Nevis Synchrocyclotron Conversion Program - RF System

The proposed three-fold symmetric and radially increasing magnetic field requires the arcelerating RF field to cover the frequency band from about 26.5 MHz to 18.5 MHz. The peak dee voltage will be between 30 and 50 kV, with the maximum near injection. The repetition rate will be ??300 per second with the RF turned on for 4%/. of the time. The (single) dee-line structure will be 150 inches wide and between one-quarter and one-half a wavelength long. One of the three pairs of sectoriron shims will be incorporated in the dee and supported on BeO insulators. For the presently favored design, tuning will be accomplished by two rotating capacitors with axes directed towards the center of the magnet. Each rotor will have four layers of 12 blades each. Each set of stator blades will be coupled to four transmission lines which will run to the dee. The rotors will operate near RF ground potential. This design permits effective magnetic shielding of the rotor to minimize eddy current losses. Excitation of the dee will be provided by two grounded-grid, triode oscillators crosscoupled to quarter-wave stubs on the two sides of the dee.