240 R-0

Fast stroke Lang. Probe, UCLA reflectometer

240 R-0

Fast stroke Lang. Probe

Located at 240, R0 incorporates 5 graphite collectors, two for a double Langmuir probe measurement of density and temperature, two probe tips for high frequency (up to 2.5 MHz) spatially separated floating potential measurements, and one tip for a high frequency particle flux measurement. The last three tips described also provide a local measurement of the fluctuation driven particle transport. The midplane probe has a round trip time of 150 msec and a programmable dwell time of more than 10 msec.

Fast stroke Lang. Probe

There are two reciprocating Langmuir probes on DIII-D which measure local density, temperature, and floating potential by plunging a graphite probe head directly in and out of the plasma boundary. As the probe travels along its path, it continuously measures the conditions at the tip. One probe system plunges 15 cm radially at the outer midplane and another system plunges 25 cm vertically up from the divertor floor. Both probe systems have the capability to make measurements a few cm inside the separatrix as well as in the scrape-off layer. These probe systems are part of a collaboration among Sandia National Laboratories, The University of California at San Diego , and General Atomics.