Spatially resolved measurements of the magnetic field of a spheromak have been analyzed and compared with expectations for the ratio of j\\/B from the pre s sure-gradientfree Taylor model and a model with pressure due to Morikawa. Better agreement is found with the model containing finite pressure.
The magnetic properties of the spheromak configuration produced by a combination of slow theta and Z discharges in the University of Maryland Spheromak experiment (MS) are reported. The magnetic structure of the plasma in MS has been mapped out by arrays of passive magnetic pickup coils. The Taylor relaxation process is observed during the formation phase. The magnetic profile evolves in such a way that the ratio of poloidal current Ip to poloidal flux ψ in the plasma approaches a constant value, where μ0Ip=kelψ. When the spheromak is formed, the magnetic field configuration is close to Taylor’s minimum energy state, μ0j=kB. This constant k is related to the size of the spheromak produced. A spheromak with 1.0 T maximum field, corresponding to 650 kA poloidal current, has been produced in MS. However, due to the high plasma density (6–8×1020 m−3) and the presence of low-Z impurities (mainly carbon and oxygen), the plasma is radiation dominated with electron temperature ≤15 eV. The magnetic field decays exponentially during the decay phase. Axisymmetric equilibrium states that could exist in the configuration are calculated with a Grad–Shafranov equilibrium code. Comparison of the numerical calculation with the experimental measurements indicates that the magnetic-field structure stays close to the equilibrium state as the plasma decays.
Intense, and evidently nonthermal, bremsstrahlung has been observed from turbulent helium plasmas that were generated in a large, high voltage theta pinch operated in two different experimental configurations. The emissions were in the wavelength range 1 mm ≲ λ ≲ 16 mm, and are identified as collective bremsstrahlung, originating from the interaction of longitudinal modes of the turbulent plasmas by wave-wave scattering.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.