Evaluation of Turbulent Particle Flux by Heavy Ion Beam Probe in the T-10 Tokamak

Abstract

In the T-10 tokamak, the local fluctuations of poloidal electric fieldẼ pol and densityñ e were simultaneously measured by heavy ion beam probe (HIBP) with 5-slit energy analyzer that allow us to estimate the turbulent particle flux and E × B rotation velocity in the gradient zone of plasma column (r/a = 0.8). It was shown that at the Ohmic heating (OH) stage of discharge, the outward flux is in the range of 2 × 10 19 m −2 s −1 , increasing at the ECRH stage by a factor of 1.5. At OH stage, the poloidal rotation velocity is about 4.5 km/s.

Bispectral analysis of broadband turbulence and geodesic acoustic modes in the T-10 tokamak

“…Figure 1 (consistent with figure 1 of Eliseev et al. 2018) diagrams the geometry of the poloidal electric field and velocity measurements. Same-flux-surface potentials , are locally measured by slits and of the five-slit energy analyser, where , and are commonly used.…”

“…Here, the interaction of GAM with ambient turbulence in T-10 (Eliseev et al. 2018) is re-investigated using a functionally similar bicoherence analysis to quantify not only the coupling, but also the energy transfer, between local fluctuations in the magnetic potential , electron density and electrostatic potential . The intention is to confirm or refine previous bicoherence interpretations (Melnikov et al.…”

“…Figure 6 of Eliseev et al. (2018), not shown here, graphs the 50–200 kHz frequency-integrated flux through the various pairs of HIBP slits. The mean flux suddenly increases upon the transition of the discharge from the ohmic (OH) stage () to the electron cyclotron resonant heating (ECRH) stage () as a result of a significant increase in amplitude of fluctuations of both and density despite the decrease of coherence between those two quantities.…”

“…GAM, the only spectral feature at 17 kHz, plays a crucial role in the three-wave interaction that involves both upper- and lower-frequency halves of the higher-frequency broadband turbulence, as evidenced by the strong coupling apparent in multi-channel, HIBP measurements of turbulent particle flux and rotation velocity in the gradient zone ( = 0.8) of the plasma column (Eliseev et al. 2018). Figure 3 shows cross-bicoherence compared with the real part of the bispectrum , which compactly illustrates both the extent and direction of energy transfer between plasma density fluctuations and magnetic potential fluctuations.…”

High Voltage Test Bench for Heavy Ion Beam Probe Diagnostics on T-15md Tokamak

“…This coupling has been studied during recent years, but it still presents an open question of modern plasma physics. As a multipurpose diagnostics HIBP is also used, to study Alfven eigen modes [7], turbulent flows [8] and plasma turbulence rotation [9,10]. On top of that, plasma density profile can also be retrieved from the secondary beam current, which gives us an additional information to study the evolution of the plasma transport [11,12].…”