Recent progress on the design of normal conducting apex2 vhf cw electron gun*

We report recent progress on the design of a normal conducting (NC) CW electron gun, APEX2 (Advanced Photo-injector Experiment2) at Lawrence Berkeley National Laboratory (LBNL). APEX2 is an upgrade of the successful APEX gun at LBNL and the LCLS-II (Linac Coherent Light Source-II) injector at SLAC, aiming at the applications for Free electron laser (FEL) such as LCLSII High Energy upgrade, UED (Ultrafast Electron Diffraction) and UEM (Ultrafast Electron Microscopy). The APEX2 adopted a two-cell cavity design with resonant frequency of 162.5 MHz. The APEX2 gun is targeting to achieve a launching gradient at the cathode exceeding 30 MV/m and output energy above 1.5 MeV with transverse emittance of 0.1 μm at 100 pC. Advanced MOGA optimization technique has been used for both the RF cavity design and extensive beam dynamics studies, both using APEX and LCLS-II like injector layouts. Detailed RF designs, beam dynamics studies, and preliminary engineering design supported by FEA analysis will be presented, along with cavity features that were demonstrated to be crucial in the operation of the APEX gun.