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Blackening
As a xenon lamp progresses through its lifetime, it is subject to blackening. This is caused by tungsten material vaporizing from the electrodes and depositing itself on the inner walls of the quartz envelope. Blackening gradually reduces light output from the lamp; it also affects the spectral characteristics of the emitted light, causing it to appear more yellow. During the course of a lamps normal lifetime, blackening will initially occur very slowly, then progresses at a more rapid rate. The blackening also causes the envelope to heat up due to absorption of energy from the radiated light. |