Rayleigh–Taylor instability (RTI) is a primary hurdle for many different fusion approaches, most of which rely on external pressure to stabilize the plasma by impeding plasma displacement. In this paper, we report a novel method that utilizes a rotating magnetic field (RMF) to drive an azimuthal electron current to reduce the charge separation caused by RTI. The fluctuation measured in the central cell of the mirror device, approximately half a device length away from the RMF, is identified as the m=1 mode and is suppressed by the RMF in the plug cell. The azimuthal electric fields of the fluctuation are found to decrease to almost zero, and the radial confinement is improved by more than a factor of ten. The separation of the RMF region from the central cell makes this stabilization method unique because the RMF, which can complicate the local magnetic field lines, has little influence on the magnetic field configuration in the central cell. This study may shed light on the use of resonant magnetic perturbations in tokamaks as well as on stabilization methods for many other fusion experiments.

Stabilization of the axisymmetric magnetic mirror relies on the pressure-weighted magnetic field curvature. We report a new experiment by configuring a magnetic cusp structure to stabilize m = 1 interchange mode in KMAX tandem mirror. The cusp configuration is formed by reversing currents in the two side cell coils, and a stronger cusp can lead to a more stable plasma once the null point of cusp is less than 35–40 cm away from the device axis. The density fluctuations measured by four axial Langmuir probes are mitigated by 70%–80%. The stabilization effect is consistent with the prediction of a theoretical calculation.

The helicon plasma source is widely used in various fields due to its high ionisation rate. The helicon wave dispersion relationship indicates that the density is proportional to axial wavenumbers. In this study, we systematically investigated how the plasma density varies with the axial wavenumber by employing several phased antenna systems. The antenna comprised different numbers of loops, and each loop was connected to an individual radio frequency power source. We adjusted the plasma density from approximately 10 11 to 10 13 cm −3 . Such two orders of magnitude adjustments may provide a novel operation mode for helicon applications. The density was linearly proportional to the axial wavenumber, when the axial wavenumber was not exceptionally large. In addition, in a low magnetic field, density peaks were observed in all three antenna configurations. The density peak appears irrespective of whether the Landau damping frequency is higher than collision frequency. This finding suggested that Landau damping and other mechanisms can lead to such a phenomenon of low field density peak.

IntroductionObservational studies have reported a relationship between iron status and the risk of prostate cancer. However, it remains uncertain whether the association is causal or due to confounding or reverse causality. To further clarify the underlying causal relationship, we conducted a Mendelian randomization (MR) analysis.MethodsWe selected three genetic variants (rs1800562, rs1799945, and rs855791) closely correlated with four iron status biomarkers (serum iron, log-transformed ferritin, transferrin saturation, and transferrin) as instrumental variables. Summary statistics for prostate cancer were obtained from the Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome consortium including 79,148 cases and 61,106 controls of European ancestry. The inverse-variance weighted (IVW) method was conducted primarily to estimate the association of genetically predicted iron status and the risk of prostate cancer, supplemented with simple-median, weighted-median and maximum-likelihood methods as sensitivity analysis. MR-Egger regression was used to detect directional pleiotropy. We also conducted a meta-analysis of observational studies to assess the associations between iron status and the risk of prostate cancer.ResultsGenetically predicted increased iron status was associated with the decreased risk of prostate cancer, with odds ratio of 0.91 [95% confidence interval (CI): 0.84, 0.99; P = 0.035] for serum iron, 0.81 (95% CI: 0.65, 1.00; P = 0.046) for log- transformed ferritin, 0.94 (95% CI: 0.88, 0.99; P = 0.029) for transferrin saturation, and 1.15 (95% CI: 0.98, 1.35; P = 0.084) for transferrin (with higher transferrin levels representing lower systemic iron status), using the inverse-variance weighted method. Sensitivity analyses produced consistent associations, and MR-Egger regression indicated no potential pleiotropy. Our replication analysis based on FinnGen research project showed compatible results with our main analysis. Results from our meta-analysis similarly showed that serum ferritin [standardized mean difference (SMD): −1.25; 95% CI: −2.34, −0.16; P = 0.024] and transferrin saturation (SMD: −1.19; 95% CI: −2.34, −0.05; P = 0.042) were lower in patients with prostate cancer compared with that in controls.DiscussionOur study suggests a protective role of iron in the risk of prostate cancer, further investigations are required to clarify the underlying mechanisms.

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