Response to “Comment on ‘Relation between space charge limited current and power loss in open drift tubes' ” [Phys Plasmas 14, 094705 (2007)]

Abstract

It is pointed out in this Response that as the collector plate is a grounded conductor whose potential is held fixed at zero, it is incorrect to assume that it becomes negatively charged due to the accumulation of electron space-charge. Further, the connection between the collector potential due to the assumed accumulation of charges and the impedance of the open boundary appears tenuous. Moreover, the use of the impedance in evaluating the power loss while at the same time stating that “electromagnetic effects are not expected to play a key role” is in itself contradictory.

Radiation from a space charge dominated linear electron beam

“…8 When the N charges move together as a single unit as in case of a linear beam below the space charge limit, the multiplying factor is in fact N 2 . 6,7,12,13 In Ref. Thus, for a beam of electrons, the macroparticle has a charge q = Ne and mass M = Nm 0 , where e and m 0 are the charge and mass of an electron.…”