The ISAC vacuum system is controlled as set of semi-autonomous sub-systems:
Section 7 is supervised by the TRIUMF central control system, all other sections by the ISAC control system
This implementation guarantees very high availability for the ion source systems and reliable interlocking. It also decouples running and protection of the ion sources from software development in EPICS.
Vacuum system control is implemented using PLCs ("Programmable Logic Controllers"), more specifically a MODICON Quantum Series PLC.
Each section contains several I/O crates, one master crate and several slave crates, which are connected using Modicon's Modbus+ network (1 Mbit/sec).
The master crate contains the CPU (PLC), a network module (NOE), a backplane power supply and different I/O modules. The network module is connected to the controls ethernet and communicates with the supervisory system using the TCP/IP protocol.
Each slave crate contains a Modbus+ network adapter and different I/O modules.