IPAC2015 - List of Authors (Yonehara, K.)

Paper	Title	Page
MOAD2	RF Breakdown of 805 MHz Cavities in Strong Magnetic Fields	53
	D.L. Bowring, A.V. Kochemirovskiy, M.A. Leonova, A. Moretti, M.A. Palmer, D.W. Peterson, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA A.A. Haase SLAC, Menlo Park, California, USA P.G. Lane, Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA D. Stratakis BNL, Upton, Long Island, New York, USA
	Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.
	Slides MOAD2 [10.792 MB]
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MOPMN013	Simulation of Beam-Induced Plasma in Gas Filled Cavities	731
	K. Yu, V. Samulyak SBU, Stony Brook, USA M. Chung UNIST, Ulsan, Republic of Korea B.T. Freemire IIT, Chicago, Illinois, USA V. Samulyak BNL, Upton, Long Island, New York, USA A.V. Tollestrup, K. Yonehara Fermilab, Batavia, Illinois, USA
	Understanding of the interaction of muon beams with plasma in muon cooling devices is important for the optimization of the muon cooling process. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code, is used for the simulation support of the experimental program on the hydrogen gas filled RF cavity in the Mucool Test Area (MTA) at Fermilab. We have investigated the plasma dynamics in the RF cavity including the process of power dump by plasma (plasma loading), recombination of plasma, and plasma interaction with dopant material. By comparison with experiments in the MTA, simulations suggest several unknown properties of plasma such as the effective recombination rate, the electron attachment time on dopant molecule, and the ion - ion recombination rate in the plasma.
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MOPWI018	New Hadron Monitor By Using A Gas-Filled RF Resonator	1189
	K. Yonehara, A.V. Tollestrup, R.M. Zwaska Fermilab, Batavia, Illinois, USA G. Fasce CNI, Roma, Italy G. Flanagan, R.P. Johnson Muons, Inc, Illinois, USA
	It is trend to build an intense neutrino beam facility for the fundamental physics research, e.g. LBNF at Fermilab, T2K at KEK, and CNGS at CERN. They have investigated a hadron monitor to diagnose the primary/secondary beam quality. The existing hadron monitor based on an ionization chamber is not robust in the high-radiation environment vicinity of MW-class secondary particle production targets. We propose a gas-filled RF resonator to use as the hadron monitor since it is simple and hence radiation robust in this environment. When charged particles pass through the resonator they produce ionized plasma via the Coulomb interaction with the inert gas. The beam-induced plasma changes the permittivity of inert gas. As a result, a resonant frequency in the resonator shifts with the amount of ionized electrons. The radiation sensitivity is adjustable by the inert gas pressure and the RF amplitude. The hadron profile will be reconstructed with a tomography technique in the hodoscope which consists of X, Y, and theta layers by using a strip-shaped gas resonator. The sensitivity and possible system design will be shown in this presentation.
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TUPTY074	Muon Beam Emittance Evolution in the Helical Ionization Cooling Channel for Bright Muon Sources	2203
	K. Yonehara, C.Y. Yoshikawa Fermilab, Batavia, Illinois, USA C.M. Ankenbrandt, R.P. Johnson, S.A. Kahn Muons, Inc, Illinois, USA M. Chung UNIST, Ulsan, Republic of Korea Y.S. Derbenev, A.V. Sy JLab, Newport News, Virginia, USA B.T. Freemire IIT, Chicago, Illinois, USA
	The six-dimensional ionization cooling is essential to design a bright muon source. A geometry constraint is a challenge issue in a compact helical cooling channel (HCC). Especially, the HCC requires a large bore helical magnet and a compact helical RF system to incorporate the RF into the magnet chamber. A new emittance evolution has been designed to mitigate the geometry constraint. The HCC was functionally separated into three parts sections. The lattice at the initial section provides a large transverse acceptance by using a strong helical focus magnet. Once the transverse beam size is small enough to get into the compact RF the HCC lattice in the middle section generates a large longitudinal beta tune to dominate the longitudinal cooling. Consequently, the longitudinal emittance becomes smaller than the transverse one at the end of middle section. In the final section, the magnetic field strength is gradually reduced to match out the helical channel to the straight solenoid. As a result, the emittance exchange takes place and the final transverse emittance becomes smaller than the longitudinal one. The new emittance evolution scenario will be discussed in this presentation.
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TUPWI033	Matching into the Helical Bunch Coalescing Channel for a High Luminosity Muon Collider	2315
	A.V. Sy, Y.S. Derbenev, V.S. Morozov JLab, Newport News, Virginia, USA C.M. Ankenbrandt, R.P. Johnson Muons, Inc, Illinois, USA D.V. Neuffer, K. Yonehara, C.Y. Yoshikawa Fermilab, Batavia, Illinois, USA
	Funding: This work was supported in part by U.S. DOE STTR Grant DE-SC0007634. This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. For high luminosity in a muon collider, muon bunches that have been cooled in the six-dimensional helical cooling channel (HCC) must be merged into a single bunch and further cooled in preparation for acceleration and transport to the collider ring. The helical bunch coalescing channel has been previously simulated [, ] and provides the most natural match from helical upstream and downstream subsystems. This work focuses on the matching from the exit of the multiple bunch HCC into the start of the helical bunch coalescing channel. The simulated helical matching section simultaneously matches the helical spatial period λ in addition to providing the necessary acceleration for efficient bunch coalescing. Previous studies assumed that the acceleration of muon bunches from p=209.15 MeV/c to 286.816 MeV/c and matching of λ from 0.5 m to 1.0 m could be accomplished with zero particle losses and zero emittance growth in the individual bunches. This study demonstrates nonzero values for both particle loss and emittance growth, and provides considerations for reducing these adverse effects to best preserve high luminosity. C. Yoshikawa, et al., “Bunch Coalescing in a Helical Channel,” MAP-doc-4302-v2. **C. Yoshikawa, et al., “Bunch Coalescing in a Helical Channel,” IPAC12 TUPPD013, New Orleans, Louisiana, USA.
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TUPWI059	Influence of Plasma Loading in a Hybrid Muon Cooling Channel	2381
	D. Stratakis BNL, Upton, Long Island, New York, USA B.T. Freemire IIT, Chicago, Illinois, USA K. Yonehara Fermilab, Batavia, Illinois, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In a hybrid 6D cooling channel, cooling is accomplished by reducing the beam momentum through ionization energy loss in wedge absorbers and replenishing the momentum loss in the longitudinal direction with gas-filled rf cavities. While the gas acts as a buffer to prevent rf breakdown, gas ionization may also occur as the beam passes through a HPRF cavity. The resulting plasma, may gain substantial energy from the rf electric field which it can transfer via collisions to the gas, an effect known as plasma loading. In this paper, we investigate the influence of plasma loading on the cooling performance of a rectilinear hybrid channel. With the aid of numerical simulations we examine the sensitivity in cooling performance and plasma loading to key parameters such as the rf gradient and gas pressure.
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WEPWA057	Design Concepts for Muon-Based Accelerators	2633
	R.D. Ryne LBNL, Berkeley, California, USA Y.I. Alexahin, A.D. Bross, K. E. Gollwitzer, N.V. Mokhov, D.V. Neuffer, M.A. Palmer, K. Yonehara Fermilab, Batavia, Illinois, USA J.S. Berg, H.G. Kirk, R.B. Palmer, D. Stratakis BNL, Upton, Long Island, New York, USA S.A. Bogacz JLab, Newport News, Virginia, USA J.-P. Delahaye SLAC, Menlo Park, California, USA T.J. Roberts Muons, Inc, Illinois, USA P. Snopok Illinois Institute of Technology, Chicago, Illinois, USA
	Muon-based accelerators have the potential to enable facilities at both the Intensity and the Energy Frontiers. Muon storage rings can serve as high precision neutrino sources, and a muon collider is an ideal technology for a TeV or multi-TeV collider. Progress in muon accelerator designs has advanced steadily in recent years. In regard to 6D muon cooling, detailed and realistic designs now exist that provide more than 5 order-of-magnitude emittance reduction. Furthermore, detector performance studies indicate that with suitable pixelation and timing resolution, backgrounds in the collider detectors can be significantly reduced thus enabling high quality physics results. Thanks to these and other advances in design & simulation of muon systems, technology development, and systems demonstrations, muon storage-ring-based neutrino sources and a muon collider appear more feasible than ever before. A muon collider is now arguably among the most compelling approaches to a multi-TeV lepton collider. This paper summarizes the current status of design concepts for muon-based accelerators for neutrino factories and a muon collider.
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WEPTY030	Breakdown Characterization in 805 MHz Pillbox-like Cavity in Strong Magnetic Fields	3335
	A.V. Kochemirovskiy, D.L. Bowring, A. Moretti, D.W. Peterson, K. Yonehara Fermilab, Batavia, Illinois, USA M. Chung UNIST, Ulsan, Republic of Korea G. Flanagan, G.M. Kazakevich Muons, Inc, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA A.V. Kochemirovskiy University of Chicago, Chicago, Illinois, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	RF Breakdown in strong magnetic fields has a negative impact on a cavity performance. The MuCool Test Area at Fermilab has unique capabilities that that allow us to study the effects of static magnetic field on RF cavity operation. We have tested an 805 MHz pillbox-like cavity in external magnetic fields up to 5T. Results confirm our basic model of breakdown in strong magnetic fields. We have measured maximum achievable surface gradient dependence on external static magnetic field. Damage inspection of cavity walls revealed a unique observed breakdown pattern. We present the analysis of breakdown damage distribution and propose the hypothesis to explain certain features of this distribution
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WEPTY032	MICE Cavity Installation and Commissioning/Operation at MTA	3342
	M.A. Leonova, M. Backfish, D.L. Bowring, A.V. Kochemirovskiy, A. Moretti, D.W. Peterson, M. Popovic, Y. Torun, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA C. Hunt Imperial College of Science and Technology, Department of Physics, London, United Kingdom P.G. Lane Illinois Institute of Technology, Chicago, Illinois, USA T.H. Luo LBNL, Berkeley, California, USA D.C. Speirs, C.G. Whyte USTRAT/SUPA, Glasgow, United Kingdom T. Stanley STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
	A first electropolished 201-MHz RF cavity for the international Muon Ionization Cooling Experiment (MICE) has been assembled inside a special vacuum vessel and installed at the Fermilab's MuCool Test Area (MTA). The cavity and the MTA hall have been equipped with numerous instrumentation to characterize cavity operation. The cavity has been commissioned to run at 14 MV/m gradient with no external magnetic field; it is also being commissioned in presence of fringe field of a multi-Tesla superconducting solenoid magnet, the condition in which cavity modules will be operated in the MICE cooling channel. The assembly, installation and operation of the Single-Cavity Module gave valuable experience for operation of full-size modules at MICE.
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WEPTY050	Low Powered RF Measurements of Dielectric Materials for use in High Pressure Gas Filled RF Cavities	3387
	B.T. Freemire IIT, Chicago, Illinois, USA G. Arriaga Northern Illinois Univerity, Dekalb, Illinois, USA D.L. Bowring, A.V. Kochemirovskiy, A. Moretti, A.V. Tollestrup, Y. Torun, K. Yonehara Fermilab, Batavia, Illinois, USA H.D. Phan McDaniel College, Westminster, USA Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA
	The Helical Cooling Channel scheme envisioned for a Muon Collider or Neutrino Factory requires high pressure gas filled radio frequency cavities to operate in superconducting magnets. One method to shrink the radii of the cavities is to load them with a dielectric material. The dielectric constant, loss tangent, and dielectric strength are important in determining the most suitable material. Low powered RF measurements of the dielectric constant and loss tangent were taken for multiple purities of alumina and magnesium calcium titanate, as well as cordierite, forsterite, and aluminum nitride. Measurements of alumina were consistent with previously reported results. The results were used to design an insert for a high powered RF test that included sending beam through the cavity.
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WEPTY059	Alternative Methods for Field Corrections in Helical Solenoids	3409
	K.E. Melconian Texas A&M University, College Station, Texas, USA G. Flanagan, S.A. Kahn Muons, Inc, Illinois, USA S. Krave, M.L. Lopes, J.C. Tompkins, K. Yonehara Fermilab, Batavia, Illinois, USA
	Funding: Fermi Research Alliance under DOE Contract DE-AC02-07CH11359 Helical cooling channels have been proposed for highly efficient 6D muon cooling. Helical solenoids produce solenoidal, helical dipole, and helical gradient field components. Previous studies explored the geometric tunability limits on these main field components. In this paper we present two alternative correction schemes, tilting the solenoids and the addition of helical lines, to reduce the required strength of the anti-solenoid and add an additional tuning knob.
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Paper

Title

Page

RF Breakdown of 805 MHz Cavities in Strong Magnetic Fields

53

D.L. Bowring, A.V. Kochemirovskiy, M.A. Leonova, A. Moretti, M.A. Palmer, D.W. Peterson, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
A.A. Haase
SLAC, Menlo Park, California, USA
P.G. Lane, Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA
D. Stratakis
BNL, Upton, Long Island, New York, USA

Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.

Slides MOAD2 [10.792 MB]

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MOPMN013

Simulation of Beam-Induced Plasma in Gas Filled Cavities

731

K. Yu, V. Samulyak
SBU, Stony Brook, USA
M. Chung
UNIST, Ulsan, Republic of Korea
B.T. Freemire
IIT, Chicago, Illinois, USA
V. Samulyak
BNL, Upton, Long Island, New York, USA
A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, Illinois, USA

Understanding of the interaction of muon beams with plasma in muon cooling devices is important for the optimization of the muon cooling process. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code, is used for the simulation support of the experimental program on the hydrogen gas filled RF cavity in the Mucool Test Area (MTA) at Fermilab. We have investigated the plasma dynamics in the RF cavity including the process of power dump by plasma (plasma loading), recombination of plasma, and plasma interaction with dopant material. By comparison with experiments in the MTA, simulations suggest several unknown properties of plasma such as the effective recombination rate, the electron attachment time on dopant molecule, and the ion - ion recombination rate in the plasma.

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MOPWI018

New Hadron Monitor By Using A Gas-Filled RF Resonator

1189

K. Yonehara, A.V. Tollestrup, R.M. Zwaska
Fermilab, Batavia, Illinois, USA
G. Fasce
CNI, Roma, Italy
G. Flanagan, R.P. Johnson
Muons, Inc, Illinois, USA

It is trend to build an intense neutrino beam facility for the fundamental physics research, e.g. LBNF at Fermilab, T2K at KEK, and CNGS at CERN. They have investigated a hadron monitor to diagnose the primary/secondary beam quality. The existing hadron monitor based on an ionization chamber is not robust in the high-radiation environment vicinity of MW-class secondary particle production targets. We propose a gas-filled RF resonator to use as the hadron monitor since it is simple and hence radiation robust in this environment. When charged particles pass through the resonator they produce ionized plasma via the Coulomb interaction with the inert gas. The beam-induced plasma changes the permittivity of inert gas. As a result, a resonant frequency in the resonator shifts with the amount of ionized electrons. The radiation sensitivity is adjustable by the inert gas pressure and the RF amplitude. The hadron profile will be reconstructed with a tomography technique in the hodoscope which consists of X, Y, and theta layers by using a strip-shaped gas resonator. The sensitivity and possible system design will be shown in this presentation.

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TUPTY074

Muon Beam Emittance Evolution in the Helical Ionization Cooling Channel for Bright Muon Sources

2203

K. Yonehara, C.Y. Yoshikawa
Fermilab, Batavia, Illinois, USA
C.M. Ankenbrandt, R.P. Johnson, S.A. Kahn
Muons, Inc, Illinois, USA
M. Chung
UNIST, Ulsan, Republic of Korea
Y.S. Derbenev, A.V. Sy
JLab, Newport News, Virginia, USA
B.T. Freemire
IIT, Chicago, Illinois, USA

The six-dimensional ionization cooling is essential to design a bright muon source. A geometry constraint is a challenge issue in a compact helical cooling channel (HCC). Especially, the HCC requires a large bore helical magnet and a compact helical RF system to incorporate the RF into the magnet chamber. A new emittance evolution has been designed to mitigate the geometry constraint. The HCC was functionally separated into three parts sections. The lattice at the initial section provides a large transverse acceptance by using a strong helical focus magnet. Once the transverse beam size is small enough to get into the compact RF the HCC lattice in the middle section generates a large longitudinal beta tune to dominate the longitudinal cooling. Consequently, the longitudinal emittance becomes smaller than the transverse one at the end of middle section. In the final section, the magnetic field strength is gradually reduced to match out the helical channel to the straight solenoid. As a result, the emittance exchange takes place and the final transverse emittance becomes smaller than the longitudinal one. The new emittance evolution scenario will be discussed in this presentation.

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TUPWI033

Matching into the Helical Bunch Coalescing Channel for a High Luminosity Muon Collider

2315

A.V. Sy, Y.S. Derbenev, V.S. Morozov
JLab, Newport News, Virginia, USA
C.M. Ankenbrandt, R.P. Johnson
Muons, Inc, Illinois, USA
D.V. Neuffer, K. Yonehara, C.Y. Yoshikawa
Fermilab, Batavia, Illinois, USA

Funding: This work was supported in part by U.S. DOE STTR Grant DE-SC0007634. This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For high luminosity in a muon collider, muon bunches that have been cooled in the six-dimensional helical cooling channel (HCC) must be merged into a single bunch and further cooled in preparation for acceleration and transport to the collider ring. The helical bunch coalescing channel has been previously simulated [*, **] and provides the most natural match from helical upstream and downstream subsystems. This work focuses on the matching from the exit of the multiple bunch HCC into the start of the helical bunch coalescing channel. The simulated helical matching section simultaneously matches the helical spatial period λ in addition to providing the necessary acceleration for efficient bunch coalescing. Previous studies assumed that the acceleration of muon bunches from p=209.15 MeV/c to 286.816 MeV/c and matching of λ from 0.5 m to 1.0 m could be accomplished with zero particle losses and zero emittance growth in the individual bunches. This study demonstrates nonzero values for both particle loss and emittance growth, and provides considerations for reducing these adverse effects to best preserve high luminosity.
*C. Yoshikawa, et al., “Bunch Coalescing in a Helical Channel,” MAP-doc-4302-v2.
**C. Yoshikawa, et al., “Bunch Coalescing in a Helical Channel,” IPAC12 TUPPD013, New Orleans, Louisiana, USA.

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TUPWI059

Influence of Plasma Loading in a Hybrid Muon Cooling Channel

2381

D. Stratakis
BNL, Upton, Long Island, New York, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
K. Yonehara
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In a hybrid 6D cooling channel, cooling is accomplished by reducing the beam momentum through ionization energy loss in wedge absorbers and replenishing the momentum loss in the longitudinal direction with gas-filled rf cavities. While the gas acts as a buffer to prevent rf breakdown, gas ionization may also occur as the beam passes through a HPRF cavity. The resulting plasma, may gain substantial energy from the rf electric field which it can transfer via collisions to the gas, an effect known as plasma loading. In this paper, we investigate the influence of plasma loading on the cooling performance of a rectilinear hybrid channel. With the aid of numerical simulations we examine the sensitivity in cooling performance and plasma loading to key parameters such as the rf gradient and gas pressure.

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WEPWA057

Design Concepts for Muon-Based Accelerators

2633

R.D. Ryne
LBNL, Berkeley, California, USA
Y.I. Alexahin, A.D. Bross, K. E. Gollwitzer, N.V. Mokhov, D.V. Neuffer, M.A. Palmer, K. Yonehara
Fermilab, Batavia, Illinois, USA
J.S. Berg, H.G. Kirk, R.B. Palmer, D. Stratakis
BNL, Upton, Long Island, New York, USA
S.A. Bogacz
JLab, Newport News, Virginia, USA
J.-P. Delahaye
SLAC, Menlo Park, California, USA
T.J. Roberts
Muons, Inc, Illinois, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

Muon-based accelerators have the potential to enable facilities at both the Intensity and the Energy Frontiers. Muon storage rings can serve as high precision neutrino sources, and a muon collider is an ideal technology for a TeV or multi-TeV collider. Progress in muon accelerator designs has advanced steadily in recent years. In regard to 6D muon cooling, detailed and realistic designs now exist that provide more than 5 order-of-magnitude emittance reduction. Furthermore, detector performance studies indicate that with suitable pixelation and timing resolution, backgrounds in the collider detectors can be significantly reduced thus enabling high quality physics results. Thanks to these and other advances in design & simulation of muon systems, technology development, and systems demonstrations, muon storage-ring-based neutrino sources and a muon collider appear more feasible than ever before. A muon collider is now arguably among the most compelling approaches to a multi-TeV lepton collider. This paper summarizes the current status of design concepts for muon-based accelerators for neutrino factories and a muon collider.

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WEPTY030

Breakdown Characterization in 805 MHz Pillbox-like Cavity in Strong Magnetic Fields

3335

A.V. Kochemirovskiy, D.L. Bowring, A. Moretti, D.W. Peterson, K. Yonehara
Fermilab, Batavia, Illinois, USA
M. Chung
UNIST, Ulsan, Republic of Korea
G. Flanagan, G.M. Kazakevich
Muons, Inc, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
A.V. Kochemirovskiy
University of Chicago, Chicago, Illinois, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

RF Breakdown in strong magnetic fields has a negative impact on a cavity performance. The MuCool Test Area at Fermilab has unique capabilities that that allow us to study the effects of static magnetic field on RF cavity operation. We have tested an 805 MHz pillbox-like cavity in external magnetic fields up to 5T. Results confirm our basic model of breakdown in strong magnetic fields. We have measured maximum achievable surface gradient dependence on external static magnetic field. Damage inspection of cavity walls revealed a unique observed breakdown pattern. We present the analysis of breakdown damage distribution and propose the hypothesis to explain certain features of this distribution

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WEPTY032

MICE Cavity Installation and Commissioning/Operation at MTA

3342

M.A. Leonova, M. Backfish, D.L. Bowring, A.V. Kochemirovskiy, A. Moretti, D.W. Peterson, M. Popovic, Y. Torun, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
C. Hunt
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
P.G. Lane
Illinois Institute of Technology, Chicago, Illinois, USA
T.H. Luo
LBNL, Berkeley, California, USA
D.C. Speirs, C.G. Whyte
USTRAT/SUPA, Glasgow, United Kingdom
T. Stanley
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

A first electropolished 201-MHz RF cavity for the international Muon Ionization Cooling Experiment (MICE) has been assembled inside a special vacuum vessel and installed at the Fermilab's MuCool Test Area (MTA). The cavity and the MTA hall have been equipped with numerous instrumentation to characterize cavity operation. The cavity has been commissioned to run at 14 MV/m gradient with no external magnetic field; it is also being commissioned in presence of fringe field of a multi-Tesla superconducting solenoid magnet, the condition in which cavity modules will be operated in the MICE cooling channel. The assembly, installation and operation of the Single-Cavity Module gave valuable experience for operation of full-size modules at MICE.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY032

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WEPTY050

Low Powered RF Measurements of Dielectric Materials for use in High Pressure Gas Filled RF Cavities

3387

B.T. Freemire
IIT, Chicago, Illinois, USA
G. Arriaga
Northern Illinois Univerity, Dekalb, Illinois, USA
D.L. Bowring, A.V. Kochemirovskiy, A. Moretti, A.V. Tollestrup, Y. Torun, K. Yonehara
Fermilab, Batavia, Illinois, USA
H.D. Phan
McDaniel College, Westminster, USA
Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA

The Helical Cooling Channel scheme envisioned for a Muon Collider or Neutrino Factory requires high pressure gas filled radio frequency cavities to operate in superconducting magnets. One method to shrink the radii of the cavities is to load them with a dielectric material. The dielectric constant, loss tangent, and dielectric strength are important in determining the most suitable material. Low powered RF measurements of the dielectric constant and loss tangent were taken for multiple purities of alumina and magnesium calcium titanate, as well as cordierite, forsterite, and aluminum nitride. Measurements of alumina were consistent with previously reported results. The results were used to design an insert for a high powered RF test that included sending beam through the cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY050

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WEPTY059

Alternative Methods for Field Corrections in Helical Solenoids

3409

K.E. Melconian
Texas A&M University, College Station, Texas, USA
G. Flanagan, S.A. Kahn
Muons, Inc, Illinois, USA
S. Krave, M.L. Lopes, J.C. Tompkins, K. Yonehara
Fermilab, Batavia, Illinois, USA

Funding: Fermi Research Alliance under DOE Contract DE-AC02-07CH11359
Helical cooling channels have been proposed for highly efficient 6D muon cooling. Helical solenoids produce solenoidal, helical dipole, and helical gradient field components. Previous studies explored the geometric tunability limits on these main field components. In this paper we present two alternative correction schemes, tilting the solenoids and the addition of helical lines, to reduce the required strength of the anti-solenoid and add an additional tuning knob.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY059

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