Microwave and Far Infrared Diagnostics

The measurement of plasma quantities is a difficult task since the plasma cannot be treated like normal material. Any measurement of plasma quantities with solid probes will yield interactions with the plasma and causes a perturbation of the measured quantity. Inside a hot plasma those methods are not applicable, since they lead to a disruption of the discharge. In addition microwave diagnostics have no big needs in terms of space requirements if coupled to a plasma. Mirrors needed for the most optical diagnostics will become a problem due to erosion and deposition of the mirror surfaces in future fusion devices as ITER and DEMO. Also in this sense microwave diagnostics are less demanding. However, this puts some pressure on a future generation of scientist to develop new methods to replace optical based diagnostics by those using microwaves to probe the plasma.