Progress in diagnostics of the COMPASS tokamak

The COMPASS tokamak at IPP Prague is a small-size device with an ITER-relevant plasma geometry and operating in both the Ohmic as well as neutral beam assisted H-modes since 2012. A basic set of diagnostics installed at the begin- ning of the COMPASS operation has been gradually broadened in type of diagnostics, extended in number of detectors and collected channels and improved by an increased data acquisition speed. In recent years, a significant progress in diagnostic development has been motivated by the improved COMPASS plasma performance and broadening of its scientific programme (H-mode and pedestal studies, magnetic perturbations, runaway electron control and mitigation, plasma-surface interaction and corresponding heat fluxes, edge localized mode observations, disruptions, etc.). In this contribution, we describe major upgrades of a broad spectrum of the COMPASS diagnostics and discuss their potential for physical studies. In particular, among optical tools, an upgraded high-resolution edge Thomson scattering diagnostic for pedestal studies and a set of new visible light (observation of edge plasma modes) and infrared (plasma-surface interaction investigations) cameras will be introduced. Scrape-off layer plasma diagnostics will be represented by a new divertor set of Langmuir and ball-pen probe arrays and newly constructed probe heads for reciprocating manipulators. Particle diagnostics will be covered by a neutral particle analyzer, an atomic beam probe on a lithium diagnostic beam, Cherenkov detectors (for a direct detection of runaway electrons) and two different kinds of neutron detectors. We will also show new modifications of the two-band microwave reflectometer for fast edge density profile measurements.