The
xenon tube is used in
cameras with an
electronic
flash,
LASERs and in strobes. The tube is made from
glass
or
quartz, has an
electrode in each end and
contains
high pressure xenon gas. It also has a third
connector
for
triggering.
To use the
tube a
capacitor connected to the
electrodes
is
charged to between 200V and 400V. Since
xenon
is normaly non
conductive, it needs some
help to
flash.
This is done by
sending a 3-6kV
pulse on the
trigger electrode
(Some flashtubes doesn't have a trigger connector, but here the
trigger voltage is
connected to the
reflector behind the
tube)
The
pulse '
injects' a flow of
electrons in to the
tube.
This causes an
avalanche effect where the electrons hit
the
xenon atoms, that
emits more
electrons and so on. This
ionizes the
gas and makes it
connductive, and the
capacitor
is
discharged through the
tube. The
accelerated electrons
that fly trough the
tube knocks away
atoms from the
electrode
when it hits, and after 5000-7000
discharges the tube must be
replaced(Strobe tubes work at lower
effects, and can
survive
several
million flashes).