PAC2013 - List of Authors (Huang, C.)

Paper	Title	Page
MOPAC23	Particle-In-Cell Modeling of Dielectric Wakefield Accelerator	114
	C. Huang, T.J. Kwan, D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory. Dielectric Wakefield Accelerator (DWA) holds the promise as an upgrade for the X-ray free electron laser of the proposed Los Alamos Matter-Radiation Interactions in Extremes signature facility. Our proof-of-concept DWA experiment aims to produce an acceleration gradient > 100 MV/m with < 0.1% induced beam energy spread. We design a 2.5ps double-triangular drive bunch and a trapezoidal witness bunch through the use of an electron beam mask followed by an Emittance Exchanger (EEX). To understand the DWA performance under transient dynamics, non-perfect EEX and other non-ideal effects, we use the Particle-In-Cell codes Merlin and LSP in 2D cylindrical and 3D geometries, respectively, to model our design. The benchmark shows good agreements with analytic theory on the longitudinal wakefield and the transformer ratio. Our simulations also indicate that longitudinal electric profile is highly insensitive to beam energy, radial distribution and emittance. We have investigated the transverse uniformity of the accelerating field and the effects of beam misalignment with radial beam offset. Full-scale simulation results for the planned experiment will be presented and discussed.

TUPAC18	Synchrotron Radiation Near Field In 3D	487
	C. Huang, B.E. Carlsten, T.J. Kwan LANL, Los Alamos, New Mexico, USA
	Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory. We extend the well-known 1D CSR analytic model into higher dimensions and develop a simple numerical algorithm based on the Lienard-Wiechert formula for the CSR field of a stiff beam. The CSR numerical model includes the 2D/3D spatial dependence of the field and is accurate for arbitrary beam energy. It also removes the singularity in space charge field presented in a 1D model. Good agreement is obtained with 1D CSR analytic result for FEL related beam parameters but deviations are also found for low-energy or large spot size beams and off-axis fields. To conduct self-consistent beam dynamics study, we also employ fully electromagnetic Particle-In-Cell (PIC) simulations for CSR modeling. The relatively large numerical phase error and anisotropy in the standard PIC algorithm is improved with a high order Finite Difference Time Domain scheme. We benchmark PIC results with our new numerical model. Detail self-consistent PIC simulations of the CSR fields and beam dynamics will be presented and discussed.

TUPMA13	Shaping Electron Bunches for Ultra-bright Electron Beam Acceleration in Dielectric Loaded Waveguides	613
	E.I. Simakov, C. Huang, T.J. Kwan, D.Y. Shchegolkov LANL, Los Alamos, New Mexico, USA
	Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory. We present the design of an Emittance Exchanger (EEX) which is employed to generate a pair of a double-triangular drive bunch and a trapezoidal witness bunch for a Dielectric Wakefield Accelerator (DWA). We consider the concept of a high-brightness DWA with the gradient of above 100 MV/m and less than 0.1% induced energy spread in the accelerated beam as a possible afterburner for the proposed Los Alamos Matter-Radiation Interactions in Extremes (MaRIE) signature facility. Scoping studies have identified large induced energy spreads as the major cause of beam quality degradation in high-gradient advanced accelerator technologies. Among advanced accelerator technologies, DWAs hold significant advantages over plasma wakefield accelerators due to the elimination of plasma-induced effects, the fact that having the wakefield in vacuum ensures linearity, and their higher technological maturity. We will present simulations with Elegant of the possible EEX beamline taking into account non-linear effects, coherent synchrotron radiation and longitudinal space charge. Possibilities for producing ideal beam shapes to demonstrate low induced energy spread in a DWA will be discussed.

Paper

Title

Page

Particle-In-Cell Modeling of Dielectric Wakefield Accelerator

114

C. Huang, T.J. Kwan, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.
Dielectric Wakefield Accelerator (DWA) holds the promise as an upgrade for the X-ray free electron laser of the proposed Los Alamos Matter-Radiation Interactions in Extremes signature facility. Our proof-of-concept DWA experiment aims to produce an acceleration gradient > 100 MV/m with < 0.1% induced beam energy spread. We design a 2.5ps double-triangular drive bunch and a trapezoidal witness bunch through the use of an electron beam mask followed by an Emittance Exchanger (EEX). To understand the DWA performance under transient dynamics, non-perfect EEX and other non-ideal effects, we use the Particle-In-Cell codes Merlin and LSP in 2D cylindrical and 3D geometries, respectively, to model our design. The benchmark shows good agreements with analytic theory on the longitudinal wakefield and the transformer ratio. Our simulations also indicate that longitudinal electric profile is highly insensitive to beam energy, radial distribution and emittance. We have investigated the transverse uniformity of the accelerating field and the effects of beam misalignment with radial beam offset. Full-scale simulation results for the planned experiment will be presented and discussed.

TUPAC18

Synchrotron Radiation Near Field In 3D

487

C. Huang, B.E. Carlsten, T.J. Kwan
LANL, Los Alamos, New Mexico, USA

Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.
We extend the well-known 1D CSR analytic model into higher dimensions and develop a simple numerical algorithm based on the Lienard-Wiechert formula for the CSR field of a stiff beam. The CSR numerical model includes the 2D/3D spatial dependence of the field and is accurate for arbitrary beam energy. It also removes the singularity in space charge field presented in a 1D model. Good agreement is obtained with 1D CSR analytic result for FEL related beam parameters but deviations are also found for low-energy or large spot size beams and off-axis fields. To conduct self-consistent beam dynamics study, we also employ fully electromagnetic Particle-In-Cell (PIC) simulations for CSR modeling. The relatively large numerical phase error and anisotropy in the standard PIC algorithm is improved with a high order Finite Difference Time Domain scheme. We benchmark PIC results with our new numerical model. Detail self-consistent PIC simulations of the CSR fields and beam dynamics will be presented and discussed.

TUPMA13

Shaping Electron Bunches for Ultra-bright Electron Beam Acceleration in Dielectric Loaded Waveguides

613

E.I. Simakov, C. Huang, T.J. Kwan, D.Y. Shchegolkov
LANL, Los Alamos, New Mexico, USA

Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.
We present the design of an Emittance Exchanger (EEX) which is employed to generate a pair of a double-triangular drive bunch and a trapezoidal witness bunch for a Dielectric Wakefield Accelerator (DWA). We consider the concept of a high-brightness DWA with the gradient of above 100 MV/m and less than 0.1% induced energy spread in the accelerated beam as a possible afterburner for the proposed Los Alamos Matter-Radiation Interactions in Extremes (MaRIE) signature facility. Scoping studies have identified large induced energy spreads as the major cause of beam quality degradation in high-gradient advanced accelerator technologies. Among advanced accelerator technologies, DWAs hold significant advantages over plasma wakefield accelerators due to the elimination of plasma-induced effects, the fact that having the wakefield in vacuum ensures linearity, and their higher technological maturity. We will present simulations with Elegant of the possible EEX beamline taking into account non-linear effects, coherent synchrotron radiation and longitudinal space charge. Possibilities for producing ideal beam shapes to demonstrate low induced energy spread in a DWA will be discussed.