LINAC2012 - List of Keywords (niobium)

Paper	Title	Other Keywords	Page
SUPB001	Analyzing Surface Roughness Dependence of Linear RF Losses	SRF, superconductivity, scattering, radio-frequency	1
	C. Xu, M.J. Kelley The College of William and Mary, Williamsburg, USA C.E. Reece JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Topographic structure on Superconductivity Radio Frequency (SRF) surfaces can contribute additional cavity RF losses describable in terms of surface RF reflectivity and absorption indices of wave scattering theory. At isotropic homogeneous extent, Power Spectrum Density (PSD) of roughness is introduced and quantifies the random surface topographic structure. PSD obtained from different surface treatments of niobium, such as Buffered Chemical Polishing (BCP), Electropolishing (EP), Nano-Mechanical Polishing (NMP) and Barrel Centrifugal Polishing (CBP) are compared. A perturbation model is utilized to calculate the additional rough surface RF losses based on PSD statistical analysis. This model will not consider that superconductor becomes normal conducting at fields higher than transition field. One can calculate the RF power dissipation ratio between rough surface and ideal smooth surface within this field range from linear loss mechanisms.

SUPB019	The Multipacting Simulation for the New-Shaped QWR using TRACK3P	cavity, simulation, accelerating-gradient, electron	50
	C. Zhang, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, M.X. Xu, Y.Z. Yang, W.M. Yue, S.H. Zhang, S.X. Zhang, H.W. Zhao IMP, Lanzhou, People's Republic of China
	In order to improve the electro-magnetic performance of the quarter wave resonator, a new-shaped cavity with an elliptical cylinder outer conductor has been proposed. This novel cavity design can provide much lower peak surface magnetic field and much higher Ra/Q0 and G. The Multipacting simulation has been done for this new QWR cavity using ACE3P/TRACK3P code, in this paper the simulation results will be presented and analyzed.

SUPB028	The Superconducting CH Cavity Development in IMP*	cavity, simulation, linac, resonance	74
	M.X. Xu, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, Z.J. Wang, J.W. Xia, Y.Z. Yang, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao IMP, Lanzhou, People's Republic of China
	Funding: Work supported by 91026001 Nature Science Foundation of China The Cross-Bar H-type (CH) cavity is a multi-gap drift tube structure operated in the H21 mode [1]. The Institute of Modern Physics (IMP) has been doing research and development on this type of superconducting CH cavity which can work at the C-ADS (accelerator driver sub-critical system of China). A new geometry CH cavity has been proposed which have smaller radius. It’s suitable in fabrication, and it’s can reduce cost too .Detailed numerical simulations with CST MicroWave Studio have been performed. An overall surface reduction of 30% against the old structure seems feasible. A copper model CH cavity is being fabrication for validating the simulations and the procedure of fabricating niobium cavity.

SUPB029	Impact of Trapped Flux and Systematic Flux Expulsion in Superconducting Niobium	cavity, SRF, controls, superconductivity	77
	J.M. Vogt, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	The intrinsic quality factor Q₀ of superconducting cavities is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We already reported an additional impact of temperature gradients during the cool-down on the obtained Q₀. We believe cooling conditions can influence the level of flux trapping and hence the residual resistance. For further studies we have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach T_c 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. Applying a similar procedure to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q₀.

MOPB018	Analyzing Surface Roughness Dependence of Linear RF Losses	SRF, superconductivity, scattering, radio-frequency	210
	C. Xu The College of William and Mary, Williamsburg, USA M.J. Kelley, C.E. Reece JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Topographic structure on Superconductivity Radio Frequency (SRF) surfaces can contribute additional cavity RF losses describable in terms of surface RF reflectivity and absorption indices of wave scattering theory. At isotropic homogeneous extent, Power Spectrum Density (PSD) of roughness is introduced and quantifies the random surface topographic structure. PSD obtained from different surface treatments of niobium, such as Buffered Chemical Polishing (BCP), Electropolishing (EP), Nano-Mechanical Polishing (NMP) and Barrel Centrifugal Polishing (CBP) are compared. A perturbation model is utilized to calculate the additional rough surface RF losses based on PSD statistical analysis. This model will not consider that superconductor becomes normal conducting at fields higher than transition field. One can calculate the RF power dissipation ratio between rough surface and ideal smooth surface within this field range from linear loss mechanisms.

MOPB059	The Superconducting CH Cavity Development in IMP*	cavity, simulation, linac, resonance	309
	M.X. Xu, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, Z.J. Wang, J.W. Xia, Y.Z. Yang, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao IMP, Lanzhou, People's Republic of China
	Funding: Work supported by 91026001 Nature Science Foundation of China The Cross-Bar H-type (CH) cavity is a multi-gap drift tube structure operated in the H21 mode [1]. The Institute of Modern Physics (IMP) has been doing research and development on this type of superconducting CH cavity which can work at the C-ADS (accelerator driver sub-critical system of China). A new geometry CH cavity has been proposed which have smaller radius. It’s suitable in fabrication, and it’s can reduce cost too .Detailed numerical simulations with CST MicroWave Studio have been performed. An overall surface reduction of 30% against the old structure seems feasible. A copper model CH cavity is being fabrication for validating the simulations and the procedure of fabricating niobium cavity.

MOPB060	RF Surface Impedance Characterization of Potential New Materials for SRF-based Accelerators	SRF, cavity, impedance, superconductivity	312
	B. P. Xiao, G.V. Eremeev, H.L. Phillips, C.E. Reece JLAB, Newport News, Virginia, USA M.J. Kelley, B. P. Xiao The College of William and Mary, Williamsburg, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. In the development of new superconducting materials for possible use in SRF-based accelerators, it is useful to work with small candidate samples rather than complete resonant cavities. The recently commissioned Jefferson Lab rf Surface Impedance Characterization (SIC) system* can presently characterize the central region of 50 mm diameter disk samples of various materials from 2 to 40 K exposed to RF magnetic fields up to 14 mT at 7.4 GHz. We report the measurement results from bulk Nb, thin film Nb on Cu and sapphire substrates, and thin film MgB₂ on sapphire substrate provided by colleagues at JLab and Temple University. We also report on efforts to extend the operating range to higher fields. * B.P. Xiao, et al., RSI, 2011. 82: p. 056104

MOPB065	Impact of Trapped Magnetic Flux and Systematic Flux Expulsion in Superconducting Niobium	cavity, SRF, controls, superconductivity	327
	J.M. Vogt, J. Knobloch, O. Kugeler HZB, Berlin, Germany
	The intrinsic quality factor Q₀ of superconducting cavities is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We already reported an additional impact of temperature gradients during the cool-down on the obtained Q₀. We believe cooling conditions can influence the level of flux trapping and hence the residual resistance. For further studies we have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach T_c 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. Applying a similar procedure to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q₀.

MOPB073	Cold Testing of Superconducting 72 MHz Quarter-wave Cavities for ATLAS	cavity, cryomodule, linac, accelerating-gradient	348
	M.P. Kelly, Z.A. Conway, S.M. Gerbick, M. Kedzie, R.C. Murphy, P.N. Ostroumov, T. Reid ANL, Argonne, USA
	A set of seven 72 MHz β=0.077 superconducting quarter-wave cavities for a beam intensity upgrade of the ATLAS heavy-ion accelerator has been completed. Cavities have been fabricated using the lessons learned from the worldwide effort to extend the performance of niobium cavities close to the limits of the material. Key developments include the use of electropolishing on the completed cavity and with a temperature control system substantially upgraded from that for elliptical-cell EP systems. Wire EDM, used instead of traditional niobium machining, appears to be effective in eliminating performance limiting defects near the weld seams. Hydrogen degassing at 600C after electropolishing permits practical acceleration at 2 Kelvin with Bpeak>120 mT and cavity voltages>5 MV/cavity.

MOPB074	Thermo-Mechanical Simulations of the Frequency Tuning Plunger for the IFMIF Half-Wave Resonator	cavity, simulation, vacuum, cryomodule	351
	N. Bazin, P. Bosland, S. Chel, G. Devanz, N. Grouas, P. Hardy, J. Migne, F. Orsini, F. Peauger CEA/DSM/IRFU, France
	In the framework of the International Fusion Materials Irradiation Facility (IFMIF), a superconducting option has been chosen for the 5 MeV RF Linac of the first phase of the project (EVEDA), based on a cryomodule composed of 8 HWRs, 8 RF couplers and 8 Solenoid packages. The frequency tuning system of the IFMIF HWR is an innovated system based on a capacitive plunger installed in the electric field region allowing a large tuning range. Following the cold test results obtained on HWR equipped with the first design of plunger in 2011, it was decided to develop a new design of a fully-niobium plunger. The paper will present the development of the new plunger concepts and the thermo-mechanical simulations. For the mechanical simulations, the aim is to sufficiently deform the plunger to tune the cavity while staying in the elastic range of the niobium material. For the thermal simulations, all the non-linear properties of the materials and the effects of the RF fields are taken into account: thermal conductivity and surface resistance are depending on the temperature, RF fields computed with dedicated software are leading to thermal dissipations in the materials and the vacuum seal. F. Orsini et al., “Vertical tests preliminary results of the IFMIF cavity prototypes and cryomodule development”, SRF 2011, Chigaco, USA

TUPLB07	Reduced-beta Cavities for High-intensity Compact Accelerators	cavity, ion, electron, heavy-ion	458
	Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, J.W. Morgan, R.C. Murphy, P.N. Ostroumov, T. Reid ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357 and WFO 8R268. This paper reports on the development and testing of a superconducting quarter-wave and a superconducting half-wave resonator. The quarter-wave resonator is designed for β = 0.077 ions, operates at 72 MHz and can provide more than 7.4 MV of accelerating voltage at the design beta, with peak surface fields of 164 mT and 117 MV/m. Operation was limited to this level not by RF surface defects but by our available RF power and administrative limits on x-ray production. A similar goal is being pursued in the development of a half-wave resonator designed for β = 0.29 ions and operated at 325 MHz.

TUPB047	Status of the Superconducting RF Activities for the HIE ISOLDE Project	cavity, factory, linac, SRF	582
	W. Venturini Delsolaro, L. Alberty Vieira, S. Calatroni, O. Capatina, A. D'Elia, B. Delaup, M.A. Fraser, N.M. Jecklin, Y. Kadi, P. Maesen, I. Mondino, E. Montesinos, M. Therasse, D. Valuch CERN, Geneva, Switzerland
	The planned upgrade of the REX ISOLDE facility at CERN will boost the energy of the machine from 3 MeV/u up to 10 MeV/u with beams of mass-to-charge ratio 2.5 < A/q < 4. For this purpose, a new superconducting post accelerator based on independently phased 10¹.28 MHz Quarter Wave Resonators (QWR) will replace part of the normal conducting Linac. The QWRs make use of the Niobium sputtering on Copper technology which was successfully applied to LEP2, LHC and to the energy upgrade of the ALPI Linac at INFN-LNL. The status of advancement of the project will be detailed, limited to the SRF activities.

TUPB049	Superconducting Low Beta Niobium Resonator for Heavy Ions	linac, ion, DTL, heavy-ion	588
	P.N. Prakash, K.K. Mistri, A. Roy, J. Sacharias, S.S. Sonti IUAC, New Delhi, India
	For the high current injector at Inter-University Accelerator Centre, a new superconducting niobium resonator optimized for β = 0.05 operating at 97 MHz, has been designed and fabricated. This resonator has the highest frequency in its class among the superconducting structures designed for such low velocity particles. The resonator has been carefully modeled using Microwave Studio code to minimize the peak magnetic field in order to achieve high accelerating gradients in it. Even though the resonance frequency is high, the physical dimensions of the resonator are large enough to allow processing of its superconducting surface effectively. The mechanical design of the resonator has been modeled using ANSYS multiphysics to increase the frequency of the lowest mechanical eigenmode of the central co-axial line, and also reduce liquid helium induced pressure fluctuations in the resonator. Bead pull measurements have been performed on the niobium resonator and they match with the design values very well. Cold tests at 4.2 K will be performed in the next few weeks. This paper will briefly present the design of the low beta resonator and details of the results from the cold tests.

TUPB055	R&D of IMP Superconducting HWR for China ADS	cavity, simulation, linac, proton	600
	W.M. Yue, X.L. Guo, S. He, Y. He, R.X. Wang, P.R. Xiong, M.X. Xu, B. Zhang, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao IMP, Lanzhou, People's Republic of China
	The R&D program of IMP superconducting HWR is based on the China ADS, The aim is to build and test a HWR prototype on December 2012. We have designed a 162.5 MHz β=0.09 half-wave resonator (HWR), and a copper HWR has been fabricated in January 2012. The fabrication of a Nb HWR will be completed by September 2012, and the fabrication of a slow tuner and a high power coupler for this HWR will be completed then. In this poster, we present the HWR electromagnetic design, mechanical design, fabrication arts, copper HWR RF test result, the design of the slow tuner and the power coupler.

TUPB056	The Multipacting Simulation for the New-shaped QWR using TRACK3P	cavity, simulation, accelerating-gradient, electron	603
	C. Zhang, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, M.X. Xu, Y.Z. Yang, W.M. Yue, S.H. Zhang, S.X. Zhang, H.W. Zhao IMP, Lanzhou, People's Republic of China
	In order to improve the electro-magnetic performance of the quarter wave resonator, a new-shaped cavity with an elliptical cylinder outer conductor has been proposed. This novel cavity design can provide much lower peak surface magnetic field and much higher Ra/Q0 and G. The Multipacting simulation has been done for this new QWR cavity using ACE3P/TRACK3P code, in this paper the simulation results will be presented and analyzed.

TUPB066	Reduced-beta Cavities for High-intensity Compact Accelerators	cavity, ion, electron, heavy-ion	621
	Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, J.W. Morgan, R.C. Murphy, P.N. Ostroumov, T. Reid ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357 and WFO 8R268. This paper reports on the development and testing of a superconducting quarter-wave and a superconducting half-wave resonator. The quarter-wave resonator is designed for β = 0.077 ions, operates at 72 MHz and can provide more than 7.4 MV of accelerating voltage at the design beta, with peak surface fields of 164 mT and 117 MV/m. Operation was limited to this level not by RF surface defects but by our available RF power and administrative limits on x-ray production. A similar goal is being pursued in the development of a half-wave resonator designed for β = 0.29 ions and operated at 325 MHz.

TUPB067	Development of a Superconducting Half-Wave Resonator for PXIE	cavity, simulation, linac, cryomodule	624
	Z.A. Conway, R.L. Fischer, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.V. Kutsaev, B. Mustapha, P.N. Ostroumov, K.W. Shepard ANL, Argonne, USA I.V. Gonin, A. Lunin, V.P. Yakovlev Fermilab, Batavia, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics and Nuclear Physics, under contract DE-AC02-76CH03000 and DE-AC02-06CH11357 An ambitious upgrade to the FNAL accelerator complex is progressing in the Project-X Injector Experiment (PXIE). The PXIE accelerator requires 8 superconducting half-wave resonators optimized for the acceleration of 1 mA β = 0.11 H⁻ ion beams. Here we present the status of the half-wave resonator development, focusing particularly on cavity design, with a brief update on prototype fabrication.

THPLB05	R&D Activities on High Intensity Superconducting Proton Linac at RRCAT	cavity, SRF, ion, linac	819
	S.C. Joshi, J. Dwivedi, P.D. Gupta, P.R. Hannurkar, P. Khare, P.K. Kush, G. Mundra, A. Puntambekar, S.B. Roy, P. Shrivastava RRCAT, Indore (M.P.), India
	Raja Ramanna Centre for Advanced Technology (RRCAT), Indore has taken up a program on development of 1 GeV high intensity superconducting proton linac for Spallation Neutron Source. This will require several multi-cell superconducting cavities operating at different RF frequencies. To start with, a number of single-cell prototype cavities at 1.3 GHz have been developed in high RRR bulk niobium. These single-cell cavities have exhibited high quality factor and accelerating gradients. Superconducting properties of niobium are being studied for varying composition of impurities and different processing conditions. Development activity on solid state RF amplifiers to power the SCRF cavities at various RF frequencies is being pursued. A building has been constructed to house the SCRF cavity fabrication and processing facility. To characterize SCRF cavity, a 2 K Vertical Test Stand is being set up including a 2 K cryostat, RF power supply and data acquisition system. Design activities for cryomodule and large 2 K cryostat for Horizontal Test Stand are also under progress. The paper will discuss the status of above R&D activities and infrastructure development at RRCAT.
	Slides THPLB05 [1.614 MB]

THPB003	R&D Activities on High Intensity Superconducting Proton Linac at RRCAT	cavity, SRF, ion, linac	843
	S.C. Joshi, J. Dwivedi, P.D. Gupta, P.R. Hannurkar, P. Khare, P.K. Kush, G. Mundra, A. Puntambekar, S.B. Roy, P. Shrivastava RRCAT, Indore (M.P.), India
	Raja Ramanna Centre for Advanced Technology (RRCAT), Indore has taken up a program on development of 1 GeV high intensity superconducting proton linac for Spallation Neutron Source. This will require several multi-cell superconducting cavities operating at different RF frequencies. To start with, a number of single-cell prototype cavities at 1.3 GHz have been developed in high RRR bulk niobium. These single-cell cavities have exhibited high quality factor and accelerating gradients. Superconducting properties of niobium are being studied for varying composition of impurities and different processing conditions. Development activity on solid state RF amplifiers to power the SCRF cavities at various RF frequencies is being pursued. A building has been constructed to house the SCRF cavity fabrication and processing facility. To characterize SCRF cavity, a 2 K Vertical Test Stand is being set up including a 2 K cryostat, RF power supply and data acquisition system. Design activities for cryomodule and large 2 K cryostat for Horizontal Test Stand are also under progress. The paper will discuss the status of above R&D activities and infrastructure development at RRCAT.

THPB027	Progress of one of 10 MeV superconducting proton linear Injectors for C-ADS	rfq, linac, proton, cavity	909
	Y. He, J. Meng, A. Shi, Z.J. Wang, J.X. Wu, W. Wu, H.S. Xu, Z. Xu, B. Zhang, J.H. Zhang, S.H. Zhang, Z.M. Zhang, H.W. Zhao, Z.Z. Zhou IMP, Lanzhou, People's Republic of China D. Li LBNL, Berkeley, California, USA
	A 10 MeV superconducting proton linac is being design and constructing at Institute of Modern Physics (IMP) of Chinese Academy of Sciences (CAS). This proton linac is one of two injectors for Chinese ADS project. It is to validate one of concepts for C-ADS front end, to demonstrate the low beta acceleration, to minimize the risk of key technoledges within the Reference Design. It consists of a 2.1 MeV RFQ and two cryomodules hosting 8 HWR cavities. The basic frequecy is 162.5 MHz. The physical design of linac and the progess of prototypes for solid state amplifiers, superconducting solenoids, supercondecting HWRs, ion source, and RFQ are presented in the paper.

Paper

Title

Other Keywords

Page

SUPB001

Analyzing Surface Roughness Dependence of Linear RF Losses

SRF, superconductivity, scattering, radio-frequency

1

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

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Topographic structure on Superconductivity Radio Frequency (SRF) surfaces can contribute additional cavity RF losses describable in terms of surface RF reflectivity and absorption indices of wave scattering theory. At isotropic homogeneous extent, Power Spectrum Density (PSD) of roughness is introduced and quantifies the random surface topographic structure. PSD obtained from different surface treatments of niobium, such as Buffered Chemical Polishing (BCP), Electropolishing (EP), Nano-Mechanical Polishing (NMP) and Barrel Centrifugal Polishing (CBP) are compared. A perturbation model is utilized to calculate the additional rough surface RF losses based on PSD statistical analysis. This model will not consider that superconductor becomes normal conducting at fields higher than transition field. One can calculate the RF power dissipation ratio between rough surface and ideal smooth surface within this field range from linear loss mechanisms.

SUPB019

The Multipacting Simulation for the New-Shaped QWR using TRACK3P

cavity, simulation, accelerating-gradient, electron

50

C. Zhang, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, M.X. Xu, Y.Z. Yang, W.M. Yue, S.H. Zhang, S.X. Zhang, H.W. Zhao
IMP, Lanzhou, People's Republic of China

In order to improve the electro-magnetic performance of the quarter wave resonator, a new-shaped cavity with an elliptical cylinder outer conductor has been proposed. This novel cavity design can provide much lower peak surface magnetic field and much higher Ra/Q0 and G. The Multipacting simulation has been done for this new QWR cavity using ACE3P/TRACK3P code, in this paper the simulation results will be presented and analyzed.

SUPB028

The Superconducting CH Cavity Development in IMP*

cavity, simulation, linac, resonance

74

M.X. Xu, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, Z.J. Wang, J.W. Xia, Y.Z. Yang, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao
IMP, Lanzhou, People's Republic of China

Funding: Work supported by 91026001 Nature Science Foundation of China
The Cross-Bar H-type (CH) cavity is a multi-gap drift tube structure operated in the H21 mode [1]. The Institute of Modern Physics (IMP) has been doing research and development on this type of superconducting CH cavity which can work at the C-ADS (accelerator driver sub-critical system of China). A new geometry CH cavity has been proposed which have smaller radius. It’s suitable in fabrication, and it’s can reduce cost too .Detailed numerical simulations with CST MicroWave Studio have been performed. An overall surface reduction of 30% against the old structure seems feasible. A copper model CH cavity is being fabrication for validating the simulations and the procedure of fabricating niobium cavity.

SUPB029

Impact of Trapped Flux and Systematic Flux Expulsion in Superconducting Niobium

cavity, SRF, controls, superconductivity

77

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

The intrinsic quality factor Q₀ of superconducting cavities is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We already reported an additional impact of temperature gradients during the cool-down on the obtained Q₀. We believe cooling conditions can influence the level of flux trapping and hence the residual resistance. For further studies we have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach T_c 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. Applying a similar procedure to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q₀.

MOPB018

Analyzing Surface Roughness Dependence of Linear RF Losses

SRF, superconductivity, scattering, radio-frequency

210

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

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Topographic structure on Superconductivity Radio Frequency (SRF) surfaces can contribute additional cavity RF losses describable in terms of surface RF reflectivity and absorption indices of wave scattering theory. At isotropic homogeneous extent, Power Spectrum Density (PSD) of roughness is introduced and quantifies the random surface topographic structure. PSD obtained from different surface treatments of niobium, such as Buffered Chemical Polishing (BCP), Electropolishing (EP), Nano-Mechanical Polishing (NMP) and Barrel Centrifugal Polishing (CBP) are compared. A perturbation model is utilized to calculate the additional rough surface RF losses based on PSD statistical analysis. This model will not consider that superconductor becomes normal conducting at fields higher than transition field. One can calculate the RF power dissipation ratio between rough surface and ideal smooth surface within this field range from linear loss mechanisms.

MOPB059

The Superconducting CH Cavity Development in IMP*

cavity, simulation, linac, resonance

309

M.X. Xu, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, Z.J. Wang, J.W. Xia, Y.Z. Yang, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao
IMP, Lanzhou, People's Republic of China

Funding: Work supported by 91026001 Nature Science Foundation of China
The Cross-Bar H-type (CH) cavity is a multi-gap drift tube structure operated in the H21 mode [1]. The Institute of Modern Physics (IMP) has been doing research and development on this type of superconducting CH cavity which can work at the C-ADS (accelerator driver sub-critical system of China). A new geometry CH cavity has been proposed which have smaller radius. It’s suitable in fabrication, and it’s can reduce cost too .Detailed numerical simulations with CST MicroWave Studio have been performed. An overall surface reduction of 30% against the old structure seems feasible. A copper model CH cavity is being fabrication for validating the simulations and the procedure of fabricating niobium cavity.

MOPB060

RF Surface Impedance Characterization of Potential New Materials for SRF-based Accelerators

SRF, cavity, impedance, superconductivity

312

B. P. Xiao, G.V. Eremeev, H.L. Phillips, C.E. Reece
JLAB, Newport News, Virginia, USA
M.J. Kelley, B. P. Xiao
The College of William and Mary, Williamsburg, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In the development of new superconducting materials for possible use in SRF-based accelerators, it is useful to work with small candidate samples rather than complete resonant cavities. The recently commissioned Jefferson Lab rf Surface Impedance Characterization (SIC) system* can presently characterize the central region of 50 mm diameter disk samples of various materials from 2 to 40 K exposed to RF magnetic fields up to 14 mT at 7.4 GHz. We report the measurement results from bulk Nb, thin film Nb on Cu and sapphire substrates, and thin film MgB₂ on sapphire substrate provided by colleagues at JLab and Temple University. We also report on efforts to extend the operating range to higher fields.
* B.P. Xiao, et al., RSI, 2011. 82: p. 056104

MOPB065

Impact of Trapped Magnetic Flux and Systematic Flux Expulsion in Superconducting Niobium

cavity, SRF, controls, superconductivity

327

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

The intrinsic quality factor Q₀ of superconducting cavities is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We already reported an additional impact of temperature gradients during the cool-down on the obtained Q₀. We believe cooling conditions can influence the level of flux trapping and hence the residual resistance. For further studies we have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach T_c 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. Applying a similar procedure to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q₀.

MOPB073

Cold Testing of Superconducting 72 MHz Quarter-wave Cavities for ATLAS

cavity, cryomodule, linac, accelerating-gradient

348

M.P. Kelly, Z.A. Conway, S.M. Gerbick, M. Kedzie, R.C. Murphy, P.N. Ostroumov, T. Reid
ANL, Argonne, USA

A set of seven 72 MHz β=0.077 superconducting quarter-wave cavities for a beam intensity upgrade of the ATLAS heavy-ion accelerator has been completed. Cavities have been fabricated using the lessons learned from the worldwide effort to extend the performance of niobium cavities close to the limits of the material. Key developments include the use of electropolishing on the completed cavity and with a temperature control system substantially upgraded from that for elliptical-cell EP systems. Wire EDM, used instead of traditional niobium machining, appears to be effective in eliminating performance limiting defects near the weld seams. Hydrogen degassing at 600C after electropolishing permits practical acceleration at 2 Kelvin with Bpeak>120 mT and cavity voltages>5 MV/cavity.

MOPB074

Thermo-Mechanical Simulations of the Frequency Tuning Plunger for the IFMIF Half-Wave Resonator

cavity, simulation, vacuum, cryomodule

351

N. Bazin, P. Bosland, S. Chel, G. Devanz, N. Grouas, P. Hardy, J. Migne, F. Orsini, F. Peauger
CEA/DSM/IRFU, France

In the framework of the International Fusion Materials Irradiation Facility (IFMIF), a superconducting option has been chosen for the 5 MeV RF Linac of the first phase of the project (EVEDA), based on a cryomodule composed of 8 HWRs, 8 RF couplers and 8 Solenoid packages. The frequency tuning system of the IFMIF HWR is an innovated system based on a capacitive plunger installed in the electric field region allowing a large tuning range. Following the cold test results obtained on HWR equipped with the first design of plunger in 2011*, it was decided to develop a new design of a fully-niobium plunger. The paper will present the development of the new plunger concepts and the thermo-mechanical simulations. For the mechanical simulations, the aim is to sufficiently deform the plunger to tune the cavity while staying in the elastic range of the niobium material. For the thermal simulations, all the non-linear properties of the materials and the effects of the RF fields are taken into account: thermal conductivity and surface resistance are depending on the temperature, RF fields computed with dedicated software are leading to thermal dissipations in the materials and the vacuum seal.
* F. Orsini et al., “Vertical tests preliminary results of the IFMIF cavity prototypes and cryomodule development”, SRF 2011, Chigaco, USA

TUPLB07

Reduced-beta Cavities for High-intensity Compact Accelerators

cavity, ion, electron, heavy-ion

458

Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, J.W. Morgan, R.C. Murphy, P.N. Ostroumov, T. Reid
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357 and WFO 8R268.
This paper reports on the development and testing of a superconducting quarter-wave and a superconducting half-wave resonator. The quarter-wave resonator is designed for β = 0.077 ions, operates at 72 MHz and can provide more than 7.4 MV of accelerating voltage at the design beta, with peak surface fields of 164 mT and 117 MV/m. Operation was limited to this level not by RF surface defects but by our available RF power and administrative limits on x-ray production. A similar goal is being pursued in the development of a half-wave resonator designed for β = 0.29 ions and operated at 325 MHz.

TUPB047

Status of the Superconducting RF Activities for the HIE ISOLDE Project

cavity, factory, linac, SRF

582

W. Venturini Delsolaro, L. Alberty Vieira, S. Calatroni, O. Capatina, A. D'Elia, B. Delaup, M.A. Fraser, N.M. Jecklin, Y. Kadi, P. Maesen, I. Mondino, E. Montesinos, M. Therasse, D. Valuch
CERN, Geneva, Switzerland

The planned upgrade of the REX ISOLDE facility at CERN will boost the energy of the machine from 3 MeV/u up to 10 MeV/u with beams of mass-to-charge ratio 2.5 < A/q < 4. For this purpose, a new superconducting post accelerator based on independently phased 10¹.28 MHz Quarter Wave Resonators (QWR) will replace part of the normal conducting Linac. The QWRs make use of the Niobium sputtering on Copper technology which was successfully applied to LEP2, LHC and to the energy upgrade of the ALPI Linac at INFN-LNL. The status of advancement of the project will be detailed, limited to the SRF activities.

TUPB049

Superconducting Low Beta Niobium Resonator for Heavy Ions

linac, ion, DTL, heavy-ion

588

P.N. Prakash, K.K. Mistri, A. Roy, J. Sacharias, S.S. Sonti
IUAC, New Delhi, India

For the high current injector at Inter-University Accelerator Centre, a new superconducting niobium resonator optimized for β = 0.05 operating at 97 MHz, has been designed and fabricated. This resonator has the highest frequency in its class among the superconducting structures designed for such low velocity particles. The resonator has been carefully modeled using Microwave Studio code to minimize the peak magnetic field in order to achieve high accelerating gradients in it. Even though the resonance frequency is high, the physical dimensions of the resonator are large enough to allow processing of its superconducting surface effectively. The mechanical design of the resonator has been modeled using ANSYS multiphysics to increase the frequency of the lowest mechanical eigenmode of the central co-axial line, and also reduce liquid helium induced pressure fluctuations in the resonator. Bead pull measurements have been performed on the niobium resonator and they match with the design values very well. Cold tests at 4.2 K will be performed in the next few weeks. This paper will briefly present the design of the low beta resonator and details of the results from the cold tests.

TUPB055

R&D of IMP Superconducting HWR for China ADS

cavity, simulation, linac, proton

600

W.M. Yue, X.L. Guo, S. He, Y. He, R.X. Wang, P.R. Xiong, M.X. Xu, B. Zhang, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao
IMP, Lanzhou, People's Republic of China

The R&D program of IMP superconducting HWR is based on the China ADS, The aim is to build and test a HWR prototype on December 2012. We have designed a 162.5 MHz β=0.09 half-wave resonator (HWR), and a copper HWR has been fabricated in January 2012. The fabrication of a Nb HWR will be completed by September 2012, and the fabrication of a slow tuner and a high power coupler for this HWR will be completed then. In this poster, we present the HWR electromagnetic design, mechanical design, fabrication arts, copper HWR RF test result, the design of the slow tuner and the power coupler.

TUPB056

The Multipacting Simulation for the New-shaped QWR using TRACK3P

cavity, simulation, accelerating-gradient, electron

603

C. Zhang, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, M.X. Xu, Y.Z. Yang, W.M. Yue, S.H. Zhang, S.X. Zhang, H.W. Zhao
IMP, Lanzhou, People's Republic of China

In order to improve the electro-magnetic performance of the quarter wave resonator, a new-shaped cavity with an elliptical cylinder outer conductor has been proposed. This novel cavity design can provide much lower peak surface magnetic field and much higher Ra/Q0 and G. The Multipacting simulation has been done for this new QWR cavity using ACE3P/TRACK3P code, in this paper the simulation results will be presented and analyzed.

TUPB066

Reduced-beta Cavities for High-intensity Compact Accelerators

cavity, ion, electron, heavy-ion

621

Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, J.W. Morgan, R.C. Murphy, P.N. Ostroumov, T. Reid
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357 and WFO 8R268.
This paper reports on the development and testing of a superconducting quarter-wave and a superconducting half-wave resonator. The quarter-wave resonator is designed for β = 0.077 ions, operates at 72 MHz and can provide more than 7.4 MV of accelerating voltage at the design beta, with peak surface fields of 164 mT and 117 MV/m. Operation was limited to this level not by RF surface defects but by our available RF power and administrative limits on x-ray production. A similar goal is being pursued in the development of a half-wave resonator designed for β = 0.29 ions and operated at 325 MHz.

TUPB067

Development of a Superconducting Half-Wave Resonator for PXIE

cavity, simulation, linac, cryomodule

624

Z.A. Conway, R.L. Fischer, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.V. Kutsaev, B. Mustapha, P.N. Ostroumov, K.W. Shepard
ANL, Argonne, USA
I.V. Gonin, A. Lunin, V.P. Yakovlev
Fermilab, Batavia, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics and Nuclear Physics, under contract DE-AC02-76CH03000 and DE-AC02-06CH11357
An ambitious upgrade to the FNAL accelerator complex is progressing in the Project-X Injector Experiment (PXIE). The PXIE accelerator requires 8 superconducting half-wave resonators optimized for the acceleration of 1 mA β = 0.11 H⁻ ion beams. Here we present the status of the half-wave resonator development, focusing particularly on cavity design, with a brief update on prototype fabrication.

THPLB05

R&D Activities on High Intensity Superconducting Proton Linac at RRCAT

cavity, SRF, ion, linac

819

S.C. Joshi, J. Dwivedi, P.D. Gupta, P.R. Hannurkar, P. Khare, P.K. Kush, G. Mundra, A. Puntambekar, S.B. Roy, P. Shrivastava
RRCAT, Indore (M.P.), India

Raja Ramanna Centre for Advanced Technology (RRCAT), Indore has taken up a program on development of 1 GeV high intensity superconducting proton linac for Spallation Neutron Source. This will require several multi-cell superconducting cavities operating at different RF frequencies. To start with, a number of single-cell prototype cavities at 1.3 GHz have been developed in high RRR bulk niobium. These single-cell cavities have exhibited high quality factor and accelerating gradients. Superconducting properties of niobium are being studied for varying composition of impurities and different processing conditions. Development activity on solid state RF amplifiers to power the SCRF cavities at various RF frequencies is being pursued. A building has been constructed to house the SCRF cavity fabrication and processing facility. To characterize SCRF cavity, a 2 K Vertical Test Stand is being set up including a 2 K cryostat, RF power supply and data acquisition system. Design activities for cryomodule and large 2 K cryostat for Horizontal Test Stand are also under progress. The paper will discuss the status of above R&D activities and infrastructure development at RRCAT.

Slides THPLB05 [1.614 MB]

THPB003

R&D Activities on High Intensity Superconducting Proton Linac at RRCAT

cavity, SRF, ion, linac

843

S.C. Joshi, J. Dwivedi, P.D. Gupta, P.R. Hannurkar, P. Khare, P.K. Kush, G. Mundra, A. Puntambekar, S.B. Roy, P. Shrivastava
RRCAT, Indore (M.P.), India

Raja Ramanna Centre for Advanced Technology (RRCAT), Indore has taken up a program on development of 1 GeV high intensity superconducting proton linac for Spallation Neutron Source. This will require several multi-cell superconducting cavities operating at different RF frequencies. To start with, a number of single-cell prototype cavities at 1.3 GHz have been developed in high RRR bulk niobium. These single-cell cavities have exhibited high quality factor and accelerating gradients. Superconducting properties of niobium are being studied for varying composition of impurities and different processing conditions. Development activity on solid state RF amplifiers to power the SCRF cavities at various RF frequencies is being pursued. A building has been constructed to house the SCRF cavity fabrication and processing facility. To characterize SCRF cavity, a 2 K Vertical Test Stand is being set up including a 2 K cryostat, RF power supply and data acquisition system. Design activities for cryomodule and large 2 K cryostat for Horizontal Test Stand are also under progress. The paper will discuss the status of above R&D activities and infrastructure development at RRCAT.

THPB027

Progress of one of 10 MeV superconducting proton linear Injectors for C-ADS

rfq, linac, proton, cavity

909

Y. He, J. Meng, A. Shi, Z.J. Wang, J.X. Wu, W. Wu, H.S. Xu, Z. Xu, B. Zhang, J.H. Zhang, S.H. Zhang, Z.M. Zhang, H.W. Zhao, Z.Z. Zhou
IMP, Lanzhou, People's Republic of China
D. Li
LBNL, Berkeley, California, USA

A 10 MeV superconducting proton linac is being design and constructing at Institute of Modern Physics (IMP) of Chinese Academy of Sciences (CAS). This proton linac is one of two injectors for Chinese ADS project. It is to validate one of concepts for C-ADS front end, to demonstrate the low beta acceleration, to minimize the risk of key technoledges within the Reference Design. It consists of a 2.1 MeV RFQ and two cryomodules hosting 8 HWR cavities. The basic frequecy is 162.5 MHz. The physical design of linac and the progess of prototypes for solid state amplifiers, superconducting solenoids, supercondecting HWRs, ion source, and RFQ are presented in the paper.