Plasma Measurements: An Overview of Requirements and Status

Abstract

This paper introduces this special issue on plasma diagnostics for magnetic fusion devices. Its primary purpose is to relate the measurements of plasma parameters to the physics challenges to be faced on operating and planned devices, and also to identify the diagnostic techniques that are used to make these measurements. The specific physics involved in the application of the techniques will be addressed in subsequent chapters.This chapter is biased toward measurements for tokamaks because of their proximity to the burning plasma frontier, and to set the scene for the development work associated with ITER. Hence, there is some emphasis on measurements for alpha-physics studies and the needs for plasma measurements as input to actuators to control the plasma, both for optimizing the device performance and for protection of the surrounding material.The very different approach to the engineering of diagnostics for a burning plasma is considered, emphasizing the needs for new calibration ideas, reliability and hardness against, and compatibility with, radiation. New ideas take a long time to be converted into "work-horse" sophisticated diagnostics so that investment in new developments is essential for ITER, particularly for the measurement of alpha-particles