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We describe a field reversed configuration (FRC) experiment featuring in-vessel θ-pinch coils and open-field-line plasmas confined in a tandem mirror. Two FRCs, formed near the west and the east mirror throats of a central cell, are ejected toward the mid-plane for colliding and merging. Each FRC consists of four groups of pulsed power supplies and four groups of coils, having diameters 35, 35, 40, and 45 cm. The rise time of the main reversal field is 7.15 μs, and the maximum voltage is 40 kV with total currents of 416 kA, corresponding to a magnetic field of 1690 G. The total capacitive stored energy is 115.2 kJ. A fast pulse gas injection system was designed and tested to inject neutral gas into the FRC formation region with controlled directions. The successful installation of the θ-pinch coils inside the vacuum vessel offers greater freedom for diagnostics and control instruments as well as preserving magnetic tandem mirror configuration. The magnetic field reversal is confirmed by internal magnetic field measurements. The plasma temperature, density, and lifetime are, respectively, ~100 eV, ~3.0 × 1018 m-3, and ~300 μs for the current operating conditions. [ABSTRACT FROM AUTHOR] more...

A high voltage pulse generator based on a silicon-controlled rectifier has been designed and implemented for a field reversed configuration experiment. A critical damping circuit is used in the generator to produce the desired pulse waveform. Depending on the load, the rise time of the output trigger signal can be less than 1 µs, and the peak amplitudes of trigger voltage and current are up to 8 kV and 85 A in a single output. The output voltage can be easily adjusted by changing the voltage on a capacitor of the generator. In addition, the generator integrates an electrically floating heater circuit so it is capable of triggering either pseudosparks (TDI-type hydrogen thyratron) or ignitrons. Details of the circuits and their implementation are described in the paper. The trigger generator has successfully controlled the discharging sequence of the pulsed power supply for a field reversed configuration experiment. [ABSTRACT FROM AUTHOR] more...

In this paper, we describe the engineering work involved in constructing two ion cyclotron resonance heating (ICRH) systems for use in the Keda Mirror with AXisymmetry tandem mirror experiment. Because they offer an effective and robust heating method, ICRH systems have been widely used in a variety of plasma experiments. The goal of our system is to heat the hydrogen plasma contained in the central cell using the fundamental ion cyclotron frequency. Both systems can deliver a radiofrequency power of ~120 kW with adjustable operating frequencies that are tuned to be slightly lower than their local ion cyclotron frequencies. Two types of antennas are installed in the central cell in an attempt to launch both slow and fast waves. The heating mechanism is reliant on the magnetic beach effect for slow waves. [ABSTRACT FROM AUTHOR] more...

Non-Maxwellian electron velocity distribution functions composed of a warm bulk population and a cold beam are directly measured during electron-only reconnection with a strong out-of-plane (guide) magnetic field in a laboratory plasma. Electron heating is localized to the separatrix, and the electron temperature increases continuously along the separatrix. The measured gain in enthalpy flux is 70% of the incoming Poynting flux. The electron beams are oppositely directed on either side of the X point, and their velocities are comparable to, and scale with, the electron Alfvén speed. Particle-in-cell simulations are consistent with the measurements. The experimental results are consistent with, and go beyond, recent observations in the magnetosheath. [ABSTRACT FROM AUTHOR] more...

The transient nature of magnetic reconnection dictates that it must be accompanied by rich electromagnetic wave activity, which can in turn affect the reconnection process. Interaction between Alfvén waves and reconnection has been simulated and recently observed in space. In this paper we report the first laboratory observation of a kinetic Alfvén wave (KAW) mode during reconnection in a linear device. The reconnection was measured by magnetic probes and the enhancement of light emission during reconnection was captured by a fast camera. The perpendicular wave pattern suggests it is an m = −2 mode rotating in ion diamagnetism direction. The wave data agrees with the theoretical prediction of KAW. The temporal correlation between KAW amplitude and reconnection rate indicates waves are generated by reconnection. [ABSTRACT FROM AUTHOR] more...