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Some preliminary results of plasma rotations in a linear plasma experiment device, Peking University Plasma Test (PPT) device, are reported in this paper. PPT has a cylindrical vacuum chamber with 500 mm diameter and 1000 mm length, and a pair of Helmholtz coils which can generate cylindrical or cusp magnetic geometry with magnitude from 0 to 2000 G. Plasma was generated by a helicon source and the typical density is about 10 cm for the argon plasma. Some Langmuir probes, magnetic probes, and one high-speed camera are set up to diagnose the rotational plasmas. The preliminary results show that magnetic fluctuations exist during some plasma rotation processes with both cylindrical and cusp magnetic geometries, which might be related to some electromagnetic processes and need further studies.

Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (B) and radial electric field (E) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D B profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.

We report the first experimental observation of zonal flow (ZF) formation through phase patterning. Here the ‘phase’ refers to the eikonal phase carried by streamer-like mode. It is observed that the phase-gradient profile tends to form ‘shock’ layer structures in regions where there are strong streamer-ZF interactions. The emergence of phase-gradient shock layers invalidate the constant-phase-gradient hypothesis, which is frequently employed in the modulational instability models of ZF generation, and is consistent with a recent theoretical work (Guo et al 2016 Phys. Rev. Lett. 117 125002), which predicts that the phase-curvature (gradient of the phase-gradient) can produce a new Reynolds force and accelerate the ZF. By decomposing the Reynolds’ force of the tilted streamers into a phase curvature driven piece and an amplitude inhomogeneity driven one, it is found that inside the shock layers the phase curvature plays a prominent role in accelerating the ZF. We also explore the formation mechanism of the phase pattern and its consistent dynamics with phase-curvature-driven ZF. These findings potentially open a new way to understand the various elusive self-organization phenomena in plasma turbulence.

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The helicon wave plasma (HWP) sources have well-known advantages of high efficiency and high plasma density, with broad applications in many areas. The crucial mechanism lies on mode transitions, which has been an outstanding issue for years. We have built a fluid simulation model and further developed the Peking University Helicon Discharge (PHD) code. The mode transitions also known as density jumps of a single-loop antenna discharge are reproduced in simulations for the first time. It is found that large-amplitude SHWs are responsible for the mode transitions, similar to those of a resonant cavity for laser generation. This paper intends to give a complete and quantitative standing helicon wave (SHW) resonance theory to explain the relationship of the mode transitions and the SHWs. The SHW resonance theory reasonably explains several key questions in helicon plasmas, such as mode transition and efficient power absorption, and helps to improve future plasma generation methods.

A Multi-Color (MC) gas puff imaging diagnostic has been developed on HL-2A tokamak. This diagnostic can simultaneously measure two-dimensional (2D, radial, and poloidal) electron density and temperature distributions with a good spatial resolution of 2.5 × 2.5 mm2 and a temporal resolution of about 100 µs at best in edge plasmas. The 2D electron density and temperature distributions are inferred from the ratios of intensities of three different neutral helium emission lines; therefore, it is also referred to as helium beam probe or beam emission spectroscopy on thermal helium. A compact light splitter is used to split the inlet visible emission beam into four channels, and the specific neutral helium lines of the wavelengths λ1 = 587.6 nm, λ2 = 667.8 nm, λ3 = 706.5 nm, and λ4 = 728.1 nm are measured, respectively. This MC diagnostic has been experimentally tested and calibrated on a linear magnetic confinement device Peking University Plasma Test device, and the measured 2D electron density and temperature distributions are compared with the Langmuir probe measurements.

Working memory (WM) deficits are recognized as serious cognitive impairment in patients with major depressive disorder (MDD). This review aims to clarify the effects of impaired WM function in patients with MDD and explore non‐invasive and effective treatments that can be adopted in clinical practice. This review (1) synthesizes extant literature examining brain function and brain areas in terms of WM in individuals with depression, (2) utilizes the outcomes of the studies presented in this review to discuss the effects of impaired WM function on cognitive processing in individuals with depression, (3) integrates the treatments explored in current studies and (4) provides some suggestions for future research. We found that (1) central executive (CE) components affect the processing of WM, and this might be one of the factors influencing cognitive biases, as it is implicated in repetitive negative thinking and rumination; (2) the left dorsal anterior cingulate cortex (dACC), the left dorsolateral prefrontal cortex (DLPFC) and the regions of the default mode network (DMN) play a vital role in CE functioning; and (3) psychotherapy, cognitive training, exercise and physical therapy can be used as complementary treatments for MDD.