PAC2013 - List of Authors (Yonehara, K.)

Paper

Title

Page

Algorithms and Self-consistent Simulations of Beam-induced Plasma in Muon Cooling Devices

186

V. Samulyak
BNL, Upton, Long Island, New York, USA
M. Chung, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, USA
R.D. Ryne
LBNL, Berkeley, California, USA
K. Yu
SBU, Stony Brook, USA

Funding: Research is partially supported by the DOE MAP program
Interaction of muon beams with plasma generated in muon cooling absorbers is an important issue affecting the efficiency of muon cooling. We have developed numerical algorithms and parallel software for self-consistent simulation of the plasma production and its interaction with particle beams and external electromagnetic fields. Simulations support the FNAL experimental program on dense hydrogen gas filled RF cavities proposed for muon beam phase space cooling and acceleration. The core code uses the particle-in-cell (PIC) method for the Maxwell equations coupled to the dynamics of particles. Electromagnetic PIC methods are combined with probabilistic treatment of atomic physics processes responsible for the plasma production. The PIC code supports the dynamics of multiple particle species undergoing rapid acceleration / deceleration (variable relativistic factor) and uses accurate charge and current conservation methods and symplectic discretization schemes. It is fully parallel and runs on multicore supercomputers. Benchmarks and simulations of experiments on gas-filled RF cavities will be discussed.

TUODA1

High Pressure Gas-Filled RF Cavities for Use in a Muon Cooling Channel

419

B.T. Freemire, P.M. Hanlet, Y. Torun
IIT, Chicago, Illinois, USA
M. Chung, M.R. Jana, M.A. Leonova, A. Moretti, T.A. Schwarz, A.V. Tollestrup, Y. Torun, K. Yonehara
Fermilab, Batavia, USA
M.G. Collura
Politecnico di Torino, Torino, Italy
R.P. Johnson
Muons, Inc, Illinois, USA

A high pressure hydrogen gas-filled RF (HPRF) cavity can operate in the multi-Tesla magnetic fields required for a muon accelerator cooling channel. A beam test was performed at the Fermilab MuCool Test Area by sending a 400 MeV proton beam through an 805 MHz cavity and quantifying the effects of the resulting plasma within the cavity. The resulting energy loss per electron-ion pair produced has been measured at 10^-18 to 10^-16 J every RF cycle. Doping the hydrogen gas with oxygen greatly decreases the lifetime of an electron, thereby improving the performance of the HPRF cavity. Electron lifetimes as short as 1 ns have been measured. The recombination rate of positive and negative ions in the cavity has been measured on the order of 10^-8 cm³/s. Extrapolation in both gas pressure and beam intensity are required to obtain Muon Collider parameters, however the results indicate HPRF cavities can be used in a muon accelerator cooling channel.

Slides TUODA1 [12.191 MB]

WEPMA12

Investigation of Breakdown Induced Surface Damage on 805 MHz Pill Box Cavity Interior Surfaces

1007

M.R. Jana, M. Chung, M.A. Leonova, A. Moretti, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, USA
D.L. Bowring
LBNL, Berkeley, California, USA
G. Flanagan
Muons, Inc, Illinois, USA
B.T. Freemire, Y. Torun
IIT, Chicago, Illinois, USA

The MuCool Test Area (MTA) at Fermilab is a facility to develop the technology required for ionization cooling for a future Muon Collider and/or Neutrino Factory. As part of this research program, we have tested an 805 MHz Pill Box RF cavity in multi-Tesla magnetic field to study the effects of the static magnetic field on the cavity operation. This study gives useful information on field emitters in the cavity, dark current, surface conditioning, breakdown mechanism and material properties of the cavity. All these factors determine the maximum accelerating gradient in the cavity. This paper discusses the image processing technique for the quantitative estimation of spark damage spot distribution on the Pill Box RF cavity interior surfaces. The distribution is compared with the electric field distribution predicted by computer code calculation. The local spark density is proportional to probability of surface breakdown and shows a power law dependence on the maximum electric field (E). This E dependence is consistent with dark current calculated from Fowler-Nordheim equation.

THPBA22

Helical Muon Beam Cooling Channel Engineering Design

1274

G. Flanagan, R.P. Johnson, S.A. Kahn, M.L. Neubauer
Muons, Inc, Illinois, USA
N. Andreev, R. Bossert, S. Krave, M.L. Lopes, J.C. Tompkins, K. Yonehara
Fermilab, Batavia, USA
F. Marhauser
MuPlus, Inc., Newport News, USA

Funding: DOE STTR Grant DE-SC0006266
The Helical Cooling Channel (HCC), a novel technique for six-dimensional (6D) ionization cooling of muon beams, has shown considerable promise based on analytic and simulation studies. However, the implementation of this revolutionary method of muon cooling requires new techniques for the integration of hydrogen-pressurized, high-power RF cavities into the low-temperature superconducting magnets of the HCC. We discuss progress and plans toward the critical path technology demonstrations of dielectric loaded 805 MHz RF cavities and 10 T Nb3Sn based Helical Solenoid magnet. Additionally we discuss integration challenges.

THPBA26

Elliptical Muon Helical Cooling Channel Coils

1286

S.A. Kahn, G. Flanagan
Muons, Inc, Illinois, USA
M.L. Lopes, K. Yonehara
Fermilab, Batavia, USA

Funding: U.S. DOE Grant Number DE-SC0006266
A helical cooling channel (HCC) consisting of a pressurized gas absorber imbedded in a magnetic channel that provides solenoid, helical dipole and helical quadrupole fields has shown considerable promise in providing six-dimensional phase space reduction for muon beams. The most effective approach to implementing the desired magnetic field is a helical solenoid (HS) channel composed of short solenoid coils arranged in a helical pattern. The HS channel along with an external solenoid allows the Bz and Bphi components along the reference orbit to be set to any desired values. To set dBphi/dr to the desired value for optimum focusing requires an additional variable. We shall show that using elliptical shaped coils in the HS channel allows the flexibility to achieve the desired dBphi/dr on orbit without significant change to Bz and Bphi.

THPHO19

A Charge Separation Study to Enable the Design of a Complete Muon Cooling Channel

1343

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

Funding: Work supported in part by DOE STTR grant DE-SC0007634
The most promising designs for 6D muon cooling channels operate on a specific sign of electric charge. In particular, the Helical Cooling Channel (HCC) and Rectilinear RFOFO designs are the leading candidates to become the baseline 6D cooling channel in the Muon Accelerator Program (MAP). Time constraints prevented the design of a realistic charge separator, so a simplified study was performed to emulate the effects of charge separation on muons exiting the front end of a muon collider. The output of the study provides particle distributions that the competing designs will use as input into their cooling channels. We report here on the study of the charge separator that created the simulated particles.

Paper	Title	Page
MOPBA06	Algorithms and Self-consistent Simulations of Beam-induced Plasma in Muon Cooling Devices	186
	V. Samulyak BNL, Upton, Long Island, New York, USA M. Chung, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, USA R.D. Ryne LBNL, Berkeley, California, USA K. Yu SBU, Stony Brook, USA
	Funding: Research is partially supported by the DOE MAP program Interaction of muon beams with plasma generated in muon cooling absorbers is an important issue affecting the efficiency of muon cooling. We have developed numerical algorithms and parallel software for self-consistent simulation of the plasma production and its interaction with particle beams and external electromagnetic fields. Simulations support the FNAL experimental program on dense hydrogen gas filled RF cavities proposed for muon beam phase space cooling and acceleration. The core code uses the particle-in-cell (PIC) method for the Maxwell equations coupled to the dynamics of particles. Electromagnetic PIC methods are combined with probabilistic treatment of atomic physics processes responsible for the plasma production. The PIC code supports the dynamics of multiple particle species undergoing rapid acceleration / deceleration (variable relativistic factor) and uses accurate charge and current conservation methods and symplectic discretization schemes. It is fully parallel and runs on multicore supercomputers. Benchmarks and simulations of experiments on gas-filled RF cavities will be discussed.

TUODA1	High Pressure Gas-Filled RF Cavities for Use in a Muon Cooling Channel	419
	B.T. Freemire, P.M. Hanlet, Y. Torun IIT, Chicago, Illinois, USA M. Chung, M.R. Jana, M.A. Leonova, A. Moretti, T.A. Schwarz, A.V. Tollestrup, Y. Torun, K. Yonehara Fermilab, Batavia, USA M.G. Collura Politecnico di Torino, Torino, Italy R.P. Johnson Muons, Inc, Illinois, USA
	A high pressure hydrogen gas-filled RF (HPRF) cavity can operate in the multi-Tesla magnetic fields required for a muon accelerator cooling channel. A beam test was performed at the Fermilab MuCool Test Area by sending a 400 MeV proton beam through an 805 MHz cavity and quantifying the effects of the resulting plasma within the cavity. The resulting energy loss per electron-ion pair produced has been measured at 10^-18 to 10^-16 J every RF cycle. Doping the hydrogen gas with oxygen greatly decreases the lifetime of an electron, thereby improving the performance of the HPRF cavity. Electron lifetimes as short as 1 ns have been measured. The recombination rate of positive and negative ions in the cavity has been measured on the order of 10^-8 cm³/s. Extrapolation in both gas pressure and beam intensity are required to obtain Muon Collider parameters, however the results indicate HPRF cavities can be used in a muon accelerator cooling channel.
	Slides TUODA1 [12.191 MB]

WEPMA12	Investigation of Breakdown Induced Surface Damage on 805 MHz Pill Box Cavity Interior Surfaces	1007
	M.R. Jana, M. Chung, M.A. Leonova, A. Moretti, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, USA D.L. Bowring LBNL, Berkeley, California, USA G. Flanagan Muons, Inc, Illinois, USA B.T. Freemire, Y. Torun IIT, Chicago, Illinois, USA
	The MuCool Test Area (MTA) at Fermilab is a facility to develop the technology required for ionization cooling for a future Muon Collider and/or Neutrino Factory. As part of this research program, we have tested an 805 MHz Pill Box RF cavity in multi-Tesla magnetic field to study the effects of the static magnetic field on the cavity operation. This study gives useful information on field emitters in the cavity, dark current, surface conditioning, breakdown mechanism and material properties of the cavity. All these factors determine the maximum accelerating gradient in the cavity. This paper discusses the image processing technique for the quantitative estimation of spark damage spot distribution on the Pill Box RF cavity interior surfaces. The distribution is compared with the electric field distribution predicted by computer code calculation. The local spark density is proportional to probability of surface breakdown and shows a power law dependence on the maximum electric field (E). This E dependence is consistent with dark current calculated from Fowler-Nordheim equation.

THPBA22	Helical Muon Beam Cooling Channel Engineering Design	1274
	G. Flanagan, R.P. Johnson, S.A. Kahn, M.L. Neubauer Muons, Inc, Illinois, USA N. Andreev, R. Bossert, S. Krave, M.L. Lopes, J.C. Tompkins, K. Yonehara Fermilab, Batavia, USA F. Marhauser MuPlus, Inc., Newport News, USA
	Funding: DOE STTR Grant DE-SC0006266 The Helical Cooling Channel (HCC), a novel technique for six-dimensional (6D) ionization cooling of muon beams, has shown considerable promise based on analytic and simulation studies. However, the implementation of this revolutionary method of muon cooling requires new techniques for the integration of hydrogen-pressurized, high-power RF cavities into the low-temperature superconducting magnets of the HCC. We discuss progress and plans toward the critical path technology demonstrations of dielectric loaded 805 MHz RF cavities and 10 T Nb3Sn based Helical Solenoid magnet. Additionally we discuss integration challenges.

THPBA26	Elliptical Muon Helical Cooling Channel Coils	1286
	S.A. Kahn, G. Flanagan Muons, Inc, Illinois, USA M.L. Lopes, K. Yonehara Fermilab, Batavia, USA
	Funding: U.S. DOE Grant Number DE-SC0006266 A helical cooling channel (HCC) consisting of a pressurized gas absorber imbedded in a magnetic channel that provides solenoid, helical dipole and helical quadrupole fields has shown considerable promise in providing six-dimensional phase space reduction for muon beams. The most effective approach to implementing the desired magnetic field is a helical solenoid (HS) channel composed of short solenoid coils arranged in a helical pattern. The HS channel along with an external solenoid allows the Bz and Bphi components along the reference orbit to be set to any desired values. To set dBphi/dr to the desired value for optimum focusing requires an additional variable. We shall show that using elliptical shaped coils in the HS channel allows the flexibility to achieve the desired dBphi/dr on orbit without significant change to Bz and Bphi.

THPHO19	A Charge Separation Study to Enable the Design of a Complete Muon Cooling Channel	1343
	C.Y. Yoshikawa, C.M. Ankenbrandt, R.P. Johnson Muons, Inc, Illinois, USA Y.S. Derbenev, V.S. Morozov JLAB, Newport News, Virginia, USA D.V. Neuffer, K. Yonehara Fermilab, Batavia, USA
	Funding: Work supported in part by DOE STTR grant DE-SC0007634 The most promising designs for 6D muon cooling channels operate on a specific sign of electric charge. In particular, the Helical Cooling Channel (HCC) and Rectilinear RFOFO designs are the leading candidates to become the baseline 6D cooling channel in the Muon Accelerator Program (MAP). Time constraints prevented the design of a realistic charge separator, so a simplified study was performed to emulate the effects of charge separation on muons exiting the front end of a muon collider. The output of the study provides particle distributions that the competing designs will use as input into their cooling channels. We report here on the study of the charge separator that created the simulated particles.