Possible, yes. Probable, no. Charged particles seldom
reach ground level (although high-altitude server farms
are a bit concerned due to huge number of exposed
logic bits and the need to advertise an acceptably low
bit error rate).
So the question is, can you live with one flashover in
a couple million years?
You would like to know just how much energy would
be needed to initiate an arc. Then you would figure
the dE/dx (in low pressure Xenon) that turns out to
be, what ion can drop that energy and then turn to
atmospheric radiation transport codes and "space
weather" flux charts to figure probabilities.
The whole thing is basically a poor-boy Geiger
counter, only lacking the actual counter, and not
at all optimized for sensitivity. The low density of
material makes it reasonably likely that even if an
ionizing particle or energetic-enough photon did
traverse the lamp volume, it would not interact.
Energy dropped by an ion track is proportional to
material density.
One question is whether 300V is enough to sustain
an arc in avalanche. There would be a holding current
and a holding voltage, I'd expect. Can you quantify
any of these aspects? Particularly, any kind of "kernel"
initiation energy? Flash tubes tend to need a lot of
high voltage energy to fire. You might be able to get
at this by determining the minimum Joule energy
behind a trigger pulse that does, and doesn't, fire
the tube off (i.e. where does the arc bloom vs self-
quench). Then compare this to what a worst case
ion, if it ever made the trip, could deliver.
In silicon you're talking picocoulombs of deposited
charge. That would be like 1mA for 1nS. Gas tube will
deliver way less from an ion strike. What is your critical
trigger pulse current*time?