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Re: Breakdown voltage at submillimeter distances?



Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx>

Tesla list wrote:
Original poster: Robert Clark <bobbygc2001@xxxxxxxxx>
 Thanks for the detailed response. I was thinking of
creating small capacitors using very small gap spacing
based on the idea that the breakdown voltage would
start rising again at the left end of the Paschen
curve. Your references seem to put the scotch on that
idea.
 However, I've read that the shape of the electrodes
has an effect on the measurements: pointed ones give
off more electrons than flat ones.
 What would be the result if we used flat plates
(atomically flat even)?

   Bob Clark

Bob,

The left side of Paschen's curve does not apply even when using optically smooth surfaces. It has been observed in optical reticles and MEM devices. Anomalous breakdown originates from points of high E-field concentration (and these are always present even on "optically flat" surfaces). "Conditioning" (the removal of high-field points by evaporation via low energy discharges) helps to slightly increase breakdown voltage of the gap, until the next, slightly lower, field concentration point initiates another breakdown.

In one series of experiments (1) thin layers of evaporated gold were applied to optically polished sapphire in order to create a very smooth air-insulated flat plate capacitor. Similar anomalous breakdown behavior was observed. Similar behavior was observed in chrome reticles (as well as a new phenomenon - Electric Field Induced Migration). See: http://www.sematech.org/meetings/past/20031212/Paper2.pdf
and
http://www.sematech.org/meetings/past/20031212/Paper3.pdf

1. Emmanouel Hourdakis, Brian J. Simonds, and Neil M. Zimmerman, "Submicron gap capacitor for measurement of breakdown voltage in air", Review of Scientific Instruments, 77, 034702 (March, 2006)

Bert
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