Development of a ultra-short pulse electron beam source for advanced accelerator/radiation source research at Northern Illinois University

We are currently developing an ultra-short pulsed RF-gun by means of a series of comprehensive modeling and design processes. A complete system will be available for applications such as ultra-fast electron diffraction (UED) system, high power coherent radiation sources (THz/X-Ray), and advanced accelerators that normally require a high brightness electron beam source. All the cavity features, including input coupler, are engineered with EM and particle-in-cell simulators (HFSS, ASTRA, and CST) for beam energy from 0.5–1 MeV (safety limited) to be powered by our S-band (2.856 GHz) klystron (max. power = 5.5 MW). The klystron (Thales TH2163) and modulator system (ScandiNova K1 turnkey system) were successfully installed and fully commissioned. Performance tests of the klystron system show peak output power > 5 MW, as per operation specifications. At the quasi-relativistic energies, the electron source is capable of generating 100fC–100 pC electron bunch with sub-ps pulse duration. Our current approach on RF-gun design is focused on preserving time of flight (TOF) of the electron bunch from the cathode to the interaction chamber. A system that is inherently time-stable can be more useful as an analytic tool in the laboratory. A stabilized system can also be used to collect more data at some desired value of time delay, such as to better resolve a fast transition. Particle-in-cell simulations have shown that the electron bunch undergoes fast RF acceleration, rapidly reaching the desired energies, which can be controlled by tuning RF injection phase and input driving power. Engineering design and beam optics assessment of the photoinjector gun is currently underway, which is scheduled to be fully installed and commissioned in 2014.