Tokamak COMPASS

Tokamak COMPASS (COMPact ASSembly) is the main experimental facility of the Tokamak Department. It has been designed and operated in 90th in UKAEA Culham in Great Britain and mothballed in 2002 due to start of the MAST tokamak operation.

The COMPASS tokamak with its size (major radius 0.6 m and height of the vessel approx. 0.7 m) ranks to smaller tokamaks capable of the H-mode operation, which represents a reference operation ("standard scenario") for the ITER tokamak. Importantly, due to its size and shape the COMPASS plasmas correspond to one tenth (in the linear scale) of the ITER plasmas. Due to its direct relevance to the ITER project - the facility was offered by the European Commission and UKAEA to the Institute of Plasma Physics AS CR in Prague in autumn 2004. Installation and operation of tokamak COMPASS in the Institute of Plasma Physics AS CR sets the Czech republic among advanced countries in research efforts in high-temperature plasmas and thermonuclear fusion. At present, besides COMPASS there are only two operational tokamaks in Europe with ITER-like configuration capable of regime with the High plasma confinement. It is the Joint European Torus JET and the German tokamak ASDEX-U (Institut fur Plasmaphysik, Garching, Germany). JET is presently the biggest experimental device of this type in the world.

Scale comparison of different tokamaks

Scale of European tokamaks with cross-section similar to ITER


Cutaway diagram of tokamak COMPASS

Cutaway diagram of tokamak COMPASS

The history of the COMPASS installation in IPP Prague

2004 - 2005 preparatory phase
June 2006 start of the project (awarding the preferential support by EURATOM)
2006-2008 design, construction and commissioning of buildings, power supplies, vacuum systems, diagnostics, control systems, dismantling, transport of the tokamak
December 2007 installation of the tokamak into new torus hall
2008 the first plasma achieved
2009-2011 final commissioning of the diagnostics, control systems, power supplies
2012 scientific exploitation (operational phase)
November 2012 H-mode scenario achieved
2013 Edge Localized Modes Type-I achieved

Tokamak COMPASS in IPP Prague

Tokamak COMPASS in IPP Prague

Tokamak COMPASS in the Institute of Plasma Physics AS CR


Parameters of the tokamak COMPASS

Parameters Values
Major radius R 0.56 m
Minor radius a 0.23 m
Plasma current Ip (max) 400 kA
Magnetic field BT (max) 0.9-2.1 T
Vacuum pressure 1x10-6 Pa
Elongation 1.8
Plasma shape D, SND, elliptical, circular
Pulse length ~ 1 s
Beam heating PNBI 40 keV 2 x 0.4 MW


Physics research programme

  • 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
  • Physics of runaways and disruption
  • Developments of advance diagnostic methods
  • Integrated modelling and code development

Main systems

  • CODAC (Control, Data Acquisition and Communication) system
  • Power Supply
  • Fast Feedback control system
  • Cooling
  • Vacuum system
  • Fuelling
  • Hydraulic preload system
  • Neutral beam injection heating system
  • Vessel baking system
  • Glow discharge system

Plasma diagnostic systems

  1. Magnetic diagnostics (400 coils)

  2. Microwave diagnostics

  3. Spectroscopic diagnostics

  4. Beam & particle diagnostics

    • HR2000+ spectrometer for Ha & Da
    • Neutron scintillation detector
    • Diagnostics using Li-beam (BES, ABP)
    • Two Neutral Particle Analyzers
    • Charge-Exchange recombination spectroscopy under construction
    • Detection of fusion products
  5. Probe diagnostics


Photo of plasma inside the vacuum chamber
Numerical reconstruction of the plasma shape

Left: Photo of plasma inside vacuum chamber. Right: Numercial reconstruction of the plasma shape.

Inside view into the COMPASS vacuum vessel
Front part of COMPASS control room

Left: Inside view into the COMPASS vacuum vessel. Right: Front part of COMPASS control room.