Abstract
An Electrodynamic tether (EDT) is an attractive propulsion device for active debris removal systems. One of the key components of the EDT system is an electron emission device, and we have studied a field emission cathode (FEC) using carbon nanotubes (CNTs) because of its simplicity and potential capabilities. Since EDT systems are operated in low earth orbit (LEO), the CNTs in the FEC may be affected by atomic oxygen (AO), so the effect of AO irradiation on the FEC was studied. We conducted AO irradiation tests on FECs using laser detonation beam facilities and compared the pre- and post-irradiation electron emission characteristics. As a result, the FEC could not emit electrons when the total AO fluence of 3×1020 /cm2 was irradiated perpendicular to the emission surface. In this case, CNTs on the emitter surface disappeared by AO irradiation. When the irradiation direction was parallel to the emission surface, on the other hand, the FEC could emit electrons after the irradiation although the required voltage increased up to 1.5 times as high as that of pre-irradiation condition. This comparison indicated that the direction of AO irradiation has strong effect on the performance degradation of the FEC on orbit.
