  We report on a new design of a vacuum ultra violet (VUV) lamp for direct
optical excitation of high laying atomic states e.g. for excitation of
metastable rare gas atoms. The lamp can be directly mounted to ultra high
vacuum vessels (p <= 10^(-10) mbar). It is driven by a 2.45 GHz microwave
source. For optimum operation it requires powers of approximately 20 W. The VUV
light is transmitted through a magnesium fluoride window, which is known to
have a decreasing transmittance for VUV photons with time. In our special
setup, after a run-time of the VUV lamp of 550 h the detected signal
continuously decreased to 25 % of its initial value. This corresponds to a
lifetime increase of two orders of magnitude compared to previous setups or
commercial lamps.
