Perveance

The perveance of a round beam of charged particles is a measure of its relative expansion (increase in diameter per length), which is caused by the Coulomb forces acting between the charges . ${\displaystyle K}$

If the current strength of the omnidirectional beam and the voltage are equivalent to the kinetic particle energy , then the perveance of the beam is given by: ${\displaystyle I}$ ${\displaystyle U}$ ${\displaystyle K}$

${\displaystyle K={\frac {I}{U^{\frac {3}{2}}}}}$

If you rearrange this equation , you get the space charge law , the current-voltage relationship for space-charge-limited diodes . The pervancy of a space-charge-limited diode is usually addressed as its space charge constant and depends only on the geometry of the arrangement, but not on the emissivity of the cathode . ${\displaystyle I}$

literature

• Frank Hinterberger: Physics of Particle Accelerators and Ion Optics . 2nd edition, Springer 2008, ISBN 978-3-540-75281-3 ; P. 111f