Status of the COMPASS tokamak and characterization of the first H-mode

Abstract

This paper summarizes the status of the COMPASS tokamak, its comprehensive diagnostic equipment and plasma scenarios as a baseline for the future studies. The former COMPASS-D tokamak was in operation at UKAEA Culham, UK in 1992-2002. Later, the device was transferred to the Institute of Plasma Physics of the Academy of Sciences of the Czech Republic (IPP AS CR), where it was installed during 2006-2011. Since 2012 the device has been in a full operation with Type-I and Type-III ELMy H-modes as a base scenario. This enables together with the ITER-like plasma shape and flexible NBI heating system (two injectors enabling co-or balanced injection) to perform ITER relevant studies in different parameter range to the other tokamaks (ASDEX-Upgrade, DIII-D, JET) and to contribute to the ITER scallings. In addition to the description of the device, current status and the main diagnostic equipment, the paper focuses on the characterization of the Ohmic as well as NBIassisted H-modes. Moreover, Edge Localized Modes (ELMs) are categorized based on their frequency dependence on power density flowing across separatrix. The filamentary structure of ELMs is studied and the parallel heat flux in individual filaments is measured by probes on the outer mid-plane and in the divertor. The measurements are supported by observation of ELM and inter-ELM filaments by an ultra-fast camera.

Filamentary probe on the COMPASS tokamak

“…6,7 This work presents a recently introduced combined diagnostic system for the measurement of the plasma filaments' electromagnetic features located in an unusual position between the midplane and divertor on the COMPASS tokamak. 8 Moreover, we confirm the presence of the parallel electric current flowing along the filament within the SOL in the L-mode. We have analysed mutual dependencies of filament properties.…”

Invited Review Article: Gas puff imaging diagnostics of edge plasma turbulence in magnetic fusion devices

“…35 Tangential passive imaging of the filamentary structure of edge localized modes (ELMs) at 150 kHz has recently been reported by the COMPASS (COMPact ASSembly) tokamak. 36 Finally, fast visible imaging of Balmer-α light was recently done near the X-point and lower divertor regions in MAST 37 and Alcator C-Mod. 38 Clear filaments with complex dynamics were observed near the inner divertor leg, in the private flux zone, and in the SOL outside of the outer divertor leg.…”

Tomographic reconstruction of tokamak edge turbulence from single visible camera data and automatic turbulence structure tracking

“…With appropriate processing, it is possible to extract useful information from plasma visible light emission. We present here tomographic inversion applied to experimental video data recorded on the COMPASS tokamak [14] without any help of gas puff. The method is first illustrated with an academic case and validated against simulation data of the 3D fluid turbulence code TOKAM3X.…”