| Autor: |
Sree Harsha NR; School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47906, USA., Halpern JM; School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47906, USA., Darr AM; School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47906, USA., Garner AL; School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47906, USA.; Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA.; Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana 47907, USA. |
| Abstrakt: |
Understanding space-charge-limited current density (SCLCD) is fundamentally and practically important for characterizing many high-power and high-current vacuum devices. Despite this, no analytic equations for SCLCD with nonzero monoenergetic initial velocity have been derived for nonplanar diodes from first principles. Obtaining analytic equations for SCLCD for nonplanar geometries is often complicated by the nonlinearity of the problem and over constrained boundary conditions. In this Letter, we use the canonical coordinates obtained by identifying Lie-point symmetries to linearize the governing differential equations to derive SCLCD for any orthogonal diode. Using this method, we derive exact analytic equations for SCLCD with a monoenergetic injection velocity for one-dimensional cylindrical, spherical, tip-to-tip (t-t), and tip-to-plate (t-p) diodes. We specifically demonstrate that the correction factor from zero initial velocity to monoenergetic emission depends only on the initial kinetic and electric potential energies and not on the diode geometry and that SCLCD is universal when plotted as a function of the canonical gap size. We also show that SCLCD for a t-p diode is a factor of four larger than a t-t diode independent of injection velocity. The results reduce to previously derived results for zero initial velocity using variational calculus and conformal mapping. |
