High-Gradient Two-Beam Electron Accelerator

In a two-beam accelerator, a high-current drive beam imparts energy to a low current test beam by generating microwave power that flows from one beam to the other. The largest project of this sort is CLIC, located at CERN in Geneva, Switzerland, that is being designed for operation at an electron-positron center-ofmass energy as high as 3 TeV. Technical complexity and low efficiency characterize the design for this project, creating technical hurdles that present serious challenges for its designers. This project proposes a new approach to two-beam acceleration by employing detuned cavities in its accelerator structure. In this way, it is possible for both the drive beam and test beam to traverse the same cavities. This could allow operation at higher acceleration gradients than CLIC because of the possibility of exciting the cavities in more than one mode simultaneously, and could allow a higher efficiency for power transfer between one beam and the other. Theoretical and computational analysis was carried out to establish a conceptual design for experiments to be conducted during Phase II. Plans for the experiments, and for further supporting analysis, were formulated. Test cavities will be built, and configured into a short accelerator structure, for measurements of transformer ratio and acceleration gradient, when the structure is driven by the modest current beam from an available 6-MeV RF gun. Analysis will be continued to improve understanding of this novel accelerator configuration. Commercial Applications and Other Benefits: For construction of a future multi-TeV electron-positron collider, costs will scale down as the working acceleration gradient rises and as the complexity of the device falls. Thus one benefit from use of the proposed accelerator structure could be a drop in the cost of the machine. This couldin turnincrease the likelihood that the international funding agencies needed to support such an endeavor will react positively to a proposal to underwrite the collider