COMPASS tokamak


COMPASStokamak chamber.jpg
COMPASS tokamak vacuum chamber
Device typeTokamak
LocationPrague, Czech Republic
AffiliationCzech Academy of Sciences
Technical specifications
Major radius0.56 m (1 ft 10 in)
Minor radius0.23 m (9.1 in)
Magnetic field0.9–2.1 T (9,000–21,000 G)
Heating power2 × 0.3 MW
Discharge duration0.5 s (pulsed)
Plasma current360 kA
Year(s) of operation1992 – 2002 (in UK)
WebsiteCOMPASS Tokamak
Other links
  • Compass Tokamak (YouTube)
  • The first high-speed colour video from the COMPASS tokamak (YouTube)
Front photograph of the COMPASS tokamak in Prague

COMPASS, short for Compact Assembly, is a compact tokamak fusion energy device originally completed at the Culham Science Centre in 1989, upgraded in 1992, and operated until 2002. It was designed as a flexible research facility dedicated mostly to plasma physics studies in circular and D-shaped plasmas.

When it was decommissioned at Culham, it was offered to the European Commission and found a new home at the Institute of Plasma Physics of the Czech Academy of Sciences in Prague where it began operations once again in 2006.[1][2][3][4] It officially ended its experimental runs on 20 August 2021 and will be disassembled to leave room for a new device, COMPASS-U.[5]


The first plasma in COMPASS was produced in 1989 in a C-shaped vacuum vessel, i.e., in a simpler vessel with a circular cross-section. Pioneering experiments followed, including for example the ITER-relevant tests of magnetic field correction with saddle coils for Resonant magnetic perturbations (RMP) experiments or experiments with non-inductive current drive in plasma.

The operation of tokamak was restarted with a D-shaped vacuum vessel in 1992. The operation mode with high plasma confinement (H-mode) was achieved, which represents a reference operation ("standard scenario") for the ITER tokamak. The COMPASS tokamak is one of the smallest tokamaks able to operate in H-mode, with a major radius 0.6 m and height of approximately 0.7 m. Due to its size and shape, the COMPASS plasmas correspond to one tenth (in the linear scale) of the ITER plasmas. Besides COMPASS, there are only two operational tokamaks in Europe with ITER-like configuration capable of H-mode, the Joint European Torus (JET) at Culham and the ASDEX Upgrade at the Institut für Plasmaphysik in Garching, Germany.

In 2002, British scientists started alternative research on larger, spherical tokamak MAST. Operation of COMPASS was discontinued due to insufficient resources for the operation of both tokamaks, however, the planned research program was not complete. The European Commission and UKAEA sent COMPASS to the Institute of Plasma Physics in Prague in the autumn of 2004. The machine restarted operations in 2006 and operated continually until its last "shot" on 20 August 2021. During its operational time in Prauge, COMPASS carried out 21,000 experimental shots.

As of August 2021, plans are to dispose of COMPASS to make way for a significantly larger machine, COMPASS-U (for Upgrade).


Parameters Values[6] Values after planned upgrade in 2021[7]
Major radius R 0.56 m 0.84 m
Minor radius a 0.23 m 0.28 m
Plasma current Ip (max) 360 kA 2 MA
Magnetic field BT 0.9 T - 2.1 T 5 T
Vacuum pressure 1×10−6 Pa
Elongation 1.8
Plasma shape D, SND, elliptical, circular
Pulse length(max) ~ 0.5 s 5 s
Beam heating PNBI 40 keV 2 × 0.3 MW 4-5 MW

See also


  1. ^ Pánek, R.; O. Bilyková; V. Fuchs; M. Hron; P. Chráska; P. Pavlo; J. Stöckel; J. Urban; V. Weinzettl; J. Zajac; F. Žáček (2006). "Reinstallation of the COMPASS-D tokamak in IPP ASCR". Czechoslovak Journal of Physics. 56 (2): 125–137. Bibcode:2006CzJPh..56B.125P. doi:10.1007/s10582-006-0188-1. ISSN 1572-9486. S2CID 53056977.
  2. ^ Weinzettl, V.; R. Panek; M. Hron; J. Stockel; F. Zacek; J.Havlicek; P.Bilkova; D.I.Naydenkova; P.Hacek; J.Zajac; R.Dejarnac; J.Horacek; J. Adamek; J. Mlynar; F. Janky; M. Aftanas; P. Bohm; J. Brotankova; D. Sestak; I. Duran; R. Melich; D. Jares; J. Ghosh; G. Anda; G. Veres; A. Szappanos; S. Zoletnik; M. Berta; V.F. Shevchenko; R. Scannell; M. Walsh; H.W. Müller; V. Igochine; A. Silva; M. Manso; R. Gomes; Tsv. Popov; D. Sarychev; V.K. Kiselov; S. Nanobashvili (2011). "Overview of the COMPASS diagnostics". Fusion Engineering and Design. 86 (6–8): 1224–1231. doi:10.1016/j.fusengdes.2010.12.024.
  3. ^ Panek, R.; J. Adamek; M. Aftanas; P. Bilkova; P. Böhm; F. Brochard; P. Cahyna; J. Cavalier; R.Dejarnac; M. Dimitrova; O. Grover; J. Harrison; P. Hacek; J. Havlicek; A. Havranek; J. Horacek; M. Hron; M. Imrisek; F. Janky; A. Kirk; M. Komm; K. Kovarik; J. Krbec; L. Kripner; T. Markovic; K. Mitosinkova; J. Mlynar; D. Naydenkova; M. Peterka; J. Seidl; J. Stöckel; E. Stefanikova; M. Tomes; J. Urban; P. Vondracek; M. Varavin; J. Varju; V. Weinzettl; J. Zajac (2015). "Status of the COMPASS tokamak and characterization of the first H-mode". Plasma Phys. Control. Fusion. 58 (1): 014015. Bibcode:2016PPCF...58a4015P. doi:10.1088/0741-3335/58/1/014015.
  4. ^ "Tokamak". Retrieved 2020-06-25.
  5. ^ "Curtain Call for the COMPASS Tokamak". ITER. 13 September 2021.
  6. ^ COMPASS on the Institute of Plasma Physics of CAS, archived from the original on 2018-01-12, retrieved 2018-05-28
  7. ^ "COMPASS Upgrade on the Institute of Plasma Physics of CAS".

External links

  • Magnetic fusion in the Czech Republic
  • Diagnostic system on COMPASS