IPAC2013 - List of Keywords (niobium)

Paper	Title	Other Keywords	Page
MOPME013	20 Years of Development of SQUID-based Cryogenic Current Comparator for Beam Diagnostics	pick-up, ion, cryogenics, shielding	497
	W. Vodel HIJ, Jena, Germany R. Geithner, R. Neubert, P. Seidel FSU Jena, Jena, Germany K.K. Knaack, K. Wittenburg DESY, Hamburg, Germany A. Peters HIT, Heidelberg, Germany H. Reeg, M. Schwickert GSI, Darmstadt, Germany
	This contribution gives an overview on the development of highly sensitive SQUID-based Cryogenic Current Comparators (CCC) for nuclear physics from the first successful demonstration of its performance at GSI Darmstadt through the latest improved version for FAIR and the Cryogenic Storage Ring at MPI Heidelberg. An absolute and exact measurement of the intensity of charged particle beams - extracted from an accelerator or circulating in a Storage Ring - is one of the major problems of beam diagnosis. Also the measurement of so-called dark currents, generated by super-conductive RF accelerator cavities at high voltage gradients to characterize the quality of these components becomes more and more important for the commissioning of new accelerators (XFEL at DESY). The Cryogenic Current Comparator (CCC) based on high precision LTS SQUIDs is an excellent tool to solve these problems.

WEPWO004	Studies of Systematic Flux Expulsion in Superconducting Niobium	cavity, simulation, lattice, controls	2316
	J.M. Vogt, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	The quality factor Q0 that can be obtained in a superconducting cavity is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We believe that cooling conditions have an additional impact, as they appear to influence the amount of trapped flux and hence the residual resistance. We have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach Tc from below in the superconducting state. Although the sample remains in the superconducting state, a change in the amount of trapped flux is visible. The procedure can be applied repeatedly resulting in a significantly lowered level of trapped flux in the sample. Furthermore, simulations using the Radia software package for Mathematica developed by the ESR were used to better unterstand the measured changes in magnetic flux around the Sample. Applying a similar procedure for minimization of trapped magnetic flux to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q0.

WEPWO022	IHEP03 Fabrication and Testing Status	cavity, HOM, cryomodule, status	2364
	Z.C. Liu, J. Gao, S. Jin, Y. Liu, J.Y. Zhai, T.X. Zhao, H.J. Zheng IHEP, Beijing, People's Republic of China J.X. Wang, H. Yu, H. Yuan BIAM, Beijing, People's Republic of China
	IHEP is developing RF superconducting technology with different type of superconducting cavities. Tesla-like cavity which is designed by KEK is one of them. We have fabricated all the parts of the cavity using Nb material from Ningxia and cavity welding will be started soon. This paper will show the cavity fabrication procedures and measurement results.

WEPWO039	Prototyping of TEM-like Mode Resonators in the RAON	cavity, multipactoring, electron, simulation	2384
	H.C. Jung, M.O. Hyun, D. Jeon, H.J. Kim IBS, Daejeon, Republic of Korea
	Preliminary electric-magnetic designs of TEM-like mode resonators(a quarter wave resonator, a half wave resonator, two single spoke resonators) are accomplished for the superconducting linear accelerator in the RAON. Resonant cavities are numerically optimized using a CST MWS code to obtain higher E-field gradient along the beam line in conditions of the peak E-field and B-field is less than 30MV/m, 60mT respectively. Prototyping test of a quater wave resonator of optimum beta 0.047 using OFC(Oxygen Free Cupper)is in progress to analyze resonant frequency shifting by tolerances in fabrication process and external perturbations. It is compared with expected one using compuational codes.

WEPWO040	Design of HWR at RISP	cavity, simulation, quadrupole, electromagnetic-fields	2387
	G.-T. Park, H.J. Cha, H.C. Jung IBS, Daejeon, Republic of Korea
	At RISP, superconducting cavity resonators to accelerate the various ions in high current are being developed. In particular, hal-wave resonator (HWR) will be used for β=0.12, f=162.5 MHz. Here we present the structural analysis of HWR, which includes the prediction of resonant frequency shift during the manufacturing and testing process, stiffening measures to minimize the shift, and the tuning mechanism. The processes of welding, polishing, vacuuming, cooling (to crygenic temperature)as well as Lorentz force, helium pressure fluctuation, microphonics, and interaction with the helium vessel and tuning system will be simulated optimizing the frequency shift.

WEPWO042	Dubna-Minsk SRF Technology Development Status Report	cavity, cryogenics, coupling, electron	2393
	N.S. Azaryan, Ju. Boudagov, D.L. Demin, V.V. Glagolev, G. Shirkov, G.V. Trubnikov JINR, Dubna, Moscow Region, Russia M.A. Baturitsky, N.M. Shumeiko NC PHEP BSU, Minsk, Belarus S.E. Demyanov, E.Yu. Kaniukov Scientific-Practical Materials Research Centre of the National Academy of Sciences of Belarus, Minsk, Belarus A. Ermakov, W. Singer, X. Singer DESY, Hamburg, Germany V.A. Karpovich, N.V. Liubetsky BSU, Minsk, Belarus S.V. Kolosov, A.A. Kurayev, A.O. Rak, A.K. Sinitsyn Belarus State University of Informatics and Radioelectronics (BSUIR), Minsk, Belarus S.I. Maximov, V.N. Rodionova Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk, Belarus A. Parshuto, V.S. Petrakovsky, I.L. Pobol, A.I. Pokrovsky, S.V. Yurevich, A.Yu. Zhuravsky Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
	In 2011 Dubna-Minsk collaboration started an activity on the development and manufacture the series of 1.3 GHz superconducting Nb cavities in the enterprises in Belarus. The current status of this work is presented in this report. Main EM characteristics of the cavity were calculated and the shop drawings for cavity fabrication were developed. Two test-benches were assembled for RF-tests of the cavities at room temperature and at liquid helium temperature. The measured SWR was about 1.01 due to special matching device developed for that. This measurement technique was applied to the single-cell cavity from FNAL at power level nearby 10 mW. Measured resonant frequency was about 1.27 GHz, while the measured Q-factor was 2.8·10⁴ at room temperature and more than 10⁸ at liquid helium temperature. To evaluate mechanical properties of sheet Nb and of model materials (Cu and Al), a number of tests were made. Series of half-cells were fabricated of Al to test the technique of hydraulic deep-drawing that will be used in production of Nb cavities. The modes for electron-beam welding of sheet Nb were explored and the first welding seams were tested. The method of chemical treatment of cavities was also elaborated.
	Poster WEPWO042 [0.897 MB]

WEPWO044	RF Characterization of Niobium Films for Superconducting Cavities	target, quadrupole, plasma, ion	2399
	S. Aull, S. Calatroni, S. Döbert, T. Junginger, G. Terenziani CERN, Geneva, Switzerland S. Aull University of Siegen, Siegen, Germany A.P. Ehiasarian, G. Terenziani Sheffield University, Sheffield, United Kingdom J. Knobloch HZB, Berlin, Germany
	Funding: Work supported by the Wolfgang-Gentner-Programme of the Bundesministerium für Bildung und Forschung (BMBF) The surface resistance RS of superconductors shows a complex dependence on the external parameters such as temperature, frequency or radio-frequency (RF) field. The excited modes of 400, 800 and 1200 MHz allow measurements at actual operating frequencies of superconducting cavities. Niobium films on copper substrates have several advantages over bulk niobium cavities. HiPIMS (High-power impulse magnetron sputtering) is a promising technique to increase the quality and therefore the performance of niobium films. This contribution will introduce CERNs recently developed HiPIMS coating apparatus. Moreover, first results of niobium coated copper samples will be presented, revealing the dominant loss mechanisms.

WEPWO046	First Test Results of the 4-rod Crab Cavity	cavity, vacuum, pick-up, coupling	2405
	R. Calaga, L.S. Alberty Vieira, S. Calatroni, O. Capatina, E. Ciapala, L.M.A. Ferreira, E. Jensen, P. Maesen, A. Mongelluzzo, T. Renaglia, M. Therasse CERN, Geneva, Switzerland P.K. Ambattu, D. Doherty, B.D.S. Hall, C. Lingwood Cockcroft Institute, Lancaster University, Lancaster, United Kingdom G. Burt Lancaster University, Lancaster, United Kingdom
	Funding: The HiLumi LHC Design Study (a sub-system of HL-LHC) is cofunded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404. The first prototype crab cavity with the 4-rod geometry has undergone surface treatment and cold testing. Due to the complex geometry and unique fabrication procedure, RF validation of the field at beyond the nominal operating voltage at a sufficiently high Q0 is an important pre-requiste. Preliminary results of the first cold tests are presented along with cavity performance at different stages of the cavity processing is described.

WEPWO051	Manufacture of a Compact Prototype 4R Crab Cavity for HL-LHC	cavity, luminosity, vacuum, electron	2420
	G. Burt, B.D.S. Hall, C. Lingwood Cockcroft Institute, Lancaster University, Lancaster, United Kingdom L. Alberty Vieira, R. Calaga, O. Capatina CERN, Geneva, Switzerland C.H. Boulware, D. Gorelov, T.L. Grimm, C. Krizmanich, T.S. Lamie Niowave, Inc., Lansing, Michigan, USA C. Hill, P.A. McIntosh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom R.A. Rimmer, H. Wang JLAB, Newport News, Virginia, USA
	Funding: This work has been funded by the EU through EUCARD and HiLumi and by STFC via the Cockcroft Institute. A prototype compact SRF deflecting cavity has been manufactured for LHC. The base of the cavity has been machined out of large grain niobium ingot to allow the manufacture of the complex rod profile. Stiffening rods have been used to increase the mechanical strength of the outer can. Details of the cavity design and manufacture will be discussed.

WEPWO054	Multistep Mechanical Analyses of Centrifugal Barrel Polishing Barrel and Cavity	cavity, simulation, SRF, acceleration	2426
	M. Chen, C.A. Cooper, L. Ristori Fermilab, Batavia, USA
	Funding: US Department of Energy Fermilab has successfully demonstrated the ability to improve the performance of damaged 1.3 GHz single cell and 9-cell Tesla–type cavities by using a modified centrifugal barrel polishing (CBP) process that leaves a mirror finish on the inside of the cavity. Fermilab now is developing and constructing a new CBP machine which can handle both 650 MHz and 1.3 GHz cavities. The new machine will have a larger moment arm and therefore impart more force on the cavity and machine. Because of these increased forces the effects on cavity supports and machine design were examined. This paper will document the multistep mechanical analyses for the CBP barrel and cavity, calculations of the fatigue life and the requirements for the structural welds.

WEPWO056	Update of the Mechanical Design of the 650 MHZ β=0.9 Cavities for Project X	cavity, simulation, resonance, linac	2432
	I.V. Gonin, M.H. Awida, M.H. Foley, C.J. Grimm, T.N. Khabiboulline, Y.M. Pischalnikov, V.P. Yakovlev Fermilab, Batavia, USA
	Five-cell elliptical 650 MHz β=0.9 cavities to accelerate 1 mA of average H⁻ beam current in the range 520-3000 MeV of the Project X Linac are currently planned. We will present the results of optimization of mechanical design of cavities with their Helium Vessel. We discuss the efforts to optimize the mechanical stability of the cavity versus the Helium bath pressure fluctuations, cavity tunability. We present also modal and thermal analysis; discuss tuner options and other issues.

WEPWO065	Optimization of Elliptical SRF Cavities for β <1	cavity, SRF, HOM, simulation	2450
	V.D. Shemelin CLASSE, Ithaca, New York, USA J. Newbolt Rochester University, Rochester, New York, USA
	Funding: NSF award DMR-0807731 A systematic approach to optimization of SRF cavities which was done earlier for β=1 is extended to β<1 Some improvements for earlier developed designs are proposed.

WEPWO066	Frequency Control in the Cornell-ERL Main-Linac Cavity Production	cavity, target, controls, LabView	2453
	V.D. Shemelin, B. Bullock, P.R. Carriere, B. Clasby, R. Eichhorn, B. Elmore, J.J. Kaufman, J. Sears CLASSE, Ithaca, New York, USA
	Funding: NSF award DMR-0807731 Cavity fabrication can be broken down into three main stages: deep-drawing cups, welding the cups in pairs to obtain “dumbbells” and end groups, and, finally, welding the obtained components into a completed cavity. Frequency measurements and precise machining were implemented after the second stage. A custom RF fixture and data acquisition system were used for this purpose. The system comprised of a mechanical press with RF contacts, a network analyzer, a load cell and custom LabVIEW and MATLAB scripts. To extract the individual frequencies of the cups from these measurements, algorithm of calculations was developed. Corrections for the ambient environment were also incorporated into the measurement protocol. Two 7-cell 1.3 GHz cavities were produced with high field flatness immediately after fabrication.

WEPWO071	Quench and High Field Q-SLOP Studies using a Single Cell Cavity with Artificial Pits	cavity, SRF, feedback, factory	2465
	Y. Xie, G.H. Hoffstaetter, M. Liepe CLASSE, Ithaca, New York, USA
	Surface defects such as pits have been identified as some of the main sources of limitations of srf cavity performance. A single cell cavity was made with 30 artificial pits in the high magnetic field region to gain new insight in how pits limit the cavity performance. The test of the pit cavity showed clear evidence that the edges of two of the largest radius pits transitioned into the normal conducting state at field just below the quench field of the cavity, and that the quench was indeed induced by these two pits. Insights about quench and non-linear rf resistances will be presented.

WEPWO076	Development of Ultra High Gradient and High Q0 Superconducting Radio Frequency Cavities	cavity, SRF, acceleration, cryogenics	2474
	R.L. Geng, W.A. Clemens, J. Follkie, T. Harris, D. Machie, R. Martin, A.D. Palczewski, E. Perry, G. Slack, R.S. Williams JLAB, Newport News, Virginia, USA C. Adolphsen, Z. Li SLAC, Menlo Park, California, USA J.K. Hao, Y.M. Li, K.X. Liu PKU, Beijing, People's Republic of China P. Kushnick JLab, Newport News, Virginia, USA
	Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. We report on the recent progress at Jefferson Lab in developing ultra high gradient and high Q0 superconducting radio frequency (SRF) cavities for future SRF based machines. A new 1300 MHz 9-cell prototype cavity is being fabricated. This cavity has an optimized shape in terms of the ratio of the peak surface field (both magnetic and electric) to the acceleration gradient, hence the name low surface field (LSF) shape. The goal of the effort is to demonstrate an acceleration gradient of 50 MV/m with Q0 of 10¹⁰ at 2 K in a 9-cell SRF cavity. Fine-grain niobium material is used. Conventional forming, machining and electron beam welding method are used for cavity fabrication. New techniques are adopted to ensure repeatable, accurate and inexpensive fabrication of components and the full assembly. The completed cavity is to be first mechanically polished to a mirror-finish, a newly acquired in-house capability at JLab, followed by the proven ILC-style processing recipe established already at JLab. In parallel, new single-cell cavities made from large-grain niobium material are made to further advance the cavity treatment and processing procedures, aiming for the demonstration of an acceleration gradient of 50 MV/m with Q0 of 2·10¹⁰ at 2K. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.

WEPWO087	Parameter Optimization for Laser Polishing of Niobium for SRF Applications	laser, cavity, SRF, target	2498
	L. Zhao, M.J. Kelley The College of William and Mary, Williamsburg, USA M.J. Kelley, J.M. Klopf, C.E. Reece JLAB, Newport News, Virginia, USA
	Surface smoothness is critical to the performance of SRF cavities. As laser technology has been widely applied to metal machining and surface treatment, we are encouraged to use it on niobium as an alternative to the traditional wet polishing process where aggressive chemicals are involved. In this study, we describe progress toward smoothing by optimizing laser parameters on BCP treated niobium surfaces. Results show that microsmoothing of the surface without ablation is achievable.
	Poster WEPWO087 [1.683 MB]

THOBB201	Pathway to a Post Processing Increase in Q0 of SRF Cavities	cavity, shielding, SRF, cryogenics	3129
	O. Kugeler, J. Knobloch, J.M. Vogt HZB, Berlin, Germany S. Aull CERN, Geneva, Switzerland
	A significant improvement of Q0 to values larger than 3.2x10¹⁰ at 1.8K has been repeatedly achieved in an SRF cavity by thermal cycling, i.e. heating the cavity briefly above transition temperature and subsequent cooling. Conceivable explanations for this effect reach from effectivity deviations of the magnetic shielding to thermal currents to hydrogen diffusion. Experimental We have experimentally verified some of these explanations, leaving a direct impact of cooling dynamics on frozen flux as the most plausible one. The pathway to this finding is being presented and the application to SRF systems is elicited.
	Slides THOBB201 [1.184 MB]

THPWO063	The Early Stage of the Cavity Fabrication Process (ECT and furnace) for RAON	cavity, vacuum, superconducting-cavity, linac	3901
	M.J. Joung, H.C. Jung, H.J. Kim IBS, Daejeon, Republic of Korea
	RAON is consist of three part about the acceleration line. These are SCL1, SCL2 and SCL3. SCL1 and SCL3 will be made from QWR (Qarter Wave Resonator) and HWR (Half Wave Resonator). And SCL2 will be made from SSR1 (Single Spoke Resonator) and SSR2 (Single Spoke Resonator). Accordingly, The RAON needs 48 QWR, 276 HWR, 88 SSR1 and 136 SSR2 to get the performance that we want. To accelerate the particle using lots of cavity, we have to make a process of cavity fabrication for RAON. We will compare to each process made from the other laboratories and to make the optimal process for RAON to get the performance that we want. And that process will consider the type of cavity and the purpose of the accelerator. I will introduce the early stage of the cavity fabrication process for RAON in this paper.

Paper

Title

Other Keywords

Page

MOPME013

20 Years of Development of SQUID-based Cryogenic Current Comparator for Beam Diagnostics

pick-up, ion, cryogenics, shielding

497

W. Vodel
HIJ, Jena, Germany
R. Geithner, R. Neubert, P. Seidel
FSU Jena, Jena, Germany
K.K. Knaack, K. Wittenburg
DESY, Hamburg, Germany
A. Peters
HIT, Heidelberg, Germany
H. Reeg, M. Schwickert
GSI, Darmstadt, Germany

This contribution gives an overview on the development of highly sensitive SQUID-based Cryogenic Current Comparators (CCC) for nuclear physics from the first successful demonstration of its performance at GSI Darmstadt through the latest improved version for FAIR and the Cryogenic Storage Ring at MPI Heidelberg. An absolute and exact measurement of the intensity of charged particle beams - extracted from an accelerator or circulating in a Storage Ring - is one of the major problems of beam diagnosis. Also the measurement of so-called dark currents, generated by super-conductive RF accelerator cavities at high voltage gradients to characterize the quality of these components becomes more and more important for the commissioning of new accelerators (XFEL at DESY). The Cryogenic Current Comparator (CCC) based on high precision LTS SQUIDs is an excellent tool to solve these problems.

WEPWO004

Studies of Systematic Flux Expulsion in Superconducting Niobium

cavity, simulation, lattice, controls

2316

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

The quality factor Q0 that can be obtained in a superconducting cavity is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We believe that cooling conditions have an additional impact, as they appear to influence the amount of trapped flux and hence the residual resistance. We have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach Tc from below in the superconducting state. Although the sample remains in the superconducting state, a change in the amount of trapped flux is visible. The procedure can be applied repeatedly resulting in a significantly lowered level of trapped flux in the sample. Furthermore, simulations using the Radia software package for Mathematica developed by the ESR were used to better unterstand the measured changes in magnetic flux around the Sample. Applying a similar procedure for minimization of trapped magnetic flux to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q0.

WEPWO022

IHEP03 Fabrication and Testing Status

cavity, HOM, cryomodule, status

2364

Z.C. Liu, J. Gao, S. Jin, Y. Liu, J.Y. Zhai, T.X. Zhao, H.J. Zheng
IHEP, Beijing, People's Republic of China
J.X. Wang, H. Yu, H. Yuan
BIAM, Beijing, People's Republic of China

IHEP is developing RF superconducting technology with different type of superconducting cavities. Tesla-like cavity which is designed by KEK is one of them. We have fabricated all the parts of the cavity using Nb material from Ningxia and cavity welding will be started soon. This paper will show the cavity fabrication procedures and measurement results.

WEPWO039

Prototyping of TEM-like Mode Resonators in the RAON

cavity, multipactoring, electron, simulation

2384

H.C. Jung, M.O. Hyun, D. Jeon, H.J. Kim
IBS, Daejeon, Republic of Korea

Preliminary electric-magnetic designs of TEM-like mode resonators(a quarter wave resonator, a half wave resonator, two single spoke resonators) are accomplished for the superconducting linear accelerator in the RAON. Resonant cavities are numerically optimized using a CST MWS code to obtain higher E-field gradient along the beam line in conditions of the peak E-field and B-field is less than 30MV/m, 60mT respectively. Prototyping test of a quater wave resonator of optimum beta 0.047 using OFC(Oxygen Free Cupper)is in progress to analyze resonant frequency shifting by tolerances in fabrication process and external perturbations. It is compared with expected one using compuational codes.

WEPWO040

Design of HWR at RISP

cavity, simulation, quadrupole, electromagnetic-fields

2387

G.-T. Park, H.J. Cha, H.C. Jung
IBS, Daejeon, Republic of Korea

At RISP, superconducting cavity resonators to accelerate the various ions in high current are being developed. In particular, hal-wave resonator (HWR) will be used for β=0.12, f=162.5 MHz. Here we present the structural analysis of HWR, which includes the prediction of resonant frequency shift during the manufacturing and testing process, stiffening measures to minimize the shift, and the tuning mechanism. The processes of welding, polishing, vacuuming, cooling (to crygenic temperature)as well as Lorentz force, helium pressure fluctuation, microphonics, and interaction with the helium vessel and tuning system will be simulated optimizing the frequency shift.

WEPWO042

Dubna-Minsk SRF Technology Development Status Report

cavity, cryogenics, coupling, electron

2393

N.S. Azaryan, Ju. Boudagov, D.L. Demin, V.V. Glagolev, G. Shirkov, G.V. Trubnikov
JINR, Dubna, Moscow Region, Russia
M.A. Baturitsky, N.M. Shumeiko
NC PHEP BSU, Minsk, Belarus
S.E. Demyanov, E.Yu. Kaniukov
Scientific-Practical Materials Research Centre of the National Academy of Sciences of Belarus, Minsk, Belarus
A. Ermakov, W. Singer, X. Singer
DESY, Hamburg, Germany
V.A. Karpovich, N.V. Liubetsky
BSU, Minsk, Belarus
S.V. Kolosov, A.A. Kurayev, A.O. Rak, A.K. Sinitsyn
Belarus State University of Informatics and Radioelectronics (BSUIR), Minsk, Belarus
S.I. Maximov, V.N. Rodionova
Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk, Belarus
A. Parshuto, V.S. Petrakovsky, I.L. Pobol, A.I. Pokrovsky, S.V. Yurevich, A.Yu. Zhuravsky
Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus

In 2011 Dubna-Minsk collaboration started an activity on the development and manufacture the series of 1.3 GHz superconducting Nb cavities in the enterprises in Belarus. The current status of this work is presented in this report. Main EM characteristics of the cavity were calculated and the shop drawings for cavity fabrication were developed. Two test-benches were assembled for RF-tests of the cavities at room temperature and at liquid helium temperature. The measured SWR was about 1.01 due to special matching device developed for that. This measurement technique was applied to the single-cell cavity from FNAL at power level nearby 10 mW. Measured resonant frequency was about 1.27 GHz, while the measured Q-factor was 2.8·10⁴ at room temperature and more than 10⁸ at liquid helium temperature. To evaluate mechanical properties of sheet Nb and of model materials (Cu and Al), a number of tests were made. Series of half-cells were fabricated of Al to test the technique of hydraulic deep-drawing that will be used in production of Nb cavities. The modes for electron-beam welding of sheet Nb were explored and the first welding seams were tested. The method of chemical treatment of cavities was also elaborated.

Poster WEPWO042 [0.897 MB]

WEPWO044

RF Characterization of Niobium Films for Superconducting Cavities

target, quadrupole, plasma, ion

2399

S. Aull, S. Calatroni, S. Döbert, T. Junginger, G. Terenziani
CERN, Geneva, Switzerland
S. Aull
University of Siegen, Siegen, Germany
A.P. Ehiasarian, G. Terenziani
Sheffield University, Sheffield, United Kingdom
J. Knobloch
HZB, Berlin, Germany

Funding: Work supported by the Wolfgang-Gentner-Programme of the Bundesministerium für Bildung und Forschung (BMBF)
The surface resistance RS of superconductors shows a complex dependence on the external parameters such as temperature, frequency or radio-frequency (RF) field. The excited modes of 400, 800 and 1200 MHz allow measurements at actual operating frequencies of superconducting cavities. Niobium films on copper substrates have several advantages over bulk niobium cavities. HiPIMS (High-power impulse magnetron sputtering) is a promising technique to increase the quality and therefore the performance of niobium films. This contribution will introduce CERNs recently developed HiPIMS coating apparatus. Moreover, first results of niobium coated copper samples will be presented, revealing the dominant loss mechanisms.

WEPWO046

First Test Results of the 4-rod Crab Cavity

cavity, vacuum, pick-up, coupling

2405

R. Calaga, L.S. Alberty Vieira, S. Calatroni, O. Capatina, E. Ciapala, L.M.A. Ferreira, E. Jensen, P. Maesen, A. Mongelluzzo, T. Renaglia, M. Therasse
CERN, Geneva, Switzerland
P.K. Ambattu, D. Doherty, B.D.S. Hall, C. Lingwood
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G. Burt
Lancaster University, Lancaster, United Kingdom

Funding: The HiLumi LHC Design Study (a sub-system of HL-LHC) is cofunded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
The first prototype crab cavity with the 4-rod geometry has undergone surface treatment and cold testing. Due to the complex geometry and unique fabrication procedure, RF validation of the field at beyond the nominal operating voltage at a sufficiently high Q0 is an important pre-requiste. Preliminary results of the first cold tests are presented along with cavity performance at different stages of the cavity processing is described.

WEPWO051

Manufacture of a Compact Prototype 4R Crab Cavity for HL-LHC

cavity, luminosity, vacuum, electron

2420

G. Burt, B.D.S. Hall, C. Lingwood
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
L. Alberty Vieira, R. Calaga, O. Capatina
CERN, Geneva, Switzerland
C.H. Boulware, D. Gorelov, T.L. Grimm, C. Krizmanich, T.S. Lamie
Niowave, Inc., Lansing, Michigan, USA
C. Hill, P.A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R.A. Rimmer, H. Wang
JLAB, Newport News, Virginia, USA

Funding: This work has been funded by the EU through EUCARD and HiLumi and by STFC via the Cockcroft Institute.
A prototype compact SRF deflecting cavity has been manufactured for LHC. The base of the cavity has been machined out of large grain niobium ingot to allow the manufacture of the complex rod profile. Stiffening rods have been used to increase the mechanical strength of the outer can. Details of the cavity design and manufacture will be discussed.

WEPWO054

Multistep Mechanical Analyses of Centrifugal Barrel Polishing Barrel and Cavity

cavity, simulation, SRF, acceleration

2426

M. Chen, C.A. Cooper, L. Ristori
Fermilab, Batavia, USA

Funding: US Department of Energy
Fermilab has successfully demonstrated the ability to improve the performance of damaged 1.3 GHz single cell and 9-cell Tesla–type cavities by using a modified centrifugal barrel polishing (CBP) process that leaves a mirror finish on the inside of the cavity. Fermilab now is developing and constructing a new CBP machine which can handle both 650 MHz and 1.3 GHz cavities. The new machine will have a larger moment arm and therefore impart more force on the cavity and machine. Because of these increased forces the effects on cavity supports and machine design were examined. This paper will document the multistep mechanical analyses for the CBP barrel and cavity, calculations of the fatigue life and the requirements for the structural welds.

WEPWO056

Update of the Mechanical Design of the 650 MHZ β=0.9 Cavities for Project X

cavity, simulation, resonance, linac

2432

I.V. Gonin, M.H. Awida, M.H. Foley, C.J. Grimm, T.N. Khabiboulline, Y.M. Pischalnikov, V.P. Yakovlev
Fermilab, Batavia, USA

Five-cell elliptical 650 MHz β=0.9 cavities to accelerate 1 mA of average H⁻ beam current in the range 520-3000 MeV of the Project X Linac are currently planned. We will present the results of optimization of mechanical design of cavities with their Helium Vessel. We discuss the efforts to optimize the mechanical stability of the cavity versus the Helium bath pressure fluctuations, cavity tunability. We present also modal and thermal analysis; discuss tuner options and other issues.

WEPWO065

Optimization of Elliptical SRF Cavities for β <1

cavity, SRF, HOM, simulation

2450

V.D. Shemelin
CLASSE, Ithaca, New York, USA
J. Newbolt
Rochester University, Rochester, New York, USA

Funding: NSF award DMR-0807731
A systematic approach to optimization of SRF cavities which was done earlier for β=1 is extended to β<1 Some improvements for earlier developed designs are proposed.

WEPWO066

Frequency Control in the Cornell-ERL Main-Linac Cavity Production

cavity, target, controls, LabView

2453

V.D. Shemelin, B. Bullock, P.R. Carriere, B. Clasby, R. Eichhorn, B. Elmore, J.J. Kaufman, J. Sears
CLASSE, Ithaca, New York, USA

Funding: NSF award DMR-0807731
Cavity fabrication can be broken down into three main stages: deep-drawing cups, welding the cups in pairs to obtain “dumbbells” and end groups, and, finally, welding the obtained components into a completed cavity. Frequency measurements and precise machining were implemented after the second stage. A custom RF fixture and data acquisition system were used for this purpose. The system comprised of a mechanical press with RF contacts, a network analyzer, a load cell and custom LabVIEW and MATLAB scripts. To extract the individual frequencies of the cups from these measurements, algorithm of calculations was developed. Corrections for the ambient environment were also incorporated into the measurement protocol. Two 7-cell 1.3 GHz cavities were produced with high field flatness immediately after fabrication.

WEPWO071

Quench and High Field Q-SLOP Studies using a Single Cell Cavity with Artificial Pits

cavity, SRF, feedback, factory

2465

Y. Xie, G.H. Hoffstaetter, M. Liepe
CLASSE, Ithaca, New York, USA

Surface defects such as pits have been identified as some of the main sources of limitations of srf cavity performance. A single cell cavity was made with 30 artificial pits in the high magnetic field region to gain new insight in how pits limit the cavity performance. The test of the pit cavity showed clear evidence that the edges of two of the largest radius pits transitioned into the normal conducting state at field just below the quench field of the cavity, and that the quench was indeed induced by these two pits. Insights about quench and non-linear rf resistances will be presented.

WEPWO076

Development of Ultra High Gradient and High Q0 Superconducting Radio Frequency Cavities

cavity, SRF, acceleration, cryogenics

2474

R.L. Geng, W.A. Clemens, J. Follkie, T. Harris, D. Machie, R. Martin, A.D. Palczewski, E. Perry, G. Slack, R.S. Williams
JLAB, Newport News, Virginia, USA
C. Adolphsen, Z. Li
SLAC, Menlo Park, California, USA
J.K. Hao, Y.M. Li, K.X. Liu
PKU, Beijing, People's Republic of China
P. Kushnick
JLab, Newport News, Virginia, USA

Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We report on the recent progress at Jefferson Lab in developing ultra high gradient and high Q0 superconducting radio frequency (SRF) cavities for future SRF based machines. A new 1300 MHz 9-cell prototype cavity is being fabricated. This cavity has an optimized shape in terms of the ratio of the peak surface field (both magnetic and electric) to the acceleration gradient, hence the name low surface field (LSF) shape. The goal of the effort is to demonstrate an acceleration gradient of 50 MV/m with Q0 of 10¹⁰ at 2 K in a 9-cell SRF cavity. Fine-grain niobium material is used. Conventional forming, machining and electron beam welding method are used for cavity fabrication. New techniques are adopted to ensure repeatable, accurate and inexpensive fabrication of components and the full assembly. The completed cavity is to be first mechanically polished to a mirror-finish, a newly acquired in-house capability at JLab, followed by the proven ILC-style processing recipe established already at JLab. In parallel, new single-cell cavities made from large-grain niobium material are made to further advance the cavity treatment and processing procedures, aiming for the demonstration of an acceleration gradient of 50 MV/m with Q0 of 2·10¹⁰ at 2K.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.

WEPWO087

Parameter Optimization for Laser Polishing of Niobium for SRF Applications

laser, cavity, SRF, target

2498

L. Zhao, M.J. Kelley
The College of William and Mary, Williamsburg, USA
M.J. Kelley, J.M. Klopf, C.E. Reece
JLAB, Newport News, Virginia, USA

Surface smoothness is critical to the performance of SRF cavities. As laser technology has been widely applied to metal machining and surface treatment, we are encouraged to use it on niobium as an alternative to the traditional wet polishing process where aggressive chemicals are involved. In this study, we describe progress toward smoothing by optimizing laser parameters on BCP treated niobium surfaces. Results show that microsmoothing of the surface without ablation is achievable.

Poster WEPWO087 [1.683 MB]

THOBB201

Pathway to a Post Processing Increase in Q0 of SRF Cavities

cavity, shielding, SRF, cryogenics

3129

O. Kugeler, J. Knobloch, J.M. Vogt
HZB, Berlin, Germany
S. Aull
CERN, Geneva, Switzerland

A significant improvement of Q0 to values larger than 3.2x10¹⁰ at 1.8K has been repeatedly achieved in an SRF cavity by thermal cycling, i.e. heating the cavity briefly above transition temperature and subsequent cooling. Conceivable explanations for this effect reach from effectivity deviations of the magnetic shielding to thermal currents to hydrogen diffusion. Experimental We have experimentally verified some of these explanations, leaving a direct impact of cooling dynamics on frozen flux as the most plausible one. The pathway to this finding is being presented and the application to SRF systems is elicited.

Slides THOBB201 [1.184 MB]

THPWO063

The Early Stage of the Cavity Fabrication Process (ECT and furnace) for RAON

cavity, vacuum, superconducting-cavity, linac

3901

M.J. Joung, H.C. Jung, H.J. Kim
IBS, Daejeon, Republic of Korea

RAON is consist of three part about the acceleration line. These are SCL1, SCL2 and SCL3. SCL1 and SCL3 will be made from QWR (Qarter Wave Resonator) and HWR (Half Wave Resonator). And SCL2 will be made from SSR1 (Single Spoke Resonator) and SSR2 (Single Spoke Resonator). Accordingly, The RAON needs 48 QWR, 276 HWR, 88 SSR1 and 136 SSR2 to get the performance that we want. To accelerate the particle using lots of cavity, we have to make a process of cavity fabrication for RAON. We will compare to each process made from the other laboratories and to make the optimal process for RAON to get the performance that we want. And that process will consider the type of cavity and the purpose of the accelerator. I will introduce the early stage of the cavity fabrication process for RAON in this paper.