Reciprocating Mach Probe (High-Field-Side)

A fast reciprocating Langmuir (electrostatic) probe system (RPS) was installed at High-Field-Side baffle (Photo from VV) in Jan.-Mar. 2001.
HFS scrape-off layer (SOL) plasma data, i.e. profiles of electron temperature, ion saturation current and floating potential, were for the first time, measured in divertor tokamak.

Langmuir probes: Two double probes for Te, Is measurement at up-stream and down-stream sides of the field lines (i.e. Mach probe), and a floating probe for potential measurement.
Head and 5 electrodes are made of carbon fiber composite (CFC).
Spatial resolution: 1-2 mm in radial direction.
It has provided high spatially resolved profiles of the local electron temperature (Te) and ion saturation current (Is) in the SOL.
Scanning speed: 35cm for ~0.5s (~70 cm/s)
Driving component: a compact pneumatic cylinder and steel springs.
Total mass of the moving components is about 30kg.
Position: P-2 section, U1 vertical port.
Operation : stopped from 2002 to 2004, due to no budget to repair broken probe head.
Probe head and electrodes were repaired, and measurement starts from 2005.

[1] N. Asakura et al., Plasma Phys. Control. Fusion 44 (2002) 2101.
[2] N. Asakura et al., Plasma Phys. Control. Fusion 44 (2002) A313.
[3] N. Asakura et al., J. Nucl. Mater. 313-316, (2003) 820.
[4] N. Asakura et al., Nucl. Fusion, 44 (2004) 503.