Experimental High-gradient Testing of an Elliptical-rod Photonic Band-gap (pbg) Structure at X-band

An 11.4 GHz photonic band-gap (PBG) structure where the rods in the inner row have an elliptical cross-section has been designed at MIT and manufactured and tested at high power and high repetition rate at SLAC. This structure exhibits lower surface magnetic fields on the rods relative to previous PBG structures tested at SLAC, which reduces the ohmic heating of the rod surface in an effort to reduce pulsed heating damage. The structure demonstrated greater than 100 MV/m gradient at a breakdown probability of less than 10 per pulse per meter for 150 ns pulses at 60 Hz repetition rate, performance comparable to an undamped disc-loaded waveguide (DLWG) structures previously tested at SLAC. This level of performance demonstrates that elliptical-rod PBG structures, which exhibit intrinsic wakefield damping, could be candidates for future accelerator applications.