Cryogenic controls for the TESLA test facility

Abstract The TESLA Test Facility (TTF) is designed to perform intensive testing of the superconducting cavities foreseen for the next generation of linear colliders. The cryogenic system is one part of this facility. The controls for this system will initially use the existing software and hardware to be able to cool down the first cavities fabricated in the TTF workshop. Later the control system will be modified to meet the current standards in process and accelerator controls. The hardware will be changed to use the VME system as the major platform. The operating system and the communication will be based on de-facto standards such as UNIX for the workstations and the front-end computers and TCP/IP for network communication. The application software (EPICS) will be part of a collaboration with several other institutes. The final goal is to port all the software to the POSIX standard and to use Object-Oriented tools wherever possible. The first part of this paper describes the migration from the existing control system to the future design. Special decisions on hardware and software solutions are highlighted. Nonproprietary field busses for remote process I/O are becoming usual for slow control. A suitable bus for our future basic I/O system had to be selected. Finally a new temperature monitor module working on the CAN-bus and its measurement procedure will be explained.