Generation　of　a　sheet　beam　directly　from　a　scandia-doped　dispenser　cathode　has　been　investigated　and　optimized　by　means　of　beam-profile　simulations　and　measurements.　Rectangular　beams　600　mu　m　wide　and　100　mu　m　thick　with　current　densities　over　50　A/cm(2)　have　been　generated.　The　beams　are　stable　for　at　least　several　hundred　hours　with　the　cathodes　operating　at　950　degrees　C-b,　making　them　promising　candidates　for　application　in　the　next　generation　of　terahertz　vacuum　electron　devices　such　as　a　0.5-THz　superradiant　Smith-Purcell　radiation　source.