Instructors: Sergey Belomestnykh and Wencan Xu, Brookhaven National Laboratory
One-week course at USPAS 2011
Purpose and Audience
This graduate level course covers application of superconducting radio frequency (SRF) technology to contemporary high-beta accelerators: storage rings, pulsed and CW linacs, including energy recovery linacs (ERLs). The course will address physics and engineering aspects of using SRF in accelerators. It will cover beam-cavity interactions issues specific to superconducting cavities, a systems approach to designing SRF systems and engineering of superconducting cavity cryomodules. The course is intended for graduate students pursuing accelerator physics and graduate engineers and physicists who want to familiarize themselves with superconducting RF systems.
Prerequisites: Classical mechanics, thermodynamics, electrodynamics, and physical or engineering mathematics, all at entrance graduate level.
Objectives
Upon completion of this course, the students are expected to understand the physics underlying RF superconductivity and its application to accelerators, the advantages and limitations of SRF technology. The aim is to provide students with ideas and approaches enabling them to evaluate and solve problems related to application of superconducting cavities to accelerators, as well actively participate in engineering of SRF systems for various accelerators.
Instruction Method
This course includes a series of about 20 lectures and exercise sessions. Homework problems will be assigned which will be graded and answers provided in the exercise sessions. There will be an open-book, “take-home” final exam at the conclusion of the course.
Course Content
The course will include a brief introduction of the basic concepts of microwave cavities and the basic concepts of RF superconductivity. Then it will cover the beam-cavity interaction issues in accelerators: wake fields and higher-order modes (HOMs) in superconducting structures, associated with them bunched beam instabilities and approaches to deal with these instabilities (HOM absorbers and couplers, polarized cavities, etc.), bunch length manipulation with SRF cavities, beam loading effects, etc. Following that we will discuss a systems approach and its application to engineering of SRF systems for accelerators. Finally, we will address issues related to engineering of the SRF system components: cryostats, cavities, input couplers, HOM loads, and frequency tuners.
Reading Requirements
(to be provided by USPAS) “RF Superconductivity for Accelerators”, by H. Padamsee, J. Knobloch, and T. Hays, John Wiley & Sons, 2nd edition (2008).
It is recommended that students re-familiarize themselves with the fundamentals of electrodynamics at the level of “Fields and Waves in Communication Electronics“ (Chapters 1 through 11) by S. Ramo, J. R. Whinnery, and T. Van Duzer, John Wiley & Sons, 3rd edition (1994) or “Classical Electrodynamics” (Chapters 1 through 8) by J. D. Jackson, John Wiley & Sons, 3rd edition (1999).
Additional suggested reference books (not provided by USPAS):
“Handbook of Accelerator Physics and Engineering”, edited by A. W. Chao and M. Tigner, World Scientific, 3rd print (2006)
“RF Superconductivity: Science, Technology, and Applications,” by H. Padamsee, Wiley-VCH (2009).
"Introduction to Wakefields and Wake Potentials" by P. B. Wilson, SLAC-PUB-4547 (1989).
"High Energy Electron Linacs: Application to Storage Ring RF Systems and Linear Colliders" by P. B. Wilson, SLAC-PUB-2884 (1982).
"Fundamental-Mode RF Design in e+e- Storage Ring Factories" by P. B. Wilson, SLAC-PUB-6062 (1993).
Credit Requirements
Students will be evaluated based on the following performances: final exam (40%), homework assignments and class participation (30%), Computer Lab project (20%).
Computer Lab and Codes
Computer Lab Project
The objective of this project is to compare two different single-cell geometries of superconducting RF cavities for a high-current storage ring, such as a third-generation light source, using two computer codes: SUPERFISH and ABCI. The cavity fundamental mode frequency is 500 MHz, the accelerating voltage is 2 MV, the beam pipe diameter is 100 mm, the peak surface electric filed should not exceed 40 MV/m, the peak surface magnetic field should not exceed 100 mT, the Nb cavity is assumed to operate at 4.5 K. Beam parameters: the average current is 500 mA, the rms bunch length is 10 mm, the beam repetition frequency is 50 MHz.
Elliptical cavity
Quarter Wave Resonator (QWR)
Comparison of two geometries
Lecture Notes and Homework Problems
Monday
Fundamentals of RF and microwave engineering
Basic concepts of RF superconductivity
Tuesday
Derivation of the RF power formula for a beam loaded cavity can be found in RF_power_with_beam_loading.pdf
Wednesday
Thursday
Friday
Fabrication techniques and cavity preparation
Questions? Send email to S. Belomestnykh or W. Xu.