High-power accelerator technology and requirements

Designs of high-power proton linear accelerators (linacs) for accelerator transmutation of waste (ATW) are being actively studied at Los Alamos National Laboratory and at several other laboratories worldwide. Beam parameters cover the 100- to 300-mA range in average current and 800 to 1600 MeV in energy. While ideas for such accelerators have been discussed for decades, the technology base has recently advanced to the point that the feasibility of machines in the ATW power class is now generally conceded. Factors contributing to this advance have been the following: experience gained with medium-power research accelerators, especially the LAMPF linac at Los Alamos; major improvements in the theory and technology of high-intensity high-brightness accelerators fostered by the SDIO Neutral Particle Beam program; and development of high-power continuous-wave (cw) radio-frequency (rf) generators for high-energy colliding-beam rings. The reference ATW accelerator concept described in this paper is based on room-temperature copper accelerating cavities. Advances in superconducting niobium cavity technology have opened the possibility of application to ATW-type linacs. Useful efficiency gains could be realized, especially for lower current systems, and there may be technical advantages as well. Technology issues that need to be addressed for superconducting rf linac designs include the development of high-powermore » rf couplers, appropriate cavity designs, and superconducting focusing elements, as well as concerns about beam damage of niobium structures and dynamic rf control with high beam currents.« less