Ideal magnetohydrodynamic simulations of low beta compact toroid injection into a hot strongly magnetized plasma

Abstract

Abstract. We present results from three-dimensional ideal magnetohydrodynamic simulations of low β compact toroid (CT) injection into a hot strongly magnetized plasma, with the aim of providing insight into CT fueling of a tokamak with parameters relevant for ITER (International Thermonuclear Experimental Reactor). A regime is identified in terms of CT injection speed and CT-to-background magnetic field ratio that appears promising for precise core fueling. Shock-dominated regimes, which are probably unfavorable for tokamak fueling, are also identified. The CT penetration depth is proportional to the CT injection speed and density. The entire CT evolution can be divided into three stages: (1) initial penetration, (2) compression in the direction of propagation, and reconnection with the background magnetic field, and (3) coming to rest and spreading in the direction perpendicular to injection. Tilting of the CT is not observed due to the fast transit time of the CT across the background plasma.

A systematical study of neutron-rich Zr isotopes by the projected shell model

“…The major differences here compared to the recent results on CT injection [4] are the very high density ratio n j /n p 500 (where n j and n p are the injected and background plasma densities, respectively) and the initially null value of the jet magnetic field. The computational domain coinciding with the background plasma is |X| ≤ 9, |Y | ≤ 9, and |Z| ≤ 9, corresponding to a cube of (180 cm) 3 in actual length units (assuming the injected jet radius r j = 5 cm).…”

“…From Fig. 6(left), the spread ∆Z ∼ 3.5 (35 cm) of this line-shaped structure is much larger than for CT fueling [4] which is about ∆Z ∼ 0.2 (2 cm). The jet in Fig.…”

“…They found that with such a stress-free boundary condition, the magnetic tension force is smaller (but not zero), and the relaxation of the tension force from magnetic reconnection is also much smaller (could even be ignored). An outflowing boundary condition is more appropriate than Suzuki et al's choice for the large aspect ratio case since in real tokamaks the toroidal dimension is much larger than the poloidal dimension, and thus it will take a long time for toroidal dynamics to re-enter the computational domain after traveling along toroidal magnetic field lines [4]. In order to minimize the influence of the entrance port on boundary conditions, the port is opened (a hole inserted into the conducting boundary) when the top of the jet reaches the bottom boundary at t = 0.5/v inj and is closed (hole removed from the conducting boundary) at t = 2/v inj after the jet has fully entered the computation domain (at t ∼ 1.5/v inj ).…”

“…The plasma volume needs to be increased to accommodate a larger total number of particles [3,5]. Preliminary simulation results [4] of unmagnetized dense plasma jets injected into an ITER-relevant background plasma suggest that deep but somewhat less-localized fueling (compared to CT's) is possible for unmagnetized dense plasma jet injection. In this paper, we employ a simple idealized model and three-dimensional (3D) ideal magnetohydrodynamic (MHD) simulations of unmagnetized dense plasma jets propagating into a uniform slab plasma with uniform magnetic field perpendicular to the jet propagation direction, mimicking jet fueling into an infinite aspect ratio tokamak.…”

Experimental investigation of coaxial-gun-formed plasmas injected into a background transverse magnetic field or plasma

“…9,10,34 In addition, nonlinear ideal MHD simulations have modeled a plasma injected into a magnetized background plasma under varying conditions. [35][36][37] In this paper, we present the Plasma Bubble Expansion eXperiment (PBEX) results of the interaction of a dynamic argon plasma with a uniform background transverse magnetic field. We explore this interaction evolution with multiple diagnostics.…”