Synthesized-reference-wave holographic techniques offer relatively simple and cost-effective measurement of antenna radiation characteristics and reconstruction of complex aperture fields using near-field intensity (power) pattern measurement. The near field is over-sampled. The phase is obtained indirectly, using the reference signal shifted linearly with the position of the probe. These methods allow utilization of advantages for probe compensation for near-field amplitude and phase measurements for planar and cylindrical scanning, including accuracy analyses. Descriptions are given of holographic nearfield measurements using probe compensation for planar and cylindrical scanning, and numerical simulations. A com-parison of holographic near-field and far-field measurements with and without probe compensation is presented.

Synthesized-reference-wave holographic techniques offer relatively simple and cost-effective measurements of antenna radiation characteristics, and reconstruction of complex aperture fields using near-field intensity-pattern measurements. These methods allow utilization of the advantages of the methods for probe compensation for near-field amplitude and phase measurements for planar and cylindrical scanning, including accuracy analyses. Accuracy analyses using mathematical models considering random processes with correlation intervals are presented. Numerical simulations, taking into account random as well as deterministic errors and the processing of measurement statistics, are also presented. It is demonstrated that the given analyses correspond to our measurements and/or numerical simUlations.

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A retarding potential technique has been employed to select electrons for extraction from a hollow cathode discharge. In ‘‘normal’’ operating pressures, the electron distribution function is Gaussian like with a superthermal tail. At low operating pressures, the electron distribution function has an additional distinct component of electrons with a very low thermal spread of 0.13 eV and an energy corresponding to the cathode potential.

To satisfy the requirements of a negative-ion-based neutral beam line for future fusion applications, an H− ion source was developed using surface production of negative ions and a steady-state plasma injection from hollow cathode discharges. Steady-state and stable generation of H− ions on a negatively biased, cesiated converter has been achieved over periods of several hours; H− beam current pulses of 0.3-A amplitude with 1-s duration have been extracted over the same period, but steady-state operation of the extractor has not been achieved yet due to a lack of extractor cooling. The source meets some of the neutral beam line requirements, i.e., the obtained linear current density, background gas pressure, and the proven capability for steady-state H− ion generation.