The Michelle Code: Advanced Emission, Multiple Design Environment Implementations, and High Energy Applications *

New advanced models and applications of the MICHELLE electrostatic particle-in-cell code are presented. MICHELLE continues to follow a strong development plan, advancing the level of physics-based models to improve simulation fidelity in more complex regimes. As a charged particle beam optics code MICHELLE [1] now includes a new model for thermionic emission that more accurately transitions through the knee of the Miram curve as a cathode crosses from temperature-limited to fully space-charge limited emission. This is fortified by a new thermal beam model to greatly reduce computation resources in the transition regime. The model correctly treats small scale geometries where the potential minimum is resolved as well as the large, cm-scale diodes. Another area that has undergone much development is MICHELLE's ability to mesh with various user design environments, including the state-of-the-art Cadence Analyst-MP [2] toolset as well as the new COMPASS II environment that enables the stitching together of native and third-party simulation tools and utility tools, all supporting UNIX & Windows, up through Windows 10. These environments and tool sets work together with the NRL Vacuum Electronics tools, including CHRISTINE-Z, TESLA-Z [3] and NEPTUNE [4] large signal and first principle codes, respectively. Lastly, high energy beam sources require high-fidelity self-magnetic fields to be calculated. Several examples and applications that stress codes such as MICHELLE will be presented, illustrating how the new capability can be used by the device designer.