SBIR-STTR Award

Superconducting rf technology has been recommended recently as the basis for the International Linear Collider, (ILC) accelerating structures. The principal goal of this proposal is development of a new experimental device - the Superconducting Traveling Wave Accelerator (STWA), a technology that may prove of crucial importance to the ILC. The present state of the art in superconducting structures has obtained a gradient of ~30 MV/m; the STWA technology in this proposal will further increase the gradient by a factor of up to ~1.40. We plan to design, develop and demonstrate the multi-cell Superconducting Traveling Wave Accelerating Structure under the scope of this project. Traveling wave SC accelerating structure need arises from demand for a high accelerating gradient. Proposed STWA structure operates at the same surface magnetic and electrical field magnitudes as the TESLA cavity surface to avoid undesirable superconductivity break down. The main goal of this new project is a 3-cell SC traveling wave cavity development and its experimental demonstration and testing. The mulitcell cavity with feedback will allow traveling wave excitation in the resonance ring and corresponding tuning studies that are of great importance for the SC traveling wave projects success. The tuning aspects of traveling wave regime stability and backward wave reduction at high power have been considered as a key issue for the SC traveling wave structure concepts. In Phase I of this project, the results of the optimization of a multi-cell L-band SC traveling wave cavity will be revisited along with the tuning issue analysis. Cavity shape, magnetic and electrical surface field ratios, inter-cell coupling coefficient, accelerating field flatness, and coupling section design will be reviewed. Special attention will be paid to feedback loop operations with the two coupler feed system. Based on these studies the requirements for the conceptual design of the traveling wave structure will be formulated. Commercialization Applications and Other

Benefits:
The main goal of the project is a development of the superconducting accelerating structure with the increased gradient for the linear collider. This structure will allow the total length of the linear collider to be reduced by 20-40% with a corresponding reduction in construction costs. The proposed structure is an inexpensive solution that permits the use of currently available accelerator components.

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.