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abstract:
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An experiment designed to test the breakdown threshold
of a dielectric subjected to the GV/m-scale electric-fields
of an intense electron-beam has been completed. In this
experiment at the Final Focus Test Beam (FFTB) facility,
the 28.5 GeV SLAC electron beam was focused down and
propagated through short fused-silica capillary-tubes with
internal diameters of as little as 100 μm. The electric field
at the inner surface of the tubes was varied from about 1
GV/m to 22 GV/m by adjusting the longitudinal compres-
sion of the electron bunch. We observed a sharp increase
in optical emissions from the capillaries in the middle part
of this surface field range which we believe indicates the
transition between sustainable field levels and breakdown.
If this initial interpretation is correct, the multi-GV/m sur-
faced fields that were sustained equate to on axis accelerat-
ing field of several GV/m.
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