M.Blaumoser,C.Alejaldre,L.Almoguera,J.Alonso,E.Ascasibar,J.Botija,R.Carrasco, A.Fraguas,A.Garcia,Jiang Qin,I.Kirpitchev,J.Knaster,A.Martinez,J.Doncel, M.Medrano, P.Mendez,L.Pacios,A.de la Peqa,J.Sanchez,P.Tabares
Asociacisn EURATOM-CIEMAT para Fusisn.
Avda. Complutense 22, 28040 Madrid, Spain
The Spanish Stellarator TJ-II is a highly flexible medium-size fusion device of the heliac- type constructed at CIEMAT in Madrid, Spain from 1991 to 1997. The magnetic field mapping at low magnetic fields were conducted through in December 1996 and January 1997 with excellent results. From January to September 1997 the commissioning of the device up to the design values is being done together with the assembly of the basic diagnostic equipment. The first plasma is expected for October 1997.
The main characteristics of TJ-II are : Major plasma radius : 1.5 m Minor plasma dimensions: 0.2 m by 0.4 m Magnetic field on axis : 1 T Pulse length : 0.2 s to 1 s (every 300 s) Iota : 0.9 to 2.5 Shear : up to 10 % Maximum beta : 6 % Heating power: 1 MW ECRH - 2/4 MW NBI (phase I/II)
The all-metal vacuum vessel of TJ-II has a helical geometry and houses 96 ports. Seven water-cooled copper coil systems with maximum currents between 7 kA and 32.5 kA provide the bean-shaped helical confinement field. The Bitter-type toroidal coils are split in halves for assembly reasons. Four sets of poloidal coils contain the vertical, radial and OH field systems.
TJ-II is a very compact experimental device with highly stressed materials and very narrow tolerances to achieve good confinement properties. This required high quality standards for the fabrication and assembly of the device. For the high precision positioning of all stellarator components a computer-based theodolite system was employed. A large number of tests were done during the assembly phase. Afterwards a comprehensive commissioning program was initiated. So far no major problems have been encountered. For the test of the pulse power supply up to the maximum current values a dummy load is being used which consists of up to five inductively coupled coils. The distances between the coils were chosen in a way such that self and mutual inductances coincide with those of the coil systems of the stellarator and thus form a electromagnetic image of TJ-II.
The paper gives a short description of the design of TJ-II and concentrates on the critical and complex construction and commissioning issues including the sophisticated test programs. In addition results of the magnetic field mapping will be presented.