Development of a compact torus injection system for the Keda Torus eXperiment

Abstract

A compact torus injection system, KTX-CTI, has been developed for the planned injection experiments on the Keda Torus eXperiment (KTX) reversed field pinch (RFP) device to investigate the physics and engineering issues associated with interaction between a compact torus (CT) and RFP. The key interests include fueling directly into the reactor center, confinement improvement, and injection of momentum and helicity into the RFP discharges. The CT velocity and mass have been measured using a multichannel optical fiber interferometer, and for the first time the time evolution of CT density profile during CT propagation is obtained. The number of injected particles, the CT velocity and density on the discharge parameters have been characterized: the maximum hydrogen CT plasma mass, m_CT, is 50 μg, corresponding to 30% of the mass in a typical KTX plasma; the CT velocity exceed 120 km/s. It is firstly observed that multiple CTs can be produced and emitted during the very short period (<100 μs) in one discharge, which is significant for the future study of repetitive CT injection, even with an ultra-high frequency.

Investigation of the compact torus plasma motion in the KTX-CTI device based on circuit analyses

“…´-(for hydrogen), and the corresponding m CT is close to 50 g m [30]. The relationship between the CT mass and the required acceleration bank voltage is obtained based on the NRAbased point model, by fixing the length of the acceleration region (36.3 cm) and the final injection velocity (100 km s −1 ) (figure 11).…”

“…where S CT is the cross-sectional area of CT plasma, and the full-width integration of the density waveform is performed [30]. According to the time-of-flight method [31], the calculated average velocity of the CT plasma between point-1 and point-2 of the acceleration region is approximately…”

“…Recently, for use in the reversed-field pinch device of the Keda Torus eXperiment (KTX) project, a CTI device is developed (KTX-CTI) [30] at the University of Science and Technology in China (USTC). In this paper, we briefly introduce the bench test results of this device in section 2 and use nonlinear regression analysis (NRA) to calculate the circuit parameters of the formation bank discharge circuit in section 3.…”

Development of electromagnetic pellet injector for disruption mitigation of tokamak plasma

“…[11] Thus, if a railgun system is used in DMS instead of pneumatic injector, the injection speed and the overall response time could be greatly improved. Similar fueling injector like compact torus injection system has also been applied in fusion devices, [12] showing that an electromagnetic device is feasible in the application of fusion devices. R. Raman had also given a more detailed discussion towards the advantage of a railgun system.…”

Development of a compact torus injector system for central fuelling technology of EAST

“…Compared to fueling techniques such as gas puffing [2], pellet injection [3], and supersonic molecular beam injection [4], compact torus (CT) injection is a promising technology for central fueling wherein the CT, which is a carrier of kinetic, thermal, and electromagnetic energy, is formed and accelerated in a coaxial plasma gun. CT is extensively employed in fusion devices for central fueling, such as TdeV [5], STOR-M [6], JFT-2M [7], C-2 [8], and KTX [9]. In addition, the CT injector is used for studying magnetic reconnection [10], magnetic target fusion [11], and space plasma propulsion [12].…”