Accelerator physics

Abstract: The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30-50 MeV m(-1) gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. These ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams.

Abstract: The use of infrared lasers to power optical-scale lithographically fabricated particle accelerators is a developing area of research that has garnered increasing interest in recent years The physics and technology of this approach is reviewed, which is referred to as dielectric laser acceleration (DLA) In the DLA scheme operating at typical laser pulse lengths of 01 to 1 ps, the laser damage fluences for robust dielectric materials correspond to peak surface electric fields in the $\mathrm{GV}/\mathrm{m}$ regime The corresponding accelerating field enhancement represents a potential reduction in active length of the accelerator between 1 and 2 orders of magnitude Power sources for DLA-based accelerators (lasers) are less costly than microwave sources (klystrons) for equivalent average power levels due to wider availability and private sector investment Because of the high laser-to-particle coupling efficiency, required pulse energies are consistent with tabletop microJoule class lasers Combined with the very high (MHz) repetition rates these lasers can provide, the DLA approach appears promising for a variety of applications, including future high-energy physics colliders, compact light sources, and portable medical scanners and radiative therapy machines

Abstract: THE possibility of creating ordered ion beams in high-energy storage rings1,2 by means of electron and laser cooling has opened up a new era in accelerator physics The enhanced luminosity and suppressed momentum spread in such systems create the highest possible phase-space density The first experimental results were obtained by cooling 7Li+ beams to temperatures of a few kelvin or even to sub-kelvin temperatures3,4, and the ordered structures have been studied theoretically5–7 by methods of molecular dynamics Predicted configurations for the lowest ion densities have been observed in low-energy quadrupole storage rings8 and linear traps9 Recently we showed that at slightly higher ion densities helical structures are obtained10 Here we present a series of new experimental results on ordered ion structures in a quadrupole storage ring In order of increasing ion number, a linear chain of ions, a zig-zag structure, helical structures and finally multiple concentric shells could be observed The experimental results agree with molecular dynamics calculations