The low-energy demonstration accelerator (LEDA) 75- keV proton injector is being developed for tests of high- current (100-mA) cw linacs. The injector comprises a microwave proton source and a space-charge neutralized magnetic low-energy beam-transport system (LEBT). The LEDA injector has been configured to provide flexible 50-keV beam matching into a cw 1.25-MeV radio-frequency quadrupole (RFQ) brought from Chalk River Laboratories (CRL). The LEBT has two solenoid focus magnets separated by 117 cm. Between the solenoids are two steering magnets and diagnostic stations for measuring the beam current, profile, and position. The ion-source extraction system was modified to a 50-keV triode to test the injector/RFQ system. Beam-matching tests showed that injector-RFQ transmission is 90% for 50-mA RFQ current. At the RFQ design current of 75 mA the beam transmission decreased to 80 - 85%. Optimized injector tuning led to 100-mA beam accelerated through the RFQ.

The small-angle source (SAS)' ant1 4X sollrce2 are Penning surface-plaslna sources (SI'S) that produce high- brightness fI- ion l)eams for acc?lrrator al)plications. Ilow- ever, electrode cooling considerations 11avr limited the duly factor for pl&ed operation to l-:3% anti the maximum cw II- 11eam to 2-4 mA. 'The addition of son,? active cooling to t Ile 4X source has allowed l"&ed operation at 6% duty factor for cw fI- beams in t,he same, or higher,'5 cllrrc11t rrgimrs. We have begun an experimental prograIn to try to increase the average extracted II- beam curr?nt, whetller pldsed or cw, from our Penning SPS. We have chosen t.he Penning SPS because it produces II- beams of high current. and low en~ittance.'3,'6 Below, we describe our ailproach to this cl>& lenge, including the experiments ihat allowed us to atta.in 6% duty factor pulsed operation of the 4X source arc; the design mobificat,ions t.hat should allow prodrlction of 20-30 mA cw II- beams from the 4X source; and the scaling to a sollrcc (C!W--Source) that should produce 100.200 IIIA cw I1 - bealns. Experiment and Results for 6% Duty Factor The operation of t.he 4X sonrre, without, rooling m$- ficatious, is discussed in some detail m Hefs. 2 a11d li. 'I'lus original configurat,ion has been operated plllsed at -1% duty fact.or. In an experiment to see if the pulsed cll1t.y fact.or could be raised, the modifications shown schematically in Fig. 1 were trade. The capacities of t.he t,wo ori inal cathode cooling