Tokamak COMPASS back in operation


    Jan Mlynar, Radomír Pánek
    Association EURATOM-IPP.CR
    Institute of Plasma Physics AS CR, v.v.i.
    Za Slovankou 3, 182 00 Prague 8, Czech Republic

    In addition, the Czech fusion research had been already associated to the EURATOM coordinated programme since 1999. However, the small Czech tokamak CASTOR was at the same time the oldest operating tokamak worldwide, with its basic components dating back to 1960 when it had started as TM-1 in the Kurchatov institute in Moscow.

    Although significantly modernised several times and quite respected in fusion community, CASTOR was not adequate for the ongoing fusion research, which is nowadays focussed on preparation for ITER, the international fusion reactor under construction in France.

    At the same time, a fully suitable facility - tokamak COMPASS - was in need of a new operator.


    COMPASS - COMP act ASSembly was commissioned in UKAEA Fusion in Culham Science Centre in the late 1980s.

    Thanks to the D-shaped chamber with a divertor installed three years later (wherefrom the former name COMPASS-D) its plasmas were similar to modern tokamak facilities including the ITER design.

    In its ten years of operation COMPASS was providing extremely valuable data and proved the UK team worthy of an even more ambitious project, a bigger spherical tokamak MAST. At this point, however, COMPASS was far from outdated.

    Cross-section scheme of tokamak COMPASS.Image - 1 - Cross-section scheme of tokamak COMPASS. The ring-shaped vessel surrounded by a system of magnetic coils allows to confine approx. half a cubic meter of very high temperature hydrogen plasma.


    In this situation it seems natural that the CASTOR operator, the Institute of Plasma Physics of the Academy of Sciences of the Czech Republic (IPP Prague) accepted the offer from UKAEA Culham to re-install tokamak COMPASS in Prague. Facing a crucial decision on how to proceed in the well developed and internationally established fusion oriented studies at IPP Prague without an adequate facility, COMPASS offer came as a miracle, says Prof Pavel Chráska, director of IPP Prague.

    "However, a singular miracle would not do. More had to be achieved - favorable attitude of the leaders of the Academy of Sciences of the Czech republic, extra financial support from the Czech Government and finally, gathering required numbers of young as well as experienced people with the needed zeal for the task."

    Thanks to the reputation of IPP Prague combined with efforts of many enthusiasts, the project was before long perceived as a major promise for the Czech science so that all the required financial and human resources were eventually found.

    Two 30 tons flywheel generators store energy for the tokamak COMPASS experimentsImage - 2 - Two 30 tons flywheel generators store energy for the tokamak COMPASS experiments. Each of them can provide up to 35 MW electric power for 2 seconds.


    Central to the success of the undertaking was also the ongoing support of EURATOM and their Associates, which culminated in award of the Priority support. Even then, COMPASS re-installation was far from simple.

    After conclusion of the agreements in 2006, a new building for the facility was designed, cleared by local administration and finally erected by the end of 2007.


    In the meantime, COMPASS auxilliaries were dismantled by the team of IPP Prague- with assistance of the UKAEA Fusion - and the COMPASS tokamak itself was lifted through the Culham hall roof in a breathtaking heavy-crane operation. The tokamak arrived to Prague as a special transport on 20th October 2007.

    In IPP Prague, most of the auxilliary systems for the facility must have been designed and built from scratch. To start with, COMPASS requires up to 50 MW electric power in 2 second pulses. Unlike in UKAEA, in IPP this power level is not available from the grid.

    Tokamak GOLEM is the oldest tokamak in service.Image - 3 - Tokamak GOLEM is the oldest tokamak in service. Built in early 1960s as TM-1 in Moscow, later upgraded in IPP Prague and known as CASTOR, it now serves to students.

    Different options of power accumulation had been discussed before launching a tender for the power supplies with flywheel generators. Winner of the tender, the Czech company CKD, installed two generators in early 2008.

    Second, it was decided to replace the Electron cyclotron resonant heating of the COMPASS plasmas by the Neutral beam heating, thus achieving higher ion temperatures in future COMPASS operations. The beam injectors are under construction now.


    Third, a brand new control and data acquisition system had to be designed.

    Last, but not least, all major diagnostic systems will have to be built. Altogether, an investment worth almost 14 million Euro.


    In all these works, the Czech Association EURATOM-IPP.CR - with IPP Prague in the role of the main co-ordinator - welcomes the increasing involvement of other european Associations.


    Among many parties involved in the current works let us mention at least the Portugese Association EURATOM-IST who are co-developing the control system for COMPASS, and the Hungarian Association EURATOM-HAS who decided to complete two demanding diagnostic systems (lithium beam and fast camera).


    As a matter of fact, one of the main motivations for the COMPASS re-installlation was the wish to continue and broaden the existing international collaborations in fusion research.


    The new COMPASS team works under a very tight schedule. The main milestone of demonstrating the first plasma by the end of 2008 was met on 9th December and on 19th February 2009 the team started regular operation by demonstrating tokamak experiments to media in live.


    Tokamak COMPASS now aspires to become a regional centre for both cutting edge fusion science and training new experts, who may later importantly contribute to the research both at home and in international centres like ITER. This in turn triggers interest of the wider academic community.


    For example, the Faculty of Nuclear Engineering and Physical Sciences of the Czech Technical University in Prague, member of the Association, introduced new fusion curricullum in 2006 and works on refurbishments of the old CASTOR tokamak under the new name "GOLEM" - for the tokamak is now installed next to the old Jewish town in Prague.


    GOLEM will therefore become a key facility for practical exercises of fusion students.

    The main programmatic plans of the COMPASS team are focused on detailed investigation of physics of the plasma edge by exploiting advanced diagnostic methods with a high temporal and spatial resolution.


    In addition, mitigation of instabilities occurring in this region will be pursued. Both these topics are highly relevant to ITER operation. We strongly believe that this scientific programme will stimulate our collaboration within Europe and attract young generation of Czech physicists to fusion research.