Applying a voltage of 1e9 across two electrodes 1 cm apart creates an electric field strength of 1e11 V/m, which is difficult to sustain without significant effort. Previous experiences indicate that exceeding 1e7 V/m can lead to arcing from the electron source, even in ultrahigh vacuum conditions. The discussion raises the possibility of vacuum breakdown, which typically requires residual gases rather than a true vacuum. Clarification is sought on the conditions necessary for vacuum breakdown, highlighting the complexity of the topic. Overall, the conversation emphasizes the challenges and phenomena associated with high-voltage applications in a vacuum environment.