U.S. Particle Accelerator School
VUV and X-ray Free Electron Lasers
Sponsoring University:
Texas A&M University
Course Name:
VUV and X-ray Free Electron Lasers
Instructors:
Dinh Nguyen, SLAC National Accelerator Laboratory and Petr Anisimov, Los Alamos National Laboratory; Nicole Neveu, SLAC National Accelerator Laboratory
Purpose and Audience
This one-week course introduces the physics of coherent radiation generation in a free electron laser (FEL) driven by RF linac and operating in the vacuum ultraviolet (VUV) and x-ray regions. The topics to be discussed include high-brightness electron beam generation and acceleration, bunch compression, incoherent undulator radiation, coherent radiation in an FEL, self-amplified spontaneous emission (SASE), Bragg crystal monochromatization, self-seeding, Regenerative Amplifiers (RAFEL) and XFEL Oscillators (XFELO), as well as various harmonic generation techniques.
Prerequisites
Upper 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 VUV and x-ray free-electron lasers (XFEL) driven by radio-frequency linear accelerators. Upon completion of this course, the students are expected to 1) understand the working principles of an FEL, 2) know the main components, such as the photoinjector, bunch compressor, RF linac and undulators, of a modern x-ray FEL, 2) become familiar with different radiation generating techniques (SASE, seeded SASE, regenerative amplifier, XFELO, harmonic generation, EEHG, etc.) and 3) be able to analyze and compare different VUV and XFEL configurations in terms of electron beam requirements and FEL performance. They will also learn the contemporary techniques of generating femtosecond x-ray pulses at high repetition rates with x-ray FELs driven by superconducting linac.
Instructional Method
The course consists of the morning lectures on FEL course materials and simulations, and afternoon laboratory for computer simulations using both one-dimensional and three-dimensional FEL codes. Help sessions are available in the evening to explain the homework assignments and to help with the computer lab work.
Course Content
- Introduction: properties of radiation, motions in an undulator, undulator radiation, harmonics, spectral brightness, interaction of electrons with the ponderomotive wave, motion in phase-space, energy and density modulations, coherent bunched beam radiation, self-amplified spontaneous emission, start-up noise, exponential gain, saturation, spectral and coherence properties.
- One-dimensional FEL theory: slowly varying envelope approximation, wave equation, FEL gain (Pierce) parameter, 3rd order differential equation, solutions to cubic equation, exponential growth, 1D gain length, and 3D parameterization.
- Components of an XFEL: RF photoinjector, emittance growth and emittance compensation, acceleration in an RF linac, chicane bunch compressors, laser heater, undulators and x-ray optics.
- X-ray monochromatization: Bragg diffraction, Bragg crystals, self-seeding, Regenerative Amplifier FEL, XFEL oscillator, optical cavity, cavity alignments, and cavity power outcoupling.
- Harmonic generation techniques: nonlinear harmonics, high-gain harmonic generation, echo-enhanced harmonic generation, and harmonic seeding.
- FEL simulations: 1D simulations (using Python) and a 3D FEL code (Genesis).
Reading Requirements
(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 Requirements
Students will be evaluated based on performance as follows: final exam (20% of final grade), homework assignments (40%) and computer lab (40%).
Indiana University course number: Physics 671, Advanced Topics in Accelerator Physics
Michigan State University course number: PHY 963, "U.S. Particle Accelerator School"
MIT course number: 8.790, Accelerator Physics