Plasma behaviour in the high density regime has been investigated on the Frascati Tokamak Upgrade (FTU). The items particularly addressed are density limit, MARFE characteristics and fuelling efficiency. With gas puffing, a maximum line average density of 3.2*1020 m-3 has been obtained in the ohmic regime at q=5.1, corresponding to 1.7 times the Greenwald limit; while with pellet injection, a value of 3.7*1020 m-3 has been reached at q=3.5. The density limit appears to be connected with the impurity content and edge parameters, so the best results are obtained with very clean plasmas and peaked electron density profiles. The MARFE phenomenon always appears beyond a critical density that depends on the total input power and the effective charge: emissivities in the range of 2 to 12 MW/m3 have been measured in this highly radiating region. The fuelling efficiency, starting from a value of about 50% at low density, progressively deteriorates, falling to 10% near the density limit: this behaviour is interpreted as being due to a decrease of the scrape-off layer transparency to incoming neutrals

High density operation on Frascati tokamak upgrade

G Granucci;
1996

Abstract

Plasma behaviour in the high density regime has been investigated on the Frascati Tokamak Upgrade (FTU). The items particularly addressed are density limit, MARFE characteristics and fuelling efficiency. With gas puffing, a maximum line average density of 3.2*1020 m-3 has been obtained in the ohmic regime at q=5.1, corresponding to 1.7 times the Greenwald limit; while with pellet injection, a value of 3.7*1020 m-3 has been reached at q=3.5. The density limit appears to be connected with the impurity content and edge parameters, so the best results are obtained with very clean plasmas and peaked electron density profiles. The MARFE phenomenon always appears beyond a critical density that depends on the total input power and the effective charge: emissivities in the range of 2 to 12 MW/m3 have been measured in this highly radiating region. The fuelling efficiency, starting from a value of about 50% at low density, progressively deteriorates, falling to 10% near the density limit: this behaviour is interpreted as being due to a decrease of the scrape-off layer transparency to incoming neutrals
1996
Istituto di fisica del plasma - IFP - Sede Milano
Tokamaks
spherical tokamaks
Fueling
heating and ignition
Plasma-material interactions
boundary layer effects
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/199643
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