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This article describes a neutral particle analyzer/isotope separator (ISEP) developed for measurement of the relative hydrogen isotope composition of Joint European Torus (JET) plasmas. The ISEP deployed on the JET can be regarded as a prototype of an instrument proposed for measurement of the spatial profile of the ratio of the density of deuterium and tritium ions in the plasma, nD(r)/nT(r), in the International Thermonuclear Experimental Reactor (ITER). The ISEP makes simultaneous measurements of the energy distribution of efflux of hydrogen isotope atoms (H, D, and T) from the plasma. From such measurements it is possible to deduce the radial profile of the relative hydrogen isotope ion composition of the plasma and radial transport of ions of one isotope across the plasma of another isotope species. The main elements of the ISEP are (a) use of a thin carbon foil for reionization of the incident atoms, thereby eliminating gas stripping cells and gas sources of conventional neutral particle analyzers (...

This article describes the overall design of the Joint European Torus (JET) motional Stark effect (MSE) diagnostic. The principle of this diagnostic has been proven on other tokamaks (TFTR and DIII-D) but its implementation on JET involves specific difficulties associated with optical access and neutral beam geometry. The solutions adopted for the access problem include the use of a novel “Air Amici” prism for beam deviation and low Verdet coefficient glass for the relay optics. MSE signals from the different beam sources are distinguished by their Doppler shift; the diagnostic uses the π+ components of the Stark spectrum to avoid contamination with signals from different beam sources. The optimum viewing location for good space resolution across the plasma profile is also one that allows good accuracy in the reconstruction of the q profile from the measurements. An assessment of the optical throughput predicts a measurement accuracy of the polarization angle of better than 0.15° with 1–10 ms time resolution.

Visible spectroscopy will be one of the key diagnostics in the study of the performance of the new JET pumped divertor. Images of the divertor plasma are obtained using a periscope and coherent optical‐fiber bundle. A CCD camera records the images, using a filter to isolate the required spectral feature. The system covers the wavelength range 400–800 nm, has spatial resolution 8 mm, can detect the continuum level for all foreseen plasma operation, and has temporal resolution of up to 6 ms.