Radial electric fields and confinement in the TJ-II stellarator

Abstract

Radial plasma potential profiles have been obtained in the TJ-II by the Heavy Ion Beam Probing (HIBP) diagnostics. Results show that the potential increases up to 1 kV near the magnetic axis in ECRH low-density plasmas. The secondary ion current profiles, which directly reflect the plasma density, are hollow. In low-density ECRH operation, radial electric fields are found to be positive in the plasma core, however, a reduction in these fields is observed with increasing density. Radial plasma potential profiles show evidence of structures in configurations with low-order rational surfaces. In particular, HIBP measurements have permitted characterization of the plasma potential profile during e-ITB formation. Experiments in TJ-II have shown that it is possible to modify the global confinement and edge plasma parameters with limiter biasing, illustrating the direct impact of radial electric fields on confinement properties. Plasma potential measurements by the HIBP diagnostic show a strong impact of heating method (ECRH versus NBI) on radial electric fields. : 52.55.Hc, 52.25.Fi, 52.70.Nc PACS

Extended estimations of neoclassical transport for the TJ-II stellarator: The bootstrap current

“…It is worth stressing the fair agreement between the results of Fig. 4 and the radial electric field measured [37] by the HIBP diagnostic in TJ-II for similar plasma parameters. Once the radial electric field was obtained it is possible to make all type of neoclassical estimates.…”

Study of the plasma potential evolution during ECRH in the T-10 tokamak and TJ-II stellarator

“…This is valid for both the core and edge plasma. This tendency was also found in TJ-II stellarator during experiments with the ECRH power modulation [9]. …”

“…The secondary (Cs 2+ ) ion current profiles, which directly reflect the plasma density, are hollow [9]. In the present experimental set-up, one gyrotron line (L1) provides a continuous heating (200 kW), whereas the second line (L2) with the same power is modulated with a 100 ms period.…”

50 Years of Hot Plasma Diagnostic With Heavy Ion Beam Probing (Hibp) at the Kharkov Institute of Physics and Technology

“…Kharkiv HIBPs were installed at the devices worked according to the worldwide fusion program. The main results were obtained on TM-4 [50], T-10 [51], and TJ-II [52][53][54][55][56][57][58][59][60][61]. The behavior of the plasma potential is similar despite the different methods of plasma creating and heating, as well as magnetic configurations of the devices.…”