LINAC2016 - Classification: 2 Proton and Ion Accelerators and Applications / 2E Superconducting Structures

Paper	Title	Page
TUP106006	Vertical Test Results on ESS Medium Beta Elliptical Cavity Prototype	631
	E. Cenni CEA/IRFU, Gif-sur-Yvette, France S. Berry, P. Bosland, F. Éozénou, L. Maurice, J. Plouin, C. Servouin CEA/DSM/IRFU, France G. Costanza Lund University, Lund, Sweden C. Darve ESS, Lund, Sweden G. Devanz, X. Hanus, F. Peauger, D. Roudier CEA/DRF/IRFU, Gif-sur-Yvette, France
	The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy at 2 GeV. The last Linac optimization, called Optimus+ [1], has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. This work presents the latest vertical test results on ESS medium beta elliptical cavity prototypes. We describe the cavity preparation procedure from buffer chemical polishing to vertical test. Finally magnetic probes (Fluxgate) were installed on the cavity to determine magnetic field background during vertical test. The latest vertical test results showed that our cavity design performance are beyond requirements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUP106006
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THPLR027	Progress Towards a 2.0 K Half-Wave Resonator Cryomodule for Fermilab's PIP-II Project	906
	Z.A. Conway, A. Barcikowski, G.L. Cherry, R.L. Fischer, B.M. Guilfoyle, C.S. Hopper, M. Kedzie, M.P. Kelly, S.H. Kim, S.W.T. MacDonald, P.N. Ostroumov, T. Reid ANL, Argonne, Illinois, USA V.A. Lebedev, A. Lunin Fermilab, Batavia, Illinois, USA
	Funding: This material is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and Office of High-Energy Physics, Contracts No. DE-AC02-76-CH03000 and DE-AC02-06CH11357. In support of Fermilab's Proton Improvement Plan-II project Argonne National Laboratory is constructing a superconducting half-wave resonator cryomodule. This cryomodule is designed to operate at 2.0 K, a first for low-velocity ion accelerators, and will accelerate ≥1 mA proton/H⁻ beams from 2.1 to 10.3 MeV. Since 2014 the construction of 9 162.5 MHz b = 0.112 superconducting half-wave resonators, the vacuum vessel and the majority of the cryomodule subsystems have been finished. Here we will update on the status of this work and report on preliminary cavity test results. This will include cavity performance measurements where we found residual resistances of < 3 nanoOhms at low fields and peak voltage gains of 5.9 MV, which corresponds to peak surface fields of 134 MV/m and 144 mT electric and magnetic respectively.
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THPLR028	Simulation of Mechanical Oscillations in PIP-II Cryomodule Using ACE3P	910
	L. Xiao, O. Kononenko, C.-K. Ng SLAC, Menlo Park, California, USA
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515. The linac in the PIP-II project at Fermilab consists of different sections of superconducting rf (SRF) cavities that can accelerate the proton beams to 800 MeV. At the end of the linac is a section containing a number of HB (β = 0.92) cryomodules operating at 650 MHz, with each cryomodule consisting of six SRF cavities. Previous calculations have been carried out to determine the mechanical modes of a single cavity in the 650 MHz cryomodule. In this paper, the parallel code suite ACE3P is used to evaluate the mechanical modes for a string of SRF cavities in the 650 MHz cryomodule. The effects of multi cavities on the mechanical mode frequencies and any possible coupling between cavities will be investigated.
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THPLR029	Update on the SC 325 MHz CH-Cavity and Power Coupler Processing	913
	M. Busch, M. Amberg, M. Basten, F.D. Dziuba, P.A. Mundine, H. Podlech, U. Ratzinger IAP, Frankfurt am Main, Germany
	Funding: Work supported by GSI, BMBF Contr. No. 05P15RFRBA The 325 MHz CH-Cavity which has been developed and successfully vertically tested at the Institute for Applied Physics, Frankfurt, has reached the final production stage. The helium vessel has been welded to the frontal joints of the cavity and further tests in a horizontal environment are in preparation. Furthermore the corresponding power couplers have been conditioned and tested at a dedicated test stand up to the power level of 40 kW (pulsed) for the targeted beam operation. The final step of the whole prototype development is a beam test with a 11.4 AMeV, 10 mA ion beam at GSI, Darmstadt.
	Poster THPLR029 [1.858 MB]
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THPLR030	Performances of the Two First Single Spoke Prototypes for the MYRRHA Project	916
	D. Longuevergne, J.-L. Biarrotte, S. Blivet, P. Duchesne, G. Olry, H. Saugnac IPN, Orsay, France Y. Gómez Martínez LPSC, Grenoble Cedex, France
	Funding: This work is being supported by the Euratom research and training program 2014-2018 under grant agreement N°662186 (MYRTE project) The MYRRHA project aims at the construction of an accelerator driven system (ADS) at MOL (Belgium) for irradiation and transmutation experiment purposes. The facility will feature a superconducting LINAC able to produce a proton flux of 2.4 MW (600 MeV - 4 mA). The first section of the superconducting LINAC will be composed of 352 MHz (β = 0.37) Single Spoke Resonators (SSR) housed in short cryomodules operating at 2K. After a brief presentation of the cryomodule design, this paper will aim at presenting the RF performances of the SSR tested in vertical cryostat in the framework of European MYRTE project (MYRRHA Research and Transmutation Endeavour) and at comparing experimental results (Lorentz forces, pressure sensitivity, multipacting barriers…) to simulated values.
	Poster THPLR030 [1.610 MB]
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THPLR032	Update on SSR2 Cavity EM Design for PIP-II	920
	P. Berrutti, T.N. Khabiboulline, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Proton Improvement Plan II (PIP-II) is the future plan for upgrading the Fermilab proton accelerator complex to a beam power capability of at least 1 MW delivered to the neutrino production target. A room temperature section accelerates H⁻ ions to 2.1 MeV and creates the desired bunch structure for injection into the superconducting (SC) linac. SC linac using five cavity types. One 162.5 MHz half wave resonator, two 325 MHz spoke resonators and two 650 MHz elliptical 5-cell cavities, provide acceleration to 800 MeV. The EM design of the second family of spoke resonator is presented in this paper. The work reported is a thorough electromagnetic study including: the RF parameters, multipacting mitigation and transverse field asymmetry. The cavity is now ready for structural design analysis.
	Poster THPLR032 [1.947 MB]
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THPLR033	R&D Status of the New Superconducting CW Heavy Ion LINAC@GSI	923
SPWR024	use link to see paper's listing under its alternate paper code
	M. Basten, M. Amberg, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany W.A. Barth, V. Gettmann, S. Mickat, M. Miski-Oglu HIM, Mainz, Germany M. Heilmann, S. Mickat, S. Yaramyshev GSI, Darmstadt, Germany
	For future research in the field of Super Heavy Elements (SHE) a superconducting (sc) continuous wave (cw) ion LINAC with high intensity is highly desirable. Presently a multi-stage R&D program conducted by GSI, HIM and IAP[] is in progress. The fundamental linac design composes a high performance ion source, a new low energy beam transport line, the High Charge State Injector (HLI) upgraded for cw, and a matching line (1.4 MeV/u) followed by the new sc-DTL LINAC for acceleration up to 7.3 MeV/u. The successful commissioning of the first Crossbar-H-mode (CH) cavity (Demonstrator), in a vertical cryo module, was a major milestone in 2015[]. The next stage of the new sc cw heavy ion LINAC is the advanced demonstrator comprising a string of cavities and focusing elements build from several short constant-beta sc CH-cavities operated at 217MHz. Currently the first two sc 8 gap CH-cavities are under construction at Research Instruments (RI), Bergisch Gladbach, Germany. The new design without girders and with stiffening brackets at the front and end cap potentially reduces the overall technical risks during the construction phase and the pressure sensitivity of the cavity. The recent status of the construction phase as well as an outlook for further cavity development 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, IPAC14, THPME004 **F.Dziuba et al.,First Performance Test on the Superconducting 217 MHz CH Cavity at 4K,LINAC16, THPLR033
	Poster THPLR033 [2.502 MB]
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THPLR035	FZJ SRF TSR with Integrated LHe Vessel	926
	E.N. Zaplatin FZJ, Jülich, Germany
	Single- or Multi-Spoke SRF cavities are one of the basic accelerating structures for the low and intermediate energy part of many accelerators. Different types of external loads on the resonator walls predetermine the main working conditions of the SC cavities. The most important of them are very high electromagnetic fields that result in strong Lorentz forces acting on cavity walls and the pressure on cavity walls from the helium tank that also deforms the cavity shape. For the accelerators operating in pulsed regime the Lorentz forces are the dominant factor. The liquid helium vessel pressure instability even for 2K operations is the source of large microphonics and dominates for cw operation. Here we propose an innovative integrated helium vessel-cavity and stiffener design that will provide an effective passive damping minimizing df/dp ratio. Minimizing df/dp may be accomplished without an enhancement of the structure rigidity, which in turn minimizes the load on the cavity tuner. A separate stiffening scheme reducing Lorentz force cavity detuning to be added without violation of df/dp optimization. The developed at the Research Center in Jülich, Germany (FZJ) the 352 MHz, β=v/c=0.48 Triple-Spoke Resonator was used as an example to demonstrate the proposed conceptual integrated helium vessel-cavity design.
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THPLR036	SRF Low-Beta Elliptical Resonator Two-Ring Stiffening	929
	E.N. Zaplatin FZJ, Jülich, Germany I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Elliptical SRF cavities are the basic accelerating structures for the high energy part of many accelerators. Since a series of external loads on the resonator walls predetermine the main working conditions of the SC cavities the detailed investigation of their mechanical properties should be conducted in parallel with the main RF design. The effects of very high electromagnetic fields that result in strong Lorentz forces and the pressure on cavity walls from the helium tank that also deforms the cavity shape, the tuning scheme resulting in the change of accelerating field profile and mechanical eigen resonances of cavities which are the main source of the microphonics must be taken into account during integrated design of the resonator and its liquid helium vessel. SRF elliptical cavities for the medium energies (β=v/c is around 0.6) inherently have more flexible shape and their ultimate stiffening with a "standard" stiffening rings installed between resonator cells becomes problematic. The second row of the rings should enhance the overall cavity rigidity. In the paper we report the basic investigations of the cavity two-row ring stiffening using FNAL 650 MHz β=0.61 as an example. The single-cell investigation results were used as the reference to develop the ultimate scheme of the helium vessel structure to ensure the best resonator stability.
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THPLR037	Development of a Superconducting Twin Axis Cavity	932
SPWR031	use link to see paper's listing under its alternate paper code
	H. Park, A. Hutton, F. Marhauser JLab, Newport News, Virginia, USA S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA
	Superconducting cavities with two separate accelerating axes have been proposed in the past for energy recovery linac applications. While the study showed the advantages of such cavity, the designs present serious fabrication challenges. Hence the proposed cavities have never been built. The new design, elliptical twin cavity, proposed by Jefferson Lab and optimized by Center for Accelerator Science at Old Dominion University, allows similar level of engineering and fabrication techniques of a typical elliptical cavity. This paper describes preliminary LOM and HOM spectrum, engineering and fabrication processes of the twin axis cavity.
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THPLR038	Resonance Control for Narrow Bandwidth PIP-II Cavities	936
	W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov Fermilab, Batavia, Illinois, USA
	The PIP-II project at FNAL calls for a SRF pulsed proton driver linac to support the expanding neutrino physics program including DUNE/LBNF. The relatively low beam current and high quality factors called for in the design means that these cavities will be operated with small RF bandwidths, meaning that they will be sensitive to microphonics. Combined with a 20 Hz pulsed operational structure and the use of four different, complex cavity geometries means that resonance control will be extremely challenging. Work is ongoing at FNAL to develop active resonance stabilization techniques using fast piezoelectric tuners in support of PIP-II. These techniques as well as testing and development results using a prototype, dressed low-beta single-spoke cavity will be presented along with an outlook for future efforts.
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THPLR040	First Vertical Test of Superconducting QWR Prototype at RIKEN	939
	K. Yamada, O. Kamigaito, K. Ozeki, N. Sakamoto, K. Suda, Y. Watanabe RIKEN Nishina Center, Wako, Japan E. Kako, H. Nakai, K. Umemori KEK, Ibaraki, Japan A. Miyamoto, K. Sennyu, T. Yanagisawa MHI-MS, Kobe, Japan
	Development of a superconducting quarter-wavelength resonator (SC-QWR) was started at RIKEN Nishina Center to realize a low-velocity part of high-intensity ion linac. First prototype of the SC-QWR, frequency of which is 75.5 MHz, is fabricating now. Preparation of its partial components such as outer conductor, stem, bottom plate, and top plate was almost completed, and we are now studying a low-power RF property by clamping the every components as an assembly to obtain data for frequency tuning. After the adjustment of geometry of components and welding them, surface treatment by buffered chemical polishing and high-pressure rinsing will be performed in the summer. Preparation of vertical test for the SC-QWR is also in progress at KEK. The first result of vertical test for the prototype of SC-QWR will be presented in this contribution. This work was funded by the ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan). N. Sakamoto et al., Proceedings of SRF2015, WEBA06.
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THPLR041	650 MHz Elliptical Superconducting RF Cavities for PIP-II Project	943
	I.V. Gonin, E. Borissov, A. Grassellino, C.J. Grimm, V. Jain, S. Kazakov, V.A. Lebedev, A. Lunin, C.S. Mishra, D.V. Mitchell, T.H. Nicol, Y.M. Pischalnikov, G.V. Romanov, A.M. Rowe, N.K. Sharma, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	The PIP-II 800 MeV linac employs 650 MHz elliptical 5-cell CW-capable cavities to accelerate up to 2 mA peak beam current of H⁻ in the energy range 185 - 800 MeV. The low beta (LB) βG = 0.61 portion should accelerate from 185 MeV-500 MeV using 33 LB dressed cavities in 11 cryomodules. The high beta (HB) βG = 0.92 portion of the linac should accelerate from 500 to 800 MeV using 24 HB dressed cavities in 4 cryomodules. The development of both LB and HB cavities is going on under IIFC collaboration. The development of LB cavity initiated at VECC Kolkatta and HB cavity is going at RRCAT, Indore. This paper present design methodology adopted starting from RF design to get mechanical dimensions of the RF cells and then explains dressing of the cavity for both low beta and high beta cavities. Further the tuner design and its integration to the dressed cavity is discussed. Paper also explains the salient design features of these dressed cavities.
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THPLR044	First Performance Test on the Superconducting 217 MHz CH Cavity at 4.2 K	953
SPWR013	use link to see paper's listing under its alternate paper code
	F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech IAP, Frankfurt am Main, Germany W.A. Barth, M. Miski-Oglu GSI, Darmstadt, Germany W.A. Barth, M. Miski-Oglu HIM, Mainz, Germany
	Funding: HIM, GSI, BMBF Contr. No. 05P15RFRBA, EU Project MYRTE At the Institute for Applied Physics (IAP) of Frankfurt University a superconducting (sc) 217 MHz Crossbar-H-mode (CH) cavity with 15 accelerating cells and a gradient of 5.5 MV/m has been designed. The cavity is the key component of the demonstrator project at GSI which is the first stage to a new sc continuous wave (cw) linac for the production of Super Heavy Element (SHE) in the future. A successful and reliable beam operation of this first prototype will be a milestone on the way to the proposed linac. After fabrication at Research Instruments (RI) GmbH, Germany, the cavity without helium vessel has been commissioned at the new cryogenic test facility of the IAP with low level rf power at 4 K. The results of this first cold test will be presented in this contribution.
	Poster THPLR044 [4.540 MB]
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Paper

Title

Page

Vertical Test Results on ESS Medium Beta Elliptical Cavity Prototype

631

E. Cenni
CEA/IRFU, Gif-sur-Yvette, France
S. Berry, P. Bosland, F. Éozénou, L. Maurice, J. Plouin, C. Servouin
CEA/DSM/IRFU, France
G. Costanza
Lund University, Lund, Sweden
C. Darve
ESS, Lund, Sweden
G. Devanz, X. Hanus, F. Peauger, D. Roudier
CEA/DRF/IRFU, Gif-sur-Yvette, France

The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy at 2 GeV. The last Linac optimization, called Optimus+ [1], has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. This work presents the latest vertical test results on ESS medium beta elliptical cavity prototypes. We describe the cavity preparation procedure from buffer chemical polishing to vertical test. Finally magnetic probes (Fluxgate) were installed on the cavity to determine magnetic field background during vertical test. The latest vertical test results showed that our cavity design performance are beyond requirements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUP106006

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THPLR027

Progress Towards a 2.0 K Half-Wave Resonator Cryomodule for Fermilab's PIP-II Project

906

Z.A. Conway, A. Barcikowski, G.L. Cherry, R.L. Fischer, B.M. Guilfoyle, C.S. Hopper, M. Kedzie, M.P. Kelly, S.H. Kim, S.W.T. MacDonald, P.N. Ostroumov, T. Reid
ANL, Argonne, Illinois, USA
V.A. Lebedev, A. Lunin
Fermilab, Batavia, Illinois, USA

Funding: This material is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and Office of High-Energy Physics, Contracts No. DE-AC02-76-CH03000 and DE-AC02-06CH11357.
In support of Fermilab's Proton Improvement Plan-II project Argonne National Laboratory is constructing a superconducting half-wave resonator cryomodule. This cryomodule is designed to operate at 2.0 K, a first for low-velocity ion accelerators, and will accelerate ≥1 mA proton/H⁻ beams from 2.1 to 10.3 MeV. Since 2014 the construction of 9 162.5 MHz b = 0.112 superconducting half-wave resonators, the vacuum vessel and the majority of the cryomodule subsystems have been finished. Here we will update on the status of this work and report on preliminary cavity test results. This will include cavity performance measurements where we found residual resistances of < 3 nanoOhms at low fields and peak voltage gains of 5.9 MV, which corresponds to peak surface fields of 134 MV/m and 144 mT electric and magnetic respectively.

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR027

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THPLR028

Simulation of Mechanical Oscillations in PIP-II Cryomodule Using ACE3P

910

L. Xiao, O. Kononenko, C.-K. Ng
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
The linac in the PIP-II project at Fermilab consists of different sections of superconducting rf (SRF) cavities that can accelerate the proton beams to 800 MeV. At the end of the linac is a section containing a number of HB (β = 0.92) cryomodules operating at 650 MHz, with each cryomodule consisting of six SRF cavities. Previous calculations have been carried out to determine the mechanical modes of a single cavity in the 650 MHz cryomodule. In this paper, the parallel code suite ACE3P is used to evaluate the mechanical modes for a string of SRF cavities in the 650 MHz cryomodule. The effects of multi cavities on the mechanical mode frequencies and any possible coupling between cavities will be investigated.

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THPLR029

Update on the SC 325 MHz CH-Cavity and Power Coupler Processing

913

M. Busch, M. Amberg, M. Basten, F.D. Dziuba, P.A. Mundine, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany

Funding: Work supported by GSI, BMBF Contr. No. 05P15RFRBA
The 325 MHz CH-Cavity which has been developed and successfully vertically tested at the Institute for Applied Physics, Frankfurt, has reached the final production stage. The helium vessel has been welded to the frontal joints of the cavity and further tests in a horizontal environment are in preparation. Furthermore the corresponding power couplers have been conditioned and tested at a dedicated test stand up to the power level of 40 kW (pulsed) for the targeted beam operation. The final step of the whole prototype development is a beam test with a 11.4 AMeV, 10 mA ion beam at GSI, Darmstadt.

Poster THPLR029 [1.858 MB]

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THPLR030

Performances of the Two First Single Spoke Prototypes for the MYRRHA Project

916

D. Longuevergne, J.-L. Biarrotte, S. Blivet, P. Duchesne, G. Olry, H. Saugnac
IPN, Orsay, France
Y. Gómez Martínez
LPSC, Grenoble Cedex, France

Funding: This work is being supported by the Euratom research and training program 2014-2018 under grant agreement N°662186 (MYRTE project)
The MYRRHA project aims at the construction of an accelerator driven system (ADS) at MOL (Belgium) for irradiation and transmutation experiment purposes. The facility will feature a superconducting LINAC able to produce a proton flux of 2.4 MW (600 MeV - 4 mA). The first section of the superconducting LINAC will be composed of 352 MHz (β = 0.37) Single Spoke Resonators (SSR) housed in short cryomodules operating at 2K. After a brief presentation of the cryomodule design, this paper will aim at presenting the RF performances of the SSR tested in vertical cryostat in the framework of European MYRTE project (MYRRHA Research and Transmutation Endeavour) and at comparing experimental results (Lorentz forces, pressure sensitivity, multipacting barriers…) to simulated values.

Poster THPLR030 [1.610 MB]

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THPLR032

Update on SSR2 Cavity EM Design for PIP-II

920

P. Berrutti, T.N. Khabiboulline, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Proton Improvement Plan II (PIP-II) is the future plan for upgrading the Fermilab proton accelerator complex to a beam power capability of at least 1 MW delivered to the neutrino production target. A room temperature section accelerates H⁻ ions to 2.1 MeV and creates the desired bunch structure for injection into the superconducting (SC) linac. SC linac using five cavity types. One 162.5 MHz half wave resonator, two 325 MHz spoke resonators and two 650 MHz elliptical 5-cell cavities, provide acceleration to 800 MeV. The EM design of the second family of spoke resonator is presented in this paper. The work reported is a thorough electromagnetic study including: the RF parameters, multipacting mitigation and transverse field asymmetry. The cavity is now ready for structural design analysis.

Poster THPLR032 [1.947 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR032

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THPLR033

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

923

SPWR024

use link to see paper's listing under its alternate paper code

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

For future research in the field of Super Heavy Elements (SHE) a superconducting (sc) continuous wave (cw) ion LINAC with high intensity is highly desirable. Presently a multi-stage R&D program conducted by GSI, HIM and IAP[*] is in progress. The fundamental linac design composes a high performance ion source, a new low energy beam transport line, the High Charge State Injector (HLI) upgraded for cw, and a matching line (1.4 MeV/u) followed by the new sc-DTL LINAC for acceleration up to 7.3 MeV/u. The successful commissioning of the first Crossbar-H-mode (CH) cavity (Demonstrator), in a vertical cryo module, was a major milestone in 2015[**]. The next stage of the new sc cw heavy ion LINAC is the advanced demonstrator comprising a string of cavities and focusing elements build from several short constant-beta sc CH-cavities operated at 217MHz. Currently the first two sc 8 gap CH-cavities are under construction at Research Instruments (RI), Bergisch Gladbach, Germany. The new design without girders and with stiffening brackets at the front and end cap potentially reduces the overall technical risks during the construction phase and the pressure sensitivity of the cavity. The recent status of the construction phase as well as an outlook for further cavity development 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, IPAC14, THPME004
**F.Dziuba et al.,First Performance Test on the Superconducting 217 MHz CH Cavity at 4K,LINAC16, THPLR033

Poster THPLR033 [2.502 MB]

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THPLR035

FZJ SRF TSR with Integrated LHe Vessel

926

E.N. Zaplatin
FZJ, Jülich, Germany

Single- or Multi-Spoke SRF cavities are one of the basic accelerating structures for the low and intermediate energy part of many accelerators. Different types of external loads on the resonator walls predetermine the main working conditions of the SC cavities. The most important of them are very high electromagnetic fields that result in strong Lorentz forces acting on cavity walls and the pressure on cavity walls from the helium tank that also deforms the cavity shape. For the accelerators operating in pulsed regime the Lorentz forces are the dominant factor. The liquid helium vessel pressure instability even for 2K operations is the source of large microphonics and dominates for cw operation. Here we propose an innovative integrated helium vessel-cavity and stiffener design that will provide an effective passive damping minimizing df/dp ratio. Minimizing df/dp may be accomplished without an enhancement of the structure rigidity, which in turn minimizes the load on the cavity tuner. A separate stiffening scheme reducing Lorentz force cavity detuning to be added without violation of df/dp optimization. The developed at the Research Center in Jülich, Germany (FZJ) the 352 MHz, β=v/c=0.48 Triple-Spoke Resonator was used as an example to demonstrate the proposed conceptual integrated helium vessel-cavity design.

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THPLR036

SRF Low-Beta Elliptical Resonator Two-Ring Stiffening

929

E.N. Zaplatin
FZJ, Jülich, Germany
I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Elliptical SRF cavities are the basic accelerating structures for the high energy part of many accelerators. Since a series of external loads on the resonator walls predetermine the main working conditions of the SC cavities the detailed investigation of their mechanical properties should be conducted in parallel with the main RF design. The effects of very high electromagnetic fields that result in strong Lorentz forces and the pressure on cavity walls from the helium tank that also deforms the cavity shape, the tuning scheme resulting in the change of accelerating field profile and mechanical eigen resonances of cavities which are the main source of the microphonics must be taken into account during integrated design of the resonator and its liquid helium vessel. SRF elliptical cavities for the medium energies (β=v/c is around 0.6) inherently have more flexible shape and their ultimate stiffening with a "standard" stiffening rings installed between resonator cells becomes problematic. The second row of the rings should enhance the overall cavity rigidity. In the paper we report the basic investigations of the cavity two-row ring stiffening using FNAL 650 MHz β=0.61 as an example. The single-cell investigation results were used as the reference to develop the ultimate scheme of the helium vessel structure to ensure the best resonator stability.

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THPLR037

Development of a Superconducting Twin Axis Cavity

932

SPWR031

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

Superconducting cavities with two separate accelerating axes have been proposed in the past for energy recovery linac applications. While the study showed the advantages of such cavity, the designs present serious fabrication challenges. Hence the proposed cavities have never been built. The new design, elliptical twin cavity, proposed by Jefferson Lab and optimized by Center for Accelerator Science at Old Dominion University, allows similar level of engineering and fabrication techniques of a typical elliptical cavity. This paper describes preliminary LOM and HOM spectrum, engineering and fabrication processes of the twin axis cavity.

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THPLR038

Resonance Control for Narrow Bandwidth PIP-II Cavities

936

W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA

The PIP-II project at FNAL calls for a SRF pulsed proton driver linac to support the expanding neutrino physics program including DUNE/LBNF. The relatively low beam current and high quality factors called for in the design means that these cavities will be operated with small RF bandwidths, meaning that they will be sensitive to microphonics. Combined with a 20 Hz pulsed operational structure and the use of four different, complex cavity geometries means that resonance control will be extremely challenging. Work is ongoing at FNAL to develop active resonance stabilization techniques using fast piezoelectric tuners in support of PIP-II. These techniques as well as testing and development results using a prototype, dressed low-beta single-spoke cavity will be presented along with an outlook for future efforts.

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THPLR040

First Vertical Test of Superconducting QWR Prototype at RIKEN

939

K. Yamada, O. Kamigaito, K. Ozeki, N. Sakamoto, K. Suda, Y. Watanabe
RIKEN Nishina Center, Wako, Japan
E. Kako, H. Nakai, K. Umemori
KEK, Ibaraki, Japan
A. Miyamoto, K. Sennyu, T. Yanagisawa
MHI-MS, Kobe, Japan

Development of a superconducting quarter-wavelength resonator (SC-QWR) was started at RIKEN Nishina Center to realize a low-velocity part of high-intensity ion linac. First prototype of the SC-QWR, frequency of which is 75.5 MHz, is fabricating now*. Preparation of its partial components such as outer conductor, stem, bottom plate, and top plate was almost completed, and we are now studying a low-power RF property by clamping the every components as an assembly to obtain data for frequency tuning. After the adjustment of geometry of components and welding them, surface treatment by buffered chemical polishing and high-pressure rinsing will be performed in the summer. Preparation of vertical test for the SC-QWR is also in progress at KEK. The first result of vertical test for the prototype of SC-QWR will be presented in this contribution. This work was funded by the ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).
* N. Sakamoto et al., Proceedings of SRF2015, WEBA06.

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THPLR041

650 MHz Elliptical Superconducting RF Cavities for PIP-II Project

943

I.V. Gonin, E. Borissov, A. Grassellino, C.J. Grimm, V. Jain, S. Kazakov, V.A. Lebedev, A. Lunin, C.S. Mishra, D.V. Mitchell, T.H. Nicol, Y.M. Pischalnikov, G.V. Romanov, A.M. Rowe, N.K. Sharma, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

The PIP-II 800 MeV linac employs 650 MHz elliptical 5-cell CW-capable cavities to accelerate up to 2 mA peak beam current of H⁻ in the energy range 185 - 800 MeV. The low beta (LB) βG = 0.61 portion should accelerate from 185 MeV-500 MeV using 33 LB dressed cavities in 11 cryomodules. The high beta (HB) βG = 0.92 portion of the linac should accelerate from 500 to 800 MeV using 24 HB dressed cavities in 4 cryomodules. The development of both LB and HB cavities is going on under IIFC collaboration. The development of LB cavity initiated at VECC Kolkatta and HB cavity is going at RRCAT, Indore. This paper present design methodology adopted starting from RF design to get mechanical dimensions of the RF cells and then explains dressing of the cavity for both low beta and high beta cavities. Further the tuner design and its integration to the dressed cavity is discussed. Paper also explains the salient design features of these dressed cavities.

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THPLR044

First Performance Test on the Superconducting 217 MHz CH Cavity at 4.2 K

953

SPWR013

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F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech
IAP, Frankfurt am Main, Germany
W.A. Barth, M. Miski-Oglu
GSI, Darmstadt, Germany
W.A. Barth, M. Miski-Oglu
HIM, Mainz, Germany

Funding: HIM, GSI, BMBF Contr. No. 05P15RFRBA, EU Project MYRTE
At the Institute for Applied Physics (IAP) of Frankfurt University a superconducting (sc) 217 MHz Crossbar-H-mode (CH) cavity with 15 accelerating cells and a gradient of 5.5 MV/m has been designed. The cavity is the key component of the demonstrator project at GSI which is the first stage to a new sc continuous wave (cw) linac for the production of Super Heavy Element (SHE) in the future. A successful and reliable beam operation of this first prototype will be a milestone on the way to the proposed linac. After fabrication at Research Instruments (RI) GmbH, Germany, the cavity without helium vessel has been commissioned at the new cryogenic test facility of the IAP with low level rf power at 4 K. The results of this first cold test will be presented in this contribution.

Poster THPLR044 [4.540 MB]

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