Present status of the control system for the KEK 2.5 GeV electron and positron linac

The control system of the KEK 2.5 GeV electron linac is a distributed-processor system with a minicomputer network interconnected in an optical token ring. It has been working well from the first operation of the linac in February 1982. The 250 MeV positron generator, the injector of positron beams, has another control system of distributed processors with a multiple MC68000-type single board computer (SBC) system as a host. The positron generator control system is connected with the minicomputer network and also has been working well from the first operation in July 1985. Minicomputers and the SBC system have CAMAC crates which provide two kinds of optical loops interconnecting microprocessor-based device controllers. Devices on a main console are connected with two minicomputers. Two kinds of improvement in the control system are proceeding now in order to respond increasing requirements to deal with more operating information and feedback to the machine. The first improvement is construction of a network of personal computers displaying linac information on the main console; this network has a file server storing the data. The second is introduction of a superminicomputer connected tightly with one of minicomputers in order to expand control program area which has reached the upper limit in the minicomputer. (author)