VUV and X-ray Free Electron Lasers

Sponsoring University:

UC Davis Continuing and Professional Education

Course Name:

VUV and X-ray Free Electron Lasers
This class is limited to 20 students

Instructors:

Dinh Nguyen and Chris Mayes, xLight Inc; Nicole Neveu, SLAC
TA: Colwyn Gulliford, Xelera Research LLC

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 understand the fundamental concepts and basic components of VUV and x-ray FELs. After completing the course, the students will be able to 1) understand the functions and requirements of various components of an FEL, 2) become familiar with different VUV and XFEL techniques (SASE, seeded SASE, regenerative amplifier, XFELO, high-gain harmonic generation, echo-enhanced harmonic generation, 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 to generate ultrafast (i.e., femtosecond and attosecond) x-ray pulses with an XFEL.

Instructional Method
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, undulator radiation, harmonics, spectral brightness. transverse motion, transverse and longitudinal velocities, ponderomotive wave, pendulum equation, motion in phase-space, energy and density modulations, coherent radiation from bunched beams, x-ray FEL.
• Components of an XFEL: Electron beam requirements, RF photoinjector, laser heater, RF linac (copper and niobium), chicane bunch compressors, dechirpers, undulators, beam dump and x-ray optics.
• One-dimensional FEL theory: slowly varying envelope approximation, 1-D wave equation, FEL gain (Pierce) parameter, 3rd order differential equation, solutions to cubic equation, growth rate, optical guiding, and tapering.
• Self-amplified spontaneous emission: start-up noise, exponential gain, saturation, spectral and coherence properties, 3-D effects and Ming-Xie parameterization. 
• X-ray monochromatization: Bragg diffraction, Bragg crystals, self-seeding, RAFEL, XFELO, optical cavity, cavity alignments, and cavity power outcoupling.
• Harmonic generation techniques: nonlinear harmonics, high-gain harmonic generation, echo-enhanced HGHG, and harmoninc seeding.
• FEL simulations: 1-D simulations (using Python) and a 3-D 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 (40% of final grade), homework assignments (30%) and computer class (30%).

USPAS Computer Requirements
There will be no Computer Lab and all participants are required to bring their own portable computer to access online course notes and computer resources. This can be a laptop or a tablet with a sufficiently large screen and keyboard. Windows, Mac, and Linux-based systems that are wifi capable and have a standard web browser and mouse are all acceptable. You should have privileges for software installs. If you are unable to bring a computer, please contact uspas@fnal.gov ASAP to request a laptop loan. Very limited IT support and spare loaner laptops will be available during the session.

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