The manufacturer of an electron beam lithography machine pushes a better understanding and higher performance of the optical column to provide a better product with each iteration. At the heart of the column is the source of electrons: the gun lens. It holds the field emitter from which the electrons originate and accelerates the beam to a first crossover. The main work in this thesis was concerned with development of a new and better gun lens design. Consideration of several physical phenomena is required in order for the gun lens to be more robust and with a more stable beam. It was found that the heating transient plays a large role in the operation of the gun lens. By defining the requirements clearly including by ray-tracing the optical geometry to find optical sensitivities, the main challenges of the project became evident. A new concept design is presented where the heat transport inside the gun lens is improved and thermal drift is greatly diminished. By using the ceramic insulators as flexures the short- and long-term stability of the lenses are improved and the thermal transient settling time is reduced from 26 hours to below 6 hours. By opening up the geometry inside the gun lens the local vacuum at the emitter is much better, which increases its lifetime. The electrostatic fields are made much more robust by burying the triple junction, which required using a new insulator shape. The final result is a gun lens concept design which improves in all aspects while remaining simple in construction.