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.
The impact of biasing on confinement properties has been studied to some depth. [1] [2] [3]
In 2009, the power source (originally DC) has been upgraded to allow modulation with a frequency of up to a few kHz.
Location: sector A4 (φ = 174.4 °). Signal names in the TJ-II database: 'PolI', 'PolV'.
References
- ↑ C. Hidalgo, M. Pedrosa, L. García, and A. Ware, Experimental evidence of coupling between sheared-flow development and an increase in the level of turbulence in the TJ-II stellarator, Phys. Rev. E, 70 (2004) 067402
- ↑ C. Silva et al, Transport and fluctuations during electrode biasing on TJ-II, Czech. J. Phys. 55 (2005) 1589
- ↑ M.A. Pedrosa et al, Transport and fluctuations during electrode biasing experiments on the TJ-II stellarator, Proc. 12st Fusion Energy Conf. (2006) EX-P4/40