Estimation of the space charge limited current with quadratic damping

In this paper we analyze the motion of charged particles under the influence of a quadratic velocity dependent frictional force inside a vacuum tube diode. Our study is performed by using the adiabatic approximation that allows for exact analytic solutions for the case of weak damping. The expressions obtained for the space charge limited current reduce to the well known Child-Langmuir law under the adiabatic approximation when the dissipation parameter goes to zero.