Fundamentals of Timing and Synchronization with Applications to Accelerators

Sponsor:

Northern Illinois University

Course Name:

Fundamentals of Timing and Synchronization with Applications to Accelerators

Instructors:

Russell Wilcox, Gang Huang, Tong Zhou, Yilun Xu and Siyun Chen, Lawrence Berkeley National Lab

Purpose and Audience
This course is intended for accelerator physicists, electrical engineers, and operators/technicians who are interested in the design of timing systems and synchronization techniques for particle accelerators and light sources. The course focuses on transmission, measurement and control of high speed electromagnetic signals in transmission lines or waveguides, whether RF/microwave or optical. These systems are important in the distribution of timing reference information in accelerating systems, and diagnostic techniques to measure beams with respect to RF or ultrafast pulse signals. Examples include ultrafast pump/probe experiments in accelerator-based light sources, or diagnostics for short particle bunches.

Prerequisites
Lower division undergraduate courses in mathematics including linear algebra, differential equations, and calculus are required. Undergraduate level Electricity and Magnetism, including electromagnetic waves and Optics is required. Working knowledge of basic DC and AC circuit theory at an undergraduate level is required. Some exposure or experience with basic signal processing concepts and RF techniques (mixers, heterodyning, filters) is recommended. Some exposure or experience with basic programming language (python) and control theory is also recommended. The USPAS course on low level RF (LLRF) prior to this course is highly recommended, to provide a solid basis for the concepts and techniques in timing.

It is the responsibility of the student to ensure that they meet the course prerequisites or have equivalent experience.

Objectives
Students will be introduced to measurement and control of EM wave propagation methods and technology, followed by examples of timing and synchronization systems and beam timing/diagnostic systems for accelerator purposes. Because pulses laser synchronization is common in accelerators, an introduction to ultrafast laser technology and control methods will be provided. Students will learn concepts and techniques that apply equally to EM waves in the RF, microwave and optical domains, as well as differences in their technical implementation. The course enables students to understand how precise timing signals are transmitted and used in state-of-the-art systems. Concepts and technology for sub-picosecond, and even sub-femtosecond synchronization of ultrafast pulse optical sources, RF, and particle beams will be covered.

This course will introduce basic components and measurement techniques in RF technology and its application in developing accelerator timing systems. Phase locked loops will be analyzed and studied in experiments. Basic digital control and Field Programmable Gate Array (FPGA) program techniques will be introduced relevant to digital RF control in accelerator timing and synchronization. While we will cover these techniques at an introductory level, the present course is synergistic with the LLRF course which precedes it. Timing and sync builds on the same physics and engineering concepts and extends them, so they are best taken together.

Instructional Method
The course centers on laboratory experiments involving RF and optical signal transmission media, RF and optical sources, and methods of detection and control -- both analog and digital. Morning lectures cover the principles and devices to be used in the laboratory exercises, while daily homework to be completed outside of class covers analysis and reporting of the experimental data. In afternoon lab sessions, students work with continuous wave (CW) and pulsed lasers, RF and optical interferometers, fiber optics, high speed digitizers, FPGA-based signal processors, optical and RF modulators, and other measurement equipment, to test components of high frequency signal transmission and stabilization systems. During daily cycles of lecture/lab/homework we build up knowledge of the physics and technology of synchronization systems. Emphasis is on practical knowledge and application. 

Course Content
Fundamental concepts relating to time in EM wave propagation will be developed, including group and phase velocity, polarization, and time and frequency domain descriptions. Processing and control techniques such as phase and amplitude modulation, heterodyning and amplification will be presented, with attention to measurement uncertainty and noise leading to timing uncertainty. Principles of mode-locked laser oscillators and their control, ultrafast amplifiers and their timing issues, and optical synchronization and measurement techniques will be covered. The course assumes some familiarity with circuit fundamentals, and covers RF, optical waves and waveguides, photodetection, interferometers, laser fundamentals, optical coherence, and key RF and fiber optic components (e.g. directional couplers, modulators, harmonic generation, polarization controllers, mixers, amplifiers, and filters). Phase-locked loop control circuits are discussed, including hybrid microwave/optical loops, analog circuits, and purely digital implementations. The course stresses the complementary time-domain and frequency-domain descriptions of these circuit elements and behavior. Methods of low-noise digital RF detection and control are covered, centering on FPGA-based, high speed control. Techniques of computation particular to FPGAs will be covered. 

The course will examine the system implementations of timing distribution in accelerators and light sources. These include RF phase distribution to accelerator cavities, synchronization of pulsed lasers for photoinjectors and pump/probe experiments, and time references for beam diagnostics. Techniques to measure beam timing are discussed. Related applications covered illustrate other uses of these techniques.

Commonly used EVG/EVR system and white rabbit system will be introduced through lectures and hands-on experiments.

Reading Requirements
A collection of papers from the optical, microwave and accelerator literature and a copy of notes by the instructors will be provided.

(To be provided by the USPAS) Phase Noise and Frequency Stability in Oscillators (The Cambridge RF and Microwave Engineering Series) by Enrico Rubiola, 2018. Cambridge: Cambridge University Press. doi:10.1017/CBO9780511812798

Credit Requirements
Students will be evaluated based on performance: lab sessions (50% grade), homework (50% grade).

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.

Northern Illinois University course number: PHYS 790D Special Topics in Physics - Beam Physics
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