TJ-II:Langmuir Probes

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Location of the reciprocating Langmuir probes at TJ-II

TJ-II has two fast reciprocating drives for Langmuir probes (with a displacement velocity of approximately 1 m/s). [1] [2] [3] Probe drive 1 is located at φ = 38.2°, R=134 cm (sector D4) and probe drive 2 at φ = 195° (sector B2).

Probe heads

Several different heads can be mounted on the reciprocating drives: e.g., staircase Langmuir probes, a rake probe (as of 2009), or a multi-pin Langmuir probe (2010). A biasing probe has also been used.

Photo of a staircase Langmuir probe head with three sets of measurement pins
Photo of a multipin Langmuir probe head
Photo of a Langmuir rake probe head

See also


  1. M.A. Pedrosa et al, Fast movable remotely controlled Langmuir probe system, Rev. Sci. Instrum. 70 (1999) 415
  2. E. Calderón et al, On the Influence of Probe Presheath on the Measurement of Fluctuation and E × B Turbulent Transport by Langmuir Probes, Contributions to Plasma Physics 44, Issue 7-8 (2004) 700 - 704
  3. M.A. Pedrosa et al, Evidence of Long-Distance Correlation of Fluctuations during Edge Transitions to Improved-Confinement Regimes in the TJ-II Stellarator, Phys. Rev. Lett. 100 (2008) 215003