Abstract
An investigation on the plasma-induced field emission (PFE) properties of a large area carbon nanotube (CNT) cathode on a 2 MeV linear induction accelerator injector is presented. Experimental results show that the cathode is able to emit intense electron beams. Intense electron beams of $14.9--127.8\text{ }\text{ }\mathrm{A}/{\mathrm{cm}}^{2}$ are obtained from the cathode. The CNT cathode desorbs gases from the CNTs during the PFE process. The fast cathode plasma expansion affects the diode perveance. The amount of outgassing is estimated to be $0.06--0.49\text{ }\text{ }\mathrm{Pa}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{L}$, and the ratio of outgassing and electron are roughly calculated to be within the range of 170--350 atoms per electron. The effect of the outgassing is analyzed, and the outgassing mass spectrum of the CNT cathode has been studied during the PFE. There is a significant desorption of ${\mathrm{CO}}_{2}$, ${\mathrm{N}}_{2}(\mathrm{CO})$, and ${\mathrm{H}}_{2}$ gases, which plays an important role during the PFE process. All the experiments demonstrate that the outgassing plays an important role in the formation of the cathode plasma. Moreover, the characteristic turn-on time of the CNT cathode was measured to be 39 ns.
Highlights
Velvet is one of the materials for explosive electron emission (EEE) in intense electron beam sources [1,2,3]
The plasma-induced field emission (PFE) properties of the carbon nanotube (CNT) cathode under pulsed electric field have been investigated for single pulse mode
Intense electron beams of 14:9–127:8 A=cm2 are obtained from the cathode at the pulsed electric field of 121–149 kV=cm and pulse duration of $100 ns
Summary
Velvet is one of the materials for explosive electron emission (EEE) in intense electron beam sources [1,2,3]. The velvet cathode generates uniform cathode plasma during the emission process under pulsed high voltage. The velvet cathode has low lifetime and high outgassing during intense electron emission. Were focused on intense current field emission properties of CNTs for application in linear induction accelerators (LIAs) [15,16,17] and high power microwave tubes [18,19]. We have utilized plasma-induced field emission (PFE) that is a little different from the EEE process. We have investigated the PFE properties of a large area CNT cathode for single pulse mode on a 2 MeV LIA injector [21], including intense electron emission, outgassing mass spectrum (OMS), and characteristic turn-on time (CTT)
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