A time-of-flight diagnostic has been implemented on the Irvine field reversed configuration (IFRC) to obtain an energy distribution function from charge-exchanged neutral hydrogen. The diagnostic includes a 13 cm radius slotted disk rotating at 165 Hz in vacuum which chops the emitted neutrals at a rate of 26 kHz. In situ timing verification was performed with a dc xenon discharge lamp with an uncertainty less than 100 ns for a 38 micros chopping period. Energy calibration was accomplished with a singly ionized lithium source in the range of 300-1500 eV, achieving an average energy uncertainty, DeltaE/E, of 0.11. The diagnostic has measured neutrals in the range of 20-80 eV from the IFRC and the corresponding energy distribution function has been obtained.

Measurements of the Doppler shift of impurity lines indicate that there is an ion flow of ∼7 km/s in the Irvine Field Reversed Configuration. A charge-exchange neutral particle analyzer shows the peak energy is below the 20 eV minimum detectable energy threshold, which is in agreement with the spectroscopic data. By evaluating the collision times between the impurities and hydrogen, the dominant plasma ion species, it is concluded that the ions rotate with an angular frequency of ∼4 × 104 rad/s. Estimates of the ion current in the laboratory frame indicate it is one to two orders of magnitude larger than the measured plasma current of 15 kA. Electron drifts are expected to cancel most of the ion current based on the measured magnetic fields and calculated electric fields. © 2009 American Institute of Physics.

Diffusion of test-ions in a flux-coil generated, collisional, field-reversed configuration is measured via time-resolved tomographic reconstruction of Ar+ optical emission in the predominantly nitrogen plasma. Azimuthal test ion diffusion across magnetic field lines is found to be classical during the stable period of the discharge. Test ion radial confinement is enhanced by a radial electric field, reducing the observed outward radial transport rate below predictions based solely on classical cross-field diffusion rates. Test ion diffusion is ∼500m2s-1 during the stable period of the discharge. The electric field inferred from plasma potential measurements and from equilibrium calculations is consistent with the observed reduction in argon transport. © 2014 IOP Publishing Ltd.

A 16 chord optical tomography system has been developed and implemented in the flux coil generated-field reversed configuration (FRC). The chords are arranged in two fans of eight, which cover ~35% of the vessel area at the midplane. Each illuminate separate photomultiplier tubes (PMTs) which are fitted with narrow band-pass filters. In this case, filters are centered at 434.8 nm to measure emission from singly ionized argon. PMT crosstalk is negligible. Background noise due to electron radiation and H(γ) line radiation is <10% of argon emission. The spatial resolution of the reconstruction is 1.5 cm. Argon is introduced using a puff valve and tube designed to impart the gas into the system as the FRC is forming. Reconstruction of experimental data results in time-dependent, 2D emissivity profiles of the impurity ions. Analysis of these data show radial, cross-field diffusion to be in the range of 10-10(3) m(2)∕s during FRC equilibrium.