What is the failure mode of a Xenon flashlamp?

Question

I know basically how they work...what I don't know is why their life is limited. Typically they are rated for X number of flashes. So what fails/wears out? Does the electrode material contaminate the gas or something else? Thanks.

Answer 1

There are a number of failure mechanisms, and degradation of the electrodes is one such. The heat of the dissipated energy may crack the glass or cause other problems.

Answer 2

Here's the MIL-HDBK-217 empirical formula for the failure rate of Xenon tubes:

F.R. = 3600 * PPS * [ 2000 * Ej / (d * L * sqrt(t))^8.58 ] * C

F.R. is the faillure rate in failures per million hours
PPS is the rep-rate of the flash pulses, per second
Ej is the Energy per pulse in Joules
d is the diamater of the tube in mm
L is the length of the tube in inches (go figure -- inches?)
t is the pulse width in microseconds
C is a cooling factor. 1.0 for air, 0.1 for water cooled tubes.

Although this doesn't give any specific mechanisms, it does indicate what is important in calculating the failure rate.

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