V.T. Astrelin2020-09-16 15:57 May be, a discharge begin between cathode grid and redistr. electrode (RE), supported by ion flow from the transporting area (TA) and electron flow from RE due to ion-electron secondary emission? For small B1 plasma in TA may diffuse to axis easy.
Vladimir Devyatkov2020-09-16 15:57 The voltage between the R-E electrode and the grid occurs only when the discharge current flows from the cathode to the R-E. Although the voltage across Ra will provide the addition of secondary electrons from the R-E electrode to the beam, the contribution to the overall picture is probably not so great at the nominal operating pressure.
V.T. Astrelin2020-09-16 15:57 May be, of course... But all events occur simultaneously and contribution of this discharge may be not small.