John Adams Institute for Accelerator Science Lecture Series

RF breakdown is one of the major factors limiting the operating accelerating gradient in thus length and cost of rf particle accelerators. During work on normal conducting linear colliders the statistical nature of rf breakdown in the accelerating structures became apparent and the rf breakdown rate turn into a quantitative measure of the linac's high gradient performance.

We conjecture that the breakdown rate is linked to the movements of crystal defects induced by periodic mechanical stress due to exposure of metal to the rf fields. Therefore, by decreasing crystal mobility and increasing yield strength we will reduce the breakdown rate for the same accelerating gradient. We can achieve these properties by cooling a copper accelerating cavity to cryogenic temperatures. As a part of our study of basic physics of the rf breakdown, we tested an 11.4 GHz cryogenic copper accelerating cavity at high power. We measured low rf breakdown rate for surface electric fields near 500 MV/m at a flat gradient of 150 ns.

We are currently planning to use this improved high gradient performance of cryogenic accelerating cavities for an rf photoinjector, where a very large gradient could help to produce electron bunches with high brightness and low transverse emittances. These better beam parameters could in turn lead to shorter undulators and thus more compact FELs.

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John Adams Institute for Accelerator Science Lecture Series

Oxford Physics Plus

The John Adams Institute for Accelerator Science (adams-institute.ac.uk) is a centre of excellence in the UK for advanced and novel accelerator technology, providing expertise, research, development and training in accelerator techniques, and…


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The John Adams Institute for Accelerator Science (adams-institute.ac.uk) is a centre of excellence in the UK for advanced and novel accelerator technology, providing expertise, research, development and training in accelerator techniques, and promoting advanced accelerator applications in science and society.

The John Adams Institute is based at the University of Oxford, Royal Holloway University of London and Imperial College. We have a vibrant programme of academic lectures in accelerator science, aimed both at academics and graduate students, with the aim of keeping abreast of the latest developments in Accelerator Science.

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