The Gnu Control System at Camd: Part Two

Louisiana State University Center for Advanced Microstructures and Devices (CAMD) began a project to upgrade the storage ring and linac control systems in February 1997. At that time, control systems for the storage ring and linac were DEC VAX/VMS and VME/OS9 based systems, respectively. The objectives were to utilize inexpensive hardware, free software, and provide a flexible architecture where new projects could be easily integrated [1]. The storage ring control system has now been replaced with a PC/Linux based system, and the VAXes removed. A superconducting wiggler from the Budker Institute has been commissioned and integrated into this system [2]. CAMD is now focusing on expanding the control system to include the linac [3] and a second RF system, and reengineering subsystems to provide more reliable control. Automationdirect.com (formerly PLCDirect) PLC hardware has been chosen as the hardware platform for these upgrades, while PC/Linux will provide the man/machine interface. The design for these upgrades and their integration into the current control system will be presented. 1 CONTROL SYSTEM DESIGN The key to the CAMD control system design is the unified API layer known as the "cht" (for "channel text" layer). Most of the control system programs, displays, and utilities are written in Tcl/Tk and rely upon this layer. The programs reference channels by a unique ASCII string, or channel name. The cht layer performs any necessary engineering unit conversion, and routes requests to the appropriate handlers for each different type of supported hardware. Using this approach, channels can be relocated among CAMAC modules or crates, or changed from CAMAC to PLC modules with no changes in the application code. The cht layer relies upon the PostgreSQL database from the University of California for channel definitions. These contain the channel’s hardware platform (i.e. CAMAC, GPIB, PLC, etc.), engineering unit conversion information, the type of channel (including analog vs. digital, input vs. output, bipolar vs. unipolar), channel limits, and the channel’s location, such as CAMAC crate, module slot, module type, and subaddress. The CAMD storage ring is “ramped” from 180MeV injection to 1.3 or 1.5GeV energy levels over a twenty five second interval. Approximately thirty channels are driven with up to two hundred and fifty synchronized setpoints per second. This requires greater throughput and level of synchronization than the PC/CAMAC crate controller combination is able to provide if channels are written individually from PC software. Hytec list processors are used to accommodate the speed and synchronization needs. Lists of CAMAC instructions (i.e. F’s, N’s, and A’s) and lists of setpoints are downloaded to each list processor and executed. The PC, using normal CAMAC communication, monitors the progress of the ramp. This system is used for the ring ramp, wiggler ramp, and transport line conditioning ramp. In the VAX based control system, each type of ramp had its own special software. In the updated control system, the ramping software has also been genericized. Each ramp is controlled by a "scenario file". These scenario files describe the type of ramp, the setpoint file, the type of interpolation used, and ramp "load" and "run" programs. These two programs control the use of the CAMAC list processors. Different programs can be specified to allow for activities such as ramping the main magnets and RF systems separately for hardware testing, slew rate measurements, or ramp performance data collection. By using generic ramping software and the unified API, the integration of the superconducting wiggler into the system was a very quick process. The wiggler was installed and tested using the vendor supplied control system. After a short cabling changeover, the wiggler was commissioned using the CAMD control system, and the new ring and wiggler ramp files were developed jointly between CAMD and the Budker Institute. 2 CONTROL SYSTEM UPGRADES Several control system upgrades are currently in progress: 1) The CGR-MeV linac currently runs on a VME/OS9 platform. Several of the cards were custom made for this project, and have large silicon components which we have be unable to identify. The equipment protection interlocks are in software, and the system is loaded to the point that if the system is "ping"ed via TCP/IP, the watchdog timers expire and the linac shuts down. The software documentation only exists at the source code level, so determining program flow is difficult. Due to the fact that CGR-MeV is no longer in the injector linac business, CAMD is left with an International Conference on Accelerator and Large Experimental Physics Control Systems 118 International Conference Accel rator and L rge Experim ntal Physics Control Systems, 1999, Trieste, Italy