Plasma diagnostic systems and methods used on the stellarator TJ-II

Abstract

The TJ-II is a heliac-type stellarator device with major radius of 1.5 m and averaged minor radius ⩽0.22 m that has been operated at CIEMAT, Madrid since 1998. Its full magnetic field is created by a system of poloidal, central, toroidal and vertical field coils, thus it possesses a fully 3-dimensional plasma structure and a bean-shaped plasma cross-section. Although this results in a complicated vacuum-vessel layout, it has excellent port access for diagnostics (96 portholes). During its initial operational phase, it was equipped with a limited set of essential diagnostics. Since then, a broad variety and large number of both passive and active diagnostics have been installed. The former include Hα monitors, light spectrometers, an electron cyclotron emission radiometer, X-ray filter monitors, neutral particle analysers, magnetic diagnostics, as well as cameras, among others, while the latter include various laser, atomic and ion beam based diagnostics, microwave probe beams, Langmuir probes plus impurity injection techniques. In this paper, after describing the TJ-II stellarator, its heating and fuelling systems, the diagnostic systems employed are outlined and discussed briefly here. Finally, results obtained with selected systems are highlighted.

Return to Volcano Town: Reassessing the 1937–1943 Volcanic Eruptions at Rabaul

“…Jean and Keith McCarthy also had an eventful time. Mrs McCarthy had been in Rabaul for only a week, and was newly wed to Keith, who was waiting for a government posting as a patrol officer elsewhere in New Guinea (McCarthy 1963(McCarthy , 1971a(McCarthy , 1971b(McCarthy , 1980. The McCarthys' wedding gifts were still crated under the house and Mrs McCarthy's wedding dress was hanging on the wardrobe door when the Vulcan eruption began.…”

“…The McCarthys returned to their home from the Cosmopolitan Hotel to collect some possessions, and then began walking again, up over Namanula Hill to Nodup. Mrs McCarthy collected her fur coat and marriage certificate, but later could not remember any of the other more important items they took (McCarthy 1980). She recalled losing one of the heels of her white high-heeled shoes so that she had to hobble along.…”

Characterization of the TJ-II stellarator plasma by means of reciprocating Langmuir probes

“…Two fast reciprocating drives for Langmuir probes are installed on the TJ-II with a speed of displacement ∼1 m/s and at a path length of 0.1 m (providing penetration of ∼10% of the minor plasma radius) [4]. At present, several types of probe heads can be mounted on the drives [2]. Thus, if the probe is swept, it can provide measurements of the plasma edge parameters -the floating potential, Vfl, the ion saturation current density, jsat, the electron temperature, Te, the electron density, ne, and the plasma potential, Vpl.…”

“…Further heating can be achieved by injecting neutral hydrogen atoms accelerated by a couple of tangential neutral-beam injectors (NBI). An overview of recent results and of systems and techniques for plasma diagnostics used on the TJ-II stellarator are presented in detail in [1][2][3].…”