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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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