Possible application of carbon nanotubes to the field emission electron source for portable betatrons

摘要

In order to study the feasibility of a carbon nanotube-based electron gun for small and portable betatrons, the characteristics of electron emission from carbon nanotubes were measured at around approximate to 1 x 10(-4) Pa, a typical pressure in the vacuum chamber of such betatrons. The sample cathodes were made from powders of single-walled nanotube (SWNT) and multi-walled nanotube (MWNT) that were fixed on the stainless steel plate with gold paste. We found that the emission was weaker at the lower vacuum for both MWNT and SWNT. However, when the vacuum level was restored to approximate to1 x 10(-4) Pa after being kept at 4. 0 x 10(-4) Pa for 15minutes, the emission-current recovered to some extent but did not fully come back to the original value. The observed current densities from SWNT and MWNT are 550 and 540 muA/mm(2), respectively, at the high-voltage we tried: 2kV for SWNT and 1.1 kV for MWNT across a 300 mum gap. It is likely that the carbon nanotube, under the pulsed operation, has advantages over the thermal cathode for the electron emitters of portable betatrons. (C) 2004 Elsevier B.V. All rights reserved.