Recent developments in high-current superconducting ion linacs

It is noted that recent experimental and analytical results in the areas of resonator geometry and beam physics are very encouraging for superconducting high-current ion accelerators. Niobium resonators fabricated for high-brightness ion acceleration have yielded continuous-wave (CW) average accelerating gradients as high as 18 MV/m. In a superconducting RFQ (radio-frequency quadrupole) geometry, high CW surface electric fields were sustained over surface areas of order 10 cm/sup 2/. Analyses of cumulative beam breakup in superconducting linacs consisting of decoupled, independently phased cavities were also encouraging. In addition to the construction and testing of a superconducting section, future work will include the development of superconducting cavities operating at higher frequencies and velocities. Fabrication of a 2-gap, 850 MHz, beta /sub 0/=0.28 spoke resonator is nearly complete.<>