DYNAMICS OF CATHODE SPOT MOVEMENT ON A CARBON/CARBON COMPOSITE IN VACUUM

摘要

The dynamics of cathode spot movements on a three-dimensional carbon fiber reinforced carbon/carbon composite were investigated by a scanning electron microscope and a digital high-speed video camera. The results show that the motion direction of the cathode spots is parallel to the carbon fibers. The directed motion of the cathode spots is accompanied by the cycle of alternative splitting and extinguishment of cathode spots. The group of the cathode spots can split into two small groups when it moves far away from the ignition site. Within 40 _s, the two small groups completely depart each other. The splitting of the cathode spots group is caused by the current degradation. The former group continues to go forward, and the latter extinguishes within 40 μs. The transient and the average velocity of the "lead" spot are estimated to be 0.9_3.4 m/s and 2.11 m/s, respectively. The diffusion constant of the cathode spot is (9.11 ± 0.59) X 10~(-5) m~2/s.