Advanced accelerator research is concerned with developing machines that can generate greater intensities, higher power, superior reliability and enhanced efficiency. Concurrently, such accelerators must be designed so that they are more compact and more cost-effective. Creating a more compact and cost-effective accelerator requires the ability to achieve high accelerating gradients in higher-frequency accelerating structures. The principal roadblock in such development is that at such high frequencies higher-order modes (parasitic, high-frequency oscillations of the accelerator structure) become excited by the very particle beam that propagates through the accelerating structure. These higher-order modes, or HOMs, interact with the accelerating beam, deteriorating its quality and intensity.
To eliminate HOMs, scientists and engineers at LANL have come up with Photonic Band Gap Structures. PBG structures filter out unwanted HOMs while fully supporting the accelerating mode, thus enabling for the first time the construction of mode-selective PBG accelerators.