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The sound field generated from a cylindrical sonochemical cell is discussed in depth. This sound field is considered with a variable operating frequency. An acoustic model is developed to predict the spatial distribution of acoustic pressure, which is compared with experimental measurements of the spatial characteristics of luminescent emission from a cylindrical cell. A sound speed (averaged in space and time) within the cavitation environment in the range of 868-1063 m s -1 was calculated. Under certain assumptions, this corresponds to a void fraction range of 2.9 × 10 -3 to 4.2 × 10 -3 %. The implications for electrochemical and chemical activity within cylindrical cells are discussed.

We have demonstrated generation and transport of a patterned electron beam from a Diamond Field-Emitter Array (DFEA) cathode in a radio frequency (rf) gun. DFEAs are arrays of micrometer-scale pyramids with nanometer-scale tips. They can be fabricated with base widths ranging from 3 μm to 25 μm and pitches as small as 5 μm. They have an inherent 1:0.7 base to height ratio. DFEAs operate as field-emitter cathodes and potentially produce intrinsically shaped electron beams, which are of interest for a number of accelerator applications. We report on the results of a recent experiment in which a beam, consisting of several beamlets, was produced from a DFEA cathode in an rf gun and transported 2.54 m along a beam line. A macrobunch charge of 60 pC was measured at a cathode field gradient of 15.1 MV/m.

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