Pressure profile before (ohmic phase) and after IBW injection in D and H discharges at 0.4MA/7.9T. The location of the absorption radius is also shown.

 

FTU Ion Bernstein Wave Heating experiment

The Ion Bernstein Wave (IBW) system is the only one on FTU to provide possible direct heating of the ions. More interesting for the FTU physics programme is the possibility of inducing a sheared flow in the plasma at the absorption layer, as has been shown for the first time by experiments carried out in PBX-M.

The FTU IBW system has the capability of up to 1.5 MW power to be injected into the plasma. With respect to similar heating experiments on other tokamaks, it has the unique feature that the coupling structure is made by waveguides, instead of by conventional antenna inside the vacuum chamber.At present two IBW launchers are operating on the machine, with the capability of injecting more than 0.5 MW. Due to the theoretically expected relatively low threshold power for inducing sheared flows and thus producing internal transport barriers and enhanced confinement, high density and high current plasmas can be studied.

In H plasmas the IBW absoption layer is located at about one third of the minor radius (at 4 fH) when operating at 7.9 T. Deuterium plasmas can also be investigated at 7.9 T: in these conditions the absorption layer is located at a larger ITB radius (r/a ~ 0.65). The use of a waveguide has limited the influx of impurities, so that Zeff does not increase (or even decrases) during IBW injection.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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