Development of a Diamond-Based Cylindrical Dielectric Loaded Accelerating Structure

This project will develop a diamond-based, cylindrical, dielectric accelerating (DLA) structure that can sustaining a record accelerating gradient greater than 600 MV/m, significantly in exess of the limits for conventional accelerating structures. The results will be applied to the development of next-generation accelerators with high efficiency and to the technology of cylindrical diamond elements for high-voltage and microwave applications. The accelerating structure will use diamond tubes fabricated by a low cost CVD (chemical vapor deposition) process. Metal rods will serve as hot-filament CVD substrates, which will be etched-off to form self-supported diamond tubes. Multipacting will be suppressed by dehydrogenation of the diamond surface. In Phase I, the cylindrical, diamond-based DLA structure will be designed, developed, and bench tested. A set of diamond tubes (1.5-3.0 cm diameter, thickness ~ 1mm, and 5-10 cm long) will be fabricated by using a hot-filament CVD process. Numerical studies will be conducted to optimize the parameters for a 30-34 GHz, diamond-based accelerating structure and to perform beam-dynamics simulations. Special attention will be paid to the coupling section design and numerical optimization. Low magnetic and electric field ratios will be achieved to satisfy surface metal breakdown limitations. Phase I will result in a final low-power test of the diamond-based cylindrical DLA structure. Commercial Applications And Other Benefits as described by the Applicant: In addition to the accelerator application, the technology should have direct application to cylindrical diamond elements for microwave power source designs and for other large-signal and high-power dielectric applications. The diamond tubes also could be used for molecular filters, drilling tools, waveguides, and hypodermic needles. This work also represents a step towards use of dielectric structure technology for efficient, cost-effective, high-gradient, future electron accelerators.