Observation of Fast Current Redistribution in an Imploding Plasma Column.

Spectroscopic measurements of the magnetic field evolution in a Z-pinch throughout stagnation and with particularly high spatial resolution reveal a sudden current redistribution from the stagnating plasma (SP) to a low-density plasma (LDP) at larger radii, while the SP continues to implode. Based on the plasma parameters it is shown that the current is transferred to an increasing-conductance LDP outside the stagnation, a process likely to be induced by the large impedance of the SP. Since an LDP often exists around imploding plasmas and in various pulsed-power systems, such a fast current redistribution may dramatically affect the behavior and achievable parameters in these systems.

Denervation of the thumb carpometacarpal joint for symptomatic osteoarthritis in 46 patients.

We investigated the effect of an extended denervation procedure in the thumb carpometacarpal (CMC) joint in patients suffering from CMC osteoarthritis. Between 2006 and 2018, 46 patients underwent the procedure in our clinic and were included in this retrospective study. Pain, strength, range of motion, DASH score, complications and overall satisfaction were determined. Assessment showed a significant decrease in pain and excellent physical function at a median 5 years' follow-up. Twelve patients needed secondary surgery due to persistent pain. Overall, 28 of the 46 patients were satisfied with the results of the denervation. Even though the results of CMC denervation are poorer than with simple trapeziectomy, considerable pain relief can be achieved in selected young, physically active patients by exclusively soft-tissue surgery, conserving the biomechanical properties of the joint. In case of failure of the procedure, all other options remain available.

Implementation of high-resolution spectroscopy for ion (and electron) temperature measurements of the divertor plasma in the Tokamak à configuration variable.

High resolution spectroscopy on the Tokamak à Configuration Variable (TCV) divertor plasma provided Doppler broadening measurements to infer the ion and neutral temperature of injected helium gas. This paper presents the Divertor Spectroscopy System's (DSS) access to He II ion temperature measurements over a broad range, ≈0.5-15 eV, with an uncertainty of <10% for most of the studied plasma discharges. TCV's shaping flexibility was employed to validate these measurements against Thomson scattering across the DSS lines of sight. In detachment-related experiments, Ti(He II) ≃ Te, making this diagnostic a reliable thermometer along the divertor leg plasma over the wide range of magnetic equilibria and divertor configurations achievable in TCV. A detailed description of the diagnostic hardware, data analysis, and sources of uncertainty is presented.

Effects of a Preembedded Axial Magnetic Field on the Current Distribution in a Z-Pinch Implosion.

The fundamental physics of the magnetic field distribution in a plasma implosion with a preembedded magnetic field is investigated within a gas-puff Z pinch. Time and space resolved spectroscopy of the polarized Zeeman effect, applied for the first time, reveals the impact of a preembedded axial field on the evolution of the current distribution driven by a pulsed-power generator. The measurements show that the azimuthal magnetic field in the imploding plasma, even in the presence of a weak axial magnetic field, is substantially smaller than expected from the ratio of the driving current to the plasma radius. Much of the current flows at large radii through a slowly imploding, low-density plasma. Previously unpredicted observations in higher-power imploding-magnetized-plasma experiments, including recent, unexplained structures observed in the magnetized liner inertial fusion experiment, may be explained by the present discovery. The development of a force-free current configuration is suggested to explain this phenomenon.