S.Ciattaglia B.Angelini, G.Buceti, R.Cesareo, F. Crisanti,V.Cocilovo, D.Frigione, F.Gravanti,
G.Maddaluno, G.Mazzitelli, M.Panella, V.Pericoli, E.Sternini, A.Tuccillo, V.Vitale, the FTU team
and the ECRH team1
Associazione Euratom ENEA sulla Fusione
Centro Ricerche Frascati, C.P. 65, 00044 Frascati, Italy
1Associazione Euratom-ENEA-CNR, Istituto di Fisica del Plasma, Milano, Italy
The paper presents a general overview of the Frascati Tokamak Upgrade (FTU) machine operation in the last two years. In the experimental sessions more than 3500 pulses have been performed (mostly in D2) with a toroidal field between 2.5 and 8 Tesla and a plasma current between 0.35 - 1.3 MA, according to experimental programmes. From technological point of view the behaviour of the molybdenum toroidal limiter installed at the end of 1994, covering the inner wall, has been positive. The hard and soft disruptions have only caused local damages probably due to runaways electrons. Plasma discharges, especially at high electron density, has been obtained without difficulties, also in presence of metallic impurity contamination.
An analysis of the operation has been performed in order to point out the availability of the FTU systems and the efficiency of the experimental sessions. The relevant indicators have been defined and the main factors and causes of the unavailability of the machine have been pointed out, as well as the corrective actions. A tool has been implemented and here discussed in details in order to analyze in real time the behaviour of the systems during pulses.
All different types of radiofrequency systems installed on FTU have been utilized: Lower Hybrid Waves (LHW), Electron Cyclotron Resonant Heating (ECRH) and Ion Bernstein waves (IBW). Multiple pellet system has been routinely used too. The main research activities have been concentrated on plasma MHD studies with different heating scenarios: LH and ECRH have been used alone and together to investigate synergetic effects. A strong effort has been devoted to current drive experiments at high density (1 102 m-3) and to investigate the possibility to obtain and to sustain shear reversal configurations. Preliminary experiments have been also performed with IBW. Multiple pellet injection to the plasma, up to three pellets, produced a neutron peak rate of 3 1021 s-1 with an energy confinement time up to 80 ms.
Finally, scientific and technological programmes planned for the next two years are reported.