2011 Particle Accelerator Conference - List of Authors (Yonehara, K.)

Paper	Title	Page
MOP047	Helical Channels with Variable Slip Factor for Neutrino Factories and Muon Colliders	187
	C. Y. Yoshikawa, C.M. Ankenbrandt Muons, Inc, Batavia, USA D.V. Neuffer, K. Yonehara Fermilab, Batavia, USA
	Funding: Supported in part by DOE SBIR grant DE-SC0002739. In order to realize a muon collider or a neutrino factory based on a muon storage ring, the muons must be captured and cooled efficiently. For a muon collider, the resulting train of bunches should be coalesced into a single bunch. Design concepts for a system to capture, cool, and coalesce a muon beam are described here. In particular, variants of a helical channel are used, taking advantage of the ability to vary the slip factor and other parameters of such a channel. The cooling application has been described before; this paper reports recent studies of a system that includes two novel concepts to accomplish capture and coalescing via a slip-controlled helical channel.

MOP032	High Pressure RF Cavity Test at Fermilab	160
	B.T. Freemire, P.M. Hanlet, Y. Torun IIT, Chicago, Illinois, USA G. Flanagan, R.P. Johnson, M. Notani Muons, Inc, Batavia, USA M.R. Jana, A. Moretti, M. Popovic, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, USA D.M. Kaplan Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: Supported in part by DOE STTR grant DE-FG02-08ER86350 Operating a high gradient radio frequency cavity embedded in a strong magnetic field is an essential requirement for muon beam cooling. However, a magnetic field influences the maximum RF gradient due to focusing of dark current in the RF cavity. This problem is suppressed by filling the RF cavity with dense hydrogen gas. As the next step, we plan to explore the beam loading effect in the high pressure cavity by using a 400 MeV kinetic energy proton beam in the MuCool Test Area at Fermilab. We discuss the experimental setup and instrumentation.

MOP046	RF Breakdown Studies Using Pressurized Cavities	184
	R. Sah, A. Dudas, R.P. Johnson, M.L. Neubauer Muons, Inc, Batavia, USA M. BastaniNejad, A.A. Elmustafa Old Dominion University, Norfolk, Virginia, USA J.M. Byrd, D. Li LBNL, Berkeley, California, USA M.E. Conde, W. Gai ANL, Argonne, USA A. Moretti, M. Popovic, K. Yonehara Fermilab, Batavia, USA D. Rose Voss Scientific, Albuquerque, New Mexico, USA
	Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86352 and FRA DOE Contract DE-AC02-07CH11359 Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved, and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual gas and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of radiofrequency and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) has been built, and a series of detailed experiments is planned at the Argonne Wakefield Accelerator. These experiments will be followed by additional experiments using a second test cell operating at 402.5 MHz.

TUP172	Studies of High-field Sections of a Muon Helical Cooling Channel with Coil Separation	1148
	M.L. Lopes, V.S. Kashikhin, K. Yonehara, M. Yu, A.V. Zlobin Fermilab, Batavia, USA
	Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. The Helical Cooling Channel (HCC) was proposed for 6D cooling of muon beams required for muon collider and some other applications. HCC uses a continuous absorber inside superconducting magnets which produce solenoidal field superimposed with transverse helical dipole and helical gradient fields. HCC is usually divided into several sections each with progressively stronger fields, smaller aperture and shorter helix period to achieve the optimal muon cooling rate. This paper presents the design issues of the high field section of HCC with coil separation. The effect of coil spacing on the longitudinal and transverse field components is presented and its impact on the muon cooling is evaluated and discussed. The paper also describes methods for field corrections and their practical limits.

TUP092	Multi-purpose 805 MHz Pillbox RF Cavity for Muon Acceleration Studies	1003
	G.M. Kazakevich, G. Flanagan, R.P. Johnson, M.L. Neubauer, R. Sah Muons, Inc, Batavia, USA K.C.D. Chan, A.J. Jason, S.S. Kurennoy, H.M. Miyadera, P.J. Turchi LANL, Los Alamos, New Mexico, USA A. Moretti, M. Popovic, K. Yonehara Fermilab, Batavia, USA Y. Torun IIT, Chicago, Illinois, USA
	Funding: Supported by DOE grant DE-FG-08ER86352. An 805 MHz RF pillbox cavity has been designed and constructed to investigate potential muon beam acceleration and cooling techniques. The cavity can operate in vacuum or under pressure to 100 atmospheres, at room temperature or in an LN2 bath at 77 K. The cavity is designed for easy assembly and disassembly with bolted construction using aluminum seals. The surfaces of the end walls of the cavity can be replaced with different materials such as copper, aluminum, beryllium, or molybdenum, and with different geometries such as shaped windows or grid structures. Different surface treatments such as electro polished, high-pressure water cleaned, and atomic layer deposition are being considered for testing. The cavity has been designed to fit inside the 5-Tesla solenoid in the MuCool Test Area at Fermilab. Performance of the cavity, including initial conditioning and operation in the external magnetic field will be reported.

Paper

Title

Page

Helical Channels with Variable Slip Factor for Neutrino Factories and Muon Colliders

187

C. Y. Yoshikawa, C.M. Ankenbrandt
Muons, Inc, Batavia, USA
D.V. Neuffer, K. Yonehara
Fermilab, Batavia, USA

Funding: Supported in part by DOE SBIR grant DE-SC0002739.
In order to realize a muon collider or a neutrino factory based on a muon storage ring, the muons must be captured and cooled efficiently. For a muon collider, the resulting train of bunches should be coalesced into a single bunch. Design concepts for a system to capture, cool, and coalesce a muon beam are described here. In particular, variants of a helical channel are used, taking advantage of the ability to vary the slip factor and other parameters of such a channel. The cooling application has been described before; this paper reports recent studies of a system that includes two novel concepts to accomplish capture and coalescing via a slip-controlled helical channel.

MOP032

High Pressure RF Cavity Test at Fermilab

160

B.T. Freemire, P.M. Hanlet, Y. Torun
IIT, Chicago, Illinois, USA
G. Flanagan, R.P. Johnson, M. Notani
Muons, Inc, Batavia, USA
M.R. Jana, A. Moretti, M. Popovic, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, USA
D.M. Kaplan
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Supported in part by DOE STTR grant DE-FG02-08ER86350
Operating a high gradient radio frequency cavity embedded in a strong magnetic field is an essential requirement for muon beam cooling. However, a magnetic field influences the maximum RF gradient due to focusing of dark current in the RF cavity. This problem is suppressed by filling the RF cavity with dense hydrogen gas. As the next step, we plan to explore the beam loading effect in the high pressure cavity by using a 400 MeV kinetic energy proton beam in the MuCool Test Area at Fermilab. We discuss the experimental setup and instrumentation.

MOP046

RF Breakdown Studies Using Pressurized Cavities

184

R. Sah, A. Dudas, R.P. Johnson, M.L. Neubauer
Muons, Inc, Batavia, USA
M. BastaniNejad, A.A. Elmustafa
Old Dominion University, Norfolk, Virginia, USA
J.M. Byrd, D. Li
LBNL, Berkeley, California, USA
M.E. Conde, W. Gai
ANL, Argonne, USA
A. Moretti, M. Popovic, K. Yonehara
Fermilab, Batavia, USA
D. Rose
Voss Scientific, Albuquerque, New Mexico, USA

Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86352 and FRA DOE Contract DE-AC02-07CH11359
Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved, and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual gas and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of radiofrequency and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) has been built, and a series of detailed experiments is planned at the Argonne Wakefield Accelerator. These experiments will be followed by additional experiments using a second test cell operating at 402.5 MHz.

TUP172

Studies of High-field Sections of a Muon Helical Cooling Channel with Coil Separation

1148

M.L. Lopes, V.S. Kashikhin, K. Yonehara, M. Yu, A.V. Zlobin
Fermilab, Batavia, USA

Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
The Helical Cooling Channel (HCC) was proposed for 6D cooling of muon beams required for muon collider and some other applications. HCC uses a continuous absorber inside superconducting magnets which produce solenoidal field superimposed with transverse helical dipole and helical gradient fields. HCC is usually divided into several sections each with progressively stronger fields, smaller aperture and shorter helix period to achieve the optimal muon cooling rate. This paper presents the design issues of the high field section of HCC with coil separation. The effect of coil spacing on the longitudinal and transverse field components is presented and its impact on the muon cooling is evaluated and discussed. The paper also describes methods for field corrections and their practical limits.

TUP092

Multi-purpose 805 MHz Pillbox RF Cavity for Muon Acceleration Studies

1003

G.M. Kazakevich, G. Flanagan, R.P. Johnson, M.L. Neubauer, R. Sah
Muons, Inc, Batavia, USA
K.C.D. Chan, A.J. Jason, S.S. Kurennoy, H.M. Miyadera, P.J. Turchi
LANL, Los Alamos, New Mexico, USA
A. Moretti, M. Popovic, K. Yonehara
Fermilab, Batavia, USA
Y. Torun
IIT, Chicago, Illinois, USA

Funding: Supported by DOE grant DE-FG-08ER86352.
An 805 MHz RF pillbox cavity has been designed and constructed to investigate potential muon beam acceleration and cooling techniques. The cavity can operate in vacuum or under pressure to 100 atmospheres, at room temperature or in an LN2 bath at 77 K. The cavity is designed for easy assembly and disassembly with bolted construction using aluminum seals. The surfaces of the end walls of the cavity can be replaced with different materials such as copper, aluminum, beryllium, or molybdenum, and with different geometries such as shaped windows or grid structures. Different surface treatments such as electro polished, high-pressure water cleaned, and atomic layer deposition are being considered for testing. The cavity has been designed to fit inside the 5-Tesla solenoid in the MuCool Test Area at Fermilab. Performance of the cavity, including initial conditioning and operation in the external magnetic field will be reported.