Physics Colloquium

Dr Steven Jamison, Accelerator Science and Technology Centre, STFC Daresbury National Laboratory

Thursday 22 October 2015, 1600-1700
Lecture Theatre 2, George Fox Building

Particle Accelerators in the femtosecond scale: from radio-frequency to laser driven acceleration

In particle accelerator x-ray sources, and in future particle physics machines, there is demand for GeV to TeV particle bunches with femtosecond duration, nearly 3-orders of magnitude shorter than possible in synchrotron storage rings.

Lasers are playing a critical role in pushing radio-frequency linear accelerators into this femtosecond regime, where even the measurement of particle beams requires new concepts to be developed. Non-linear optical processes allow non-destructive temporal measurements of particle bunches; optical clocks provide synchronisation for kilometre-scale machines, and laser-electron interactions are employed to stimulate (or suppress) collective instabilities in the particle beams. Looking further ahead, laser driven acceleration offers a route to particle accelerators that are inherently in the femtosecond scale, and with the potential to shrink physical scale of accelerators from kilometres to metres.

Starting with a tour of the physics behind femtosecond RF linear accelerators and x-ray sources, the talk will move on to discuss the potential and challenges of laser driven acceleration for future Free-electron laser x-ray sources. Recent work in the direct acceleration with laser-generated sub-picosecond single-cycle THz pulses will presented. With a novel concept for matching the phase velocity of the accelerating field with an electron beam, and >5MV/m accelerating fields demonstrated, the sources are already comparable to that of superconducting accelerators. A programme aimed at observing acceleration with injection of few-MeV beams from a conventional accelerator is underway, and experiments on the ALICE and VELA test accelerators at Daresbury Laboratory and will described.