ap400b
Thanks for the reply, G4BCH. Unfortunately, the capacitance of this load is a lot higher than found in a CRT 'scope so I need to deliver "real" (er, apparent) power here. Right now they are using an ENI AP400B 400W power amplifier to drive the device* at 250kHz, 440Vpp and the amplifier reads 40W output. This implies a capacitance of approx. 180pF., though that doesn't even remotely match what I measured with my LCR meter (more like 5800pF) so I'm assuming the wattmeter on the AP400B is measuring actual power, rather than apparent... At any rate, I am planning on a power level of around 100W. Obviously, if I have to go with a single-ended Class A amplifier with choke loaded drain that means I'll need to design (and power) the thing for 400W or so. If I can get away with a push-pull design, even if it is biased more Class A than B I can at least save a few watts in the power supply (understanding that when the VSWR=∞, the reflected and forward voltages add together, and in a choke loaded single ended Class A that, I believe, results in the drain seeing 4x the supply voltage... I may be wrong, though, and, frankly, I would love to be).
* - an ion "concentrator" or funnel; it uses RF to focus a stream of ions onto a target substrate.