Calculation of the electrostatic potential field for an open-endcap cylindrical penning trap

A calculation of the electrostatic potential field for a compensated, open-endcap, cylindrical-type Penning trap is presented. Sufficient detail is given so that various parts of the calculation can be easily modified as needed. The effects of finite-length endcaps and of a non-negligibly sized gap between the electrodes are explicitly included. It is shown that inclusion of a realistic gap has a significant effect on the calculated electrostatic field.