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Transmission electron microscopy was applied to study GaN nanowires grown on carbon nanotube surfaces by chemical reaction between Ga{sub 2}O and NH{sub 3} gas in a conventional furnace. These wires grew in two crystallographic directions, <2{und 11}0> and <01{und 1}0> (fast growth directions of GaN), in the form of whiskers covered by small elongated GaN platelets. The morphology of these platelets is similar to that observed during the growth of single crystals from a Ga melt at high temperatures under high nitrogen pressure. It is thought that growth of nanowires in two different crystallographic directions and the arrangement of the platelets to the central whisker may be influenced by the presence of Ga{sub 2}O{sub 3} (based on the observation of the energy dispersive x-ray spectra), the interplanar spacings in the wire, and the presence of defects on the interface between the central part of the nanowire and the platelets surrounding it.

Significant ionization appears to occur in the Rapid Cycling Synchrotron (RCS) during its 14 ms acceleration period leading to plasma formation and neutralization. The beam may in fact be over-neutralized, causing the tune to increase during the acceleration cycle. The overall tune shift in the RCS appears to be close to +0.5. The presence of plasma may help explain why longitudinal phase modulation can so quickly couple to transverse motion. In addition, plasmas tend to be inductive and the RCS appears to exhibit a relatively high inductance. Measurements of the electron cloud and plasma densities adjacent to the beam should be made. In addition to the RFA and Swept Analyzer diagnostics mentioned at the Workshop, other techniques might be attempted. If plasma is present, then a small, biased-probe might be useful (e.g., a Langmuir probe), or with the proper choice of geometry, an optics-based measurement for line density (e.g., an interferometer) might be employed, perhaps using microwaves for increased sensitivity.

The performance of static rotationally symmetric electron lenses is limited by unavoidable chromatic and spherical aberrations. In 1936, Scherzer demonstrated that the integrands of the integral expressions for the coefficients of these aberrations can be written as a sum of positive quadratic terms. Hence these coefficients can never change sign. This important result is called the Scherzer theorem, the only theorem existing in electron optics. Employing variational methods, Tretner determined the field of magnetic and electrostatic round lenses, which yields the smallest spherical aberration coefficient for particular constraints [2]. Unfortunately, these coefficients are still too large for realistic boundaries to enable sub-Angstrom resolution at medium voltages of about 200 to 300 kV. Therefore, the only possibility to directly reach this limit is the correction of the troublesome aberrations. It was again Scherzer who showed different procedures for canceling these aberrations [3]. The most promising is the incorporation of a corrector consisting of multipole elements or of a tetrode mirror in the case of low voltages. Although the mirror is rotationally symmetric, a non-rotationally symmetric beam splitter is needed to separate the incident beam from the reflected beam.

This work presents preliminary measurements designed to explore a new approach to neutron diffraction that is somewhat analogous to the pseudo-Laue technique, except that instead of using a broad energy (wavelength) bandwidth it uses a broad angular bandwidth. We have used a polycapillary focusing optic to focus neutrons from a monochromatic beam (using the BT-8 spectrometer on the NIST research reactor) and from a polychromatic beam at a pulsed spallation source (the Intense Pulsed Neutron Source, IPNS at Argonne National Laboratory) into a small, intense spot and have carried out preliminary diffraction measurements. Using the single crystal diffraction (SCD) facility on IPNS, diffraction of a 3{sup o} convergent beam from an alpha quartz crystal showed six diffraction beams in the 1-5{angstrom} wavelength bandwidth transmitted by the optic. The diffraction spots showed an intensity gain of 5.8 {+-} 0.9 compared to a direct beam diffracting from the same sample volume as that illuminated by the convergent beam.