Design and simulation of an imaging neutral particle analyzer for the ASDEX Upgrade tokamak

Abstract

An Imaging Neutral Particle Analyzer (INPA) diagnostic has been designed for the ASDEX Upgrade (AUG) tokamak. The AUG INPA diagnostic will measure fast neutrals escaping the plasma after charge exchange reactions. The neutrals will be ionized by a 20 nm carbon foil and deflected toward a scintillator by the local magnetic field. The use of a neutral beam injector (NBI) as an active source of neutrals will provide radially resolved measurements, while the use of a scintillator as an active component will allow us to cover the whole plasma along the NBI line with unprecedented phase-space resolution (<12 keV and 8 cm) and a fast temporal response (up to 1 kHz with the high resolution acquisition system and above 100 kHz with the low resolution one), making it suitable to study localized fast-ion redistributions in phase space.

Commissioning of the imaging neutral particle analyser for the ASDEX Upgrade tokamak

“…This is due to the low concentration of background neutrals within the core region, and the low density of fast ions at the edge, where the background neutral concentration is large, as reported for FIDA studies at AUG [13]. This allows to establish a relation, via modelling, between the measured pitch angle and the radial birth location of the CX particle, as detailed in [9].…”

“…The complete synthetic signal is depicted in subplot (b). As depicted in figure 3(c), the halo contribution turns out to dominate in the plasma core and is wider than the NBI contribution while the passive contribution is well below the active level and is apparently distributed along all the possible radii (the relation between pitch and radial position can only be accurately established for CX neutrals originated along the NBI line [9]). For the case of the signal per units of energy, depicted in figure 3(d), the contribution is dominated by the active component at high energy, while the passive signal becomes significant at low energy, as neutrals coming from the edge suffer almost no attenuation due to reionisation.…”

“…For this purpose, new diagnostics techniques to measure the confined FI population in phase space with fast temporal response and high resolution in phase space are needed. We hereby report on the commissioning of such a new FI diagnostic, an imaging neutral particle analyser (INPA) installed in the ASDEX Upgrade (AUG) tokamak [9,10]. This diagnostic provides energy-resolved FI profiles, complementing the state-of-the-art suite of FI diagnostics installed in AUG; among which fast-ion loss detector (FILD) [11], neutron detectors [12], fast-ion D-α (FIDA) [13], neutral particle analysers (NPAs) [14], ion cyclotron emission (ICE) diagnostics [15] and collective Thomson scattering [16] out-stand.…”

“…Finally, the upgraded synthetic diagnostic is presented and compared against experimental results. The design and the installation was already presented in [9,10]. The reader is referred to those publications for a detailed description of the mechanical system and the design process.…”

Visualization of phase-space orbit topological boundary using imaging neutral particle analyzer

“…More recently, INPA systems have been developed worldwide. INPA is successfully commissioned in ASDEX-upgrade [9] and systems are under development in Large Helical Device (LHD), TCV, EAST and HL-2M. To date, all of the INPA systems focus on measurement of fast ions on passing orbits.…”