To　meet　the　requirements　for　advanced　vacuum　electron　devices　and　modern　electron　beam　instruments,　dc　emission　properties　of　nanosized-scandia-doped　impregnated　(SDI)　cathodes　have　been　investigated　in　a　closely　spaced　diode　configuration　system　with　water-cooled　copper　anode.　The　SDI　cathodes　were　made　from　nanosized-scandia-doped　tungsten　powder,　which　was　produced　by　a　spray-drying　process.　A　space-charge-limited　dc　current　density　of　over　60　A/cm(2)　has　been　measured　at　950　degrees　C-b.　An　on-going　life　test　with　a　dc　load　of　30　A/cm(2)　at　950　degrees　C-b　has　completed　more　than　2000　h　of　operation　to　date.　The　electron　cooling　for　dc　beam　emission　is　discussed.