The separated-sector cyclotron

The separated-sector cyclotron (SSC) has now been in operation for more than two years, and has produced proton beams with energy ranging from 27 to 200 MeV as well as alpha-particle beams. The SSC has proved to be a reliable machine and easy to operate. The rf system works very well, and at voltages of up to 250 kV has a spark-over rate of about once in three days. It normally requires less than 10 seconds to restart the rf automatically after such a spark-over. Variations in the temperature of the sector magnets caused by different excitations of the main coils initially affected the stability of the magnetic field of the sector magnets. The temperature is now regulated by controlling the inlet cooling water temperature in such a way that the average temperature of the inlet and outlet water is kept constant during different coil excitations. This measure has improved the stability appreciably. The vacuum system operates reliably in the 10-7 mbar range. Unscheduled interruptions were mainly due to the power supplies and cooling water of the separated-sector cyclotron, the buncher in the transfer beamline and the electrostatic extraction channel of the injector cyclotron. Numerous power dips in the grid supply (resulting in considerable loss of beam time) led to the decision to acquire a 3.2 MVA uninterruptible power supply (UPS) which can keep the main components of the facility supplied for ten minutes in the event of a power failure. This UPS has been delivered and is presently being installed. A slit to limit the beam width soon after injection into the SSC is being developed and should be installed at the end of the year. The main beam loss occurs on the front collimator of the first septum magnet, which has a septum thickness of 7 mm. 2 figs., 4 tabs