The Imaging Neutral Particle Analyzer

The Imaging Neutral Particle Analyser (INPA)1⁠ is the new generation of neutral particle detectors. It combines the best of FILD2⁠ detectors with the traditional diagnosis techniques of NPA3⁠, allowing us to prove simultaneously the energy and radial position of the confined fast-ion population over a vast region of the phase space with unprecedented resolution and fast temporal response.

As standard NPAs, the INPA diagnostic extracts the information on the confined FI population analysing the fast neutrals (neutralised FI) which exit the plasma after CX reactions. These neutrals are ionised by an ultra-thin (20 nm) carbon foil and deflected into the scintillator by the local magnetic field. From the impact point on the scintillator plate, the energy and pitch of the incident particle can be determined. With the particle pitch, its radial birth position can be reconstructed, as there is a one-to-one relation between particle pitch at the scintillator and radial birth position thanks to the use of a neutral beam injector as source of neutrals.

The INPA, currently in the final design phase, will feature a radial resolution of 7 cm and energy resolution of 12 keV while using the high resolution acquisition system and a bandwidth of 150 kHz using the fast one (PMTs). Its unprecedented measurements will open a new era of fast-ion diagnostics in the AUG tokamak and will shed light on the fundamental mechanisms underlying the observed fast-ion transport in the presence of a wide varity of MHD fluctuations.

For more details about the Imaging Neutral Particle Analyser see: Design and implementation of an imaging neutral particle analyser at the ASDEX Upgrade tokamak.

Fig. 1.  CAD design of the head of the INPA diagnostic for AUG.

[1] Du, X. D., Van Zeeland, M. A., Heidbrink, W. W. & Su, D., Development and verification of a novel scintillator-based, imaging neutral particle analyzer in DIII-D tokamak, Nucl. Fusion 58, 082006 (2018).
[2] García-Muñoz, M., Fahrbach, H. U. & Zohm, H., Scintillator based detector for fast-ion losses induced by magnetohydrodynamic instabilities in the ASDEX upgrade tokamak, Rev. Sci. Instrum. 80 (2009).
[3] Medley, S. S. et al. Invited review article: Contemporary instrumentation and application of charge exchange neutral particle diagnostics in magnetic fusion energy experiments, Rev. Sci. Instrum. 79, 1–16 (2008).