Influence of gas pressure on electron beam emission current of pulsed cathodic-arc-based forevacuum plasma electron source

Abstract

We describe our experimental investigation of the effect of background gas pressure on the emission parameters of a pulsed cathodic-arc-based forevacuum-pressure plasma-cathode electron source. We find that increased gas pressure over the range 4–16 Pa significantly reduces the beam current rise-time and significantly increases the emission current amplitude. For example, at a discharge current of 20 A, increasing the working gas pressure from 4 Pa to 16 Pa increases the emission current from 8 A to 18 A and shortens the beam rise-time from 50 μs to 20 μs. This influence of gas pressure on the electron beam parameters can be explained by the effect of arc discharge current switching from the anode to emission. In our case, the current switching effect is caused by increased working gas pressure. In the forevacuum pressure range, the increase of the electron emission current with the growth of gas pressure is due to a rise in the emission plasma potential which is caused by ion back-streaming from the plasma formed in the electron beam transport region. A model describing the influence of gas pressure on the electron emission from the plasma is presented.

Powerful electron beam transport from a plasma–cathode electron source at forevacuum pressure

“…The accumulation of slow ions in the discharge gap leads to a noticeable increase in the concentration and potential of the emission plasma, which leads to an increase in the emission current due to the 'switching effect' of the discharge current into emission. The experimental results presented in [25] show that, for constant discharge current, increase in the beam-plasma density and the reverse ion current due to increased gas pressure in the forevacuum pressure range can lead to an increase in the extraction efficiency of up to 50%. As seen from figure 3(c), increasing the accelerating voltage from 4 to 6 kV increases the current I e by 260 mA, with the extraction efficiency increasing by 17%.…”

“…Part of this ion flux is incident on the emission electrode, and secondary electrons are produced there. The remaining ions pass through the emission channel to the discharge gap and further exchange charge on neutrals, which results in increased density and potential of the emission plasma near the electron extraction region [25]. Both of these factors can lead to an increase in total emission current, which is prominently manifested only at high beam-plasma density.…”

“…The remaining part of the ion current I i2 = 0.7 mA passes through the emission holes and enters the discharge region. The mechanism behind the increase of emission current due to back-stream ions in a forevacuum plasma source is described in [25]. As a result of charge exchange of accelerated ions that have come from the accelerating gap, slow ions are formed in the discharge region.…”

Penentuan Massa Tererosi Untuk Berbagai Material Katoda Ignitor

“…Rogowski mempunyai prinsip kerja menangkap medan magnet di dalam ruang di sekitar konduktor yang dialiri arus. Tegangan keluaran koil dirumuskan sebagai laju perubahan fluks magnet [6,7].…”