U.S. Particle Accelerator School

Particle Driven Wakefield Accelerators

Sponsors:

University of California, San Diego Extension

Course Name:

Particle Driven Wakefield Accelerators

Instructors:

James Rosenzweig, UCLA; Michael Litos, University of Colorado; Spencer Gessner, CERN


Purpose and Audience
This course will introduce the physics associated with one of the most promising new accelerations techniques for enabling compact next generation accelerators through obtaining ultra-high gradients (i.e. > GV/m) byparticle-beam-driven wakefields. It is suitable for graduate students or upper division undergraduate students with an interest in this promising multi-disciplinary field. The course is also appropriate for physicists or engineers working in accelerator-related fields who wish to familiarize themselves with advanced accelerator concepts.

Prerequisites
Upper division Electromagnetism, Classical Mechanics, and knowledge of accelerators science and technology at the level of USPAS Fundamentals of Accelerator Physics and Technology with Simulations and Measurements Lab or USPAS graduate Accelerator Physics is required.

It is the responsibility of the student to ensure that he or she meets the course prerequisites or has equivalent experience.

Objectives
This course provides the fundamentals needed to understand particle-driven wakefield acceleration mechanisms, as well as some of the computational and experimental tools needed to explore the physical phenomena involved. It gives an introduction to the field, permitting the student to be conversant in the research literature describing the state-of-the-art, as well as a foundation for entering into this exciting field with promise to enable high gradient acceleration.

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
(To be provided by the USPAS) Fundamentals of Beam Physics II: Collective and Radiative Effects, by James Rosenzweig and Agostino Marinelli, (to be published). Additional materials and lecture notes will be provided by the instructors.

Suggested Reading 
- J. Rosenzweig, Fundamentals of Beam Physics, Oxford Univ. Press, 2003

- J. D. Lawson, The Physics of Charged-Particle Beams, Oxford Univ. Press, 1988

- A. Seryi, Unifying Physics of Accelerators, Lasers and Plasma, CRC Press, 2015

- F. Chen, Introduction to Plasma Physics, Springer, 2012

Credit Requirements
Students evaluation will be based on the homework and computer assignments (70 % of course grade) and a comprehensive final exam (30% of course grade).


UC San Diego course number: PHYS 40016
Indiana University course number and title on transcript: Physics 671, Advanced Topics in Accelerator Physics
Michigan State University course number: PHY 963
MIT course number: 8.790 Accelerator Physics