PAC2013 - List of Authors (Tollestrup, A.V.)

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.

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.