SRF2015 - List of Keywords (operation)

Paper	Title	Other Keywords	Page
MOAA02	Recent Progress with EU-XFEL	cryomodule, cavity, linac, cryogenics	14
	D. Reschke DESY, Hamburg, Germany
	The superconducting accelerator of the European XFEL consists of the injector part and the main linac. The injector includes one 1.3 GHz accelerator module and one 3.9 GHz third-harmonic module, while the main linac will consist of 100 accelerator modules, operating at an average design gradient of 23.6 MV/m. The fabrication and surface treatment by industry as well as RF acceptance tests of the required 808 superconducting 1.3 GHz cavities are close to an end by the time of SRF15. The accelerator module assembly, testing and installation in the tunnel is in full swing. First steps of commissioning have been made. The status and results of cavity and module RF tests at 1.3 GHz and 3.9 GHz are presented.
	Slides MOAA02 [2.903 MB]
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MOBA04	High-Q Operation of SRF Cavities: The Impact of Thermocurrents on the RF Surface Resistance	cavity, simulation, shielding, niobium	37
	J.M. Köszegi, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	For CW applications much effort is being expended to minimize the power dissipation (surface resistance) of niobium cavities. Previous studies have shown that residual resistance can be reduced by performing a thermal cycle, a procedure of warming up a cavity after initial cooldown to about 20K and cooling it down again. It was postulated that thermocurrents during cooldown generate additional trapped magnetic flux that impacts the cavity quality factor. Here, we present a more extensive study that includes measurements of two additional passband modes and that confirms the effect. A change in surface resistance of more than a factor seven was observed. In this paper, we also discuss simulations that support the claim. While the layout of the cavity LHe tank system is cylindrically symmetric, we show that the temperature dependence of the material parameters results in a non-symmetric current distribution.
	Slides MOBA04 [2.830 MB]
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MOPB001	RF Performance of Ingot Niobium Cavities of Medium-Low Purity	cavity, SRF, vacuum, radio-frequency	61
	G. Ciovati, P. Dhakal, P. Kneisel, G.R. Myneni, J.K. Spradlin JLab, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q0-values, because of the well-known dependence of the BCS-surface resistance on mean free path. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR=100-150) and low (RRR=60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with Q0-values above 1.5·10¹⁰ at 2 K. The performance of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.
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MOPB030	Measurements of Thermal Impedance on Superconducting Radiofrequency Cavities	cavity, impedance, SRF, niobium	154
	P. Dhakal, G. Ciovati, G.R. Myneni JLab, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The thermal impedance of niobium plays an important role in the stability of the superconducting radio frequency cavities used in particle accelerators. During the operation of SRF cavities, the RF power dissipated on the inner surface of the cavities and the heat transport to the helium bath depend on the thermal conductivity of niobium and the Kapitza conductance of the interface between the niobium and superfluid helium. Here, we present the results of measurements done on samples as well as on SRF cavities made of both ingot and fine-grain Nb to explore the effect of the surface preparation and crystal structure on the thermal impedance.
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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, ion, vacuum	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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MOPB039	Analysis of BCS RF Loss Dependence on N-Doping Protocols	cavity, niobium, SRF, linac	174
	A.D. Palczewski, P. Dhakal, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 with supplemental funding from the LCLS-II Project U.S. DOE Contract No. DE-AC02-76SF00515. We present a study on two parallel-path SRF cavities (one large grain and one fine grain, 1.3 GHz) which seeks to explain the correlation between the amount of nitrogen on the inner surface of a “nitrogen doped” SRF cavity and the change in the temperature dependant (packaged into term BCS) RF losses. For each doping/EP, the cavities were tested at multiple temperatures (2.0 K to 1.5 K in 0.1 K steps) to create a Q0 vs. Eacc vs. T matrix which then could be used to extract temperature dependant and independent components. After each test, the cavities were thermally cycled to 120 K and then re-cooled and retested to assess if evidence of hydrogen migration might appear even at a small level. In addition, TD-5 was also tested at fixed low field (Q0 vs. T) to fit standard BCS theory. In parallel, SIMS data was taken on like-treated samples to correlate the amount of nitrogen within the RF surface to the change in the temperature dependant fitting parameter “A”.** [] H.Tian et al., contributed to SRF2015.
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MOPB052	Determination of Bulk and Surface Superconducting Properties of N2-Doped Cold Worked, Heat Treated and Electro-polished SRF Grade Niobium	cavity, SRF, superconductivity, niobium	214
	S. Chetri, D.C. Larbalestier, Z-H. Sung ASC, Tallahassee, Florida, USA P. Dhakal JLab, Newport News, Virginia, USA P.J. Lee NHMFL, Tallahassee, Florida, USA
	Funding: Support for this work at FSU was from US DOE Award# DE-SC0009960 and the State of Florida Additional support for the National High Magnetic Field Laboratory facilities is from the NSF: NSF-DMR-1157490 Nitrogen-doped cavities show significant performance improvement in the medium accelerating field regime due to a lowered RF surface resistivity. However, the mechanism of enhancement has not been clearly explained. Our experiments explore how N2-doping influences Nb bulk and surface superconducting properties, and compare the N2-doped properties with those obtained previously with conventionally treated samples. High purity Nb-rod was mechanically deformed and post treated based on a typical SRF cavity treatment recipe. The onset of flux penetration at Hc1, and the upper and the surface critical fields, Hc2 and Hc3, were characterized by magnetic hysteresis and AC susceptibility techniques. The surface depth profile responsible for superconductivity was examined by changing AC amplitude in AC susceptibility, and the microstructure was directly observed with EBSD-OIM. We are also investigating surface chemistry for detailed composition using XPS. We have found that N2-doping at 800 °C significantly reduces the Hc3/Hc2 ratio towards the ideal value of ~1.7, and conclude that AC susceptibility is capable of following changes to the surface properties induced by N2-doping.
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MOPB066	R&D Status of the New Superconducting CW Heavy Ion LINAC@GSI	cavity, linac, simulation, ion	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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MOPB068	Pulsed SC Ion Linac as an Injector to Booster of Electron Ion Collider	ion, linac, 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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MOPB076	Horizontal RF Test of a Fully Equipped 3.9 GHz Cavity for the European XFEL in the DESY AMTF	cavity, HOM, cryomodule, controls	301
	C.G. Maiano, C. Albrecht, R. Bospflug, J. Branlard, L. Butkowski, T. Delfs, J. Eschke, A. Gössel, F. Hoffmann, M. Hüning, K. Jensch, R. Jonas, R. Klos, D. Kostin, W. Maschmann, A. Matheisen, U. Mavrič, W.-D. Möller, C. Müller, K. Mueller, B. Petersen, P. Pierini, J. Rothenburg, O. Sawlanski, M. Schmökel, A.A. Sulimov, E. Vogel DESY, Hamburg, Germany A. Bosotti, M. Moretti, R. Paparella, P. Pierini, D. Sertore INFN/LASA, Segrate (MI), Italy E.R. Harms Fermilab, Batavia, Illinois, USA C.R. Montiel ANL, Argonne, Illinois, USA S. Pivovarov BINP SB RAS, Novosibirsk, Russia
	In order to validate the cavity package concept before the module preparation for the European XFEL Injector, one 3.9 GHz cavity, complete with magnetic shielding, power coupler and frequency tuner was tested in a specially designed single cavity cryomodule in one of the caves of the DESY Accelerator Module Test Facility (AMTF). The cavity was tested in high power pulsed operation up to the quench limit of 24 MV/m, above the vertical test qualifications and all subsystems under test (coupler, tuner, waveguide tuners, LLRF system) were qualified to design performances.
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MOPB077	Vertical Tests of XFEL 3rd Harmonic Cavities	cavity, vacuum, HOM, instrumentation	306
	D. Sertore, M. Bertucci, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, M. Moretti, R. Paparella, P. Pierini INFN/LASA, Segrate (MI), Italy A. Matheisen, M. Schmökel DESY, Hamburg, Germany C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	The 10 cavities of the EXFEL 3rd Harmonic Cryomodule have been tested and qualified, before integration in the He-tank, in our upgraded Vertical Test stand. In this paper, we report the measured RF performance of these cavities together with the main features of the test facility.
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MOPB078	Mode Sensitivity Analysis of 704.4 MHz Superconducting RF Cavities	HOM, cavity, linac, dipole	311
	K. Papke, F. Gerigk, S. Horvath-Mikulas, S. Papadopoulos, E. Pilicer, F. Pillon CERN, Geneva, Switzerland U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
	Due to the large variety of beam patterns considered for the superconducting proton linac (SPL) at CERN it is likely that the frequencies of some HOMs are close to machine lines during operation. Hence, in the interest of developing a method to shift HOM frequencies away from machine lines, we study the influence of cavity detuning and re-tuning (e.g. by Lorentz forces, field flatness tuning, frequency tuning during operation) on HOMs. The sensitivity of HOMs with respect to the fundamental mode was studied for a mono-cell and for 5-cell high-beta SPL cavities operating at 704.4 MHz. First, the variation of the HOMs during the flat-field tuning was measured. In this process, several detuning and re-tuning cycles were made to estimate the range of possible HOM frequency shifts. Secondly the effect of the frequency tuner on the HOMs is presented and finally the frequency shifts of all modes due to the cool down.
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MOPB094	Inspection and Repair Techniques for the EXFEL Superconducting 1.3 GHz Cavities at Ettore Zanon S.p.A: Methods and Results	cavity, accelerating-gradient, electron, controls	368
	G. Massaro, G. Corniani, N. Maragno Ettore Zanon S.p.A., Schio, Italy A. Matheisen, A. Navitski DESY, Hamburg, Germany P. Michelato, L. Monaco INFN/LASA, Segrate (MI), Italy
	The quality control of the inner surface of superconducting RF cavities is essential in order to assure high accelerating gradient and quality factor. Ettore Zanon S.p.A. (EZ) has implemented in the serial production an optical system that use an high-resolution camera, in order to detect various types of defects. This system is added to a grinding machine, that was specifically designed and built to repair imperfections of the cavities inner surface. This inspection and repair system is applied to recover performance limited cavities of the 1.3 GHz European XFEL project, where surface irregularities are detected, either by the Obacht inspection system at Desy or the optical system at EZ. The optical system and the grinding procedure are qualified using two series cavities limited in gradient and showing different types of surface defects. The performances of these cavities have been recovered to reach the specifications of the project. Until now, all the series XFEL cavities built by EZ, repaired with this technique, have shown an accelerating gradient well above the EXFEL goal.
	Poster MOPB094 [0.795 MB]
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MOPB095	SRF Cavity Processing and Chemical Etching Development for the FRIB Linac	cavity, SRF, linac, controls	373
	I.M. Malloch, E.S. Metzgar, L. Popielarski FRIB, East Lansing, Michigan, USA M.J. LaVere MSU, East Lansing, Michigan, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661, the State of Michigan and Michigan State University. In preparation of a rigorous superconducting RF (SRF) cavity processing and test plan for the production of the Facility for Rare Isotope Beams (FRIB) driver linac, a state-of-the-art chemical etching tool has been installed in the FRIB coldmass production facility. This paper seeks to summarize the etching equipment design, installation, and validation program and subsequent etching results for a variety of SRF cavity types and etching configurations. Bulk etching, light etching, and custom (frequency tuning) etching results for different FRIB cavities are discussed. Special emphasis is placed on the etching removal uniformity and frequency tuning reliability of these processes.
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MOPB096	Vertical Electro-Polishing at TRIUMF	cathode, cavity, TRIUMF, niobium	378
	J.J. Keir, P.R. Harmer, D. Lang, R.E. Laxdal, T. Shishido, R. Smith TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada T. Shishido KEK, Ibaraki, Japan
	A setup for electropolishing of a superconducting niobium single-cell cavity has been installed at TRIUMF. A vertical method was selected to make the setup compact. To increase removal speed at the equator and remove hydrogen bubbles at the iris surface, 4 cathode paddles were rotated in the cavity cell during electropolishing. We will report on our first electropolishing result.
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MOPB100	Cathode Geometry and Flow Dynamics Impact on Vertical Electropolishing of Superconducting Niobium Cavities	cavity, cathode, niobium, simulation	385
	L.M.A. Ferreira CERN, Geneva, Switzerland
	CERN has now a fully operating vertical electropolishing installation, which has been used for the processing of 704 MHz high-beta five-cell Superconducting Proton Linac (SPL) niobium cavities. This installation relies only on the electrolyte circulation (HF/H2SO4) for power dissipation, evacuation of gases and homogeneous finishing; thus, parameters like cathode geometry, electrolyte flow and temperature become even more crucial when compared with horizontal electropolishing installations. Based on computational simulations performed with Comsol Multiphysics® and on a methodology developed at CERN, it is possible to assess the impact of the different cathode geometries as well as of the flow on the etching rate distribution. The data obtained with two different cathode geometries are presented: electrolyte velocity distribution, etching rate distribution, average current density and minimum working potential. One geometry was defined through a purely electrochemical approach while the second was defined to minimise the difference between the maximum and the minimum electrolyte speed inside the cavity; in both cases, the influence of the electrolyte flow was taken into account.
	Poster MOPB100 [1.794 MB]
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MOPB113	Study of the Evolution of Artificial Defects on the Surface of Niobium During Electrochemical and Chemical Polishing	SRF, controls, laser, cavity	433
	L. Monaco, P. Michelato INFN/LASA, Segrate (MI), Italy A. Navitski, J. Schaffran, W. Singer DESY, Hamburg, Germany C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy A.L. Prudnikava, Y. Tamashevich University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	The presence of defects on the inner surface of Nb superconducting RF structures might limit its final performance. For this reason, strict requirements are imposed during mechanical production of the cavities, specifically on the quality control of the inner surface of components, to avoid the presence of defects or scratches. Nevertheless, some defects may remain also after control or can arise from the following production steps. Understanding the evolution of the defect might shine new insight on its origin and help in defining possible repair techniques. This paper reports the topographical evolution of defects on a Nb sample polished with the standard recipe used for the 1.3 GHz cavities of the EXFEL project. Various artificial defects of different shape, dimensions, and thicknesses/depths, with geometrical characteristics similar to the one that may occur during the machining and handling of cavities, have been “ad hoc” produced on the sample of the same material used for the cell fabrication. Analysis shows the evolution of the shape and profile of the defects at the different polishing steps.
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MOPB116	Developments of Horizontal High Pressure Rinsing for SuperKEKB SRF Cavities	cavity, vacuum, factory, SRF	443
	Y. Morita, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, M. Nishiwaki KEK, Ibaraki, Japan
	The Q factors of the eight superconducting accelerating cavities gradually degraded during the long-term operation of the KEKB accelerator. Since we will re-use those SRF cavities for the SuperKEKB, the performance degradation will be a serious problem. Several cavities degraded their performance significantly at high accelerating fields. The Q degradation is still acceptable for the 1.5 MV operations at SuperKEKB. However, further degradation will make the operation difficult. In order to recover the cavity performance, we developed horizontal high pressure water rinsing (HHPR). This method uses a horizontal high pressure water nozzle and inserts it directly into the cavity module. We applied this method to two degraded cavities and their degraded Q factors recovered above 10⁹ at around 2 MV. In this paper we will present the HHPR method, high power test results after the HHPR and the residual gas analysis.
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MOPB118	Cleanliness and Vacuum Acceptance Tests for the UHV Cavity String of the XFEL Linac	cavity, vacuum, controls, cryomodule	452
	S. Berry, O. Napoly, B. Visentin CEA/DSM/IRFU, France C. Boulch, C. Cloué, C. Madec, T. Trublet CEA/IRFU, Gif-sur-Yvette, France D. Henning, L. Lilje, A. Matheisen, M. Schmökel DESY, Hamburg, Germany
	The main linac of the European XFEL will consist of 100 accelerator modules, i.e. 800 superconducting accelerator cavities operated at a design gradient of 23.6MV/m. In this context CEA-Saclay built an assembly facility designed to produce one module per week, ready to be tested at DESY. The facility overcame the foreseen production rate. We would like to highlight and discuss the critical fields: cleanliness and vacuum. A new assembly method to protect final assembly against particulates contamination has been implemented on the production line. Impact on cryomodule RF test is presented. Particle transport measurements on components used for the European XFEL accelerator module are presented. The results indicate that the nominal operation of the automated pumping and venting units will not lead to particle transport. Vacuum acceptance tests are of major interest: leak tests and residual gas analysis (RGA) are used to control the absence of air leak and contamination. The RGA specifications have been slightly relaxed to ensure the production rate.
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TUPB002	Elimination of High Frequency Noise From the Beam in the Diamond Light Source Storage Ring	storage-ring, synchrotron, controls, power-supply	525
	C. Christou, A. Bogusz, P.J. Marten DLS, Oxfordshire, United Kingdom
	High frequency beam motion has been identified as a source of noise in infrared beamlines in a number of synchrotron light sources. Diamond is a third generation synchrotron light source with storage ring current maintained by two superconducting CESR-B cavities powered by IOT-driven RF amplifiers. In our case, undesirable beam motion in the kilohertz range is predominantly driven by spectral content in the voltage across the IOTs arising from the switched mode nature of the high voltage power supply. Spectral noise on the amplifiers and beam has been identified and characterised and efforts to eliminate this noise are described. Care has been taken to maintain the overall stability of the RF at Diamond and tests have been carried out on an infrared beamline to investigate the degree to which beam noise impacts beamline operation in its different operating configurations.
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TUPB008	A New Cryogenic Control System for the Vertical Test Area at Jefferson Lab	controls, PLC, cryogenics, SRF	549
	G.K. Davis, T. Goodman, P. Kushnick, T. Powers, C.M. Wilson JLab, Newport News, Virginia, USA
	Funding: DOE The Vertical Test Area at Jefferson Lab, consisting of eight vertical dewars, recently received a major upgrade by replacing the original (1995) cryogenic control system. A new, state-of-the-art, distributed control system (DC S) based on Programmable Logic Controllers (PLCs) was installed and commissioned. The new system increases facility throughput, reliability and cryogenic efficiency, while improving safety. The system employs a touchscreen graphical user interface and a highly redundant architecture on an Ethernet backbone.
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TUPB010	Plug Transfer System for GaAs Photocathodes	gun, SRF, cathode, vacuum	553
	P. Murcek, A. Arnold, P.N. Lu, J. Teichert, H. Vennekate, R. Xiang HZDR, Dresden, Germany A. Burrill HZB, Berlin, Germany
	The transport and exchange technology of Cs2Te photocathode for the ELBE superconducting rf photoinjector (SRF gun) has been successfully developed and tested at HZDR. The next goal is to realize the transport of GaAs photocathode into SRF gun, which will need a new transfer system with XHV 10^-11 mbar. The key component of the system is the transfer chamber and the load-lock system that will be connected to the SRF-gun. In the carrier four small plugs will be transported, and one of them will be plug on the cathode-body and inserted into the cavity. The new transport chamber allows the transfer and exchange of plugs between HZDR, HZB and other cooperating institutes. In HZDR this transfer system will also provide a direct connection between the SRFGUN and the GaAs preparation chamber in the Elbe-accelerator hall.
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TUPB011	HPRF Transmission Componenets Study and Distribution in TRIUMF E-Linac	linac, klystron, simulation, TRIUMF	557
	Z.T. Ang TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	TRIUMF e-lianc was commissioning last September for the first stage. High power rf systems were in operation stable. Two 300 kW klystrons along with the key waveguide components were tested before feeding rf power into 1.3 GHz 9-cell superconducting cavities. The rf high power variable divider and 360 degree waveguide phase shifters are working successfully. The simulations on different waveguide structures for the power dividers, phase shifters have been studied. The comparisons of the calculation results are reported in the paper. The rf signal level tests of the components and waveguide distribution systems will also be present in this paper.
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TUPB014	First Operation of a Superconducting RF Electron Test Accelerator at Fermilab	electron, gun, cavity, superconducting-RF	571
	E.R. Harms, R. Andrews, C.M. Baffes, D.R. Broemmelsiek, K. Carlson, D.J. Crawford, N. Eddy, D.R. Edstrom, J.R. Leibfritz, A.H. Lumpkin, S. Nagaitsev, P. Piot, P.S. Prieto, J. Reid, J. Ruan, J.K. Santucci, V.D. Shiltsev, W.M. Soyars, D. Sun, R.M. Thurman-Keup, A. Valishev, A. Warner Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. A test accelerator utilizing SRF technology recently accelerated its first electrons to 20 MeV at Fermilab. Foreseen enhancements will make acceleration to 300 MeV possible at a maximum beam power of 80 kW. A summary of commissioning steps and first experiments as well as current beam parameters compared to design is presented. Plans for expansion and the future physics program are also summarized.
	Poster TUPB014 [11.582 MB]
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TUPB018	Preparation of the 3.9 GHz System for the European XFEL Injector Commissioning	cavity, HOM, alignment, vacuum	584
	P. Pierini, M. Bertucci, M. Bonezzi, A. Bosotti, J.F. Chen, M. Chiodini, P. Michelato, L. Monaco, M. Moretti, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy C. Albrecht, N. Baboi, S. Barbanotti, J. Branlard, Th. Buettner, L. Butkowski, T. Delfs, H. Hintz, F. Hoffmann, M. Hüning, K. Jensch, R. Jonas, R. Klos, D. Kostin, L. Lilje, C.G. Maiano, W. Maschmann, A. Matheisen, U. Mavrič, W.-D. Möller, C. Müller, P. Pierini, J. Prenting, J. Rothenburg, O. Sawlanski, M. Schlösser, M. Schmökel, A.A. Sulimov, E. Vogel DESY, Hamburg, Germany E.R. Harms Fermilab, Batavia, Illinois, USA C.R. Montiel ANL, Argonne, Illinois, USA C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	The 3.9 GHz cryomodule and RF system for the XFEL Injector is being assembled and delivered to the underground building in summer 2015, for the injector commissioning in Fall 2015. This contribution outlines the status of the activity and reports the preparation stages of the technical commissioning of the system.
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TUPB021	Measurement of the Cavity Performances of Compact ERL Main Linac Cryomodule During Beam Operation	cavity, linac, radiation, cryomodule	592
	H. Sakai, M. Egi, K. Enami, T. Furuya, S. Michizono, T. Miura, F. Qiu, K. Shinoe, K. Umemori KEK, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	We developed ERL main linac cryomodule for Compact ERL (cERL) in KEK. The module consists of two 9-cell 1.3 GHz superconducting cavities, two 20 kW high power coupler, two mechanical tuner and three HOM dampers. After construction of cERL recirculation loop, beam operation was started in 2013 Dec. First electron beam of 20 MeV successfully passed the main linac cavities. After adjusting beam optics, energy recovery operation was achieved. Main linac cavity was enough stable for ERL beam operation with digital LLRF system and energy recovery was successfully done with CW 80 uA beam. However, field emission was a problem for long term operation. In this paper, we express the measurement of the cavity performances of long term beam operation.
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TUPB025	Tuning the Superconducting Linac at Low Beam Intensities	linac, ion, bunching, acceleration	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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TUPB026	Cryogenic Performance of the HNOSS Test Facility at Uppsala University	cavity, cryogenics, vacuum, controls	612
	R. Santiago Kern, K.J. Gajewski, L. Hermansson, R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden P. Bujard, T. Junquera, J.P. Thermeau Accelerators and Cryogenic Systems, Orsay, France
	Funding: Knut and Alice Wallenbergs foundation The FREIA Laboratory at Uppsala University, Sweden, is developing part of the RF system and testing the superconducting double spoke cavitites for ESS. During 2014 it was equipped with HNOSS, a versatile horizontal cryostat system for testing superconducting cavities. HNOSS is designed for high power RF testing of up to two superconducting accelerating cavities equipped with helium tank, fundamental power coupler and tuning system. In particular it will be used to characterise the performance of spoke cavities like used in the accelerator for the ESS project. HNOSS is connected to a cryogenic plant providing liquid helium and a sub-atmospheric pumping system enabling operation in the range 1.8 to 4.5~K. We present a brief description of the major components, installation and results from the recent operation and tests.
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TUPB058	Characterization of Thin Films Using Local Magneometer	experiment, SRF, superconductivity, cavity	712
	N. Katyan, C.Z. Antoine CEA/DSM/IRFU, Grenoble, France C.Z. Antoine CEA/IRFU, Gif-sur-Yvette, France
	Funding: CEA SIS nanocomposite (Superconductor/Insulator/Superconductor) could improve efficiency of accelerating cavities. The SRF multilayers concept focuses on the enhancement of HC1 using thin layers (d~λ). The use of thin layers makes it easier to avoid avalanche penetration of vortices in case of local defects. Several layers are needed in order to attenuate the external field to values below Nb HC1, decoupled using dielectric layers. We don’t know yet how the predicted properties evolve in realistic conditions; hence it seems reasonable to do their optimization. Two parameters need to be measured to study their behavior in cavity operating conditions: HC1 and Rs surface resistance (especially residual). For that purpose two instruments were developed in Saclay and in Orsay. A local magnetometer allows measuring the vortex penetration on samples without the orientation and edge effects encountered in SQUID magnetometers. Its operating conditions range from 2-40 K, with field up to 150 mT, and upgradation to higher field. A pill-box cavity working on TE011 and TE012 modes with removable sample/top measures surface resistance up to 60 mT based on calorimetric method from 1.6-4.5 K.* *SRF cavities, 3rd Harmonic Analysis
	Poster TUPB058 [1.581 MB]
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TUPB067	Design and First Measurements of an Alternative Calorimetry Chamber for the HZB Quadrupole Resonator	niobium, quadrupole, SRF, simulation	739
	S. Keckert, R. Kleindienst, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453. The systematic research on superconducting thin films requires dedicated testing equipment. The Quadrupole Resonator (QPR) is a specialized tool to characterize the superconducting properties of circular samples. A calorimetric measurement of the RF surface losses allows the surface resistance to be measured with sub nano-ohm resolution. This measurement can be performed over a wide temperature and magnetic field range, at frequencies of 433, 866 and 1300 MHz. The system at Helmholtz-Zentrum Berlin (HZB) is based on a resonator built at CERN and has been optimized to lower peak electric fields and an improved resolution. An alternative calorimetry chamber has been designed in order to provide flat samples for coating and to ease changing of samples. Furthermore it enables exchangeability of samples between the QPRs at HZB and CERN. With this poster the design and first measurements of the new calorimetry chamber is presented.
	Poster TUPB067 [1.776 MB]
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TUPB075	Measurements on the Superconducting 217 MHz CH Cavity During the Manufacturing Phase	cavity, simulation, resonance, linac	757
	F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech IAP, Frankfurt am Main, Germany M. Amberg, K. Aulenbacher, W.A. Barth, S. Mickat HIM, Mainz, Germany K. Aulenbacher IKP, Mainz, Germany W.A. Barth, S. Mickat GSI, Darmstadt, Germany
	Funding: GSI, HIM, BMBF Contr. No. 05P12RFRBL Since in future the existing UNILAC (Universal Linear Accelerator) will be used as an injector for the FAIR (Facility for Antiproton and Ion Research) project, a new superconducting (sc) continuous wave (cw) linac at GSI is proposed to keep the Super Heavy Element (SHE) program at a competitive high level. In this context, a sc 217 MHz crossbar-H-mode (CH) cavity has been designed at the Institute for Applied Physics (IAP), Frankfurt University, and was built at Research Instruments (RI) GmbH, Germany. The cavity serves as a first prototype to demonstrate the reliable operability under a realistic accelerator environment and its successful beam operation will be a milestone on the way to the new linac. In this contribution measurements during the production process of the cavity as well as corresponding simulations will be presented.
	Poster TUPB075 [2.476 MB]
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TUPB078	Developments on a Cold Bead-Pull Test Stand for SRF Cavities	cavity, HOM, SRF, factory	770
	A.V. Vélez, A. Frahm, J. Knobloch, A. Neumann HZB, Berlin, Germany
	Final tuning and field profile characterization of SRF cavities always takes place at room temperature. However, important questions remains as to what happens when the cavity is cooled to LHe temperature, in particular with multi cell systems. To enable the characterization of cavities in the cold, we have designed and commissioned a "cold bead-pull" test stand at HZB. The present test stand is designed to be integrated in HoBiCaT (Horizontal bi-cavity testing facility) with the ability to provide electric field profile measurements under realistic superconducting conditions (T=1.8K). In this paper mechanical and operational details of the apparatus will be described as well as future plans for the development and usage of this facility.
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TUPB093	Initial Commissioning Experience with the Spallation Neutron Source Vertical Test Area RF System	cavity, software, controls, hardware	819
	M.T. Crofford, J.A. Ball, M. Doleans, S.-H. Kim, S.W. Lee, J.D. Mammosser, J. Saunders ORNL, Oak Ridge, Tennessee, USA T.L. Davidson, S. Whaley ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. The Spallation Neutron Source (SNS) has developed a vertical test area (VTA) for the testing and qualification of superconducting radio frequency cavities. The associated RF System successfully supported the initial commissioning of the VTA system and has been utilized for cavity testing at both 4 and 2 K. As operational experience was gained, improvements to the RF system were implemented to better utilize the dynamic range of the system, and software updates and additions were made to meet the operational needs. The system continues to evolve as we gain better understanding of the testing needs.
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TUPB095	Resonance Control for Narrow-Bandwidth, Superconducting RF Applications	cavity, resonance, feedback, SRF	828
	W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov Fermilab, Batavia, Illinois, USA D. Gonnella Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA M. Liepe Cornell University, Ithaca, New York, USA
	Optimal control techniques have been employed in a variety of applications since they were first developed more than 60 years ago but until now they have been used in few if any accelerator-related applications. The next generation of superconducting accelerators will require both precise control of the gradient and active stabilization of the resonance frequency. Optimal control techniques provide a self-consistent framework within which to construct a combined electro-mechanical controller. Results from recent cold cavity tests at Fermilab are presented.
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TUPB101	Design of the Thermal and Magnetic Shielding for the LHC High Luminosity Crab-Cavity Upgrade	cavity, shielding, cryomodule, simulation	852
	N. Templeton, T.J. Jones STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, R. Leuxe, C. Zanoni CERN, Geneva, Switzerland G. Burt, S.M. Pattalwar Cockcroft Institute, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom G. Burt Lancaster University, Lancaster, United Kingdom K.B. Marinov, A.J. May, S.M. Pattalwar STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom A. Ratti LBNL, Berkeley, California, USA
	Before the High Luminosity (Hi-Lumi) upgrade of the Large Hadron Collider (LHC), two pairs of superconducting compact Crab Cavities are to be tested within separate cryomodules, on the Super Proton Synchrotron (SPS) at CERN in 2018 prior to Long Shutdown 2. Two novel side-loaded cryomodules, which allow ease of access for assembly, inspection and maintenance, have been developed for the prototype tests. The cryomodule shielding includes a thermal shield and double layer magnetic shield, consisting of a warm-outer shield, and two cold-inner shields (one per cavity). Various constraints and considerations have led to unique cold shielding, mounted inside the cavity helium vessels, resulting in several design challenges. The shielding adopts and utilises the module’s side-loaded configuration, for continuity and accessibility, while satisfying tight spatial constraints and requirements to meet the functional specification. This paper outlines the design, analysis, manufacture and assembly of the Hi-Lumi SPS test cryomodule’s thermal and magnetic shielding, which are critical to achieving the operational stability.
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TUPB102	Validation of Local Magnetic Shielding for FRIB Using a Prototype Cryomodule	solenoid, cavity, shielding, cryomodule	857
	S.K. Chandrasekaran, K. Saito FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, and the U.S. National Science Foundation under Grant No. PHY-1102511. The local magnetic shield design and cryogenic magnetic shielding material for the FRIB QWR cryomodule was validated in a two cavity, one solenoid prototype cryomodule. The magnetic fields were measured inside and outside the magnetic shielding before, during, and after operation of an 8 T superconducting solenoid. The effect of demagnetization cycles of the solenoid was also examined. The magnetic field at the cavity’s high RF magnetic field area, inside the magnetic shield and with the solenoid off, was measured using a single-axis fluxgate to be less than 0.3 μT (3 mG) after cool down of the cryomodule. A 3.07 μT (30.7 mG) residual field was observed at high magnetic field area after conclusion of solenoid operation. This was attributed to the persistent currents circulating in the superconducting solenoid. Demagnetization cycles were therefore determined to be unnecessary for FRIB cryomodules, as long as the solenoid is normal conducting when the cavity is cooled through the superconducting critical temperature. S.K. Chandrasekaran currently at Fermi National Accelerator Laboratory, Batavia, IL, USA.
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TUPB108	Connection of EU-XFEL Cryomodules, Caps, Boxes in EU-XFEL Main Linac and Injector: Welding of Cryo-Pipes and Assembly of Beam-Line Absorbers Under Requirements of PED Regulation	linac, cryomodule, vacuum, cryogenics	883
	S. Barbanotti, C. Buhr, H. Hintz, K. Jensch, L. Lilje, W. Maschmann, P. Pierini, A. Wagner DESY, Hamburg, Germany P. Pierini INFN/LASA, Segrate (MI), Italy
	The European X-ray Free Electron Laser (EU-XFEL) cold linac consists of 100 assembled cryomodules, 6 feed-/end-boxes and 6 string connection boxes fixed to the ceiling of the accelerator tunnel; the injector consists of a radio frequency gun, one 1.3 GHz and one 3.9 GHz cryomodule, one feed- and one end-cap lying on ground supports. The components are connected together in the tunnel, after cold testing, transport, final positioning and alignment. The cold linac is a pressure equipment and is therefore subjected to the requirements of the Pressure Equipment Directive (PED). This paper describes the welding and subsequent non-destructive testing of the cryo-pipes (with a deeper look at the technical solutions adopted to satisfy the PED requirements), the assembly of the beam line absorbers and the final steps before closing the connection with a DN1000 bellows. A special paragraph will be dedicated to the connection of the injector components, where the lack of space makes this installation a particularly challenging task.
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TUPB115	Improvements of the Mechanical, Vacuum and Cryogenic Procedures for European XFEL Cryomodule Testing	cryomodule, vacuum, cryogenics, detector	906
	J. Świerbleski, M. Bednarski, B. Dzieza, W. Gaj, L. Grudnik, P. Halczynski, A. Kotarba, A. Krawczyk, K. Myalski, T. Ostrowicz, B. Prochal, J. Rafalski, M. Sienkiewicz, M. Skiba, M. Wartak, M. Wiencek, J. Zbroja, P. Ziolkowski IFJ-PAN, Kraków, Poland
	The European X-ray Free Electron Laser is under construction at DESY, Hamburg. The linear accelerator part of the laser consists of 100 SRF cryomodules. Before installation in the tunnel the cryomodules undergo a series of performance tests at the AMTF Hall. Testing procedures have been implemented based on TTF (Tesla Test Facility) experience. However, the rate of testing and number of test benches is greater than in the TTF infrastructure. To maintain the goal testing rate of one module per week, improvement to the existing procedures were implemented at AMTF. Around 50% of the testing time is taken by connection of the cryomodule to the test bench, performing all necessary checks and cool down. Most of the preparation procedures have been optimized to decrease mounting time. This paper describes improvements made to the mechanical connections, vacuum checks and cryogenics operation.
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WEBA07	Beam Commissioning of the 56 MHz QW Cavity in RHIC	cavity, HOM, damping, SRF	982
	Q. Wu, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, T. Hayes, K. Mernick, F. Severino, K.S. Smith, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA
	Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. A 56 MHz superconducting RF cavity has been designed, fabricated and installed in the Relativistic Heavy Ion Collider (RHIC). The cavity operates at 4.4 K with a “quiet helium source” to isolate the cavity from environmental acoustic noise. The cavity is a beam driven quarter wave resonator. It is detuned and damped during injection and acceleration cycles and is brought to operation only at store energy. We have observed clear luminosity increase and bunch length reduction in the first operation of the cavity with Au + Au and Au + He3 collisions. The cavity voltage was limited by quenching in the Higher Order Mode coupler. This paper also discusses the cavity beam experiments with no higher order mode coupler in p + p and p + Au RHIC operation.
	Slides WEBA07 [2.522 MB]
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THAA06	Precise Studies on He-Processing and HPR for Recovery From Field Emission by Using X-Ray Mapping System	cavity, radiation, cryomodule, linac	1019
	H. Sakai, K. Enami, T. Furuya, M. Satoh, K. Shinoe, K. Umemori KEK, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	We usually met the degradation of superconducting RF cavity on the cryomodule test and beam operation even if the performance of this cavity is good on the vertical test (V.T). Field emission is the most severe problem for this degradation after reassembly work from vertical test. Not only high pressure rinsing (HPR) but also He-processing, which is more suitable method without the reassembly work for recovery, is recommended and tried to recover this degradation. However, we did not investigate the details of how field emission sources were processed and removed after HPR and He-processing. We deeply investigated the processing procedure during He-processing and how many field emission sources removed after HPR by using rotating X-ray mapping system* in V.T . *H.Sakai et.al., Proc. of IPAC10 p2950-2952.
	Slides THAA06 [4.347 MB]
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THBA04	Overview of Recent HOM Coupler Development	HOM, cavity, damping, SRF	1031
	B. P. Xiao BNL, Upton, Long Island, New York, USA
	Funding: Work partly supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE， by the US LARP, and by EU FP7 HiLumi LHC - Grant Agreement 284404. HOM damping is important for SRF applications, especially for high intensity machines. A good HOM damping design will help to reduce power load to the cryogenic system and to reduce the risk of beam breakup. The design of HOM damping, including antenna/loop HOM couplers, beam pipe HOM absorbers and waveguide HOM couplers, is to solve a multi-physics problem that involves RF, thermal, mechanical, and beam-cavity interaction issues. In this talk, the author provides an overview on the latest advances of the HOM couplers for high intensity SRF applications.
	Slides THBA04 [2.619 MB]
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THBA05	Higher Order Mode Absorbers for High Current SRF Applications	HOM, cavity, higher-order-mode, linac	1036
	R.G. Eichhorn, J.V. Conway, T. Gruber, Y. He, G.H. Hoffstaetter, Y. Li, M. Liepe, T.I. O'Connell, P. Quigley, J. Sears, V.D. Shemelin, E.N. Smith, M. Tigner Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Efficient damping of the higher-order modes (HOMs) of the superconducting cavities is essential for any high current operation. The talk will provide an overview on the latest advances of HOM absorber development for high intensity SRF applications. As the ideal absorber does not exist, the different conceptual approaches will be presented and the associated issues are outlined. Design examples from various labs will be given that help explain the issues and resolutions. Some focus will be given to the Cornell HOM beamline absorber that was design for high current, short bunch operation with up to 400 W heating. The design will be reviewed and testing results will be reported.
	Slides THBA05 [4.022 MB]
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THPB005	Simulations of 3.9 GHz CW Coupler for LCLS-II Project	cavity, simulation, linac, cryomodule	1066
	I.V. Gonin, T.N. Khabiboulline, A. Lunin, N. Solyak Fermilab, Batavia, Illinois, USA
	LCLS-II linac is based on XFEL/ILC superconducting technology. TTF-III fundamental power coupler for the 3.9 GHz 9-cell cavities has been modifies to satisfy requirements of LCLS-II, operating in CW regime. In this paper we discuss the results of COMSOL analysis of the possible modification of couplers, working at various operating regimes. We present also the results of mechanical study.
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THPB011	Superconducting Travelling Wave Accelerating Structure Development	cavity, accelerating-gradient, status, feedback	1085
	R.A. Kostin, P.V. Avrakhov, A.D. Didenko, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA T.N. Khabiboulline, Y.M. Pischalnikov, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by US Department of Energy # DE-SC0006300 The 3 cell superconducting TW accelerating structure was developed to experimentally demonstrate and to study tuning issues for a new experimental device - the superconducting traveling wave accelerator (STWA), a technology that may prove of crucial importance to the high energy SRF linacs by raising the effective gradient and therefore reducing the overall cost. Recently, a STWA structure with a feedback waveguide has been suggested. The structure was optimized and has phase advance per cell of 105° which provide 24% higher accelerating gradient than in SW cavities. Also STWA structure has no strong sensitivity of the field flatness and its length may be much longer than SW structure. With this presentation, we discuss the current status of a 3-cell L-band SC traveling wave along with the analysis of its tuning issues. Special attention will be paid to feedback loop operation with the two-coupler feed system. We also report on the development and fabrication of a niobium prototype 3-cell SC traveling wave structure to be tested at 2°K in fall 2015.
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THPB014	Mechanical Optimization of High Beta 650 MHz Cavity for Pulse and CW Operation of PIP-II Project	cavity, simulation, resonance, cryomodule	1093
	T.N. Khabiboulline, I.V. Gonin, C.J. Grimm, A. Lunin, T.H. Nicol, V.P. Yakovlev Fermilab, Batavia, Illinois, USA P. Kumar RRCAT, Indore (M.P.), India
	The proposed design of the 0.8 GeV PIP-II SC Linac employs two families of 650 MHz 5-cell elliptical cavities with 2 different beta. The β=0.61 will cover the 185-500 MeV range and the β=0.92 will cover the 500-800 MeV range. In this paper we will present update of RF and mechanical design of dressed high beta cavity (β=0.92) for pulse regime of operation at 2 mA beam current. In previous CW version of PIP-II project the mechanical design was concentrated on minimization of frequency shift due to helium pressure fluctuation. In current case of pulse regime operation the main goal was Lorentz force detuning minimization. We present the scope of coupled RF-Mechanical issues and their resolution. Also detailed stress analysis of dresses cavity will be presented.
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THPB015	Design of a Medium Beta Half-Wave SC Prototype Cavity at IMP	cavity, linac, electromagnetic-fields, accelerating-gradient	1097
	A.D. Wu, Y. He, T.C. Jiang, Y.M. Li, F.F. Wang, R.X. Wang, L.J. Wen, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao IMP/CAS, Lanzhou, People's Republic of China
	A superconducting half-wave resonator has been designed with frequency of 325 MHz and beta of 0.51. The geometry parameters and the three shapes of inner conductors (racetrack, ring-shape and elliptical-shape) were studied in details to decrease the peak electromagnetic fields to obtain higher accelerating gradients and minimize the dissipated power on the RF walls. To suppress the operation frequency shift caused by the helium pressure fluctuations and maximize the tuner ranges, the frequency shifts and mechanical characters were simulated in the electric and magnetic areas separately. At the end, the helium vessel was also designed to keep stability as possible. The fabrication and test of the prototype will be complete at the beginning of 2016.
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THPB027	Welding a Helium Vessel to a 1.3 GHz 9-Cell Nitrogen Doped Cavity at Fermilab for LCLS-II	cavity, alignment, vacuum, pick-up	1132
	C.J. Grimm, J.A. Kaluzny, D.J. Watkins Fermilab, Batavia, Illinois, USA
	Fermilab has developed a TIG welding procedure that is used attach a nitrogen doped 1.3 GHz 9-cell niobium (Nb) cavity to a titanium (Ti) helium vessel. These cavities will be used in the two prototype cryomodules for the Linac Coherent Light Source (LCLS-II) upgrade at SLAC National Accelerator Laboratory. Discussion in further detail will include setting up TIG welding parameters and tooling requirements for assembly and alignment of the cavity to the helium vessel. The weld designs and glovebox environment produce the best quality TIG welds that meet ASME Boiler and Pressure Vessel Code. The cavity temperature was monitored to assure the nitrogen doping is preserved, and RF measurements are taken throughout the process to monitor the cavity for excessive cell deformation due to heat loads from welding.
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THPB031	Operation Experience with Half Cell Measurement Machine and Cavity Tuning Machine in 3 Years of European XFEL Cavity Series Production	cavity, controls, SRF, HOM	1149
	J.H. Thie, A. Gössel, J. Iversen, D. Klinke, C. Müller, A.A. Sulimov, D. Tischhauser DESY, Hamburg, Germany
	For the European XFEL superconducting Cavity series production at both cavity vendors’ four manufacturing machines for production key functions, HAZEMEMA and CTM, are supplied by DESY. Among three years of cavity production in two companies a lot of experience is gathered about influence of surroundings and production quality on cycle times, machine drop outs, general stability time of machines and parts subject to wear. Significant factors on cycle time for tuning operation like temperature stability and drift during tuning and measurements, precision of cell trimming before welding and tuning and generally geometrical factors are shown. RF aspects of tuning and production quality control as additional measurements for TM011-mode to estimate quality of its damping is presented. Performed full Cavity RF measurements exceeds XFEL specifications gives a possibility for additional quality control on welding shrinkage stability and it’s homogeneously distribution. The use of HAZEMEMA and CTM to assess the impact of asymmetric trimming, including calculation of it’s influence on the higher-order modes, is shown.
	Poster THPB031 [0.201 MB]
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THPB035	Fabrication of the 3.9 GHz SRF Structures for the European XFEL	cavity, controls, linac, status	1162
	P. Pierini, M. Bertucci, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, M. Moretti, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy A. Gresele Ettore Zanon S.p.A., Nuclear Division, Schio, Italy C.G. Maiano, P. Pierini, E. Vogel DESY, Hamburg, Germany C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy M. Rizzi Ettore Zanon S.p.A., Schio, Italy
	One batch of 10 cavities has been completed and eight structures have been installed in the 3.9 GHz cryomodule for the European XFEL Injector operation. A second batch of 10 RF structures for a spare injector module is under fabrication. The fabrication has been performed according to the European Pressure Vessel regulations, as needed for the EXFEL operation. This paper describes the fabrication, quality control/assurance procedures and frequency preparation steps in order to achieve cavities at the correct frequency and length within the specifications.
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THPB056	SRF Gun Cavity R&D at DESY	cavity, SRF, gun, cathode	1231
	D. Kostin, C. Albrecht, A. Brinkmann, Th. Buettner, J. Eschke, T. Feldmann, A. Gössel, D. Klinke, A. Matheisen, W.-D. Möller, D. Reschke, M. Schmökel, J.K. Sekutowicz, W. Singer, X. Singer, N. Steinhau-Kühl, J. Ziegler, B. van der Horst DESY, Hamburg, Germany M. Barlak, J.A. Lorkiewicz, R. Nietubyć NCBJ, Świerk/Otwock, Poland
	SRF Gun Cavity is an ongoing accelerator R&D project at DESY, being developed since several years. Currently several SRF Gun cavity prototypes were simulated, built and tested in our Lab and elsewhere. Lately the 1.6 cells Pb thin film cathode niobium cavity was tested in a vertical cryostat with a different cathode plug configurations. Cathode plug design was improved, as well as SRF Gun Cavity cleaning procedures. Results of the last cavity performance tests are presented and discussed.
	Poster THPB056 [1.257 MB]
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THPB060	Development of SRF Cavity Tuners for CERN	cavity, cryomodule, vacuum, SRF	1247
	K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, N. Kuder, R. Leuxe, P. Minginette, W. Venturini Delsolaro, G. Villiger, C. Zanoni, P. Zhang CERN, Geneva, Switzerland G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA T.J. Jones, N. Templeton STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom S. Verdú-Andrés, B. P. Xiao BNL, Upton, Long Island, New York, USA
	Superconducting RF cavity developments are currently on-going for new accelerator projects at CERN such as HIE ISOLDE and HL-LHC. Mechanical RF tuning systems are required to compensate cavity frequency shifts of the cavities due to temperature, mechanical, pressure and RF effects on the cavity geometry. A rich history and experience is available for such mechanical tuners developed for existing RF cavities. Design constraints in the context of HIE ISOLDE and HL-LHC such as required resolution, space limitation, reliability and maintainability have led to new concepts in the tuning mechanisms. This paper will discuss such new approaches, their performances and planned developments.
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THPB062	Accelerated Life Testing of LCLS-II Cavity Tuner Motor	cavity, cryomodule, acceleration, SRF	1257
	N.A. Huque, M.E. Abdelwhab, E. Daly JLab, Newport News, Virginia, USA Y.M. Pischalnikov Fermilab, Batavia, Illinois, USA
	An Accelerated Life Test (ALT) of the Phytron stepper motor used in the LCLS-II cavity tuner is being carried out at JLab. Since the motor will reside inside the cryomodule, any failure would lead to a very costly and arduous repair. As such, the motor will be tested for the equivalent of five lifetimes before being approved for use in the production cryomodules. The 9-cell LCLS-II cavity will be simulated by disc springs with an equivalent spring constant. Hysteresis plots of the motor position vs. tuner position – measured via an installed linear variable differential transformer (LVDT) – will be used to determine any drift from the required performance. The titanium spindle will also be inspected for loss of lubrication. This paper outlines the ALT plan and latest results.
	Poster THPB062 [2.794 MB]
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THPB065	Reliability of the LCLS II SRF Cavity Tuner	radiation, vacuum, SRF, cavity	1267
	Y.M. Pischalnikov, B. Hartman, J.P. Holzbauer, W. Schappert, S.J. Smith, J.C. Yun Fermilab, Batavia, Illinois, USA
	The SRF cavity tuner for LCLS II must work reliably for more than 20 years in a cryomodule environment. Tuner’s active components- electromechanical actuator and piezo-actuators must work reliably in an insulating vacuum environment at low temperature for the lifetime of the machine. Summary of the accelerated lifetime tests (ALT) of the electromechanical and piezo actuators inside cold/ insulated vacuum environment and irradiation hardness test (dose level up to 5*10⁸ Rad) of tuner components are presented. Methodology to design and build reliable SRF cavity tuner, based on “lessons learned” approach, are discussed.
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THPB070	Design of Dressed Crab Cavities for the HL-LHC Upgrade	cavity, niobium, cryomodule, SRF	1284
	C. Zanoni, K. Artoos, S. Atieh, I. Aviles Santillana, J.P. Brachet, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, G. Favre, P. Freijedo Menendez, M. Garlaschè, M. Guinchard, N. Kuder, S.A.E. Langeslag, R. Leuxe, L. Prever-Loiri, G. Vandoni CERN, Geneva, Switzerland S.A. Belomestnykh, I. Ben-Zvi, S. Verdú-Andrés, Q. Wu, B. P. Xiao BNL, Upton, Long Island, New York, USA I. Ben-Zvi Stony Brook University, Stony Brook, USA G. Burt Lancaster University, Lancaster, United Kingdom S.U. De Silva, R.G. Olave, H. Park ODU, Norfolk, Virginia, USA J.R. Delayen JLab, Newport News, Virginia, USA T.J. Jones, N. Templeton STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom Z. Li SLAC, Menlo Park, California, USA K.B. Marinov, A.J. May, S.M. Pattalwar STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom T.H. Nicol Fermilab, Batavia, Illinois, USA A. Ratti LBNL, Berkeley, California, USA
	The HL-LHC upgrade relies on a set of RF crab cavities for reaching its goals. Two parallel concepts, the Double Quarter Wave (DQW) and the RF Dipole (RFD), are going through a comprehensive design process along with preparation of fabrication in view of extensive tests with beam in SPS. High Order Modes (HOM) couplers are critical in providing damping in RF cavities for operation in accelerators. HOM prototyping and fabrication have recently started at CERN. In this paper, an overview of the final geometry is provided along with an insight in the mechanical and thermal analyses performed to validate the design of this critical component. Emphasis is also given to material selection, prototyping, initial fabrication and test campaigns that are aimed at fulfilling the highly demanding tolerances of the couplers.
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THPB071	Developments of SiC Damper for SuperKEKB Superconducting Cavity	HOM, cavity, factory, higher-order-mode	1289
	M. Nishiwaki, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, Y. Morita KEK, Ibaraki, Japan
	Upgrade works for SuperKEKB is in the final stage and the commissioning operation will start in this JFY. Eight superconducting accelerating cavities were operated for more than ten years at KEKB electron ring and are to be used at SuperKEKB. The cavity operation at those high current accelerators requires sufficient absorption of the beam-induced HOM power. In KEKB, the absorbed HOM power of 16 kW in two ferrite dampers attached to each cavity was achieved at the beam current of 1.4 A. On the other hand, the expected HOM power at SuperKEKB is calculated to be 37 kW in the beam current of 2.6 A. To cope with the HOM power issue, we developed additional HOM dampers made of SiC to be installed to the downstream of the cavity module. From precise calculations, it was found that the additional dampers reduce the HOM power loads of the ferrite dampers more effectively than the large beam pipe model of cavity module, which is another option to reduce the HOM loads. New SiC dampers were fabricated and high power-tested. Those SiC dampers successfully absorbed the expected HOM power. In this report, we will describe the results of calculations and high-power RF tests of new SiC dampers.
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THPB077	Modified TTF3 Couplers for LCLS-II	vacuum, simulation, cavity, linac	1306
	C. Adolphsen, K. Fant, Z. Li, C.D. Nantista, G. Stupakov, J. Tice, F.Y. Wang, L. Xiao SLAC, Menlo Park, California, USA I.V. Gonin, K. Premo, N. Solyak Fermilab, Batavia, Illinois, USA
	The LCLS-II 4 GeV SC electron linac will use 280 TESLA cavities and TTF3 couplers, modified for CW operation with input power up to about 7 kW. The coupler modifications include shortening the antenna to achieve higher Qext and thickening the copper plating on the warm section inner conductor to lower the peak temperature. Another change is the use a waveguide transition box that is machined out of a solid piece of aluminum, significantly reducing its cost and improving its fit to the warm coupler window section. This paper describes the changes, simulations of the coupler operation (heat loads and temperatures), rf processing results and CW tests with LCLS-II dressed cavities.
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THPB080	Next Generation Cavity and Coupler Interlock for the European XFEL	FPGA, vacuum, interface, timing	1316
	D. Tischhauser, A. Gössel, M. Mommertz DESY, Hamburg, Germany
	The safe operation of cavities and couplers in the European XFEL accelerator environment is secured by a new technical interlock (TIL) design, which is based on the XFEL crate standard (MTCA(TM).4). The new interlock is located inside the accelerator tunnel. Several remote test capabilities ensure the correct operation of sensors for light, temperature and free electrons. Due to the space costs and the very high number of channels, the electronic concept was moved from a conservative, mostly analog electronic approach, with real comparators and thresholds, to a concept, where the digitizing of the signals is done at a very early stage. Filters, thresholds and comparators are moved into the digital part. The usage of an FPGA and an additional watchdog increase the flexibility dramatically, with respect to be as reliable as possible. An overview of the system is shown. MTCA (Micro Telecommunications Computing Architecture) is a standard defined by the PCI Industrial Computer Manufacturers Group (PICMG, www.picmg.org).
	Poster THPB080 [1.123 MB]
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THPB081	FPC and HOM Coupler Test Boxes for HL-LHC Crab Cavities	HOM, cavity, dipole, coupling	1321
	A.R.J. Tutte, G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R. Calaga, A. Macpherson, E. Montesinos CERN, Geneva, Switzerland S.U. De Silva ODU, Norfolk, Virginia, USA Z. Li SLAC, Menlo Park, California, USA B. P. Xiao BNL, Upton, Long Island, New York, USA
	The LHC luminosity upgrade will involve the installation of thirty-two 400 MHz SRF crab cavities. The cavities have two variants known as the RF dipole and double quarter-wave crab cavities. Each cavity has a fundamental power coupler (FPC) at 400 MHz and two or three HOM couplers. Before integration onto the cavities it is necessary to condition the FPC, and to measure the transmission on the HOM couplers at low power to ensure the operate as designed, each requiring a special test box. The FPC test box should provide a high transmission between two couplers without creating high surface fields. The low power HOM test boxes should be terminated to a load such that the natural stop and pass-bands of the couplers are preserved allowing the reflection to me measured and compared to simulations. In addition, due to the possibility of high HOM power in the LHC crab cavities, the concept of creating a broadband high power HOM coupler test box in order to condition and test the couplers at high power has been investigated. The Rf design of all test boxes is presented and discussed.
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THPB086	LCLS-II Fundamental Power Coupler Mechanical Integration	interface, cryomodule, pick-up, vacuum	1340
	K.S. Premo, T.T. Arkan, Y.O. Orlov, N. Solyak Fermilab, Batavia, Illinois, USA
	Funding: DOE LCLSII is a planned upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLSII linac will consist of thirtyfive 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab will assemble in collaboration with SLAC. The LCLSII 1.3 GHz cryomodule design is based on the European XFEL pulsed mode cryomodule design with modifications needed for CW operation. The 1.3 GHz cryomodules for LCLSII will utilize a modified TTF3 syle fundamental power coupler design. Due to CW operation heat removal from the power coupler is critical. This paper presents the details of the mechanical integration of the power coupler into the cryomodule. Details of thermal braids, connections, and other interfaces are discussed.
	Poster THPB086 [1.031 MB]
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THPB088	20 kW CW Power Couplers for the APS-U Harmonic Cavity	cavity, Windows, storage-ring, electron	1346
	M.P. Kelly, A. Barcikowski, Z.A. Conway, D. Horan, M. Kedzie, S.H. Kim, P.N. Ostroumov ANL, Argonne, Illinois, USA S.V. Kutsaev RadiaBeam, Santa Monica, California, USA J. Rathke AES, Medford, New York, USA
	Funding: This work supported by the U.S. DOE, Office of Nuclear Physics, Contract No. DE-AC02-06CH11357. This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility. A pair of 20 kW CW adjustable RF power couplers optimized for 1.4 GHz have been designed and are being built as part of the APS-U bunch lengthening system. The system uses one superconducting RF cavity to be installed into the APS Upgrade electron storage ring and will provide a tremendous practical benefit to the majority of users by increasing the beam lifetime by 2-3 times. The 80 mm diameter, 50 Ω coaxial couplers include 4 cm (~20 dB) of adjustability. This allows optimization of bunch lengthening for a range of storage ring beam currents and fill patterns while, simultaneously, maintaining the required 0.84 MV harmonic cavity voltage. To provide bunch lengthening, the cavity/coupler system must extract RF power (up to 32 kW) from the beam. Each coupler will transmit roughly half of the total extracted power to external water-cooled loads. The design extends upon on a well-tested ANL two RF window concept, using a pair of simple rugged 80 mm diameter alumina disks. A new feature is the ‘hourglass-shaped’ inner conductor chosen to maximize transmission at 1.4 GHz. Results of electromagnetic and thermal simulations, as well as, prototyping and initial RF testing are presented.
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THPB089	HOM Coupler Performance in CW Regime in Horizontal and Vertical Tests	HOM, cavity, coupling, higher-order-mode	1349
	N. Solyak, M.H. Awida, A. Grassellino, C.J. Grimm, A. Hocker, J.P. Holzbauer, T.N. Khabiboulline, O.S. Melnychuk, A.M. Rowe, D.A. Sergatskov, N. Solyak Fermilab, Batavia, Illinois, USA J.K. Sekutowicz DESY, Hamburg, Germany
	Power dissipation in HOM coupler antenna can limit cavity gradient in cw operation. XFEL design of HOM coupler, feedthrough and thermal connection to 2K pipe was accepted for LCLS-II cavity based on simulation results. Recently a series of vertical and horizontal tests was done to prove design for cw operation. In vertical test was found no effect of HOM coupler heating on high-Q cavity performance. In horizontal cryostat HOM coupler was tested up-to 23MV/m in continuous wave mode. Result proves that XFEL HOM coupler meets LCLS-II specifications.
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THPB109	ESS Spoke Cryomodule and Test Valve Box	cryomodule, cryogenics, vacuum, linac	1400
	D. Reynet, S. Bousson, S. Brault, P. Duchesne, P. Duthil, N. Gandolfo, G. Olry, M. Pierens, E. Rampnoux IPN, Orsay, France C. Darve ESS, Lund, Sweden
	ESS project aims being the world’s most powerful neutron source feeding multidisplinary researches. The superconducting part of the ESS linear accelerator includes 28 b=0.5 352.2 MHz SRF niobium double Spoke cavities. Paired in 13 cryomodules and held at 2K in a saturated helium bath those cavities will generate of an accelerating field of 9MV/m. The prototype Spoke cryomodule holds two cavities and their RF power couplers and integrates all the interfaces necessary to be operational within the linac machine. It is now being fabricated and its assembly will be performed with dedicated tooling and procedures in and out of the clean room. This prototype will be tested by the end of 2015 at IPNO site and then at full power at FREIA (Uppsala university) test stand. A valve box has thus been designed to take into account the specific features of this prototype cryomodule and of the cryogenic environments of both test sites. This valve box is also considered as a prototype of the cryogenic distribution of the linac Spoke section. This element will then be used for the tests of the series cryomodules. We propose to present this prototype Spoke cryomodule for ESS and the test valve box.
	Poster THPB109 [2.852 MB]
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THPB110	Procurements for LCLS-II Cryomodules at JLab	cavity, HOM, cryomodule, vacuum	1405
	E. Daly, G. Cheng, G.K. Davis, T. Hiatt, N.A. Huque, F. Marhauser, H. Park, J.P. Preble, K.M. Wilson JLab, Newport News, Virginia, USA
	Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515. The Thomas Jefferson National Accelerator Facility is currently engaged, along with several other DOE national laboratories, in the Linac Coherent Light Source II project (LCLS II). The SRF Institute at Jefferson Lab will be building 1 prototype and 17 production cryomodules based on the TESLA / ILC / XFEL design. Each cryomodule will contain eight nine cell cavities with coaxial power couplers operating at 1.3 GHz. Procurement of components for cryomodule construction has been divided amongst partner laboratories in a collaborative manner. JLab has primary responsibility for six procurements include the dressed cavities, cold gate valves, higher-order-mode (HOM) and field probe feedthroughs, beamline bellows cartridges, cavity tuner assemblies and HOM absorbers. For procurements led by partner laboratories, JLab collaborates and provides technical input on specifications, requirements and assembly considerations. This paper will give a detailed description of plans and status for JLab procurements.
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THPB116	Modified ELBE Type Cryomodules for the Mainz Energy-Recovering Superconducting Accelerator MESA	cryomodule, HOM, niobium, electron	1413
	T. Stengler, K. Aulenbacher, R.G. Heine, F. Schlander, D. Simon IKP, Mainz, Germany M. Pekeler, D. Trompetter RI Research Instruments GmbH, Bergisch Gladbach, Germany
	At the Institut für Kernphysik of Johannes Gutenberg-Universität Mainz, the new multiturn energy recovery linac MESA is under construction. Two modified ELBE-type cryomodules with two 9-cell TESLA/XFEL cavities each will provide an energy gain of 50 MeV per turn. Those are currently in the production process at RI Research Instruments GmbH, Bergisch Gladbach, Germany. Modifications for the tuner and the HOM damper are under development. In addition, a 4K/2K Joule Thomson expansion stage will also be integrated into the cryomodule. The current status of the development of the cryomodules and their modifications will be discussed.
	Poster THPB116 [1.472 MB]
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THPB119	LCLS-II 1.3 GHz Cryomodule Design – Modified TESLA-Style Cryomodule for CW Operation	cryomodule, vacuum, cryogenics, cavity	1417
	T.J. Peterson, T.T. Arkan, C.M. Ginsburg, Y. He, J.A. Kaluzny, M.W. McGee, Y.O. Orlov Fermilab, Batavia, Illinois, USA
	Funding: Work supported, in part, by the US DOE and the LCLS-II Project. We will present the design of the 1.3 GHz cryomodule for the Linear Coherent Light Source upgrade (LCLS-II) at SLAC. Fermilab is responsible for the design of this cryomodule, a modified TESLA-style cryomodule to accommodate continuous wave (CW) mode operation and LCLS-II beam parameters, consisting of eight 1.3 GHz superconducting RF cavities, a corrector magnet package, and instrumentation. Thirty-five of these cryomodules, approximately half built at Fermilab and half at Jefferson Lab, will become the main accelerating elements of the 4 GeV linac. The modifications and special features of the cryomodule include: thermal and cryogenic design to handle high heat loads in CW operation, magnetic shielding and cool-down configurations to enable high quality factor (Q0) performance of the cavities, liquid helium management to address the different liquid levels in the 2-phase pipe with 0.5% SLAC tunnel longitudinal slope, support structure design to meet California seismic design requirements, and with the overall design consistent with space constrains in the existing SLAC tunnel. The prototype cryomodule assembly will begin in August 2015 and is to be completed in early 2016.
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FRAA01	Overview of Recent Tuner Development on Elliptical and Low-Beta Cavities	cavity, linac, cryomodule, controls	1425
	R. Paparella INFN/LASA, Segrate (MI), Italy
	The talk will provide an overview on the latest advances of tuner development for SRF applications. Issues and present approaches on how to resolve them will be emphasized for both TM and TEM cavities and examples from various labs and projects (XFEL, LCLS-II, ESS, SPL, ARIEL, SPIRAL2, FRIB, ANL, IFMIF) will be given in order to better explain issues and solutions. Details on author’s contributions to European-XFEL tuner activity for 1.3 GHz and 3.9 GHz cavities will be also shown.
	Slides FRAA01 [3.421 MB]
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FRAA03	High Gradient Performance in Fermilab ILC Cryomodule	cavity, cryomodule, vacuum, detector	1432
	E.R. Harms, C.M. Baffes, K. Carlson, B.E. Chase, D.J. Crawford, E. Cullerton, D.R. Edstrom, A. Hocker, A.L. Klebaner, M.J. Kucera, J.R. Leibfritz, J.N. Makara, D. McDowell, O.A. Nezhevenko, D.J. Nicklaus, Y.M. Pischalnikov, P.S. Prieto, J. Reid, W. Schappert, W.M. Soyars, P. Varghese, A. Warner Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Fermilab has assembled an ILC like cryomodule using U.S. processed high gradient cavities and achieved an average gradient of 31.5 MV/m for the entire cryomodule. Test results and challenges along the way will be discussed.
	Slides FRAA03 [5.878 MB]
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FRAA04	Performance of the Cornell ERL Main Linac Prototype Cryomodule	cavity, HOM, linac, cryomodule	1437
	F. Furuta, B. Clasby, R.G. Eichhorn, B. Elmore, G.M. Ge, D. Gonnella, D.L. Hall, G.H. Hoffstaetter, R.P.K. Kaplan, J.J. Kaufman, M. Liepe, T.I. O'Connell, S. Posen, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cornell has designed, fabricated, and tested (by the time of the conference) a high current (100 mA) CW SRF prototype cryomodule for the Cornell ERL. This talk will report on the design and performance of this very high Q0 CW cryomodule including design issues and mitigation strategies.
	Slides FRAA04 [4.614 MB]
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FRAA05	A 1.3 GHz Cryomodule with 2x9-Cell Cavity for SETF at Peking University	cavity, SRF, cryomodule, experiment	1443
	F. Zhu, J.E. Chen, L.W. Feng, Y. Gao, J.K. Hao, S. Huang, L. Lin, K.X. Liu, S.W. Quan, F. Wang, X.D. Wen, D.H. Zhuang PKU, Beijing, People's Republic of China
	Funding: Work supported by National Basic Research Project (No. 2011CB808304 and 2011CB808302）and NDRC project. The straight beam line of SETF at Peking University is under construction, which consists of a DC-SRF photoinjector and a superconducting linac with two 9-cell cavities. Stable operation of the DC-SRF photoinjector has been realized and the design, manufacture and assembly of the cryomodule with two 9-cell cavities have been completed. Improved capacitive coupling RF power coupler and fast tuner with piezo are adopted
	Slides FRAA05 [3.709 MB]
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FRBA02	Crab Cavity and Cryomodule Development for HL-LHC	cavity, HOM, cryomodule, shielding	1460
	F. Carra, A. Amorim Carvalho, K. Artoos, S. Atieh, I. Aviles Santillana, A.B. Boucherie, J.P. Brachet, K. Brodzinski, R. Calaga, O. Capatina, T. Capelli, L. Dassa, T. Dijoud, H.M. Durand, G. Favre, L.M.A. Ferreira, P. Freijedo Menendez, M. Garlaschè, M. Guinchard, N. Kuder, S.A.E. Langeslag, R. Leuxe, A. Macpherson, P. Minginette, E. Montesinos, F. Motschmann, C. Parente, L. Prever-Loiri, D. Pugnat, E. Rigutto, V. Rude, M. Sosin, G. Vandoni, G. Villiger, C. Zanoni CERN, Geneva, Switzerland S.A. Belomestnykh, S. Verdú-Andrés, Q. Wu, B. P. Xiao BNL, Upton, Long Island, New York, USA G. Burt Lancaster University, Lancaster, United Kingdom S.U. De Silva, J.R. Delayen, R.G. Olave, R.G. Olave, H. Park ODU, Norfolk, Virginia, USA T.J. Jones, N. Templeton STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom Z. Li SLAC, Menlo Park, California, USA K.B. Marinov, S.M. Pattalwar STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom T.H. Nicol Fermilab, Batavia, Illinois, USA A. Ratti LBNL, Berkeley, California, USA
	The HL-LHC project aims at increasing the LHC luminosity by a factor 10 beyond the design value. The installation of a set of RF Crab Cavities to increase bunch crossing angle is one of the key upgrades of the program. Two concepts, Double Quarter Wave (DQW) and RF Dipole (RFD) have been proposed and are being produced in parallel for test in the SPS beam before the next long shutdown of CERN accelerator’s complex. In the retained concept, two cavities are hosted in one single cryomodule, providing thermal insulation and interfacing with RF coupling, tuning, cryogenics and beam vacuum. This paper overviews the main design choices for the cryomodule and its different components, which have the goal of optimizing the structural, thermal and electro-magnetic behavior of the system, while respecting the existing constraints in terms of integration in the accelerator environment. Prototyping and testing of the most critical components, manufacturing, preparation and installation strategies are also described.
	Slides FRBA02 [4.678 MB]
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MOAA02

Recent Progress with EU-XFEL

cryomodule, cavity, linac, cryogenics

14

D. Reschke
DESY, Hamburg, Germany

The superconducting accelerator of the European XFEL consists of the injector part and the main linac. The injector includes one 1.3 GHz accelerator module and one 3.9 GHz third-harmonic module, while the main linac will consist of 100 accelerator modules, operating at an average design gradient of 23.6 MV/m. The fabrication and surface treatment by industry as well as RF acceptance tests of the required 808 superconducting 1.3 GHz cavities are close to an end by the time of SRF15. The accelerator module assembly, testing and installation in the tunnel is in full swing. First steps of commissioning have been made. The status and results of cavity and module RF tests at 1.3 GHz and 3.9 GHz are presented.

Slides MOAA02 [2.903 MB]

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MOBA04

High-Q Operation of SRF Cavities: The Impact of Thermocurrents on the RF Surface Resistance

cavity, simulation, shielding, niobium

37

J.M. Köszegi, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

For CW applications much effort is being expended to minimize the power dissipation (surface resistance) of niobium cavities. Previous studies have shown that residual resistance can be reduced by performing a thermal cycle, a procedure of warming up a cavity after initial cooldown to about 20K and cooling it down again. It was postulated that thermocurrents during cooldown generate additional trapped magnetic flux that impacts the cavity quality factor. Here, we present a more extensive study that includes measurements of two additional passband modes and that confirms the effect. A change in surface resistance of more than a factor seven was observed. In this paper, we also discuss simulations that support the claim. While the layout of the cavity LHe tank system is cylindrically symmetric, we show that the temperature dependence of the material parameters results in a non-symmetric current distribution.

Slides MOBA04 [2.830 MB]

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MOPB001

RF Performance of Ingot Niobium Cavities of Medium-Low Purity

cavity, SRF, vacuum, radio-frequency

61

G. Ciovati, P. Dhakal, P. Kneisel, G.R. Myneni, J.K. Spradlin
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q0-values, because of the well-known dependence of the BCS-surface resistance on mean free path. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR=100-150) and low (RRR=60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with Q0-values above 1.5·10¹⁰ at 2 K. The performance of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.

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MOPB030

Measurements of Thermal Impedance on Superconducting Radiofrequency Cavities

cavity, impedance, SRF, niobium

154

P. Dhakal, G. Ciovati, G.R. Myneni
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The thermal impedance of niobium plays an important role in the stability of the superconducting radio frequency cavities used in particle accelerators. During the operation of SRF cavities, the RF power dissipated on the inner surface of the cavities and the heat transport to the helium bath depend on the thermal conductivity of niobium and the Kapitza conductance of the interface between the niobium and superfluid helium. Here, we present the results of measurements done on samples as well as on SRF cavities made of both ingot and fine-grain Nb to explore the effect of the surface preparation and crystal structure on the thermal impedance.

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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, ion, vacuum

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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MOPB039

Analysis of BCS RF Loss Dependence on N-Doping Protocols

cavity, niobium, SRF, linac

174

A.D. Palczewski, P. Dhakal, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 with supplemental funding from the LCLS-II Project U.S. DOE Contract No. DE-AC02-76SF00515.
We present a study on two parallel-path SRF cavities (one large grain and one fine grain, 1.3 GHz) which seeks to explain the correlation between the amount of nitrogen on the inner surface of a “nitrogen doped” SRF cavity and the change in the temperature dependant (packaged into term BCS) RF losses. For each doping/EP, the cavities were tested at multiple temperatures (2.0 K to 1.5 K in 0.1 K steps) to create a Q0 vs. Eacc vs. T matrix which then could be used to extract temperature dependant and independent components. After each test, the cavities were thermally cycled to 120 K and then re-cooled and retested to assess if evidence of hydrogen migration might appear even at a small level. In addition, TD-5 was also tested at fixed low field (Q0 vs. T) to fit standard BCS theory. In parallel, SIMS data was taken on like-treated samples to correlate the amount of nitrogen within the RF surface to the change in the temperature dependant fitting parameter “A”.**
[**] H.Tian et al., contributed to SRF2015.

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MOPB052

Determination of Bulk and Surface Superconducting Properties of N2-Doped Cold Worked, Heat Treated and Electro-polished SRF Grade Niobium

cavity, SRF, superconductivity, niobium

214

S. Chetri, D.C. Larbalestier, Z-H. Sung
ASC, Tallahassee, Florida, USA
P. Dhakal
JLab, Newport News, Virginia, USA
P.J. Lee
NHMFL, Tallahassee, Florida, USA

Funding: Support for this work at FSU was from US DOE Award# DE-SC0009960 and the State of Florida Additional support for the National High Magnetic Field Laboratory facilities is from the NSF: NSF-DMR-1157490
Nitrogen-doped cavities show significant performance improvement in the medium accelerating field regime due to a lowered RF surface resistivity. However, the mechanism of enhancement has not been clearly explained. Our experiments explore how N2-doping influences Nb bulk and surface superconducting properties, and compare the N2-doped properties with those obtained previously with conventionally treated samples. High purity Nb-rod was mechanically deformed and post treated based on a typical SRF cavity treatment recipe. The onset of flux penetration at Hc1, and the upper and the surface critical fields, Hc2 and Hc3, were characterized by magnetic hysteresis and AC susceptibility techniques. The surface depth profile responsible for superconductivity was examined by changing AC amplitude in AC susceptibility, and the microstructure was directly observed with EBSD-OIM. We are also investigating surface chemistry for detailed composition using XPS. We have found that N2-doping at 800 °C significantly reduces the Hc3/Hc2 ratio towards the ideal value of ~1.7, and conclude that AC susceptibility is capable of following changes to the surface properties induced by N2-doping.

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MOPB066

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

cavity, linac, simulation, ion

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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MOPB068

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

ion, linac, 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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MOPB076

Horizontal RF Test of a Fully Equipped 3.9 GHz Cavity for the European XFEL in the DESY AMTF

cavity, HOM, cryomodule, controls

301

C.G. Maiano, C. Albrecht, R. Bospflug, J. Branlard, L. Butkowski, T. Delfs, J. Eschke, A. Gössel, F. Hoffmann, M. Hüning, K. Jensch, R. Jonas, R. Klos, D. Kostin, W. Maschmann, A. Matheisen, U. Mavrič, W.-D. Möller, C. Müller, K. Mueller, B. Petersen, P. Pierini, J. Rothenburg, O. Sawlanski, M. Schmökel, A.A. Sulimov, E. Vogel
DESY, Hamburg, Germany
A. Bosotti, M. Moretti, R. Paparella, P. Pierini, D. Sertore
INFN/LASA, Segrate (MI), Italy
E.R. Harms
Fermilab, Batavia, Illinois, USA
C.R. Montiel
ANL, Argonne, Illinois, USA
S. Pivovarov
BINP SB RAS, Novosibirsk, Russia

In order to validate the cavity package concept before the module preparation for the European XFEL Injector, one 3.9 GHz cavity, complete with magnetic shielding, power coupler and frequency tuner was tested in a specially designed single cavity cryomodule in one of the caves of the DESY Accelerator Module Test Facility (AMTF). The cavity was tested in high power pulsed operation up to the quench limit of 24 MV/m, above the vertical test qualifications and all subsystems under test (coupler, tuner, waveguide tuners, LLRF system) were qualified to design performances.

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MOPB077

Vertical Tests of XFEL 3rd Harmonic Cavities

cavity, vacuum, HOM, instrumentation

306

D. Sertore, M. Bertucci, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, M. Moretti, R. Paparella, P. Pierini
INFN/LASA, Segrate (MI), Italy
A. Matheisen, M. Schmökel
DESY, Hamburg, Germany
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

The 10 cavities of the EXFEL 3rd Harmonic Cryomodule have been tested and qualified, before integration in the He-tank, in our upgraded Vertical Test stand. In this paper, we report the measured RF performance of these cavities together with the main features of the test facility.

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MOPB078

Mode Sensitivity Analysis of 704.4 MHz Superconducting RF Cavities

HOM, cavity, linac, dipole

311

K. Papke, F. Gerigk, S. Horvath-Mikulas, S. Papadopoulos, E. Pilicer, F. Pillon
CERN, Geneva, Switzerland
U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany

Due to the large variety of beam patterns considered for the superconducting proton linac (SPL) at CERN it is likely that the frequencies of some HOMs are close to machine lines during operation. Hence, in the interest of developing a method to shift HOM frequencies away from machine lines, we study the influence of cavity detuning and re-tuning (e.g. by Lorentz forces, field flatness tuning, frequency tuning during operation) on HOMs. The sensitivity of HOMs with respect to the fundamental mode was studied for a mono-cell and for 5-cell high-beta SPL cavities operating at 704.4 MHz. First, the variation of the HOMs during the flat-field tuning was measured. In this process, several detuning and re-tuning cycles were made to estimate the range of possible HOM frequency shifts. Secondly the effect of the frequency tuner on the HOMs is presented and finally the frequency shifts of all modes due to the cool down.

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MOPB094

Inspection and Repair Techniques for the EXFEL Superconducting 1.3 GHz Cavities at Ettore Zanon S.p.A: Methods and Results

cavity, accelerating-gradient, electron, controls

368

G. Massaro, G. Corniani, N. Maragno
Ettore Zanon S.p.A., Schio, Italy
A. Matheisen, A. Navitski
DESY, Hamburg, Germany
P. Michelato, L. Monaco
INFN/LASA, Segrate (MI), Italy

The quality control of the inner surface of superconducting RF cavities is essential in order to assure high accelerating gradient and quality factor. Ettore Zanon S.p.A. (EZ) has implemented in the serial production an optical system that use an high-resolution camera, in order to detect various types of defects. This system is added to a grinding machine, that was specifically designed and built to repair imperfections of the cavities inner surface. This inspection and repair system is applied to recover performance limited cavities of the 1.3 GHz European XFEL project, where surface irregularities are detected, either by the Obacht inspection system at Desy or the optical system at EZ. The optical system and the grinding procedure are qualified using two series cavities limited in gradient and showing different types of surface defects. The performances of these cavities have been recovered to reach the specifications of the project. Until now, all the series XFEL cavities built by EZ, repaired with this technique, have shown an accelerating gradient well above the EXFEL goal.

Poster MOPB094 [0.795 MB]

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MOPB095

SRF Cavity Processing and Chemical Etching Development for the FRIB Linac

cavity, SRF, linac, controls

373

I.M. Malloch, E.S. Metzgar, L. Popielarski
FRIB, East Lansing, Michigan, USA
M.J. LaVere
MSU, East Lansing, Michigan, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661, the State of Michigan and Michigan State University.
In preparation of a rigorous superconducting RF (SRF) cavity processing and test plan for the production of the Facility for Rare Isotope Beams (FRIB) driver linac, a state-of-the-art chemical etching tool has been installed in the FRIB coldmass production facility. This paper seeks to summarize the etching equipment design, installation, and validation program and subsequent etching results for a variety of SRF cavity types and etching configurations. Bulk etching, light etching, and custom (frequency tuning) etching results for different FRIB cavities are discussed. Special emphasis is placed on the etching removal uniformity and frequency tuning reliability of these processes.

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MOPB096

Vertical Electro-Polishing at TRIUMF

cathode, cavity, TRIUMF, niobium

378

J.J. Keir, P.R. Harmer, D. Lang, R.E. Laxdal, T. Shishido, R. Smith
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
T. Shishido
KEK, Ibaraki, Japan

A setup for electropolishing of a superconducting niobium single-cell cavity has been installed at TRIUMF. A vertical method was selected to make the setup compact. To increase removal speed at the equator and remove hydrogen bubbles at the iris surface, 4 cathode paddles were rotated in the cavity cell during electropolishing. We will report on our first electropolishing result.

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MOPB100

Cathode Geometry and Flow Dynamics Impact on Vertical Electropolishing of Superconducting Niobium Cavities

cavity, cathode, niobium, simulation

385

L.M.A. Ferreira
CERN, Geneva, Switzerland

CERN has now a fully operating vertical electropolishing installation, which has been used for the processing of 704 MHz high-beta five-cell Superconducting Proton Linac (SPL) niobium cavities. This installation relies only on the electrolyte circulation (HF/H2SO4) for power dissipation, evacuation of gases and homogeneous finishing; thus, parameters like cathode geometry, electrolyte flow and temperature become even more crucial when compared with horizontal electropolishing installations. Based on computational simulations performed with Comsol Multiphysics® and on a methodology developed at CERN, it is possible to assess the impact of the different cathode geometries as well as of the flow on the etching rate distribution. The data obtained with two different cathode geometries are presented: electrolyte velocity distribution, etching rate distribution, average current density and minimum working potential. One geometry was defined through a purely electrochemical approach while the second was defined to minimise the difference between the maximum and the minimum electrolyte speed inside the cavity; in both cases, the influence of the electrolyte flow was taken into account.

Poster MOPB100 [1.794 MB]

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MOPB113

Study of the Evolution of Artificial Defects on the Surface of Niobium During Electrochemical and Chemical Polishing

SRF, controls, laser, cavity

433

L. Monaco, P. Michelato
INFN/LASA, Segrate (MI), Italy
A. Navitski, J. Schaffran, W. Singer
DESY, Hamburg, Germany
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
A.L. Prudnikava, Y. Tamashevich
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

The presence of defects on the inner surface of Nb superconducting RF structures might limit its final performance. For this reason, strict requirements are imposed during mechanical production of the cavities, specifically on the quality control of the inner surface of components, to avoid the presence of defects or scratches. Nevertheless, some defects may remain also after control or can arise from the following production steps. Understanding the evolution of the defect might shine new insight on its origin and help in defining possible repair techniques. This paper reports the topographical evolution of defects on a Nb sample polished with the standard recipe used for the 1.3 GHz cavities of the EXFEL project. Various artificial defects of different shape, dimensions, and thicknesses/depths, with geometrical characteristics similar to the one that may occur during the machining and handling of cavities, have been “ad hoc” produced on the sample of the same material used for the cell fabrication. Analysis shows the evolution of the shape and profile of the defects at the different polishing steps.

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MOPB116

Developments of Horizontal High Pressure Rinsing for SuperKEKB SRF Cavities

cavity, vacuum, factory, SRF

443

Y. Morita, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, M. Nishiwaki
KEK, Ibaraki, Japan

The Q factors of the eight superconducting accelerating cavities gradually degraded during the long-term operation of the KEKB accelerator. Since we will re-use those SRF cavities for the SuperKEKB, the performance degradation will be a serious problem. Several cavities degraded their performance significantly at high accelerating fields. The Q degradation is still acceptable for the 1.5 MV operations at SuperKEKB. However, further degradation will make the operation difficult. In order to recover the cavity performance, we developed horizontal high pressure water rinsing (HHPR). This method uses a horizontal high pressure water nozzle and inserts it directly into the cavity module. We applied this method to two degraded cavities and their degraded Q factors recovered above 10⁹ at around 2 MV. In this paper we will present the HHPR method, high power test results after the HHPR and the residual gas analysis.

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MOPB118

Cleanliness and Vacuum Acceptance Tests for the UHV Cavity String of the XFEL Linac

cavity, vacuum, controls, cryomodule

452

S. Berry, O. Napoly, B. Visentin
CEA/DSM/IRFU, France
C. Boulch, C. Cloué, C. Madec, T. Trublet
CEA/IRFU, Gif-sur-Yvette, France
D. Henning, L. Lilje, A. Matheisen, M. Schmökel
DESY, Hamburg, Germany

The main linac of the European XFEL will consist of 100 accelerator modules, i.e. 800 superconducting accelerator cavities operated at a design gradient of 23.6MV/m. In this context CEA-Saclay built an assembly facility designed to produce one module per week, ready to be tested at DESY. The facility overcame the foreseen production rate. We would like to highlight and discuss the critical fields: cleanliness and vacuum. A new assembly method to protect final assembly against particulates contamination has been implemented on the production line. Impact on cryomodule RF test is presented. Particle transport measurements on components used for the European XFEL accelerator module are presented. The results indicate that the nominal operation of the automated pumping and venting units will not lead to particle transport. Vacuum acceptance tests are of major interest: leak tests and residual gas analysis (RGA) are used to control the absence of air leak and contamination. The RGA specifications have been slightly relaxed to ensure the production rate.

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TUPB002

Elimination of High Frequency Noise From the Beam in the Diamond Light Source Storage Ring

storage-ring, synchrotron, controls, power-supply

525

C. Christou, A. Bogusz, P.J. Marten
DLS, Oxfordshire, United Kingdom

High frequency beam motion has been identified as a source of noise in infrared beamlines in a number of synchrotron light sources. Diamond is a third generation synchrotron light source with storage ring current maintained by two superconducting CESR-B cavities powered by IOT-driven RF amplifiers. In our case, undesirable beam motion in the kilohertz range is predominantly driven by spectral content in the voltage across the IOTs arising from the switched mode nature of the high voltage power supply. Spectral noise on the amplifiers and beam has been identified and characterised and efforts to eliminate this noise are described. Care has been taken to maintain the overall stability of the RF at Diamond and tests have been carried out on an infrared beamline to investigate the degree to which beam noise impacts beamline operation in its different operating configurations.

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TUPB008

A New Cryogenic Control System for the Vertical Test Area at Jefferson Lab

controls, PLC, cryogenics, SRF

549

G.K. Davis, T. Goodman, P. Kushnick, T. Powers, C.M. Wilson
JLab, Newport News, Virginia, USA

Funding: DOE
The Vertical Test Area at Jefferson Lab, consisting of eight vertical dewars, recently received a major upgrade by replacing the original (1995) cryogenic control system. A new, state-of-the-art, distributed control system (DC S) based on Programmable Logic Controllers (PLCs) was installed and commissioned. The new system increases facility throughput, reliability and cryogenic efficiency, while improving safety. The system employs a touchscreen graphical user interface and a highly redundant architecture on an Ethernet backbone.

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TUPB010

Plug Transfer System for GaAs Photocathodes

gun, SRF, cathode, vacuum

553

P. Murcek, A. Arnold, P.N. Lu, J. Teichert, H. Vennekate, R. Xiang
HZDR, Dresden, Germany
A. Burrill
HZB, Berlin, Germany

The transport and exchange technology of Cs2Te photocathode for the ELBE superconducting rf photoinjector (SRF gun) has been successfully developed and tested at HZDR. The next goal is to realize the transport of GaAs photocathode into SRF gun, which will need a new transfer system with XHV 10^-11 mbar. The key component of the system is the transfer chamber and the load-lock system that will be connected to the SRF-gun. In the carrier four small plugs will be transported, and one of them will be plug on the cathode-body and inserted into the cavity. The new transport chamber allows the transfer and exchange of plugs between HZDR, HZB and other cooperating institutes. In HZDR this transfer system will also provide a direct connection between the SRFGUN and the GaAs preparation chamber in the Elbe-accelerator hall.

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TUPB011

HPRF Transmission Componenets Study and Distribution in TRIUMF E-Linac

linac, klystron, simulation, TRIUMF

557

Z.T. Ang
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

TRIUMF e-lianc was commissioning last September for the first stage. High power rf systems were in operation stable. Two 300 kW klystrons along with the key waveguide components were tested before feeding rf power into 1.3 GHz 9-cell superconducting cavities. The rf high power variable divider and 360 degree waveguide phase shifters are working successfully. The simulations on different waveguide structures for the power dividers, phase shifters have been studied. The comparisons of the calculation results are reported in the paper. The rf signal level tests of the components and waveguide distribution systems will also be present in this paper.

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TUPB014

First Operation of a Superconducting RF Electron Test Accelerator at Fermilab

electron, gun, cavity, superconducting-RF

571

E.R. Harms, R. Andrews, C.M. Baffes, D.R. Broemmelsiek, K. Carlson, D.J. Crawford, N. Eddy, D.R. Edstrom, J.R. Leibfritz, A.H. Lumpkin, S. Nagaitsev, P. Piot, P.S. Prieto, J. Reid, J. Ruan, J.K. Santucci, V.D. Shiltsev, W.M. Soyars, D. Sun, R.M. Thurman-Keup, A. Valishev, A. Warner
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
A test accelerator utilizing SRF technology recently accelerated its first electrons to 20 MeV at Fermilab. Foreseen enhancements will make acceleration to 300 MeV possible at a maximum beam power of 80 kW. A summary of commissioning steps and first experiments as well as current beam parameters compared to design is presented. Plans for expansion and the future physics program are also summarized.

Poster TUPB014 [11.582 MB]

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TUPB018

Preparation of the 3.9 GHz System for the European XFEL Injector Commissioning

cavity, HOM, alignment, vacuum

584

P. Pierini, M. Bertucci, M. Bonezzi, A. Bosotti, J.F. Chen, M. Chiodini, P. Michelato, L. Monaco, M. Moretti, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Albrecht, N. Baboi, S. Barbanotti, J. Branlard, Th. Buettner, L. Butkowski, T. Delfs, H. Hintz, F. Hoffmann, M. Hüning, K. Jensch, R. Jonas, R. Klos, D. Kostin, L. Lilje, C.G. Maiano, W. Maschmann, A. Matheisen, U. Mavrič, W.-D. Möller, C. Müller, P. Pierini, J. Prenting, J. Rothenburg, O. Sawlanski, M. Schlösser, M. Schmökel, A.A. Sulimov, E. Vogel
DESY, Hamburg, Germany
E.R. Harms
Fermilab, Batavia, Illinois, USA
C.R. Montiel
ANL, Argonne, Illinois, USA
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

The 3.9 GHz cryomodule and RF system for the XFEL Injector is being assembled and delivered to the underground building in summer 2015, for the injector commissioning in Fall 2015. This contribution outlines the status of the activity and reports the preparation stages of the technical commissioning of the system.

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TUPB021

Measurement of the Cavity Performances of Compact ERL Main Linac Cryomodule During Beam Operation

cavity, linac, radiation, cryomodule

592

H. Sakai, M. Egi, K. Enami, T. Furuya, S. Michizono, T. Miura, F. Qiu, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

We developed ERL main linac cryomodule for Compact ERL (cERL) in KEK. The module consists of two 9-cell 1.3 GHz superconducting cavities, two 20 kW high power coupler, two mechanical tuner and three HOM dampers. After construction of cERL recirculation loop, beam operation was started in 2013 Dec. First electron beam of 20 MeV successfully passed the main linac cavities. After adjusting beam optics, energy recovery operation was achieved. Main linac cavity was enough stable for ERL beam operation with digital LLRF system and energy recovery was successfully done with CW 80 uA beam. However, field emission was a problem for long term operation. In this paper, we express the measurement of the cavity performances of long term beam operation.

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TUPB025

Tuning the Superconducting Linac at Low Beam Intensities

linac, ion, bunching, acceleration

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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TUPB026

Cryogenic Performance of the HNOSS Test Facility at Uppsala University

cavity, cryogenics, vacuum, controls

612

R. Santiago Kern, K.J. Gajewski, L. Hermansson, R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden
P. Bujard, T. Junquera, J.P. Thermeau
Accelerators and Cryogenic Systems, Orsay, France

Funding: Knut and Alice Wallenbergs foundation
The FREIA Laboratory at Uppsala University, Sweden, is developing part of the RF system and testing the superconducting double spoke cavitites for ESS. During 2014 it was equipped with HNOSS, a versatile horizontal cryostat system for testing superconducting cavities. HNOSS is designed for high power RF testing of up to two superconducting accelerating cavities equipped with helium tank, fundamental power coupler and tuning system. In particular it will be used to characterise the performance of spoke cavities like used in the accelerator for the ESS project. HNOSS is connected to a cryogenic plant providing liquid helium and a sub-atmospheric pumping system enabling operation in the range 1.8 to 4.5~K. We present a brief description of the major components, installation and results from the recent operation and tests.

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TUPB058

Characterization of Thin Films Using Local Magneometer

experiment, SRF, superconductivity, cavity

712

N. Katyan, C.Z. Antoine
CEA/DSM/IRFU, Grenoble, France
C.Z. Antoine
CEA/IRFU, Gif-sur-Yvette, France

Funding: CEA
SIS nanocomposite (Superconductor/Insulator/Superconductor) could improve efficiency of accelerating cavities. The SRF multilayers concept focuses on the enhancement of HC1 using thin layers (d~λ). The use of thin layers makes it easier to avoid avalanche penetration of vortices in case of local defects. Several layers are needed in order to attenuate the external field to values below Nb HC1, decoupled using dielectric layers. We don’t know yet how the predicted properties evolve in realistic conditions; hence it seems reasonable to do their optimization. Two parameters need to be measured to study their behavior in cavity operating conditions: HC1 and Rs surface resistance (especially residual). For that purpose two instruments were developed in Saclay and in Orsay. A local magnetometer allows measuring the vortex penetration on samples without the orientation and edge effects encountered in SQUID magnetometers. Its operating conditions range from 2-40 K, with field up to 150 mT, and upgradation to higher field. A pill-box cavity working on TE011 and TE012 modes with removable sample/top measures surface resistance up to 60 mT based on calorimetric method from 1.6-4.5 K.*
*SRF cavities, 3rd Harmonic Analysis

Poster TUPB058 [1.581 MB]

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TUPB067

Design and First Measurements of an Alternative Calorimetry Chamber for the HZB Quadrupole Resonator

niobium, quadrupole, SRF, simulation

739

S. Keckert, R. Kleindienst, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453.
The systematic research on superconducting thin films requires dedicated testing equipment. The Quadrupole Resonator (QPR) is a specialized tool to characterize the superconducting properties of circular samples. A calorimetric measurement of the RF surface losses allows the surface resistance to be measured with sub nano-ohm resolution. This measurement can be performed over a wide temperature and magnetic field range, at frequencies of 433, 866 and 1300 MHz. The system at Helmholtz-Zentrum Berlin (HZB) is based on a resonator built at CERN and has been optimized to lower peak electric fields and an improved resolution. An alternative calorimetry chamber has been designed in order to provide flat samples for coating and to ease changing of samples. Furthermore it enables exchangeability of samples between the QPRs at HZB and CERN. With this poster the design and first measurements of the new calorimetry chamber is presented.

Poster TUPB067 [1.776 MB]

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TUPB075

Measurements on the Superconducting 217 MHz CH Cavity During the Manufacturing Phase

cavity, simulation, resonance, linac

757

F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher, W.A. Barth, S. Mickat
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: GSI, HIM, BMBF Contr. No. 05P12RFRBL
Since in future the existing UNILAC (Universal Linear Accelerator) will be used as an injector for the FAIR (Facility for Antiproton and Ion Research) project, a new superconducting (sc) continuous wave (cw) linac at GSI is proposed to keep the Super Heavy Element (SHE) program at a competitive high level. In this context, a sc 217 MHz crossbar-H-mode (CH) cavity has been designed at the Institute for Applied Physics (IAP), Frankfurt University, and was built at Research Instruments (RI) GmbH, Germany. The cavity serves as a first prototype to demonstrate the reliable operability under a realistic accelerator environment and its successful beam operation will be a milestone on the way to the new linac. In this contribution measurements during the production process of the cavity as well as corresponding simulations will be presented.

Poster TUPB075 [2.476 MB]

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TUPB078

Developments on a Cold Bead-Pull Test Stand for SRF Cavities

cavity, HOM, SRF, factory

770

A.V. Vélez, A. Frahm, J. Knobloch, A. Neumann
HZB, Berlin, Germany

Final tuning and field profile characterization of SRF cavities always takes place at room temperature. However, important questions remains as to what happens when the cavity is cooled to LHe temperature, in particular with multi cell systems. To enable the characterization of cavities in the cold, we have designed and commissioned a "cold bead-pull" test stand at HZB. The present test stand is designed to be integrated in HoBiCaT (Horizontal bi-cavity testing facility) with the ability to provide electric field profile measurements under realistic superconducting conditions (T=1.8K). In this paper mechanical and operational details of the apparatus will be described as well as future plans for the development and usage of this facility.

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TUPB093

Initial Commissioning Experience with the Spallation Neutron Source Vertical Test Area RF System

cavity, software, controls, hardware

819

M.T. Crofford, J.A. Ball, M. Doleans, S.-H. Kim, S.W. Lee, J.D. Mammosser, J. Saunders
ORNL, Oak Ridge, Tennessee, USA
T.L. Davidson, S. Whaley
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
The Spallation Neutron Source (SNS) has developed a vertical test area (VTA) for the testing and qualification of superconducting radio frequency cavities. The associated RF System successfully supported the initial commissioning of the VTA system and has been utilized for cavity testing at both 4 and 2 K. As operational experience was gained, improvements to the RF system were implemented to better utilize the dynamic range of the system, and software updates and additions were made to meet the operational needs. The system continues to evolve as we gain better understanding of the testing needs.

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TUPB095

Resonance Control for Narrow-Bandwidth, Superconducting RF Applications

cavity, resonance, feedback, SRF

828

W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA
D. Gonnella
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
M. Liepe
Cornell University, Ithaca, New York, USA

Optimal control techniques have been employed in a variety of applications since they were first developed more than 60 years ago but until now they have been used in few if any accelerator-related applications. The next generation of superconducting accelerators will require both precise control of the gradient and active stabilization of the resonance frequency. Optimal control techniques provide a self-consistent framework within which to construct a combined electro-mechanical controller. Results from recent cold cavity tests at Fermilab are presented.

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TUPB101

Design of the Thermal and Magnetic Shielding for the LHC High Luminosity Crab-Cavity Upgrade

cavity, shielding, cryomodule, simulation

852

N. Templeton, T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, R. Leuxe, C. Zanoni
CERN, Geneva, Switzerland
G. Burt, S.M. Pattalwar
Cockcroft Institute, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G. Burt
Lancaster University, Lancaster, United Kingdom
K.B. Marinov, A.J. May, S.M. Pattalwar
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A. Ratti
LBNL, Berkeley, California, USA

Before the High Luminosity (Hi-Lumi) upgrade of the Large Hadron Collider (LHC), two pairs of superconducting compact Crab Cavities are to be tested within separate cryomodules, on the Super Proton Synchrotron (SPS) at CERN in 2018 prior to Long Shutdown 2. Two novel side-loaded cryomodules, which allow ease of access for assembly, inspection and maintenance, have been developed for the prototype tests. The cryomodule shielding includes a thermal shield and double layer magnetic shield, consisting of a warm-outer shield, and two cold-inner shields (one per cavity). Various constraints and considerations have led to unique cold shielding, mounted inside the cavity helium vessels, resulting in several design challenges. The shielding adopts and utilises the module’s side-loaded configuration, for continuity and accessibility, while satisfying tight spatial constraints and requirements to meet the functional specification. This paper outlines the design, analysis, manufacture and assembly of the Hi-Lumi SPS test cryomodule’s thermal and magnetic shielding, which are critical to achieving the operational stability.

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TUPB102

Validation of Local Magnetic Shielding for FRIB Using a Prototype Cryomodule

solenoid, cavity, shielding, cryomodule

857

S.K. Chandrasekaran, K. Saito
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, and the U.S. National Science Foundation under Grant No. PHY-1102511.
The local magnetic shield design and cryogenic magnetic shielding material for the FRIB QWR cryomodule was validated in a two cavity, one solenoid prototype cryomodule. The magnetic fields were measured inside and outside the magnetic shielding before, during, and after operation of an 8 T superconducting solenoid. The effect of demagnetization cycles of the solenoid was also examined. The magnetic field at the cavity’s high RF magnetic field area, inside the magnetic shield and with the solenoid off, was measured using a single-axis fluxgate to be less than 0.3 μT (3 mG) after cool down of the cryomodule. A 3.07 μT (30.7 mG) residual field was observed at high magnetic field area after conclusion of solenoid operation. This was attributed to the persistent currents circulating in the superconducting solenoid. Demagnetization cycles were therefore determined to be unnecessary for FRIB cryomodules, as long as the solenoid is normal conducting when the cavity is cooled through the superconducting critical temperature.
S.K. Chandrasekaran currently at Fermi National Accelerator Laboratory, Batavia, IL, USA.

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TUPB108

Connection of EU-XFEL Cryomodules, Caps, Boxes in EU-XFEL Main Linac and Injector: Welding of Cryo-Pipes and Assembly of Beam-Line Absorbers Under Requirements of PED Regulation

linac, cryomodule, vacuum, cryogenics

883

S. Barbanotti, C. Buhr, H. Hintz, K. Jensch, L. Lilje, W. Maschmann, P. Pierini, A. Wagner
DESY, Hamburg, Germany
P. Pierini
INFN/LASA, Segrate (MI), Italy

The European X-ray Free Electron Laser (EU-XFEL) cold linac consists of 100 assembled cryomodules, 6 feed-/end-boxes and 6 string connection boxes fixed to the ceiling of the accelerator tunnel; the injector consists of a radio frequency gun, one 1.3 GHz and one 3.9 GHz cryomodule, one feed- and one end-cap lying on ground supports. The components are connected together in the tunnel, after cold testing, transport, final positioning and alignment. The cold linac is a pressure equipment and is therefore subjected to the requirements of the Pressure Equipment Directive (PED). This paper describes the welding and subsequent non-destructive testing of the cryo-pipes (with a deeper look at the technical solutions adopted to satisfy the PED requirements), the assembly of the beam line absorbers and the final steps before closing the connection with a DN1000 bellows. A special paragraph will be dedicated to the connection of the injector components, where the lack of space makes this installation a particularly challenging task.

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TUPB115

Improvements of the Mechanical, Vacuum and Cryogenic Procedures for European XFEL Cryomodule Testing

cryomodule, vacuum, cryogenics, detector

906

J. Świerbleski, M. Bednarski, B. Dzieza, W. Gaj, L. Grudnik, P. Halczynski, A. Kotarba, A. Krawczyk, K. Myalski, T. Ostrowicz, B. Prochal, J. Rafalski, M. Sienkiewicz, M. Skiba, M. Wartak, M. Wiencek, J. Zbroja, P. Ziolkowski
IFJ-PAN, Kraków, Poland

The European X-ray Free Electron Laser is under construction at DESY, Hamburg. The linear accelerator part of the laser consists of 100 SRF cryomodules. Before installation in the tunnel the cryomodules undergo a series of performance tests at the AMTF Hall. Testing procedures have been implemented based on TTF (Tesla Test Facility) experience. However, the rate of testing and number of test benches is greater than in the TTF infrastructure. To maintain the goal testing rate of one module per week, improvement to the existing procedures were implemented at AMTF. Around 50% of the testing time is taken by connection of the cryomodule to the test bench, performing all necessary checks and cool down. Most of the preparation procedures have been optimized to decrease mounting time. This paper describes improvements made to the mechanical connections, vacuum checks and cryogenics operation.

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WEBA07

Beam Commissioning of the 56 MHz QW Cavity in RHIC

cavity, HOM, damping, SRF

982

Q. Wu, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, T. Hayes, K. Mernick, F. Severino, K.S. Smith, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
A 56 MHz superconducting RF cavity has been designed, fabricated and installed in the Relativistic Heavy Ion Collider (RHIC). The cavity operates at 4.4 K with a “quiet helium source” to isolate the cavity from environmental acoustic noise. The cavity is a beam driven quarter wave resonator. It is detuned and damped during injection and acceleration cycles and is brought to operation only at store energy. We have observed clear luminosity increase and bunch length reduction in the first operation of the cavity with Au + Au and Au + He3 collisions. The cavity voltage was limited by quenching in the Higher Order Mode coupler. This paper also discusses the cavity beam experiments with no higher order mode coupler in p + p and p + Au RHIC operation.

Slides WEBA07 [2.522 MB]

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THAA06

Precise Studies on He-Processing and HPR for Recovery From Field Emission by Using X-Ray Mapping System

cavity, radiation, cryomodule, linac

1019

H. Sakai, K. Enami, T. Furuya, M. Satoh, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

We usually met the degradation of superconducting RF cavity on the cryomodule test and beam operation even if the performance of this cavity is good on the vertical test (V.T). Field emission is the most severe problem for this degradation after reassembly work from vertical test. Not only high pressure rinsing (HPR) but also He-processing, which is more suitable method without the reassembly work for recovery, is recommended and tried to recover this degradation. However, we did not investigate the details of how field emission sources were processed and removed after HPR and He-processing. We deeply investigated the processing procedure during He-processing and how many field emission sources removed after HPR by using rotating X-ray mapping system* in V.T .
*H.Sakai et.al., Proc. of IPAC10 p2950-2952.

Slides THAA06 [4.347 MB]

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THBA04

Overview of Recent HOM Coupler Development

HOM, cavity, damping, SRF

1031

B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: Work partly supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE， by the US LARP, and by EU FP7 HiLumi LHC - Grant Agreement 284404.
HOM damping is important for SRF applications, especially for high intensity machines. A good HOM damping design will help to reduce power load to the cryogenic system and to reduce the risk of beam breakup. The design of HOM damping, including antenna/loop HOM couplers, beam pipe HOM absorbers and waveguide HOM couplers, is to solve a multi-physics problem that involves RF, thermal, mechanical, and beam-cavity interaction issues. In this talk, the author provides an overview on the latest advances of the HOM couplers for high intensity SRF applications.

Slides THBA04 [2.619 MB]

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THBA05

Higher Order Mode Absorbers for High Current SRF Applications

HOM, cavity, higher-order-mode, linac

1036

R.G. Eichhorn, J.V. Conway, T. Gruber, Y. He, G.H. Hoffstaetter, Y. Li, M. Liepe, T.I. O'Connell, P. Quigley, J. Sears, V.D. Shemelin, E.N. Smith, M. Tigner
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Efficient damping of the higher-order modes (HOMs) of the superconducting cavities is essential for any high current operation. The talk will provide an overview on the latest advances of HOM absorber development for high intensity SRF applications. As the ideal absorber does not exist, the different conceptual approaches will be presented and the associated issues are outlined. Design examples from various labs will be given that help explain the issues and resolutions. Some focus will be given to the Cornell HOM beamline absorber that was design for high current, short bunch operation with up to 400 W heating. The design will be reviewed and testing results will be reported.

Slides THBA05 [4.022 MB]

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THPB005

Simulations of 3.9 GHz CW Coupler for LCLS-II Project

cavity, simulation, linac, cryomodule

1066

I.V. Gonin, T.N. Khabiboulline, A. Lunin, N. Solyak
Fermilab, Batavia, Illinois, USA

LCLS-II linac is based on XFEL/ILC superconducting technology. TTF-III fundamental power coupler for the 3.9 GHz 9-cell cavities has been modifies to satisfy requirements of LCLS-II, operating in CW regime. In this paper we discuss the results of COMSOL analysis of the possible modification of couplers, working at various operating regimes. We present also the results of mechanical study.

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THPB011

Superconducting Travelling Wave Accelerating Structure Development

cavity, accelerating-gradient, status, feedback

1085

R.A. Kostin, P.V. Avrakhov, A.D. Didenko, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
T.N. Khabiboulline, Y.M. Pischalnikov, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by US Department of Energy # DE-SC0006300
The 3 cell superconducting TW accelerating structure was developed to experimentally demonstrate and to study tuning issues for a new experimental device - the superconducting traveling wave accelerator (STWA), a technology that may prove of crucial importance to the high energy SRF linacs by raising the effective gradient and therefore reducing the overall cost. Recently, a STWA structure with a feedback waveguide has been suggested. The structure was optimized and has phase advance per cell of 105° which provide 24% higher accelerating gradient than in SW cavities. Also STWA structure has no strong sensitivity of the field flatness and its length may be much longer than SW structure. With this presentation, we discuss the current status of a 3-cell L-band SC traveling wave along with the analysis of its tuning issues. Special attention will be paid to feedback loop operation with the two-coupler feed system. We also report on the development and fabrication of a niobium prototype 3-cell SC traveling wave structure to be tested at 2°K in fall 2015.

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THPB014

Mechanical Optimization of High Beta 650 MHz Cavity for Pulse and CW Operation of PIP-II Project

cavity, simulation, resonance, cryomodule

1093

T.N. Khabiboulline, I.V. Gonin, C.J. Grimm, A. Lunin, T.H. Nicol, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
P. Kumar
RRCAT, Indore (M.P.), India

The proposed design of the 0.8 GeV PIP-II SC Linac employs two families of 650 MHz 5-cell elliptical cavities with 2 different beta. The β=0.61 will cover the 185-500 MeV range and the β=0.92 will cover the 500-800 MeV range. In this paper we will present update of RF and mechanical design of dressed high beta cavity (β=0.92) for pulse regime of operation at 2 mA beam current. In previous CW version of PIP-II project the mechanical design was concentrated on minimization of frequency shift due to helium pressure fluctuation. In current case of pulse regime operation the main goal was Lorentz force detuning minimization. We present the scope of coupled RF-Mechanical issues and their resolution. Also detailed stress analysis of dresses cavity will be presented.

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THPB015

Design of a Medium Beta Half-Wave SC Prototype Cavity at IMP

cavity, linac, electromagnetic-fields, accelerating-gradient

1097

A.D. Wu, Y. He, T.C. Jiang, Y.M. Li, F.F. Wang, R.X. Wang, L.J. Wen, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China

A superconducting half-wave resonator has been designed with frequency of 325 MHz and beta of 0.51. The geometry parameters and the three shapes of inner conductors (racetrack, ring-shape and elliptical-shape) were studied in details to decrease the peak electromagnetic fields to obtain higher accelerating gradients and minimize the dissipated power on the RF walls. To suppress the operation frequency shift caused by the helium pressure fluctuations and maximize the tuner ranges, the frequency shifts and mechanical characters were simulated in the electric and magnetic areas separately. At the end, the helium vessel was also designed to keep stability as possible. The fabrication and test of the prototype will be complete at the beginning of 2016.

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THPB027

Welding a Helium Vessel to a 1.3 GHz 9-Cell Nitrogen Doped Cavity at Fermilab for LCLS-II

cavity, alignment, vacuum, pick-up

1132

C.J. Grimm, J.A. Kaluzny, D.J. Watkins
Fermilab, Batavia, Illinois, USA

Fermilab has developed a TIG welding procedure that is used attach a nitrogen doped 1.3 GHz 9-cell niobium (Nb) cavity to a titanium (Ti) helium vessel. These cavities will be used in the two prototype cryomodules for the Linac Coherent Light Source (LCLS-II) upgrade at SLAC National Accelerator Laboratory. Discussion in further detail will include setting up TIG welding parameters and tooling requirements for assembly and alignment of the cavity to the helium vessel. The weld designs and glovebox environment produce the best quality TIG welds that meet ASME Boiler and Pressure Vessel Code. The cavity temperature was monitored to assure the nitrogen doping is preserved, and RF measurements are taken throughout the process to monitor the cavity for excessive cell deformation due to heat loads from welding.

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THPB031

Operation Experience with Half Cell Measurement Machine and Cavity Tuning Machine in 3 Years of European XFEL Cavity Series Production

cavity, controls, SRF, HOM

1149

J.H. Thie, A. Gössel, J. Iversen, D. Klinke, C. Müller, A.A. Sulimov, D. Tischhauser
DESY, Hamburg, Germany

For the European XFEL superconducting Cavity series production at both cavity vendors’ four manufacturing machines for production key functions, HAZEMEMA and CTM, are supplied by DESY. Among three years of cavity production in two companies a lot of experience is gathered about influence of surroundings and production quality on cycle times, machine drop outs, general stability time of machines and parts subject to wear. Significant factors on cycle time for tuning operation like temperature stability and drift during tuning and measurements, precision of cell trimming before welding and tuning and generally geometrical factors are shown. RF aspects of tuning and production quality control as additional measurements for TM011-mode to estimate quality of its damping is presented. Performed full Cavity RF measurements exceeds XFEL specifications gives a possibility for additional quality control on welding shrinkage stability and it’s homogeneously distribution. The use of HAZEMEMA and CTM to assess the impact of asymmetric trimming, including calculation of it’s influence on the higher-order modes, is shown.

Poster THPB031 [0.201 MB]

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THPB035

Fabrication of the 3.9 GHz SRF Structures for the European XFEL

cavity, controls, linac, status

1162

P. Pierini, M. Bertucci, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, M. Moretti, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
A. Gresele
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
C.G. Maiano, P. Pierini, E. Vogel
DESY, Hamburg, Germany
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
M. Rizzi
Ettore Zanon S.p.A., Schio, Italy

One batch of 10 cavities has been completed and eight structures have been installed in the 3.9 GHz cryomodule for the European XFEL Injector operation. A second batch of 10 RF structures for a spare injector module is under fabrication. The fabrication has been performed according to the European Pressure Vessel regulations, as needed for the EXFEL operation. This paper describes the fabrication, quality control/assurance procedures and frequency preparation steps in order to achieve cavities at the correct frequency and length within the specifications.

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THPB056

SRF Gun Cavity R&D at DESY

cavity, SRF, gun, cathode

1231

D. Kostin, C. Albrecht, A. Brinkmann, Th. Buettner, J. Eschke, T. Feldmann, A. Gössel, D. Klinke, A. Matheisen, W.-D. Möller, D. Reschke, M. Schmökel, J.K. Sekutowicz, W. Singer, X. Singer, N. Steinhau-Kühl, J. Ziegler, B. van der Horst
DESY, Hamburg, Germany
M. Barlak, J.A. Lorkiewicz, R. Nietubyć
NCBJ, Świerk/Otwock, Poland

SRF Gun Cavity is an ongoing accelerator R&D project at DESY, being developed since several years. Currently several SRF Gun cavity prototypes were simulated, built and tested in our Lab and elsewhere. Lately the 1.6 cells Pb thin film cathode niobium cavity was tested in a vertical cryostat with a different cathode plug configurations. Cathode plug design was improved, as well as SRF Gun Cavity cleaning procedures. Results of the last cavity performance tests are presented and discussed.

Poster THPB056 [1.257 MB]

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THPB060

Development of SRF Cavity Tuners for CERN

cavity, cryomodule, vacuum, SRF

1247

K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, N. Kuder, R. Leuxe, P. Minginette, W. Venturini Delsolaro, G. Villiger, C. Zanoni, P. Zhang
CERN, Geneva, Switzerland
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
T.J. Jones, N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
S. Verdú-Andrés, B. P. Xiao
BNL, Upton, Long Island, New York, USA

Superconducting RF cavity developments are currently on-going for new accelerator projects at CERN such as HIE ISOLDE and HL-LHC. Mechanical RF tuning systems are required to compensate cavity frequency shifts of the cavities due to temperature, mechanical, pressure and RF effects on the cavity geometry. A rich history and experience is available for such mechanical tuners developed for existing RF cavities. Design constraints in the context of HIE ISOLDE and HL-LHC such as required resolution, space limitation, reliability and maintainability have led to new concepts in the tuning mechanisms. This paper will discuss such new approaches, their performances and planned developments.

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THPB062

Accelerated Life Testing of LCLS-II Cavity Tuner Motor

cavity, cryomodule, acceleration, SRF

1257

N.A. Huque, M.E. Abdelwhab, E. Daly
JLab, Newport News, Virginia, USA
Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA

An Accelerated Life Test (ALT) of the Phytron stepper motor used in the LCLS-II cavity tuner is being carried out at JLab. Since the motor will reside inside the cryomodule, any failure would lead to a very costly and arduous repair. As such, the motor will be tested for the equivalent of five lifetimes before being approved for use in the production cryomodules. The 9-cell LCLS-II cavity will be simulated by disc springs with an equivalent spring constant. Hysteresis plots of the motor position vs. tuner position – measured via an installed linear variable differential transformer (LVDT) – will be used to determine any drift from the required performance. The titanium spindle will also be inspected for loss of lubrication. This paper outlines the ALT plan and latest results.

Poster THPB062 [2.794 MB]

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THPB065

Reliability of the LCLS II SRF Cavity Tuner

radiation, vacuum, SRF, cavity

1267

Y.M. Pischalnikov, B. Hartman, J.P. Holzbauer, W. Schappert, S.J. Smith, J.C. Yun
Fermilab, Batavia, Illinois, USA

The SRF cavity tuner for LCLS II must work reliably for more than 20 years in a cryomodule environment. Tuner’s active components- electromechanical actuator and piezo-actuators must work reliably in an insulating vacuum environment at low temperature for the lifetime of the machine. Summary of the accelerated lifetime tests (ALT) of the electromechanical and piezo actuators inside cold/ insulated vacuum environment and irradiation hardness test (dose level up to 5*10⁸ Rad) of tuner components are presented. Methodology to design and build reliable SRF cavity tuner, based on “lessons learned” approach, are discussed.

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THPB070

Design of Dressed Crab Cavities for the HL-LHC Upgrade

cavity, niobium, cryomodule, SRF

1284

C. Zanoni, K. Artoos, S. Atieh, I. Aviles Santillana, J.P. Brachet, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, G. Favre, P. Freijedo Menendez, M. Garlaschè, M. Guinchard, N. Kuder, S.A.E. Langeslag, R. Leuxe, L. Prever-Loiri, G. Vandoni
CERN, Geneva, Switzerland
S.A. Belomestnykh, I. Ben-Zvi, S. Verdú-Andrés, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA
G. Burt
Lancaster University, Lancaster, United Kingdom
S.U. De Silva, R.G. Olave, H. Park
ODU, Norfolk, Virginia, USA
J.R. Delayen
JLab, Newport News, Virginia, USA
T.J. Jones, N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
Z. Li
SLAC, Menlo Park, California, USA
K.B. Marinov, A.J. May, S.M. Pattalwar
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
T.H. Nicol
Fermilab, Batavia, Illinois, USA
A. Ratti
LBNL, Berkeley, California, USA

The HL-LHC upgrade relies on a set of RF crab cavities for reaching its goals. Two parallel concepts, the Double Quarter Wave (DQW) and the RF Dipole (RFD), are going through a comprehensive design process along with preparation of fabrication in view of extensive tests with beam in SPS. High Order Modes (HOM) couplers are critical in providing damping in RF cavities for operation in accelerators. HOM prototyping and fabrication have recently started at CERN. In this paper, an overview of the final geometry is provided along with an insight in the mechanical and thermal analyses performed to validate the design of this critical component. Emphasis is also given to material selection, prototyping, initial fabrication and test campaigns that are aimed at fulfilling the highly demanding tolerances of the couplers.

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THPB071

Developments of SiC Damper for SuperKEKB Superconducting Cavity

HOM, cavity, factory, higher-order-mode

1289

M. Nishiwaki, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, Y. Morita
KEK, Ibaraki, Japan

Upgrade works for SuperKEKB is in the final stage and the commissioning operation will start in this JFY. Eight superconducting accelerating cavities were operated for more than ten years at KEKB electron ring and are to be used at SuperKEKB. The cavity operation at those high current accelerators requires sufficient absorption of the beam-induced HOM power. In KEKB, the absorbed HOM power of 16 kW in two ferrite dampers attached to each cavity was achieved at the beam current of 1.4 A. On the other hand, the expected HOM power at SuperKEKB is calculated to be 37 kW in the beam current of 2.6 A. To cope with the HOM power issue, we developed additional HOM dampers made of SiC to be installed to the downstream of the cavity module. From precise calculations, it was found that the additional dampers reduce the HOM power loads of the ferrite dampers more effectively than the large beam pipe model of cavity module, which is another option to reduce the HOM loads. New SiC dampers were fabricated and high power-tested. Those SiC dampers successfully absorbed the expected HOM power. In this report, we will describe the results of calculations and high-power RF tests of new SiC dampers.

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THPB077

Modified TTF3 Couplers for LCLS-II

vacuum, simulation, cavity, linac

1306

C. Adolphsen, K. Fant, Z. Li, C.D. Nantista, G. Stupakov, J. Tice, F.Y. Wang, L. Xiao
SLAC, Menlo Park, California, USA
I.V. Gonin, K. Premo, N. Solyak
Fermilab, Batavia, Illinois, USA

The LCLS-II 4 GeV SC electron linac will use 280 TESLA cavities and TTF3 couplers, modified for CW operation with input power up to about 7 kW. The coupler modifications include shortening the antenna to achieve higher Qext and thickening the copper plating on the warm section inner conductor to lower the peak temperature. Another change is the use a waveguide transition box that is machined out of a solid piece of aluminum, significantly reducing its cost and improving its fit to the warm coupler window section. This paper describes the changes, simulations of the coupler operation (heat loads and temperatures), rf processing results and CW tests with LCLS-II dressed cavities.

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THPB080

Next Generation Cavity and Coupler Interlock for the European XFEL

FPGA, vacuum, interface, timing

1316

D. Tischhauser, A. Gössel, M. Mommertz
DESY, Hamburg, Germany

The safe operation of cavities and couplers in the European XFEL accelerator environment is secured by a new technical interlock (TIL) design, which is based on the XFEL crate standard (MTCA(TM).4). The new interlock is located inside the accelerator tunnel. Several remote test capabilities ensure the correct operation of sensors for light, temperature and free electrons. Due to the space costs and the very high number of channels, the electronic concept was moved from a conservative, mostly analog electronic approach, with real comparators and thresholds, to a concept, where the digitizing of the signals is done at a very early stage. Filters, thresholds and comparators are moved into the digital part. The usage of an FPGA and an additional watchdog increase the flexibility dramatically, with respect to be as reliable as possible. An overview of the system is shown.
MTCA (Micro Telecommunications Computing Architecture) is a standard defined by the PCI Industrial Computer Manufacturers Group (PICMG, www.picmg.org).

Poster THPB080 [1.123 MB]

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THPB081

FPC and HOM Coupler Test Boxes for HL-LHC Crab Cavities

HOM, cavity, dipole, coupling

1321

A.R.J. Tutte, G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga, A. Macpherson, E. Montesinos
CERN, Geneva, Switzerland
S.U. De Silva
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
B. P. Xiao
BNL, Upton, Long Island, New York, USA

The LHC luminosity upgrade will involve the installation of thirty-two 400 MHz SRF crab cavities. The cavities have two variants known as the RF dipole and double quarter-wave crab cavities. Each cavity has a fundamental power coupler (FPC) at 400 MHz and two or three HOM couplers. Before integration onto the cavities it is necessary to condition the FPC, and to measure the transmission on the HOM couplers at low power to ensure the operate as designed, each requiring a special test box. The FPC test box should provide a high transmission between two couplers without creating high surface fields. The low power HOM test boxes should be terminated to a load such that the natural stop and pass-bands of the couplers are preserved allowing the reflection to me measured and compared to simulations. In addition, due to the possibility of high HOM power in the LHC crab cavities, the concept of creating a broadband high power HOM coupler test box in order to condition and test the couplers at high power has been investigated. The Rf design of all test boxes is presented and discussed.

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THPB086

LCLS-II Fundamental Power Coupler Mechanical Integration

interface, cryomodule, pick-up, vacuum

1340

K.S. Premo, T.T. Arkan, Y.O. Orlov, N. Solyak
Fermilab, Batavia, Illinois, USA

Funding: DOE
LCLSII is a planned upgrade project for the linear coherent light source (LCLS) at SLAC. The LCLSII linac will consist of thirtyfive 1.3 GHz and two 3.9 GHz superconducting RF continuous wave (CW) cryomodules that Fermilab and Jefferson Lab will assemble in collaboration with SLAC. The LCLSII 1.3 GHz cryomodule design is based on the European XFEL pulsed mode cryomodule design with modifications needed for CW operation. The 1.3 GHz cryomodules for LCLSII will utilize a modified TTF3 syle fundamental power coupler design. Due to CW operation heat removal from the power coupler is critical. This paper presents the details of the mechanical integration of the power coupler into the cryomodule. Details of thermal braids, connections, and other interfaces are discussed.

Poster THPB086 [1.031 MB]

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THPB088

20 kW CW Power Couplers for the APS-U Harmonic Cavity

cavity, Windows, storage-ring, electron

1346

M.P. Kelly, A. Barcikowski, Z.A. Conway, D. Horan, M. Kedzie, S.H. Kim, P.N. Ostroumov
ANL, Argonne, Illinois, USA
S.V. Kutsaev
RadiaBeam, Santa Monica, California, USA
J. Rathke
AES, Medford, New York, USA

Funding: This work supported by the U.S. DOE, Office of Nuclear Physics, Contract No. DE-AC02-06CH11357. This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility.
A pair of 20 kW CW adjustable RF power couplers optimized for 1.4 GHz have been designed and are being built as part of the APS-U bunch lengthening system. The system uses one superconducting RF cavity to be installed into the APS Upgrade electron storage ring and will provide a tremendous practical benefit to the majority of users by increasing the beam lifetime by 2-3 times. The 80 mm diameter, 50 Ω coaxial couplers include 4 cm (~20 dB) of adjustability. This allows optimization of bunch lengthening for a range of storage ring beam currents and fill patterns while, simultaneously, maintaining the required 0.84 MV harmonic cavity voltage. To provide bunch lengthening, the cavity/coupler system must extract RF power (up to 32 kW) from the beam. Each coupler will transmit roughly half of the total extracted power to external water-cooled loads. The design extends upon on a well-tested ANL two RF window concept, using a pair of simple rugged 80 mm diameter alumina disks. A new feature is the ‘hourglass-shaped’ inner conductor chosen to maximize transmission at 1.4 GHz. Results of electromagnetic and thermal simulations, as well as, prototyping and initial RF testing are presented.

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THPB089

HOM Coupler Performance in CW Regime in Horizontal and Vertical Tests

HOM, cavity, coupling, higher-order-mode

1349

N. Solyak, M.H. Awida, A. Grassellino, C.J. Grimm, A. Hocker, J.P. Holzbauer, T.N. Khabiboulline, O.S. Melnychuk, A.M. Rowe, D.A. Sergatskov, N. Solyak
Fermilab, Batavia, Illinois, USA
J.K. Sekutowicz
DESY, Hamburg, Germany

Power dissipation in HOM coupler antenna can limit cavity gradient in cw operation. XFEL design of HOM coupler, feedthrough and thermal connection to 2K pipe was accepted for LCLS-II cavity based on simulation results. Recently a series of vertical and horizontal tests was done to prove design for cw operation. In vertical test was found no effect of HOM coupler heating on high-Q cavity performance. In horizontal cryostat HOM coupler was tested up-to 23MV/m in continuous wave mode. Result proves that XFEL HOM coupler meets LCLS-II specifications.

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THPB109

ESS Spoke Cryomodule and Test Valve Box

cryomodule, cryogenics, vacuum, linac

1400

D. Reynet, S. Bousson, S. Brault, P. Duchesne, P. Duthil, N. Gandolfo, G. Olry, M. Pierens, E. Rampnoux
IPN, Orsay, France
C. Darve
ESS, Lund, Sweden

ESS project aims being the world’s most powerful neutron source feeding multidisplinary researches. The superconducting part of the ESS linear accelerator includes 28 b=0.5 352.2 MHz SRF niobium double Spoke cavities. Paired in 13 cryomodules and held at 2K in a saturated helium bath those cavities will generate of an accelerating field of 9MV/m. The prototype Spoke cryomodule holds two cavities and their RF power couplers and integrates all the interfaces necessary to be operational within the linac machine. It is now being fabricated and its assembly will be performed with dedicated tooling and procedures in and out of the clean room. This prototype will be tested by the end of 2015 at IPNO site and then at full power at FREIA (Uppsala university) test stand. A valve box has thus been designed to take into account the specific features of this prototype cryomodule and of the cryogenic environments of both test sites. This valve box is also considered as a prototype of the cryogenic distribution of the linac Spoke section. This element will then be used for the tests of the series cryomodules. We propose to present this prototype Spoke cryomodule for ESS and the test valve box.

Poster THPB109 [2.852 MB]

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THPB110

Procurements for LCLS-II Cryomodules at JLab

cavity, HOM, cryomodule, vacuum

1405

E. Daly, G. Cheng, G.K. Davis, T. Hiatt, N.A. Huque, F. Marhauser, H. Park, J.P. Preble, K.M. Wilson
JLab, Newport News, Virginia, USA

Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515.
The Thomas Jefferson National Accelerator Facility is currently engaged, along with several other DOE national laboratories, in the Linac Coherent Light Source II project (LCLS II). The SRF Institute at Jefferson Lab will be building 1 prototype and 17 production cryomodules based on the TESLA / ILC / XFEL design. Each cryomodule will contain eight nine cell cavities with coaxial power couplers operating at 1.3 GHz. Procurement of components for cryomodule construction has been divided amongst partner laboratories in a collaborative manner. JLab has primary responsibility for six procurements include the dressed cavities, cold gate valves, higher-order-mode (HOM) and field probe feedthroughs, beamline bellows cartridges, cavity tuner assemblies and HOM absorbers. For procurements led by partner laboratories, JLab collaborates and provides technical input on specifications, requirements and assembly considerations. This paper will give a detailed description of plans and status for JLab procurements.

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THPB116

Modified ELBE Type Cryomodules for the Mainz Energy-Recovering Superconducting Accelerator MESA

cryomodule, HOM, niobium, electron

1413

T. Stengler, K. Aulenbacher, R.G. Heine, F. Schlander, D. Simon
IKP, Mainz, Germany
M. Pekeler, D. Trompetter
RI Research Instruments GmbH, Bergisch Gladbach, Germany

At the Institut für Kernphysik of Johannes Gutenberg-Universität Mainz, the new multiturn energy recovery linac MESA is under construction. Two modified ELBE-type cryomodules with two 9-cell TESLA/XFEL cavities each will provide an energy gain of 50 MeV per turn. Those are currently in the production process at RI Research Instruments GmbH, Bergisch Gladbach, Germany. Modifications for the tuner and the HOM damper are under development. In addition, a 4K/2K Joule Thomson expansion stage will also be integrated into the cryomodule. The current status of the development of the cryomodules and their modifications will be discussed.

Poster THPB116 [1.472 MB]

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THPB119

LCLS-II 1.3 GHz Cryomodule Design – Modified TESLA-Style Cryomodule for CW Operation

cryomodule, vacuum, cryogenics, cavity

1417

T.J. Peterson, T.T. Arkan, C.M. Ginsburg, Y. He, J.A. Kaluzny, M.W. McGee, Y.O. Orlov
Fermilab, Batavia, Illinois, USA

Funding: Work supported, in part, by the US DOE and the LCLS-II Project.
We will present the design of the 1.3 GHz cryomodule for the Linear Coherent Light Source upgrade (LCLS-II) at SLAC. Fermilab is responsible for the design of this cryomodule, a modified TESLA-style cryomodule to accommodate continuous wave (CW) mode operation and LCLS-II beam parameters, consisting of eight 1.3 GHz superconducting RF cavities, a corrector magnet package, and instrumentation. Thirty-five of these cryomodules, approximately half built at Fermilab and half at Jefferson Lab, will become the main accelerating elements of the 4 GeV linac. The modifications and special features of the cryomodule include: thermal and cryogenic design to handle high heat loads in CW operation, magnetic shielding and cool-down configurations to enable high quality factor (Q0) performance of the cavities, liquid helium management to address the different liquid levels in the 2-phase pipe with 0.5% SLAC tunnel longitudinal slope, support structure design to meet California seismic design requirements, and with the overall design consistent with space constrains in the existing SLAC tunnel. The prototype cryomodule assembly will begin in August 2015 and is to be completed in early 2016.

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FRAA01

Overview of Recent Tuner Development on Elliptical and Low-Beta Cavities

cavity, linac, cryomodule, controls

1425

R. Paparella
INFN/LASA, Segrate (MI), Italy

The talk will provide an overview on the latest advances of tuner development for SRF applications. Issues and present approaches on how to resolve them will be emphasized for both TM and TEM cavities and examples from various labs and projects (XFEL, LCLS-II, ESS, SPL, ARIEL, SPIRAL2, FRIB, ANL, IFMIF) will be given in order to better explain issues and solutions. Details on author’s contributions to European-XFEL tuner activity for 1.3 GHz and 3.9 GHz cavities will be also shown.

Slides FRAA01 [3.421 MB]

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FRAA03

High Gradient Performance in Fermilab ILC Cryomodule

cavity, cryomodule, vacuum, detector

1432

E.R. Harms, C.M. Baffes, K. Carlson, B.E. Chase, D.J. Crawford, E. Cullerton, D.R. Edstrom, A. Hocker, A.L. Klebaner, M.J. Kucera, J.R. Leibfritz, J.N. Makara, D. McDowell, O.A. Nezhevenko, D.J. Nicklaus, Y.M. Pischalnikov, P.S. Prieto, J. Reid, W. Schappert, W.M. Soyars, P. Varghese, A. Warner
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Fermilab has assembled an ILC like cryomodule using U.S. processed high gradient cavities and achieved an average gradient of 31.5 MV/m for the entire cryomodule. Test results and challenges along the way will be discussed.

Slides FRAA03 [5.878 MB]

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FRAA04

Performance of the Cornell ERL Main Linac Prototype Cryomodule

cavity, HOM, linac, cryomodule

1437

F. Furuta, B. Clasby, R.G. Eichhorn, B. Elmore, G.M. Ge, D. Gonnella, D.L. Hall, G.H. Hoffstaetter, R.P.K. Kaplan, J.J. Kaufman, M. Liepe, T.I. O'Connell, S. Posen, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell has designed, fabricated, and tested (by the time of the conference) a high current (100 mA) CW SRF prototype cryomodule for the Cornell ERL. This talk will report on the design and performance of this very high Q0 CW cryomodule including design issues and mitigation strategies.

Slides FRAA04 [4.614 MB]

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FRAA05

A 1.3 GHz Cryomodule with 2x9-Cell Cavity for SETF at Peking University

cavity, SRF, cryomodule, experiment

1443

F. Zhu, J.E. Chen, L.W. Feng, Y. Gao, J.K. Hao, S. Huang, L. Lin, K.X. Liu, S.W. Quan, F. Wang, X.D. Wen, D.H. Zhuang
PKU, Beijing, People's Republic of China

Funding: Work supported by National Basic Research Project (No. 2011CB808304 and 2011CB808302）and NDRC project.
The straight beam line of SETF at Peking University is under construction, which consists of a DC-SRF photoinjector and a superconducting linac with two 9-cell cavities. Stable operation of the DC-SRF photoinjector has been realized and the design, manufacture and assembly of the cryomodule with two 9-cell cavities have been completed. Improved capacitive coupling RF power coupler and fast tuner with piezo are adopted

Slides FRAA05 [3.709 MB]

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FRBA02

Crab Cavity and Cryomodule Development for HL-LHC

cavity, HOM, cryomodule, shielding

1460

F. Carra, A. Amorim Carvalho, K. Artoos, S. Atieh, I. Aviles Santillana, A.B. Boucherie, J.P. Brachet, K. Brodzinski, R. Calaga, O. Capatina, T. Capelli, L. Dassa, T. Dijoud, H.M. Durand, G. Favre, L.M.A. Ferreira, P. Freijedo Menendez, M. Garlaschè, M. Guinchard, N. Kuder, S.A.E. Langeslag, R. Leuxe, A. Macpherson, P. Minginette, E. Montesinos, F. Motschmann, C. Parente, L. Prever-Loiri, D. Pugnat, E. Rigutto, V. Rude, M. Sosin, G. Vandoni, G. Villiger, C. Zanoni
CERN, Geneva, Switzerland
S.A. Belomestnykh, S. Verdú-Andrés, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA
G. Burt
Lancaster University, Lancaster, United Kingdom
S.U. De Silva, J.R. Delayen, R.G. Olave, R.G. Olave, H. Park
ODU, Norfolk, Virginia, USA
T.J. Jones, N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
Z. Li
SLAC, Menlo Park, California, USA
K.B. Marinov, S.M. Pattalwar
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
T.H. Nicol
Fermilab, Batavia, Illinois, USA
A. Ratti
LBNL, Berkeley, California, USA

The HL-LHC project aims at increasing the LHC luminosity by a factor 10 beyond the design value. The installation of a set of RF Crab Cavities to increase bunch crossing angle is one of the key upgrades of the program. Two concepts, Double Quarter Wave (DQW) and RF Dipole (RFD) have been proposed and are being produced in parallel for test in the SPS beam before the next long shutdown of CERN accelerator’s complex. In the retained concept, two cavities are hosted in one single cryomodule, providing thermal insulation and interfacing with RF coupling, tuning, cryogenics and beam vacuum. This paper overviews the main design choices for the cryomodule and its different components, which have the goal of optimizing the structural, thermal and electro-magnetic behavior of the system, while respecting the existing constraints in terms of integration in the accelerator environment. Prototyping and testing of the most critical components, manufacturing, preparation and installation strategies are also described.

Slides FRBA02 [4.678 MB]

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