Overview of Keda Torus eXperiment initial results

Abstract

The Keda Torus eXperiment (KTX) is a new reversed field pinch (RFP) device at the University of Science and Technology of China. The construction and assembly of KTX, including the vacuum chamber, conducting shell, magnetic field windings, power supply system, active control coils, vacuum pump and data acquisition system, have been completed on August 1, 2015. Immediately following that, the first plasma was obtained on August 15, 2015. Intensive conditioning of the machine is underway to ramp up the plasma current toward its full operation. An active feedback mode control system has been built and has been implemented to control the error field around the vertical gaps of the conducting shell. The pulsed power supply systems of ohmic heating field and toroidal field (TF), using thyristor and energy storage capacitors, have been tested and commissioned. The TF power supply has flexibility in being able to operate with a reversed TF configuration and stable TF configuration. The fundamental diagnostic tools are developed for early KTX operation. Currently, the plasma current is up to 205 kA and the maximum discharge length is 21 ms, approaching to the conducting shell penetration time. Furthermore, typical RFP discharges are being produced with RFP state lasting 2 ms. These initial operation results for KTX are described in detail.

A Data-Assimilation Based Method for Equilibrium Reconstruction of Magnetic Fusion Plasma and its Application to Reversed Field Pinch

“…Step4 Obtain the gradient ∂E/∂p by calculating (7) and (9), and by using the results of Steps 2 and 3. Step5 If |∂E/∂p| is small enough, stop.…”

“…The cost function is defined by (7) where N m = 6. The Algorithm for Equilibrium Reconstruction described in Sec.…”

“…We apply the reconstruction algorithm with starting from some different initial guesses. The weights w i of cost function (7) are chosen as (w 1 , w 2 , w 3 , w 4 , w 5 , w…”

Construction of an H α diagnostic system and its application to determine neutral hydrogen densities on the Keda Torus eXperiment*

“…The KTX is a new RFP device with a major radius of R = 1.4 m and a minor radius of a = 0.4 m. [9,[11][12][13] The materials of the first wall and limiter are stainless steel and molybdenum, respectively. The height of the poloidal and toroidal molybdenum limiters is 2 cm.…”

“…Currently, the KTX has attained a maximum plasma current of 205 kA and a maximum discharge time of 21 ms, and it has achieved typical reversed field pinch (RFP) discharges lasting 2 ms in RFP state. Presently, there are a few foundational diagnostic systems operating on the KTX [8][9][10] and the H α diagnostic is one of the most fundamental diagnostics on KTX.…”