controlled, constant-power circuit required

I need to design a power supply to flash-heat a low resistance material to drive off solvents ( say about 30 seconds duration -variable up to 1min ideally). The material impedance is micro-ohm range and drops with rise in temperature. The power required is around 15 - 50Watts (adjustable) and should be constant or, at least, limited. I want the voltage to be low (say under 10Vdc) for safety (ac power might be acceptable). The power should be able to be ramped up over a brief adjustable period to avoid thermal runaway. Anybody got any good ideas?

How about just a constant voltage / constant current power supply. You could use a micro as the actuator for your control loop to ramp up the current and then shut it down after some time.

constant power circuit

Sounds fine to me - I have had similar thoughts. What I really need is a working circuit diagram to build a prototype.

If you have a very low resistance material, then a good idea is to heat it through high frequency magnetic field.
Simply put your material inside of one solenoid that is supply with a high frequency voltage at desired power.
In this case you avoid all problems linked with case of electrical contact heating, and minimize the risk of contamination.

Have you considered that it takes 1000 amps through 1 microohm to cause it to dissipate 1watt? The voltage would be 1 millivolt. I know that your element's resistance is more than 1 uohm, but you might want to do some calculations.

Thanks for the postings guys. There's some good info there. I'll keep you posted on the progress.

Any other advice/ideas gratefully accepted