TJ-II:Biasing probe
At TJ-II, a 2-D carbon composite mushroom shaped electrode (12 mm high with a diameter of 25 mm) has been developed and installed on a fast reciprocating probe drive. Typically, the electrode is inserted to a position 2 cm inside the last closed flux surface (LCFS) and biased positively (200-300 V) with respect to one of the two TJ-II limiters located in the scrape-off layer region (about 0.5 cm beyond the LCFS). Measured electrode currents are in the range of 30-50 A. [1] [2]
Layout of the biasing probe, mounted on the reciprocating probe drive
In 2009, the power source (originally DC) has been upgraded to allow modulation with a frequency of up to a few kHz.