U.S. Particle Accelerator School
The Physics of Free Electron Lasers course
Sponsoring University:
University of New Mexico
Course:
The Physics of Free Electron Lasers
Instructors:
Dinh Nguyen and Quinn R. Marksteiner, Los Alamos National Lab
Purpose and Audience
This introductory course explores the physics of high-brightness radiation generated by relativistic electrons in free electron lasers (FEL) based on various configurations including low-gain oscillators, high-gain self-amplified spontaneous emission, seeded amplifiers, regenerative amplifiers, high-gain harmonic generation, and echo-enhanced harmonic generation.
PrerequisitesUpper division undergraduate courses in classical mechanics and in electromagnetism (at the level of "Introduction to Electrodynamics" by David J. Griffiths).
It is the responsibility of the student to ensure that they meet the course prerequisites or have equivalent experience.
Objectives
The purpose of this course is to introduce students, scientists and technologists to the physics of free‑electron lasers (FEL) driven by radio-frequency linear accelerators. Upon completion of this course, the students are expected to understand the basic concepts of how an FEL works. These basic concepts include (but not limited to) bunched beam radiation, energy and density modulations, gain, FEL saturation and synchrotron oscillations. They will be able to analyze the various FEL architectures (oscillator, self-amplified spontaneous emission, seeded amplifiers, regenerative amplifier, high-gain harmonic generation) in terms of electron beam requirements and FEL performance. They will also learn the quasi-coherent nature of the radiation produced by today’s SASE FEL and the contemporary techniques to improve the radiation coherence.
The course consists of lectures in both morning (theory and experiments) and afternoon sessions (simulations). Some of the afternoon sessions involve FEL simulation work. Optional evening sessions can be held to explain homework assignments.
Course Content- Introduction: properties of radiation, special relativity, basic features of FEL, fourth-generation light sources, brightness, pulse format.
- Synchrotron radiation: radiation from bending magnets, wigglers and undulators, harmonics, spectral brightness.
- Radiation from ensembles of electrons: superposition of wave trains, incoherent synchrotron radiation, coherent radiation from bunched beams, bunching factor.
- Motions in an undulator: transverse motion, transverse and longitudinal velocities, ponderomotive wave, pendulum equation, motion in phase-space, energy and density modulations.
- One-dimensional FEL theory: slowly varying envelope approximation, 1-D wave equation, Pierce parameter, 3rd order differential equation, solutions to cubic equation, growth rate.
- Low-gain oscillators: optical resonators, small-signal gain, gain saturation, cavity length detuning, gain and efficiency.
- Self-amplified spontaneous emission: start-up noise, exponential gain, saturation, spectral and coherence properties, 3-D effects, X-ray FELs.
- Seeded high-gain amplifier: optical guiding, group velocity reduction, regenerative amplifier, self-seeding, pre-bunching
- Harmonic generation: nonlinear harmonics, high-gain harmonic generation, echo-enhanced HGHG.
- FEL simulations: 1-D simulations (using MATLAB) and a 3-D FEL code (Genesis).
(to be provided by USPAS) “Free-Electron Lasers in the Ultraviolet and X-Ray Regime” 2nd edition (Springer 2014) by Peter Schmüser, Martin Dohlus and Jörg Rossbach. Instructors will also provide lecture notes.
Credit RequirementsStudents will be evaluated based on performance as follows: final exam (40% of final grade), homework assignments (30%) and computer class (30%).
IU/USPAS course number P671