Upgrading the Control and Monitoring system for the TOFOR neutron time-of-flight spectrometer at JET

Sammanfattning: This report describes the development and testing of the upgraded Control and Monitoring (C&Mu) system for the TOFOR neutron spectrometer. TOFOR is currently performing plasma diagnostics for the JET experimental fusion reactor. The purpose of the C&Mu system is to enable monitoring of the amplitude dependent time delays of TOFOR. In order to perform this monitoring function the C&Mu system must comprise a pulsed light source with variable intensity and a reference time signal. In this work a reference time signal has been retrieved from a laser comprising a motorized polarizer. This has been accomplished by installing a photomultiplier tube and a beamsplitter cube. The beamsplitter cube splits the laser light into two parts and directs one part into the photomultiplier tube. The photomultiplier tube converts the light into an electrical reference time signal. A control program has been developed for the motorized polarizer, enabling the user to vary the intensity of the light over the interval from 0% to 100%. The C&Mu system has been performance tested and it was found that the time resolution of the system is about 0.1ns and the time stability of the system is about 0.12ns over 27 hours. The system is more than adequate to monitor variations in time delays at TOFOR of several nanoseconds, over a full JET day. The C&Mu system is ready to be installed on TOFOR.