EPICS upgrade of IPNS accelerator control and data acquisition system

The Intense Pulsed Neutron Source (IPNS) facility operates a 450MeV proton accelerator to generate neutrons for science. The accelerator data acquisition and control system was growing increasingly stagnant and difficult to maintain due to its reliance on computer technology from the 1970's. A concerted effort was put forth to upgrade that system to a new, distributed system utilizing the Experimental Physics and Industrial Control System (EPICS). There were several issues that needed to be addressed in order to accomplish this transition. The computer system has to be synchronized with the 30Hz repetition rate of the accelerator. The transition from Computer Aided Measurement And Control (CAMAC) to Versa Module Europa (VME) requires that different connectors be installed for all of the I/O cabling and, in some cases, special hardware modifications. Completely new operator displays and controls had to be developed. The IPNS facility operates year-round with only a week or two between runs and roughly one month off in the summer and one in the winter. This paper describes the transition to the present system and how the upgrades were accomplished in an incremental fashion during the short shutdown periods.