles [4] is to grow a thick film (~3-5 microns), followed by mechanical polishing (MP) using the finest media as might be applied in Centrifugal Barrel Polishing (CBP) to achieve a 0.4 micron surface figure, and an electropolishing (EP) step to remove ~1 micron of Nb that also removes all traces of embedded media in the film. The residual 2-4 micron Nb film should more nearly resemble the surface of a bulk Nb cavity that has been subjected to the same steps. This paper describes experiments conducted on Cu coupons as a prelude to an SRF Cu cavity coating.
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TUPB046	Structure and Composition of Nb3Sn Diffusion Coated Films on Nb	niobium, electron, SRF, cavity	669
	J. Tuggle, M.J. Kelley Virginia Polytechnic Institute and State University, Blacksburg, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA M.J. Kelley, H. Xu The College of William and Mary, Williamsburg, Virginia, USA
	Funding: Co-authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. College of William & Mary supported by U.S. DOE Office of High Energy Physics under grant DE-SC-0014475 The structure and composition of Nb3Sn films obtained by diffusion coating niobium coupons and SRF cavities were investigated by x-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS) and electron back-scatter diffraction (EBSD), including native surfaces, depth profiles and cross-sections. We find that the native surface oxide is significantly tin-rich, we have measured depth profiles. We find that the grains apparent in the SEM images are individual crystallites having no evident relationship to the substrate or each other.
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TUPB056	Characterization of Nb3Sn Coated Nb Samples	SRF, electron, cavity, niobium	708
	Y. Trenikhina, S. Posen, A. Romanenko Fermilab, Batavia, Illinois, USA D.L. Hall Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA M. Liepe Cornell University, Ithaca, New York, USA
	Nb3Sn has a great potential to replace traditional Nb for the fabrication of SRF cavities. The higher critical temperature of Nb3Sn potentially allows for an increased operational temperature for SRF cavities, which promises cryogenic cost savings. We present preliminary characterization of Nb3Sn layer grown on flat Nb sample prepared by the same chemical vapor deposition method that is used for the cavity coating. SEM, TEM/EDS, TEM imaging and diffraction characterization was used in order to evaluate any chemical and structural defects that could be responsible for the limited quench field and high residual resistance. Variation of local stoichiometry was found in the Nb3Sn layer, which is in line with previous studies. Regions of decreased Sn content can have a lower Tc in comparison to the stoichiometric composition, which may be responsible for the limited performance. AES investigations of the Nb3Sn surface before and after HF-rinse were done in order to explore the mechanism that is responsible for the performance degradation of HF-rinsed Nb3Sn coated cavities.
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TUPB062	Evaluation of Sc Property Coated on a Surface	vacuum, gun, neutron, cavity	723
	Y. Iwashita, Y. Fuwa Kyoto ICR, Uji, Kyoto, Japan M. Hino Kyoto University, Research Reactor Institute, Osaka, Japan T. Kubo, T. Saeki KEK, Ibaraki, Japan
	Funding: This work was supported by JSPS KAKENHI Grant Number 26600142. We are trying to deposit thin superconducting material on a substrate for higher accelerating field gradients. In order to evaluate the deposit method, surface properties are under measurement. Some results on measurements at DC and a preparation status toward RF measurement will be reported.
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TUPB072	Report of Vertical Test of the β=0.12 Half-Wave Resonator at RISP	cavity, vacuum, TRIUMF, simulation	747
	G.-T. Park, H.J. Cha, H. Kim, W.K. Kim IBS, Daejeon, Republic of Korea Z.Y. Yao TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	β=0.12, f=162.5 MHz half-wave resonator for Rare Isotope Science Project (RISP) was recently tested at TRIUMF. We briefly report the vertical test result: At 2K, the cavity achieved Q₀=2·10⁹ at E_acc=6.4 MV/m and the performance was limited at E_acc=7.8 MV/m by intense field emission. The surface processing was standard: 120 micron buffered chemical polishing followed by high pressure rinsing. After first cold test, 120C baking was done and the corresponding result was also obtained.
	Poster TUPB072 [0.414 MB]
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WEA2A01	High-Velocity Spoke Cavities	cavity, simulation, linac, proton	943
	C.S. Hopper ODU, Norfolk, Virginia, USA H. Park JLab, Newport News, Virginia, USA
	There are several current and recent projects which explore the feasibility of spoke-loaded cavities operating in the high-velocity region. Spoke cavities have a large number of geometric parameters which often influence multiple rf properties. Fabricating, handling, and processing these cavities presents some unique challenges, not unlike other TEM-class structures. This paper will summarize the current efforts toward the design, fabrication, and testing of spoke cavities with optimum beta greater than 0.8.
	Slides WEA2A01 [1.029 MB]
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WEBA04	Performances of Spiral2 Low and High Beta Cryomodules	cryomodule, linac, cavity, cryogenics	967
	C. Marchand, P. Bosland, G. Devanz, O. Piquet CEA/IRFU, Gif-sur-Yvette, France P.-E. Bernaudin, R. Ferdinand GANIL, Caen, France Y. Gómez Martínez LPSC, Grenoble Cedex, France D. Longuevergne, G. Olry IPN, Orsay, France
	All SPIRAL2 cryomodules (twelve with one quarter wave resonator (QWR) at β=0.07 and seven with two QWRs at β=0.12) have been produced and qualified, and are now in installation phase on the LINAC at GANIL. After a general introduction on the LINAC, we will first remember and compare the different design choices taken for the two families of cryomodules. We will then present a summary of the techniques used for the preparation and integration of the cavities in the cryomodules, and compare the achieved performances with design parameters. At last, we describe the status of the LINAC installation as of end of August 2015.
	Slides WEBA04 [4.577 MB]
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WEBA06	Design Studies for Quarter-Wave Resonators and Cryomodules for the Riken SC-LINAC	linac, cryomodule, beam-loading, simulation	976
	N. Sakamoto, O. Kamigaito, H. Okuno, K. Ozeki, K. Suda, Y. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan H. Hara, K. Okihira, K. Sennyu, T. Yanagisawa MHI, Hiroshima, Japan E. Kako, H. Nakai, K. Umemori KEK, Ibaraki, Japan
	Recently we proposed a new project aimed at intensity upgrade of uranium beams of RIKEN RIBF. In this new project, construction of a superconducting linac is planned replacing the injector cyclotron so called RRC. The RIKEN superconducting linac consists of 14 cryomodules each of which contains four quarter-wave-resonators (QWRs) in each. The QWR operates at an rf frequency of 73 MHz in the continuous wave mode with beta as low as 0.055-1.008. A coaxial probe-type RF fundamental power-coupler which transmits RF power of several kW will be utilized for beam loading of 1.3 kW/resonator at the maximum with Qext of several x10⁶. Tuning of the resonant frequency will be realized with a mechanical tuner pressing the resonator wall in the direction parallel to the beam. This year, we started a development of a test cryomodule with SC-QWRs. In this paper, design studies for a SC-QWR and its cryomodule, e.g., QWR, coupler, and, tuner will be presented together with a construction schedule of the prototype. Prototyping of a superconducting cavity and its test cryomodule was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).
	Slides WEBA06 [17.564 MB]
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THBA02	Recent Development in Vertical Electropolishing	cavity, cathode, experiment, SRF	1024
	V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan K. Ishimi MGI, Chiba, Japan
	Horizontal electropolishing (HEP) is being used for final surface treatment of niobium SRF cavities. However a HEP system is equipped with complicated mechanism that makes it expensive and enhances cost of surface treatment of cavities especially when mass production is considered. Vertical electropolishing (VEP) has been introduced by other labs and the research is being carried out to establish the VEP technique. The VEP system requires simple mechanism and has advantages over HEP setup. Positive results have been obtained from the VEPed cavities also as shown by other labs. However further improvement in a VEP setup, cathode and VEP parameters is required. Marui Galvanizing Co., Ltd in collaboration with KEK has been working for development of VEP system, optimization of cathode and VEP parameters to obtain uniform Nb removal with a smooth surface of a cavity. Here we report our recent development of VEP system, unique Ninja cathode and parameter optimization with a 1-cell coupon cavity containing 6 Nb disk coupons at the beam pipes, irises and equator. The coupon surfaces were analyzed to obtain detail of the cavity surface.
	Slides THBA02 [5.703 MB]
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THPB083	Energetic Copper Coating on Stainless Steel Power Couplers for SRF Application	SRF, cathode, plasma, laser	1330
	I. Irfan, S.F. Chapman, M. Krishnan, K.M. Velas AASC, San Leandro, California, USA W. Kaabi LAL, Orsay, France
	Funding: This research is supported by the US DOE via and SBIR grant: DE-SC0009581 Delivering RF power from the outside (at room temperature) to the inside of SRF cavities (at ~4 K temperature), requires a power coupler to be thermally isolating, while still electrically conducting on the inside. Stainless steel parts that are coated on the insides with a few skin depths of copper can meet these conflicting requirements. The challenge has been the adhesion strength of copper coating on stainless steel coupler parts when using electroplating methods. These methods also require a nickel flash layer that is magnetic and can therefore pose problems. Alameda Applied Sciences Corporation (AASC) uses Coaxial Energetic Deposition (CED) from a cathodic arc plasma to grow copper films directly on stainless steel coupler parts with no Ni layer and no electrochemistry. The vacuum arc plasma consists of ~100 eV Cu ions that penetrate a few monolayers into the stainless steel substrate to promote growth of highly adhesive films with crystalline structure. Adhesion strength and coating quality of copper coatings on complex stainless steel tubes, bellows, mock coupler parts and an actual Tesla Test Facility (TTF) type coupler part, are discussed. * Adhesion and Cu quality testing were done for us by the Fermilab Technical Division, Superconducting RF Development Department
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THPB084	Design of Input Coupler for RIKEN Superconducting Quarter-Wavelength Resonator	cavity, radiation, cryomodule, Windows	1335
	K. Ozeki, O. Kamigaito, H. Okuno, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan E. Kako, H. Nakai, K. Umemori KEK, Ibaraki, Japan K. Okihira, K. Sennyu, T. Yanagisawa MHI, Hiroshima, Japan
	In RIKEN Nishina Center, for the purpose of development of elemental technology for the superconducting linear accelerator, the designing and construction of accelerator system based on superconducting quarter-wavelength resonator are carried out. The basic designs of the input coupler are as follows: The resonance frequency of the cavity is 75.5 MHz and assumed beam loading is about 1 kW. Double vacuum windows, which are disk-type, are adopted. A thermal anchor of 40 K is installed near the cold-window. The optimum positions of the cold-window and the thermal anchor depending on the effective RRR of copper-plate are being studied. In this contribution, the details of these designs will be reported. This work was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).
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THPB092	Mechanical Design of a High Power Coupler for the PIP-II 162.5 MHz RF Quadrupole	rfq, vacuum, cavity, ion-source	1357
	O.V. Pronitchev, S. Kazakov Fermilab, Batavia, Illinois, USA
	PXIE is a prototype front end system for the proposed PIP-II accelerator upgrade at Fermilab. An integral component of the front end is a 162.5 MHz, normal conducting, continuous wave (CW), radiofrequency quadrupole (RFQ) cavity. Two identical couplers will deliver approximately 100 kW total CW RF power to the RFQ. Fermilab has designed and procured main couplers for the CW RFQ accelerating cavity. The mechanical design of the coupler, along with production status, is presented below.
	Poster THPB092 [0.476 MB]
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THPB100	Nb Coatings on Bellows Used in SRF Accelerators	SRF, cavity, impedance, plasma	1379
	S.F. Chapman, I. Irfan, M. Krishnan, K.M. Velas AASC, San Leandro, California, USA
	Funding: This research is supported by the US DOE via SBIR grant: DE-SC0007678 Alameda Applied Sciences Corporation (AASC) is developing bellows with the strength and flexibility of stainless steel and the low surface impedance of a superconductor. Such unique bellows would enable alignment of SRF cavity sections with greatly reduced RF losses. To that end, we grow Nb thin films via Coaxial Energetic Deposition (CED) from a cathodic arc plasma. Films of Nb were grown on stainless steel bellows, with and without an intermediate layer of Cu deposited via the same technique, to produce a working bellows with a well adhered superconducting inner layer. The Nb coated bellows have undergone tests conducted by our collaborators to evaluate their RF performance.
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Paper

Title

Other Keywords

Page

MOAA05

Status of the RISP Superconducting Heavy Ion Accelerator

cryomodule, linac, rfq, ECR

31

D. Jeon
IBS, Daejeon, Republic of Korea

Funding: This work was supported by the the Institute for Basic Science funded by the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of Korea.
Construction of the RISP heavy ion accelerator facility is in progress in Korea. The driver linac is a superconducting linac that can accelerate uranium to proton beams, delivering 400 kW beam power to various targets. Prototyping and test of the superconducting cavities and cryomodules are proceeding. Prototype superconducting cavities were fabricated through domestic vendors and their vertical tests were performed in collaboration with TRIUMF. Vertical tests showed good performance of the prototype cavities, which verified that there were no significant issues of the cavity design and fabrication. SRF Test Facility is under construction to be completed by early 2016. Progress report of the RAON accelerator systems is presented.

Slides MOAA05 [5.587 MB]

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MOPB035

Nature and Implication of Found Actual Particulates on the Inner Surface of Cavities in a Full-Scale Cryomodule Previously Operated With Beams

cavity, cryomodule, vacuum, operation

164

R.L. Geng, J.F. Fischer, E.A. McEwen, O. Trofimova
JLab, Newport News, Virginia, USA

Field emission in an SRF cavity is often the result of small foreign particulates lodging on the cavity inner surface. To avoid these particulate field emitters, careful cleaning and handling of individual cavities and clean room assembly of cavity strings are common practice. Despite these elaborate processes, some particulates persist to stay on the final surface of a beam-ready cavity. Moreover, as will be shown in this contribution, new particulates accumulate after a cryomodule is placed in the accelerator tunnel. The nature of these accumulated particulates on the inner surface of a beam-accelerating cavity is largely unknown for two reasons: (1) lack of access to such surfaces; (2) lack of a workable procedure for investigation without destroying the cavity. In this contribution, we report the first study on found actual particulates on the inner surface of 5-cell CEBAF cavities in a full-scale cryomodule previously operated with beam. The nature of the studied particulates is presented. The implication of the findings will be discussed in view of reliable and efficient operation of CEBAF and future large-scale SRF accelerators.

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MOPB036

TOF-SIMS Study of Nitrogen Doping Niobium Samples

niobium, experiment, cavity, vacuum

169

Z.Q. Yang, L. Lin, X.Y. Lu, W.W. Tan, D.Y. Yang, J. Zhao
PKU, Beijing, People's Republic of China

Nitrogen doping treatment with the subsequent electropolishing (EP) of the niobium superconducting cavity can significantly increase the cavity’s quality factor up to a factor of 3. The nitrogen doping experiment has been successfully repeated and demonstrated. But the mechanism of the nitrogen doping effect remains unclear. Nitrogen doping study on niobium samples was carried out in Peking University. The niobium samples were manual processed to avoid heat generation. The experiment condition is close to that of the Fermilab. After the nitrogen doping treatment, the samples were mildly electropolished with the thickness of 1.3μm, 1.9μm, 3.3μm, 4.2μm, 5.1μm, 5.9μm and 7.0μm. The time of flight secondary ion mass spectrometry (TOF-SIMS) measurements show that the samples directly after nitrogen doping have a much higher nitrogen concentration in the depth of about 90nm. When the EP removal is larger than 1.3μm, the samples’ impurity elements is remarkably reduced and their distribution is similar to each other. Also the measured results to some extent prove that EP removal can introduce H to the niobium surface.

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MOPB065

Recent Measurements on the SC 325 MHz CH-Cavity

cavity, linac, heavy-ion, controls

255

M. Busch, M. Amberg, M. Basten, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
M. Amberg
HIM, Mainz, Germany

Funding: Work supported by GSI, BMBF Contr. No. 06FY7102
At the Institute for Applied Physics (IAP), Frankfurt University, a sc 325 MHz CH-Cavity has been designed and fabricated. Successful tests at 4 K and 2 K with gradients up to 14.1 MV/m have been performed. The cavity is destined for a 11.4 AMeV 10 mA ion beam at the GSI UNILAC, Darmstadt. Consisting of 7 gaps and a geometrical beta of 0.16 this resonator is designed to provide a gradient of 5 MV/m. Novel features of this structure comprise a compact design, low electric peak fields, improved surface processing possibilities and power coupling. In addition a tuner system based on mechanically deformable bellow tuners attached inside the cavity and driven either by a stepping motor or a piezo actuator will keep the cavity on resonance. This contribution reports about the latest measurements on the cavity with the recently attached helium vessel and a renewed surface processing.

Poster MOPB065 [1.270 MB]

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MOPB066

R&D Status of the New Superconducting CW Heavy Ion LINAC@GSI

cavity, linac, simulation, operation

258

M. Basten, M. Busch, F.D. Dziuba, D. Mäder, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, V. Gettmann, M. Heilmann, S. Mickat
GSI, Darmstadt, Germany

To keep the ambitious Super Heavy Element (SHE) physics program at GSI competitive a superconducting (sc) continuous wave (cw) high intensity heavy ion LINAC is currently under progress as a multi-stage R&D program of GSI, HIM and IAP*. The baseline linac design consists of a high performance ion source, a new low energy beam transport line, an (cw) upgraded High Charge State Injector (HLI), and a matching line (1.4 MeV/u) which is followed by the new sc-DTL LINAC for post acceleration up to 7.3 MeV/u. In the present design the new cw-heavy ion LINAC comprises constant-beta sc Crossbar-H-mode (CH) cavities operated at 217 MHz. The advantages of the proposed beam dynamics concept applying a constant beta profile are easy manufacturing with minimized costs as well as a straightforward energy variation**. An important milestone will be the full performance test of the first CH cavity (Demonstrator), in a horizontal cryo module with beam. An advanced demonstrator setup comprising a string of cavities and focussing elements is proposed to build from 10 short CH-cavities with 8 gaps. The corresponding simulations and technical layout of the new cw heavy ion LINAC will be presented.
* W. Barth et al., Further R&D for a new Superconducting cw Heavy Ion LINAC@GSI, IPAC2014, THPME004
**M. Schwarz et al., Beam Dynamics for the sc cw Heavy Ion Linac at GSI, IPAC2015, THPF025

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MOPB067

Steps Towards Superconducting CW-LINAC for Heavy Ions at GSI

linac, heavy-ion, quadrupole, cavity

262

M. Miski-Oglu, M. Amberg, K. Aulenbacher, V. Gettmann
HIM, Mainz, Germany
W.A. Barth, M. Heilmann, S. Mickat, S. Yaramyshev
GSI, Darmstadt, Germany
M. Basten, D. Bänsch, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany

Providing heavy ion beams for the ambitious experiment program at GSI, the Universal Linear Accelerator (UNILAC) serves as a powerful high duty factor (25%) accelerator. Beam time availability for SHE-research will be decreased due to the limitation of the UNILAC providing a proper beam for FAIR simultaneously. To keep the GSI-SHE program competitive on a high level, a standalone sc cw-LINAC in combination with the upgraded GSI High Charge State injector is planned to build. In preparation for this the first linac section (financed by HIM and partly by HGF-ARD-initiative) will be tested in 2015 as a demonstrator. After successful testing the construction of an extended cryomodule comprising two further, but shorter CH cavities is foreseen to test until end of 2017. In this contribution the measurement of the beam parameters at the entrance of CW-Demonstartor, the preliminary simulation of beam dynamics for the first stage of advanced demonstrator will be presented. As a final R&D step towards an entire linac an advanced cryo module comprising up to five CH cavities is envisaged for 2019 serving for first user experiments at the coulomb barrier.

Poster MOPB067 [2.807 MB]

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MOPB068

Pulsed SC Ion Linac as an Injector to Booster of Electron Ion Collider

linac, operation, cavity, proton

265

P.N. Ostroumov, Z.A. Conway, B. Mustapha
ANL, Argonne, USA
B. Erdelyi
Northern Illinois University, DeKalb, Illinois, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under contract number DE-AC02-06CH11357.
The electron-ion collider (EIC) being developed at JLAB requires a new ion accelerator complex (IAC). The IAC includes a new linac and a booster accelerator facility. The new facility is required for the acceleration of ions from protons to lead for colliding beam experiments with electrons in the EIC storage ring. Originally, we proposed a pulsed linac which is based upon a NC front end, < 5 MeV/u, with a SC section for energies > 5 MeV/u and capable of providing 285 MeV protons and ~100 MeV/u lead ions for injection into the IAC booster. A recent cost optimization study of the IAC suggested that lower injection energy into the booster may reduce the overall project cost with ~120 MeV protons and ~40 MeV/u lead ions. Stronger space charge effects in the booster caused by lower injection energy will be mitigated by the booster design. In this paper we discuss both linac options.

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MOPB115

Surface Studies of Plasma Processed Nb Samples

plasma, cavity, vacuum, SRF

438

P.V. Tyagi, R. Afanador, B. DeGraff, M. Doleans, B.S. Hannah, M.P. Howell, S.-H. Kim, J.D. Mammosser, C.J. McMahan, J. Saunders, S.E. Stewart
ORNL, Oak Ridge, Tennessee, USA

Funding: This work is supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
Contaminants present at top surface of superconducting radio frequency (SRF) cavities can act as field emitters and restrict the cavity accelerating gradient. A room temperature in-situ plasma processing technology for SRF cavities aiming to clean hydrocarbons from inner surface of cavities has been recently developed at the Spallation Neutron Source (SNS). Surface studies of the plasma processed Nb samples by Secondary ion mass spectrometry (SIMS) and Scanning Kelvin Probe (SKP) showed that the NeO2 plasma processing is very effective to remove carbonaceous contaminants from top surface and improves the surface work function by 0.5 to 1.0 eV.
*M. Doleans et al., Proc. 2013 SRF, Paris, France.
**P. V. Tyagi, et al., Proc. Linac14, Geneva, Switzerland.
***M. Doleans et al., These proceedings.

Poster MOPB115 [0.524 MB]

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TUBA03

On the Understanding of Q-Slope of Niobium Thin Films

ECR, niobium, SRF, cavity

494

S. Aull, T. Junginger, A. Sublet, W. Venturini Delsolaro, P. Zhang
CERN, Geneva, Switzerland
J. Knobloch
HZB, Berlin, Germany
J. Knobloch
University of Siegen, Siegen, Germany
A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

The Q-slope of niobium coated copper cavities at medium fields is still the limiting factor for the application the Nb/Cu technology in accelerators. This paper presents a dedicated study of a niobium coating with bulk-like characteristics which shows a Q-slope comparable to bulk Nb at 400 MHz and 4 K. Combining the bulk like film with recent findings of the HIE Isolde indicates that the film microstructure and the Nb/Cu interface are the key aspects to understanding the Q-slope.

Slides TUBA03 [3.414 MB]

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TUPB015

A New Cleanroom With Facilities for Cleaning and Assembly of Superconducting Cavities at Helmholtz-Institut Mainz

cavity, linac, heavy-ion, status

575

F. Schlander, K. Aulenbacher, R.G. Heine
IKP, Mainz, Germany
K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

The Helmholtz-Institut Mainz HIM will operate a clean room facility for the assembly and possible re-treatment of superconducting cavities. This is mandatory for several SRF accelerator projects, like the advanced demonstrator for a dedicated sc heavy ion cw-linac at HIM or other projects pursued by research facilities or universities close by. While the installation of the clean room is in progress, the procurement of the appliances is ongoing. The present equipment planned and the current status of the installation will be presented.

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TUPB016

Progress on Superconducting Linac for the RAON Heavy Ion Accelerator

cavity, linac, cryomodule, electron

578

H.J. Kim
IBS, Daejeon, Republic of Korea

The RISP (Rare Isotope Science Project) has been proposed as a multi-purpose accelerator facility for providing beams of exotic rare isotopes of various energies. It can deliver ions from proton to uranium. Proton and uranium ions are accelerated upto 600 MeV and 200 MeV/u respectively. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. In this paper, we present the RISP linac design, the prototyping of superconducting cavity and cryomodule.

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TUPB020

Recent Status New Superconducting CW Heavy Ion LINAC@GSI

cavity, solenoid, linac, heavy-ion

589

V. Gettmann, M. Amberg, K. Aulenbacher, W.A. Barth, M. Miski-Oglu
HIM, Mainz, Germany
M. Amberg, M. Basten, D. Bänsch, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, M. Heilmann, S. Mickat, S. Yaramyshev
GSI, Darmstadt, Germany

The demonstrator is a prototype of the first section of the proposed cw-LINAC@GSI, comprising a superconducting CH-cavity embedded by two superconducting solenoids. The sc CH-structure is the key component and offers a variety of research and development. The beam focusing solenoids provide maximum fields of 9.3 T at an overall length of 380 mm and a free beam aperture of 30 mm. The magnetic induction of the fringe is minimized to 50 mT at the inner NbTi-surface of the neighboring cavity. The fabrication of the key components is still in progress and is near to completion. After cold performance testing of the RF cavity, the helium jacket will be welded on. The cryostat is partly assembled and will be finished in the next weeks. The test environment is completely prepared. Advanced emittance measurement is foreseen to prepare for best matching of the heavy ion beam from the injector. Integration of the cryostat into the beam line, the first cool down of the module and commissioning of the RF elements will be performed as next steps towards a complete testing of the demonstrator.

Poster TUPB020 [8.595 MB]

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TUPB024

Tuning the Linac With Superconducting Resonator Used as a Phase Detector

linac, acceleration, detector, bunching

602

N.R. Lobanov, P. Linardakis, D. Tsifakis
Research School of Physics and Engineering, Australian National University, Canberra, Australian Capitol Territory, Australia

The ANU Heavy Ion Facility is comprised of a 15 MV electrostatic accelerator and superconducting linac booster. The beam is double terminal stripped to provide high charge states at the entrance to the linac, which consists of twelve β=0.1 Split Loop Resonators (SLR). Each SLR needs to be individually tuned in phase and amplitude for optimum acceleration efficiency. The amplitude and phase of the superbuncher and time energy lens also have to be correctly set. The linac set up procedure developed at ANU utilises a beam profile monitor in the middle of a 180 degree achromat and a new technique based on a superconducting resonator operating in a beam bunch detection mode. Both techniques are used to derive a full set of phase distributions for quick and efficient setting up of the entire linac. Verification of the superconducting phase detector is accomplished during routine linac operations and is complemented by longitudinal phase space simulations. The new technique allows better resolution for setting the resonator acceleration phase and better sensitivity to accelerating current.

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TUPB025

Tuning the Superconducting Linac at Low Beam Intensities

linac, bunching, acceleration, operation

607

N.R. Lobanov, P. Linardakis, D. Tsifakis
Research School of Physics and Engineering, Australian National University, Canberra, Australian Capitol Territory, Australia

The ANU Heavy Ion Facility comprises a 15 MV electrostatic accelerator followed by a superconducting linac booster. The beam is foil stripped in the terminal and then stripped again to provide high charge states at the entrance to the linac. Employment of double terminal stripping allows the system to accelerate beams with mass up to 70 amu. The disadvantage of double terminal stripping is low beam intensity of few particle nA delivered to the linac. The linac encompasses twelve β=0.1 lead tin plated Split Loop Resonators (SLR) housed in four module cryostats. One of the linac set up procedures that developed at ANU utilises U-bend at the end of the linac. One special wide Beam Profile Monitor (BPM) is installed after 90 degrees magnet. The technique allows to set correct phase by observing the displacement of beam profile versus phase shift of the last phase locked resonator. In this paper a simple method has been proposed to improve sensitivity of commercially available BPM for efficient operation with low beam intensities. The system demonstrated very high stability, simplicity of operation and high reliability allowing sustained operation of the LINAC facility.

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TUPB029

Material Quality & SRF Performance of Nb Films Grown on Cu via ECR Plasma Energetic Condensation

ECR, SRF, plasma, interface

622

A-M. Valente-Feliciano, G.V. Eremeev, C.E. Reece, J.K. Spradlin
JLab, Newport News, Virginia, USA
S. Aull
CERN, Geneva, Switzerland
Th. Proslier
ANL, Argonne, Illinois, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The RF performance of bulk Nb cavities has continuously improved over the years and is approaching the intrinsic limit of the material. Although some margin seems still available with processes such as N surface doping, long term solutions for SRF surfaces efficiency enhancement need to be pursued. Over the years, Nb/Cu technology, despite its shortcomings, has positioned itself as an alternative route for the future of superconducting structures used in accelerators. Significant progress has been made in recent years in the development of energetic deposition techniques such as Electron Cyclotron Resonance (ECR) plasma deposition. Nb films with very high material quality have then been produced by varying the deposition energy alluding to the promise of performing SRF films. This paper presents RF measurements, correlated with surface and material properties, for Nb films showing how, by varying the film growth conditions, the Nb film quality and surface resistance can be altered and how the Q-slope can be eventually overcome.

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TUPB034

Bulk Niobium Polishing and Electropolishing Steps for Thinfilm Coated Copper SRF Cavities

cavity, SRF, plasma, cathode

633

M. Krishnan, S.F. Chapman, I. Irfan, K.M. Velas
AASC, San Leandro, California, USA
J.K. Spradlin, H. Tian
JLab, Newport News, Virginia, USA

Funding: Research supported at AASC by the US DOE via SBIR grant: DE-SC0011371. The JLab effort was provided by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Alameda Applied Sciences Corporation (AASC) grows Nb thin films via Coaxial Energetic Deposition (CED) from a cathodic arc plasma. The plasma consists of 60-120eV Nb ions (Nb+ and Nb++) [1] that penetrate a few monolayers into the substrate [2] and enable sufficient surface mobility to ensure that the lowest energy state (crystalline structure with minimal defects) is accessible to the film [3]. One limitation of CED thinfilms is the presence of Nb macroparticles (~0.1-10 microns) that could be deleterious to high field performance of the SRF cavity. One way to remove such macroparticles [4] is to grow a thick film (~3-5 microns), followed by mechanical polishing (MP) using the finest media as might be applied in Centrifugal Barrel Polishing (CBP) to achieve a 0.4 micron surface figure, and an electropolishing (EP) step to remove ~1 micron of Nb that also removes all traces of embedded media in the film. The residual 2-4 micron Nb film should more nearly resemble the surface of a bulk Nb cavity that has been subjected to the same steps. This paper describes experiments conducted on Cu coupons as a prelude to an SRF Cu cavity coating.

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TUPB046

Structure and Composition of Nb3Sn Diffusion Coated Films on Nb

niobium, electron, SRF, cavity

669

J. Tuggle, M.J. Kelley
Virginia Polytechnic Institute and State University, Blacksburg, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA
M.J. Kelley, H. Xu
The College of William and Mary, Williamsburg, Virginia, USA

Funding: Co-authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. College of William & Mary supported by U.S. DOE Office of High Energy Physics under grant DE-SC-0014475
The structure and composition of Nb3Sn films obtained by diffusion coating niobium coupons and SRF cavities were investigated by x-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS) and electron back-scatter diffraction (EBSD), including native surfaces, depth profiles and cross-sections. We find that the native surface oxide is significantly tin-rich, we have measured depth profiles. We find that the grains apparent in the SEM images are individual crystallites having no evident relationship to the substrate or each other.

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TUPB056

Characterization of Nb3Sn Coated Nb Samples

SRF, electron, cavity, niobium

708

Y. Trenikhina, S. Posen, A. Romanenko
Fermilab, Batavia, Illinois, USA
D.L. Hall
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
M. Liepe
Cornell University, Ithaca, New York, USA

Nb3Sn has a great potential to replace traditional Nb for the fabrication of SRF cavities. The higher critical temperature of Nb3Sn potentially allows for an increased operational temperature for SRF cavities, which promises cryogenic cost savings. We present preliminary characterization of Nb3Sn layer grown on flat Nb sample prepared by the same chemical vapor deposition method that is used for the cavity coating. SEM, TEM/EDS, TEM imaging and diffraction characterization was used in order to evaluate any chemical and structural defects that could be responsible for the limited quench field and high residual resistance. Variation of local stoichiometry was found in the Nb3Sn layer, which is in line with previous studies. Regions of decreased Sn content can have a lower Tc in comparison to the stoichiometric composition, which may be responsible for the limited performance. AES investigations of the Nb3Sn surface before and after HF-rinse were done in order to explore the mechanism that is responsible for the performance degradation of HF-rinsed Nb3Sn coated cavities.

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TUPB062

Evaluation of Sc Property Coated on a Surface

vacuum, gun, neutron, cavity

723

Y. Iwashita, Y. Fuwa
Kyoto ICR, Uji, Kyoto, Japan
M. Hino
Kyoto University, Research Reactor Institute, Osaka, Japan
T. Kubo, T. Saeki
KEK, Ibaraki, Japan

Funding: This work was supported by JSPS KAKENHI Grant Number 26600142.
We are trying to deposit thin superconducting material on a substrate for higher accelerating field gradients. In order to evaluate the deposit method, surface properties are under measurement. Some results on measurements at DC and a preparation status toward RF measurement will be reported.

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TUPB072

Report of Vertical Test of the β=0.12 Half-Wave Resonator at RISP

cavity, vacuum, TRIUMF, simulation

747

G.-T. Park, H.J. Cha, H. Kim, W.K. Kim
IBS, Daejeon, Republic of Korea
Z.Y. Yao
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

β=0.12, f=162.5 MHz half-wave resonator for Rare Isotope Science Project (RISP) was recently tested at TRIUMF. We briefly report the vertical test result: At 2K, the cavity achieved Q₀=2·10⁹ at E_acc=6.4 MV/m and the performance was limited at E_acc=7.8 MV/m by intense field emission. The surface processing was standard: 120 micron buffered chemical polishing followed by high pressure rinsing. After first cold test, 120C baking was done and the corresponding result was also obtained.

Poster TUPB072 [0.414 MB]

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WEA2A01

High-Velocity Spoke Cavities

cavity, simulation, linac, proton

943

C.S. Hopper
ODU, Norfolk, Virginia, USA
H. Park
JLab, Newport News, Virginia, USA

There are several current and recent projects which explore the feasibility of spoke-loaded cavities operating in the high-velocity region. Spoke cavities have a large number of geometric parameters which often influence multiple rf properties. Fabricating, handling, and processing these cavities presents some unique challenges, not unlike other TEM-class structures. This paper will summarize the current efforts toward the design, fabrication, and testing of spoke cavities with optimum beta greater than 0.8.

Slides WEA2A01 [1.029 MB]

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WEBA04

Performances of Spiral2 Low and High Beta Cryomodules

cryomodule, linac, cavity, cryogenics

967

C. Marchand, P. Bosland, G. Devanz, O. Piquet
CEA/IRFU, Gif-sur-Yvette, France
P.-E. Bernaudin, R. Ferdinand
GANIL, Caen, France
Y. Gómez Martínez
LPSC, Grenoble Cedex, France
D. Longuevergne, G. Olry
IPN, Orsay, France

All SPIRAL2 cryomodules (twelve with one quarter wave resonator (QWR) at β=0.07 and seven with two QWRs at β=0.12) have been produced and qualified, and are now in installation phase on the LINAC at GANIL. After a general introduction on the LINAC, we will first remember and compare the different design choices taken for the two families of cryomodules. We will then present a summary of the techniques used for the preparation and integration of the cavities in the cryomodules, and compare the achieved performances with design parameters. At last, we describe the status of the LINAC installation as of end of August 2015.

Slides WEBA04 [4.577 MB]

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WEBA06

Design Studies for Quarter-Wave Resonators and Cryomodules for the Riken SC-LINAC

linac, cryomodule, beam-loading, simulation

976

N. Sakamoto, O. Kamigaito, H. Okuno, K. Ozeki, K. Suda, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
H. Hara, K. Okihira, K. Sennyu, T. Yanagisawa
MHI, Hiroshima, Japan
E. Kako, H. Nakai, K. Umemori
KEK, Ibaraki, Japan

Recently we proposed a new project aimed at intensity upgrade of uranium beams of RIKEN RIBF. In this new project, construction of a superconducting linac is planned replacing the injector cyclotron so called RRC. The RIKEN superconducting linac consists of 14 cryomodules each of which contains four quarter-wave-resonators (QWRs) in each. The QWR operates at an rf frequency of 73 MHz in the continuous wave mode with beta as low as 0.055-1.008. A coaxial probe-type RF fundamental power-coupler which transmits RF power of several kW will be utilized for beam loading of 1.3 kW/resonator at the maximum with Qext of several x10⁶. Tuning of the resonant frequency will be realized with a mechanical tuner pressing the resonator wall in the direction parallel to the beam. This year, we started a development of a test cryomodule with SC-QWRs. In this paper, design studies for a SC-QWR and its cryomodule, e.g., QWR, coupler, and, tuner will be presented together with a construction schedule of the prototype. Prototyping of a superconducting cavity and its test cryomodule was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

Slides WEBA06 [17.564 MB]

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THBA02

Recent Development in Vertical Electropolishing

cavity, cathode, experiment, SRF

1024

V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
K. Ishimi
MGI, Chiba, Japan

Horizontal electropolishing (HEP) is being used for final surface treatment of niobium SRF cavities. However a HEP system is equipped with complicated mechanism that makes it expensive and enhances cost of surface treatment of cavities especially when mass production is considered. Vertical electropolishing (VEP) has been introduced by other labs and the research is being carried out to establish the VEP technique. The VEP system requires simple mechanism and has advantages over HEP setup. Positive results have been obtained from the VEPed cavities also as shown by other labs. However further improvement in a VEP setup, cathode and VEP parameters is required. Marui Galvanizing Co., Ltd in collaboration with KEK has been working for development of VEP system, optimization of cathode and VEP parameters to obtain uniform Nb removal with a smooth surface of a cavity. Here we report our recent development of VEP system, unique Ninja cathode and parameter optimization with a 1-cell coupon cavity containing 6 Nb disk coupons at the beam pipes, irises and equator. The coupon surfaces were analyzed to obtain detail of the cavity surface.

Slides THBA02 [5.703 MB]

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THPB083

Energetic Copper Coating on Stainless Steel Power Couplers for SRF Application

SRF, cathode, plasma, laser

1330

I. Irfan, S.F. Chapman, M. Krishnan, K.M. Velas
AASC, San Leandro, California, USA
W. Kaabi
LAL, Orsay, France

Funding: This research is supported by the US DOE via and SBIR grant: DE-SC0009581
Delivering RF power from the outside (at room temperature) to the inside of SRF cavities (at ~4 K temperature), requires a power coupler to be thermally isolating, while still electrically conducting on the inside. Stainless steel parts that are coated on the insides with a few skin depths of copper can meet these conflicting requirements. The challenge has been the adhesion strength of copper coating on stainless steel coupler parts when using electroplating methods. These methods also require a nickel flash layer that is magnetic and can therefore pose problems. Alameda Applied Sciences Corporation (AASC) uses Coaxial Energetic Deposition (CED) from a cathodic arc plasma to grow copper films directly on stainless steel coupler parts with no Ni layer and no electrochemistry. The vacuum arc plasma consists of ~100 eV Cu ions that penetrate a few monolayers into the stainless steel substrate to promote growth of highly adhesive films with crystalline structure. Adhesion strength and coating quality of copper coatings on complex stainless steel tubes, bellows, mock coupler parts and an actual Tesla Test Facility (TTF) type coupler part, are discussed.
* Adhesion and Cu quality testing were done for us by the Fermilab Technical Division, Superconducting RF Development Department

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THPB084

Design of Input Coupler for RIKEN Superconducting Quarter-Wavelength Resonator

cavity, radiation, cryomodule, Windows

1335

K. Ozeki, O. Kamigaito, H. Okuno, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
E. Kako, H. Nakai, K. Umemori
KEK, Ibaraki, Japan
K. Okihira, K. Sennyu, T. Yanagisawa
MHI, Hiroshima, Japan

In RIKEN Nishina Center, for the purpose of development of elemental technology for the superconducting linear accelerator, the designing and construction of accelerator system based on superconducting quarter-wavelength resonator are carried out. The basic designs of the input coupler are as follows: The resonance frequency of the cavity is 75.5 MHz and assumed beam loading is about 1 kW. Double vacuum windows, which are disk-type, are adopted. A thermal anchor of 40 K is installed near the cold-window. The optimum positions of the cold-window and the thermal anchor depending on the effective RRR of copper-plate are being studied. In this contribution, the details of these designs will be reported. This work was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

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THPB092

Mechanical Design of a High Power Coupler for the PIP-II 162.5 MHz RF Quadrupole

rfq, vacuum, cavity, ion-source

1357

O.V. Pronitchev, S. Kazakov
Fermilab, Batavia, Illinois, USA

PXIE is a prototype front end system for the proposed PIP-II accelerator upgrade at Fermilab. An integral component of the front end is a 162.5 MHz, normal conducting, continuous wave (CW), radiofrequency quadrupole (RFQ) cavity. Two identical couplers will deliver approximately 100 kW total CW RF power to the RFQ. Fermilab has designed and procured main couplers for the CW RFQ accelerating cavity. The mechanical design of the coupler, along with production status, is presented below.

Poster THPB092 [0.476 MB]

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THPB100

Nb Coatings on Bellows Used in SRF Accelerators

SRF, cavity, impedance, plasma

1379

S.F. Chapman, I. Irfan, M. Krishnan, K.M. Velas
AASC, San Leandro, California, USA

Funding: This research is supported by the US DOE via SBIR grant: DE-SC0007678
Alameda Applied Sciences Corporation (AASC) is developing bellows with the strength and flexibility of stainless steel and the low surface impedance of a superconductor. Such unique bellows would enable alignment of SRF cavity sections with greatly reduced RF losses. To that end, we grow Nb thin films via Coaxial Energetic Deposition (CED) from a cathodic arc plasma. Films of Nb were grown on stainless steel bellows, with and without an intermediate layer of Cu deposited via the same technique, to produce a working bellows with a well adhered superconducting inner layer. The Nb coated bellows have undergone tests conducted by our collaborators to evaluate their RF performance.

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