Diagnostics

A prominence on the sun, an arc of plasma rising into the corona. Image credit: Solar Dynamics Observatory (April, 2010)

Diagnostics are the eyes and ears of fusion reactors. They return vital parameters such as the temperature, the density, the impurity content, the magnetic field et cetera. A distinction can be made between active and passive diagnostics (the former requiring the injection of light beams, particles, or probes, while the latter is based on the observation of radiation and particles emitted spontaneously by the plasma). Below follows a list of different diagnostics, together with their main measurement parameters.

Name	Abbreviation	Measurement parameters
Thomson Scattering	TS	Electron temperature $T_e$, electron density $n_e$
Charge Exchange Recombination Spectroscopy	CXRS, CXS, CHERS, CER	Ion temperature $T_i$, toroidal and poloidal plasma rotation velocity $v_{\varphi }$, $v_{\theta }$, impurity density $n_Z$
Motional Stark Effect	MSE	Magnetic pitch angle $\tan (\gamma )=B_{\theta }/B_{\varphi }$
Electron Cyclotron Emission	ECE, ECEi	Electron temperature $T_e$, electron temperature fluctuations (turbulence) ${\tilde{T}}_e$
Soft X-Ray Emission	SXR	A combination of electron temperature $T_e$, electron density $n_e$, and effective charge $Z_{eff}$
Mirnov coils, pickup coils	-	magnetic field components and fluctuations (outside plasma)
Heavy Ion Beam Probe	HIBP	Electron density $n_e$, plasma potential $\varphi$
Interferometry	-	Electron density $n_e$ (line integral)
Polarimetry	-	Magnetic field pitch (line integral)
Reflectometry	-	Electron density $n_e$ (edge profile, fluctuations)

A special bi-annual conference on fusion diagnostics is held in the U.S.: The Topical Conference on High Temperature Plasma Diagnostics (HTPD)

References

• I.H. Hutchinson, Principles of Plasma Diagnostics, Cambridge University Press; 2^nd edition (2002) ISBN 978-0521803892