The COMPASS (COMPact ASSembly) Tokamak in Prague is the main experimental facility of the Tokamak department of the Institue for Plasma Physics at the Czech Academy of Sciences (Akademie věd České republiky).

COMPASS was shut down in august of 2021 due to preparations for the installation of the new COMPASS-Upgrade tokamak - a high magnetic field device with an enlarged operational space and broader flexibility. The goal of the project is to build a unique experimental facility that can support the operation of ITER and address some of the key challenges for the design and construction of a next-phase reactor, DEMO. COMPASS-U's characteristics will enable the exploration of advanced confinement modes and plasma configurations, and the testing of new plasma-facing materials and liquid metal divertor concepts. The start of the operation is planned in 2023.


According to CAS, research topics mostly comprise of:

  • H-mode physics
  • Pedestal width physics
  • L-H power threshold, isotope effects
  • Edge Localized Modes, their control by magnetic perturbation and vertical kicks
  • Zonal flows
  • Transport in edge plasma and SOL
  • Turbulent structures and intermittency in edge plasma – experiment and modelling
  • MHD equilibrium and instabilities
  • Plasma-wall interaction

Technical Data

  • Major radius R: 0.56 metres
  • Minor radius a: 0.23 metres
  • Plasma current Ip (max): 400 kA
  • Magnetic field BT: 0.9 - 2.1 T
  • Vacuum pressure: 1 × 10⁻⁶ Pa
  • Elongation: 1.8
  • Plasma shape: D, SND, elliptical, circular
  • Pulse length: ~ 1 s
  • Beam heating Pɴʙɪ 40 keV: 2 × 0.4 MW