I am in need of constructing a heater probe for a reaction chamber. I need to put out a maxium of 500 Watts continuous from the 5 cm end of a probe of either 1/4" or 5/16" in diameter. I am constrained to either of these standard sizes. My first inclinations are to wind nichrome wire around a ceramic mandrel, and sleve it with fibre glass shoe string woven insulation in a probe body of stainless steel. I need to be capable of withstanding 50 Bar of external pressure at the temperatures generated. The exterior temperature could be as high as 600 C. Is this design even possible? Will I melt the wire or glass trying to put out this much heat?