Anode Materials for High-Average-Power Operation in Vacuum at Gigawatt Instantaneous Power Levels

Abstract

The thermal behavior of several electrically conducting solids under high incident electron fluence in high vacuum was evaluated. At electron energies of up to ∼200 keV, the depth-dose relationship for electron penetration into the materials was considered, and the resulting energy deposition profile from the surface was revealed to extend to a maximum of ∼175 µm below the surface depending on the anode material. Black body radiation is considered as the major mechanism that balances the power deposited in the material on the timescales of interest. Comparing the radiated power density at the sublimation temperature for different materials, metallic/nonmetallic, revealed that pyrolytic graphite anodes may radiate over 20 times more power than metallic anodes before failure due to sublimation. In addition, transparent pyrolytic graphite anodes (with a thickness on the order of several tens of micrometer) potentially radiate up to 40 times that of metallic anodes, since heating by the electron beam is approximately uniform throughout the thickness of the material, thus radiation is emitted from both sides. Experimental results obtained from titanium and pyrolytic graphite anodes validate the thermal analysis.

Effects of anode material on the evolution of anode plasma and characteristics of intense electron beam diode

“…Intense electron beam (IEB) planar diodes have important applications in high-energy radiation generation [1][2][3][4] and virtual cathode oscillators [5][6][7][8][9][10]. The IEB is generated from the cold cathode by explosive electron emission process, which initiates from the surface microprotrusions of cathode under the localized high electrical field.…”

“…Considering the difficulty of transient temperature measurement, some researches paid more attention to electron incident depth and resistance to thermal destruction of the anode materials [7,10,16,17]. They simulated the process that IEBs bombard on different simple materials, the results show that the accelerating voltage and the material properties, such as atomic number, atomic mass, and density of the material, affect the depth-energy relationship [7,10]. Then the surface temperature rise can be calculated from the depthenergy relationship, current density, density and heat capacity of the material if diffusion, convection and heat radiation are neglected [7,10,16,17].…”

“…They simulated the process that IEBs bombard on different simple materials, the results show that the accelerating voltage and the material properties, such as atomic number, atomic mass, and density of the material, affect the depth-energy relationship [7,10]. Then the surface temperature rise can be calculated from the depthenergy relationship, current density, density and heat capacity of the material if diffusion, convection and heat radiation are neglected [7,10,16,17].…”

“…Graphite, titanium (Ti) and molybdenum (Mo) have different in atomic numbers, density, heat capacities, and melting points [10,16]. This results in different performances in heating effects of IEB to the anode material as well as diode characteristics [10,16,17].…”

“…Graphite, titanium (Ti) and molybdenum (Mo) have different in atomic numbers, density, heat capacities, and melting points [10,16]. This results in different performances in heating effects of IEB to the anode material as well as diode characteristics [10,16,17]. To clearly figure out the influence of anode materials on the characteristics of the diode, in this work, three simple materials are respectively used as anodes in an IEB diode.…”