High Power Rf Testing Of A 3-Cell Superconducting Traveling Wave Accelerating Structure

The total length and hence cost of the ILC is in part due to limitations of its superconducting standing wave accelerating cavities. We have invented a new technology that can reduce the total length of the ILC by 2/3. We have developed a design for a traveling wave superconducting accelerating structure that supports a larger gradient compared to SW structures, and also allows less wasted space in a cryomodule. The net effect is an effective gradient increase by nearly a factor of 1.5. We focused on the design of a three cell traveling wave prototype, performing a numerical analysis of the resonance ring model of the SC traveling wave structure with feedback and double coupler feed system. We finished the greater part of the engineering design of the 3-cell SC traveling wave cavity. Special attention was paid to backward wave reduction and studies of tuning issues. A 3-cell SC traveling wave accelerating (STWA) structure prototype will be manufactured and demonstrated. Special attention will be paid to traveling wave regime detection, control, and adjustment along with the design of the feedback waveguide. We will optimize the STWA for the double-coupler TW structure with feedback option. The double coupler will allow more precise tuning and relaxed parameters for TW regime operation with no reflections. We will consider long structure issues and technological limitations of the STWA. Commercial Applications and Other Benefits: The techniques we propose in this project can overcome conventional limitations on the transformer ratio to obtain a significantly higher energy transfer efficiency from the drive to the witness beam, leading to a breakthrough in the performance of the beam driven wakefield accelerator, one of the most promising schemes in the category of advanced accelerator concepts for high energy physics research applications.