COMPASS tokamak
The COMPASS tokamak in Prague is the main experimental facility of Tokamak department of Institute of Plasma Physics of the Czech Academy of Sciences since 2006. It was designed in the 1980s in the British Culham Science Centre as a flexible research facility dedicated mostly to plasma physics studies in circular and D-shaped plasmas.
History
The first plasma in COMPASS "broke down" 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 experiments or experiments with non-inductive current drive in plasma.The operation of tokamak restarted with a D-shaped vacuum vessel in 1992. The operation mode with high plasma confinement was achieved, which represents a reference operation for the ITER tokamak. The COMPASS tokamak with its size ranks to smaller tokamaks capable of the H-mode operation. Importantly, due to its size and shape the COMPASS plasmas correspond to one tenth of the ITER plasmas. 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 and the German tokamak ASDEX Upgrade. JET is the biggest experimental device of this type in the world.
In 2002, British scientists started alternative research on larger, spherical tokamak MAST. Operation of COMPASS was discontinued due to insufficient resources for operation of both tokamaks, however, the research program foreseen for the latter tokamak was not concluded. Due to its important and not completely realised opportunities - and, in particular, due to its direct relevance to the ITER project - the facility was offered for free by the European Commission and UKAEA to the Institute of Plasma Physics AS CR in Prague in autumn 2004. The Prague institute has been coordinating research in thermonuclear fusion in the Czech Republic in the framework of EURATOM since 1999. Team of physicists from the institute has a long-time experience in this field of research including operation of a small tokamak CASTOR. The European Commission has declared that the institute is fully competent to operate the tokamak COMPASS.
Parameters of the tokamak COMPASS
| Parameters | Values | Values after planned upgrade in 2021 |
| Major radius R | 0.56 m | 0.84 m |
| Minor radius a | 0.23 m | 0.28 m |
| Plasma current Ip | 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 | ~ 0.5 s | 5 s |
| Beam heating PNBI 40 keV | 2 × 0.3 MW | 4-5 MW |