AI Plasma Control

Safety Interlocks and Instrumented Systems

Interlocks are simple, independent safety functions that act automatically when a hard limit is crossed, regardless of the control software.

The purpose of an interlock

An interlock is a safety function that takes a defined protective action when a condition is met, independent of the main control system. If the vacuum fails or a coil current exceeds its structural limit, an interlock acts even if the control software is confused or crashed. Interlocks are the simplest, most trustworthy layer of protection.

Independence and simplicity

Kronos motion — control room

Interlocks are kept simple, often implemented in hardware or in small dedicated logic rather than in the complex control code. Simplicity makes them analyzable and reliable: a function that does one thing when one signal crosses one threshold can be verified exhaustively. Independence ensures a bug in the performance software cannot disable them.

Safety instrumented functions

Formal safety engineering describes these as safety instrumented functions, each with a required reliability level. Sensors, logic, and final actuators are chosen and tested so the function meets its target failure rate. This discipline, borrowed from process industries, applies to the interlocks that protect fusion hardware.

Relationship to the control stack

Interlocks sit beneath the machine protection system, which sits beneath performance control. Performance control tries to do well; protection tries to prevent harm using the same actuators intelligently; interlocks are the blunt, final guarantee. Each layer is more trustworthy and less capable than the one above it.

In the Kronos program

The Hyperion breeder and the burner generators use interlocks to guard their high-field magnets, at 16.84 tesla and 26.49 tesla respectively, along with vacuum, cooling, and power-supply limits. These functions are independent of the performance control software and engineered to formal reliability targets. Their design is part of the machine specification developed ahead of construction.