Experimental investigation of SiC velvet cathode for MILO

SiC velvet cathode is applied to improve the performance of the L-band magnetically insulated line oscillator(MILO)
^1–2
. The SiC velvet is manufactured by electrostatic flocking technique which flocks the SiC fibers on a carbon blanket base. The SiC velvet is adhered on a stainless steel cathode to act as the emission material in the MILO tube. Comparative test were carried out between SiC velvet and polymer velvet in the same MILO tube. Current and microwave parameters without any sig-nificant differences between the two cathodes were detected. The plasma expansion velocity of SiC velvet is about 1.4
$\text{cm}/\mu\mathrm{s}$
which is calculated by impedance coupling method, while for polymer velvet the plasma expansion velocity is about
$1.8 \text{cm}/\mu \mathrm{s}$
. SEM images show that no observable damage can be detected for the SiC fibers after several tens of shots. However, a small area of SiC fibers with dimensions of 3mm
^x
3mm broke away from the carbon blanket base after several tens of shots which probably caused by poor binding strength between the SiC fibers and the carbon blanket. The SiC velvet shows comparable emission performance with polymer velvet. If the binding strength is enhanced the SiC velvet will be a preferred emission material for high power microwave tubes such as MILO.