Non-circular cross-section screw-pinch experiment on TPE-1a

TPE-1a is a slow screw-pinch device with D-shaped cross-section and metal shell. After implosion, slow outward drift, inward drift and axial contraction, the plasma settles in the quasi-steady equilibrium state, in which the safety factor, the half-axis ratio and the displacement of plasma are almost constant and the beta value varies slowly. A high beta (>5%) plasma is maintained for more than 30 μs. No gross instability is observed. It is found that the elongation of the plasma varies significantly as the filling gas pressure. The plasma column is surrounded by the force-free current and the magnetic field configuration is a typical screw-pinch type. (author)