PAC2013 - List of Authors (Chung, M.)

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.

TUOBB1

Space-charge Compensation for High-intensity Linear and Circular Accelerators at Fermilab

402

M. Chung, L.R. Prost, V.D. Shiltsev
Fermilab, Batavia, USA

Funding: Research supported by the U.S. Department of Energy.
Space-charge effects have long been recognized as a fundamental intensity limitation in high-intensity linear and circular accelerators. As the mission of the US high energy physics program is pushing the Intensity Frontier, it is very timely to explore novel schemes of space-charge compensation that could significantly improve the performance of leading high-intensity proton accelerator facilities such as Project-X. In this work, we present two activities at Fermilab on the space-charge compensation experiments based on residual gas ionization: 1) neutralized beam transport of continuous-wave (CW) H⁻ beam in Project-X Injector Experiment (PXIE); and 2) trapped electron plasmas for space-charge compensation in the newly proposed Integrable Optics Test Accelerators (IOTA) ring. Characteristics of the stability in the beam-plasma system, the dynamics of beam neutralization, and the transition between neutralized and un-neutralized beam transports are discussed for each configuration.

Slides TUOBB1 [1.543 MB]

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]

TUPAC15

Calculation of the Kick Maps Generated by a Hollow Electron Lens for Studies of High-energy Hadron Beam Collimation

481

G. Stancari, M. Chung, A. Valishev
Fermilab, Batavia, USA
H.-J. Lee
Pusan National University, Pusan, Republic of Korea
V. Moens
EPFL, Lausanne, Switzerland

Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. Research supported in part by US LARP and EU FP7 HiLumi LHC, Grant Agreement 284404.
Collimation with hollow electron beams is a technique for halo removal in high-power hadron beams. It was experimentally studied at the Fermilab Tevatron collider using electron lenses and it is being considered as an option to complement the collimation system for the LHC upgrades. In the ideal case, the magnetically confined electron beam has a hollow, axially symmetric current-density distribution, whose fields affect the beam halo, leaving the core of the circulating beam unperturbed. We address the effects of imperfections in the current density based upon profiles measured in the Fermilab electron lens test stand. We also study the effect of the bends used to inject and to extract the electron beam from the overlap region. The calculated field distributions will serve as inputs for tracking simulations, which are needed to estimate the effects of the electron lens imperfections on beam core dynamics, such as nonlinearities and emittance growth.

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.

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.

TUOBB1	Space-charge Compensation for High-intensity Linear and Circular Accelerators at Fermilab	402
	M. Chung, L.R. Prost, V.D. Shiltsev Fermilab, Batavia, USA
	Funding: Research supported by the U.S. Department of Energy. Space-charge effects have long been recognized as a fundamental intensity limitation in high-intensity linear and circular accelerators. As the mission of the US high energy physics program is pushing the Intensity Frontier, it is very timely to explore novel schemes of space-charge compensation that could significantly improve the performance of leading high-intensity proton accelerator facilities such as Project-X. In this work, we present two activities at Fermilab on the space-charge compensation experiments based on residual gas ionization: 1) neutralized beam transport of continuous-wave (CW) H⁻ beam in Project-X Injector Experiment (PXIE); and 2) trapped electron plasmas for space-charge compensation in the newly proposed Integrable Optics Test Accelerators (IOTA) ring. Characteristics of the stability in the beam-plasma system, the dynamics of beam neutralization, and the transition between neutralized and un-neutralized beam transports are discussed for each configuration.
	Slides TUOBB1 [1.543 MB]

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]

TUPAC15	Calculation of the Kick Maps Generated by a Hollow Electron Lens for Studies of High-energy Hadron Beam Collimation	481
	G. Stancari, M. Chung, A. Valishev Fermilab, Batavia, USA H.-J. Lee Pusan National University, Pusan, Republic of Korea V. Moens EPFL, Lausanne, Switzerland
	Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. Research supported in part by US LARP and EU FP7 HiLumi LHC, Grant Agreement 284404. Collimation with hollow electron beams is a technique for halo removal in high-power hadron beams. It was experimentally studied at the Fermilab Tevatron collider using electron lenses and it is being considered as an option to complement the collimation system for the LHC upgrades. In the ideal case, the magnetically confined electron beam has a hollow, axially symmetric current-density distribution, whose fields affect the beam halo, leaving the core of the circulating beam unperturbed. We address the effects of imperfections in the current density based upon profiles measured in the Fermilab electron lens test stand. We also study the effect of the bends used to inject and to extract the electron beam from the overlap region. The calculated field distributions will serve as inputs for tracking simulations, which are needed to estimate the effects of the electron lens imperfections on beam core dynamics, such as nonlinearities and emittance growth.

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.