A development project was undertaken at IBM to meet the needs of production e-beam lithography at increased beam energies up to 100 kV. The project was divided into two separate development efforts. The first part, which is the topic of this article, dealt with the gun vacuum and its overall design. The second half dealt with the high voltage design. This article describes the design of the overall gun and its vacuum system and the initial results of testing as they pertain to the vacuum system of the gun and its operation with the integral ion pump design.