Particle Driven Wakefield Accelerators

Instructional Method
This course includes a series of lectures in the morning and in the afternoon, followed by computational laboratory sessions on related subject matter. Daily problem sets, to be completed outside of scheduled class time, will be assigned in the lecture sessions. The instructors will be available for guidance during evening homework sessions. There will be an open-book final exam at the conclusion of the course. 

Course Content

The course will begin with a review of the effects limiting the accelerating gradient in current accelerators within the context of applications to energy frontier colliders and next generation free-electron lasers. Noting the demand for scaling the accelerator electromagnetic wavelength to the mm-level or below in order to achieve GV/m fields, we introduce an alternative mechanism for producing the needed power: particle-beam driven wakefields. We first examine purely electromagnetic wakefields in metallic and dielectric structures.  A formalism for wakefield analysis is developed including the Panofsky-Wenzel theorem, the Fundamental Theorem of beam loading, and transformer ratio enhancement. Beam acceleration and transverse instability are discussed. Advanced dielectric wakefield accelerator designs with slab symmetry, photonic confinement, and electromagnetic focusing properties are examined. The use of dielectric wakefield accelerators (DWA) as very high-power mm-wave to THz sources is analyzed. Very high field nonlinear effects in dielectrics, and breakdown phenomena, are discussed.

Charged particle wakefields above a few GV/m field are supported in ionized matter, or plasma.  A linear electrostatic theory of plasma wakefield acceleration (PWFA) is developed and  used to analyze acceleration and focusing in the linear regime, as well as plasma compensation of beam self- and beam-beam- effects. The formation of beam equilibria such as Bennett pinches and related issues of emittance growth are covered.  The limitations of the linear regime being noted, we proceed to discuss the nonlinear “blowout” regime, in which emittance dilution in all phase planes is mitigated. Nonlinear plasma response in 1D and in 3D, accelerating wave steepening, and linear ion focusing is examined. Scaling laws governing the nonlinear regime of PWFA are developed. Issues such as beam-ion collisions and ion collapse are examined. Betatron motion and its attendant radiative processes are discussed. Problems such ion motion and hosing instability are analyzed. Injection of background electrons or through laser-controlled ionization, for production of extreme low emittance beams, are discussed. The use of positron and proton drivers for plasma wakefields and their relevant physics are introduced. 

The experimental state-of-the-art, including advanced methods developed specifically for PWFA and DWA experiments, is reviewed. Potential applications in particle physics and light source development, such as: electron-positron colliders, compact FELs, adiabatic plasma lenses, betatron radiation, terrestrial production of space-radiation spectra, and quasi-nonlinear resonance are discussed. Powerful computing tools will be used to understand and visualize wakefield concepts.

Reading Requirements
Course materials and lecture notes will be provided by the instructors.