Patent ID: 7759849

Claim:
A laser excitation lamp comprising: a discharge tube having a longitudinal length and enclosing a gas space; a hot cathode having a length X extending longitudinally into the gas space from a feedthrough seal in one end of the discharge tube; the gas space comprising a gas discharge space distal to the cathode and a gas space radially surrounding the cathode along its length; the hot cathode having a shape of a pin and extending from the feedthrough seal to a working surface at a free distal end of the cathode facing the gas discharge space; the gas discharge space having a first gas volume per unit of longitudinal length and the gas space radially surrounding the cathode having a second gas volume per unit of longitudinal length, the second gas volume having a reduced gas volume per unit of longitudinal length starting at a longitudinal distance Z proximal from the working surface and extending toward the feedthrough seal, wherein the distance Z is small compared to the length X and is a maximum of about 1 cm, wherein the reduced gas volume per unit of longitudinal length is in addition to any reduction in the second gas volume due to narrowing of the end of the discharge tube for mounting and sealing the cathode.