Simultaneous Measurements of Electrostatic and Magnetic Fluctuations in ASDEX Upgrade Edge Plasma

In ASDEX Upgrade (AUG) electrostatic and magnetic fluctuations in the edge plasma region were measured simultaneously during ELMy H-mode (high confinement) plasmas and L-mode (low confinement) plasmas and during a transition between the two modes. A special probe was used containing six Langmuir probe pins of graphite of which one is protruding radially.

In addition, 20 mm behind the front side a triple magnetic pick-up coil is mounted inside the probe head by which temporal variations of the magnetic field in all three directions of space can be detected. The probe pins are arranged in such a way that simultaneously the poloidal and radial electric field components, the ion saturation current and the current-voltage characteristic can be registered.

During the AUG discharges of 7 s lengths the probe head is inserted two to three times for 100 ms each by the midplane manipulator into the scrape-off layer outside the last closed flux surface. The main emphasis is put on type I ELMs and from the results the radial turbulent particle flux and magnetic field variations are determined.