The background deuterium neutral gas pressure is a major operational parameter affecting the physics of the ionized gas discharge in the inertial electrostatic confinement (IEC) axial-cylindrical fusion neutron generator device (C-Device). There is uncertainty in its actual value in previous experiments. The cylindrical hollow IEC modeling program (CHIMP) computer code is a particle-in-cell, Monte Carlo-collision (PIC-MCC) model that includes ionization and secondary electron emission processes and is used to give preliminary results for the ionized gas physics behavior and neutron generation in the C-Device for a range of pressure calibration factors.