High Current Density Advanced Cold Cathode Facility * ECE Department, University of Wisconsin, Madisona; University of MichiganAnn Arborb *Research Supported through AFOSR by a USDOD MURI05 grant on the Nano-physics of High Current Density Cathode and BreakdownAbstractWe report measurements and analyses of field emission from both copper and aluminum cathodes. The copper cathodes have been micromachined to have raised ridges or knife edges to enhance the surface electric field. Raised ridges have also been formed into the aluminum cathodes, using Ablation Line Focus (ALF) laser-micromachining, developed at the University of Michigan. The measurements are conducted in the Madison Cathode eXperiment (MACX) facility after baking and processing to a UHV base pressure of 10-10 Torr. The anode-cathode gap is variable from 0-10 mm with 50 m accuracy and the cathode voltage is variable from 0 20 kV (negative). Pulse lengths are variable between 1 s 500 ms. The MACX facility also provides the ability to heat the cathode from ~ 300 650 oK while measuring electron emission currents. Research ObjectivesUHV (10-10 Torr) facility for high current density cathode research

Develope TMM model to predict the entire range of emission from thermionic to field emission and mixed emission (field + thermionic)

Analyze the experimental data with TMM model codes

Design high-current density cathode with high local field enhancement factor (=Eloc/(V/d)) and low work function

Vacuum System IntroductionVacuum System: A scroll pump, turbo pump and a VacIon pump are used to bring the whole system to 10-10 Torr with the system baked to 450 C. Cathode and Anode: The cathodes are made of Al, Cu, C or Mo and may be coated with CsI. The anode is made of stainless steel. It is a tube about 1-cm in diameter and 8-cm long. A tiny second anode is applied to measure the emission current density distribution.Cathode Electrical Test Facility SystemTMM Method ModelReferences(1) R.H.Fowler and L.W.Nordheim, Proc. Roy.Soc, (London), A119, 173 (1928)(2) E.L.Murphy and R.H.Dood, Phys Rev, 102, 1464, (1956)(3) Kevin L. Jensen, Patrick G. OShea, and Donald W. Feldman, Appl. Phys. Lett. 81, 3867, (2002)(4) Kevin L. Jensen, Marc Cahay, Appl. Phys. Lett, 88, 154105 (2006)(5) Kevin L. Jensen, J. Vac. Sci. Technol. B 21, (2003)X. Hea, J. Scharera, J. Booskea, S. Sengelea, V. Vlahosa; N. Jordanb, R. Gilgenbachb Electrical System1. -0.1~ -20 kV, 1 s -500 ms long duration with