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Helium helicon wave plasma (He-HWP) wall conditioning was performed with a specially designed antenna system on the Experimental Advanced Superconducting Tokamak (EAST) under strong magnetic field (0.5–1 T). The maximum effective RF power $P_{\mathrm {eff}}$ was 30 kW at 27 MHz, and the He pressure was fixed at ~0.27 Pa. Charge-coupled device (CCD) images indicated that toroidal homogeneous but poloidal inhomogeneous He-HWPs were obtained. An obvious desorption of H2 and HD was found during He-HWP operation. Deuterium was desorbed mainly in the form of HD, with a removal rate of ~1021–1022D atoms/h. Additionally, the residual gas analyzer (RGA) results also showed a steep rise in H/D desorption during mode transition (inductively coupled plasma (ICP) $\to $ HWP) with increased $P_{\mathrm {eff}}$ from 5 to 15 kW, then a slight decline in the HWP mode with relatively higher $P_{\mathrm {eff}}$ (>15 kW), which was further verified by the spectral data of hydrogen Balmer series ($\text{H}_{\alpha }$ and $\text{D}_{\alpha }$). [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films were grown on Si substrates by high-density helicon wave plasma (HWP) generated under low pressure, with the help of CH4 as an important single-source precursor. The influence of magnetic field (${B}_{0}$ : 1200–2400 Gs) on the film structure, morphology, composition, and mechanical properties has been studied. The high deposition rate of the films exhibits a maximum of 800 nm/min, which is contributed by the high-density plasma generation of HWP. By the X-ray photoelectron spectroscopy (XPS) analysis, the as-deposited DLC film is composed mainly of sp2 C-C. The DLC film deposited at ${B}_{0} =2400$ Gs exhibits that the friction coefficient reaches its minimum value of $5 \times 10^{-3}$ , with small surface roughness (root mean square (RMS) ~ 10 nm). Considering that ${B}_{0}$ can be easily controlled, this article opens up a new approach to achieve ultralow friction coefficient DLC films with a high deposited rate at room temperature. [ABSTRACT FROM AUTHOR]