RF acceleration with short pulses: Breaking the high-gradient barrier

Achieving high-gradient acceleration is critical to enabling future linear colliders, free-electron lasers, and other compact accelerator applications. The Argonne Wakefield Accelerator (AWA) group has pioneered short-pulse structure wakefield acceleration technology, which has shown remarkable promise for surpassing the long-standing barrier of ~100 MV/m in X-band normal-conducting structures. Recent experiments have demonstrated the feasibility of this approach, with gradients exceeding 300 MV/m in a variety of X-band accelerating structures and an X-band photogun. Experimental results indicate that the empirical scaling law used to estimate the RF breakdown rate (BDR ~ E^30 * t^5) may be too conservative for RF pulse durations below 10 ns. Potential advanced accelerator designs based on short-pulse acceleration will also be presented, including a conceptual design for an ultra-compact XFEL.