For control, and reminding F&P fantastic calorimeter (fast and sensible), PID problems, and control/command problem, maybe one should also reduce thermal mass to avoid overshoot or late reaction with PID or simply with natural cooling.
if thermal resistance is high, system may have a high COP, but with high thermal mass it will runaway without any hope of cooling... using conductive and thin but solid material may allow fast heat transfer, at least between part of the powder...
I was not thinking of agility, but that is also an issue that might also be addressed, that is the agility of the measurements and rapidity of the internal heat flows to avoid runaways could be important. Since we are interested in the time integrated power otherwise known as energy, and runaway heating has occsionally been seen or at least suspected, the agility might also be considered a leading issue. Agility of measurement and rapid response to runaway heating (positive feedback loops) might also become important once manipulations of EM or other variables become of interest.
It is my view that at the basic demonstration level where our replicators are currently working they should be mainly looking at the ratio of heat OUT to heat IN, this is the basis for calculating a COP. Lost heat from the IN side of the fraction effectively raises the denominator without contributing to actual heat in the reactor itself. Further lost heat OUT can falsely lower the numerator and hence the estimate or measure of the actual heat that may be generated by the reactions / reactor. Reflectors, high temperature insulation and thermal breaks in the leads and supports for the reactor can all go a long way toward making the COP calculation more "real". Parkhomov's double boiler was a simple attempt or start towards resolving such concerns. His system had the issue of phase change which may not have worked well there, since boiled water is not readily conducted away at the instant of its evolution-- and of course any effort such as that has the issue of entrained droplets of water as well. A simple, well insulated bath which does not reach boiling, and does not allow evaporation, might go some way toward the calorimetry that will ultimately be necessary--- as long as the whole experiment does not raise the whole bath to the boiling point (the phase change involves much more energy than simple temperature elevation-- hundreds of times more energy is required to pass through the boiling point than to raise say liquid water one degree without the phase change).
It seems to be a compromise? may gas, metal or ceramic help to increase heat transfer speed?
F&P used low mass thermal barrier, the vacuum and silvered glass... the idea to use mirrors seems interesting, as it increase resistance without thermal mass... don't laugh, but low emissivity (high reflectivity) treatment may help, but it seems impractical and uncontrollable.
light foam is probably a good idea, as it have high thermal resistance with few weight.
Again I would point to the losses. An incandescent heater "dogbone" is pouring out hundreds of watts of power by radiation and convection, in fact nearly all of its power is going toward those paths. To get to or maintain a desired operating temperature, this is heat that has to be replaced by the nichrome / Kanthal heater elements. It is a major source of heat loss that is at best poorly accounted in the COP calculations to come. It can be largely avoided by good insulation, by good reflection, perhaps by other design changes. Further, heat losses such as this can also be accounted using a large calorimetric bath that catches all the heat (ohmic and possible LENR) and converts it to temperature rise in the known (by empirical testing and heat / temperature rise curves) that is the behavior of the bath / reactor system. The heat in can be measured by several means, one being simply the integrated electrical power delivered to the system.
The fiber insulations such as FiberFrax are quite lightweight. Most foams are not rated at the temperatures such as 1500 C. But thermal inertia is just another loss of agility, it can otherwise ultimately be accounted for in the temperature rise / calorimetric calculations, since the whole can be assessed by ohmic heating without any LENR, to create a "standard" energy v. temperature curve.
Much greater agility and response to "runaway" could be provided by nearly all radiant system based on quartz halogen tungsten lamps, focused on say an black oxide coated Inconel or other high temperature metallic reactor vessel (relatively thin walls), lined inside, if necessary, with an alumina or other refractory. That way any sudden rise in output can be quelled by turning off the lamps (much less thermal inertia than the big Kanthal and ceramic cement "brick". In addition to rapidly shutting down the heating current, a blast of cold air, argon, CO2 or even water spray can be blown across or even through, if necessary, to rapidly quench any unexpected runaway.
It is funny, though, because when I drew that wire diagram, it struck me too. I will try that as soon as I get back to the lab. I plan to do a continuation run Monday, and will rewire according to your suggestion.
