Extraction system design for 50A, 50keV, 2 sec ion beam

The basic ORMAK injection unit was operated at 40 keV, 6A, 0.3 sec and a 15% duty cycle, while monitoring power loading to the various extraction system electrodes, in order to pinpoint the critical power loading areas. A 40A scaleup of this ORMAK unit is being built. Thermal time constants for these water-cooled extraction electrodes are about 0.5 sec. Going from 0.3 to 2 sec will therefore increase the power loading. An increase in beam energy above 40 keV will also increase the loading. ORMAK unit data indicate that the ground electrode and the plasma-forming electrode have relatively high power loadings. For the 40 keV, 6A operation these were 400 watts per sq cm of Cu extraction surface and 200 watts per sq cm respectively. The extraction electrode loading was relatively small, 40 watts per sq cm.