Imaging Neutral Particle Analyzer Engineering Design and Installation for the ASDEX Upgrade Tokamak

Abstract

An imaging neutral particle analyzer (INPA) has been installed in the ASDEX Upgrade (AUG) tokamak to provide simultaneous measurements of the radial profile and the energy of the confined fast-ion (FI) population. The INPA diagnostic leverages the advantages of neutral particle analyzers (NPAs) and FI loss detectors (FILDs) by measuring charge exchange (CX) neutrals ionized by an ultrathin carbon foil is deflected into a scintillator by the local magnetic field. The design of this diagnostic has been developed under a series of constraints, such as the lack of space and hazardous environment (high level of neutron and gamma radiation), the need of high precision in the alignment of the nonsequential optical system (with six optical axes), and the optimization of the scintillator plate (signal emitter). To this end, a modular and adjustable design has been pursued with several degrees of freedom to ensure precise positioning during the installation and optical calibration. The induced electromagnetic and thermal stresses have been assessed and compared against the material limits of the detector, showing that no significant stress is expected for the system. The thermal analysis shows that the diagnostic scintillator can work efficiently during normal operation conditions. The CAD design, a comparison between the synthetic and real optical signals and the mechanical assessment [based on finite element analysis (FEA)], is presented in this contribution.