The SLAC Long Ion Chamber System for Machine Protection

To protect the Stanford 3 km accelerator from damage caused by its own electron beam, a single ion chamber has been installed, which runs the whole length of the accelerator. The pulse train from the ion chamber is displayed on an oscilloscope, giving a representation of beam power loss along the machine as a function of distance from the injector. It also operates a system that shuts off the electron beam within 1 ms whenever the signal level exceeds a preset value.