I have completed my work on an initial ladder model of the hotcat http://lenr.qumbu.com/rossi_hotcat_may2003_spice_130605.php
It's a long document, but I summarize the results in section 2. (No need to read the rest unless you want to see how I got there). It confirms my initial guess that a triangular waveform of HOTCAT heat might produce the required SINE-like output reported by Levi. But when I progressed from a lumped to a ladder model I found that a Sawtooth (slow rise, quick fall) was a better fit. The bad news is that when I look at the temperature curves at the center it is hard to see how to make a control system which produces a sawtooth. The March 2013 HT2 (COP=3, 300C) is an odd case ... the central waveform has a local minimum which could be of importance -- but it is a "ripple" of 0.1 degrees in a signal of 300 degrees (in a simulation which is about 20% accurate). When I re-ran it with the December results (COP=6,500C) it gave more robust results which might be useful to a control system. In addition to the Spice model itself, I have collected various information from the Levi and Penon reports. I extracted and annotated a lot of their photos. (But if you use them, see the copyright section near the end). For various reasons I believe that the reaction takes place in the "pixie dust", but the thermalization is most likely in the steel wall of the inner cylinder. My final thermal model injects the hotcat heat there, rather than at the center. (It made only a very small difference to the waveforms at the center). Next steps : calibrate the model, using actual physical values of specific heat etc. Possibly extend the ladder with a few more stages in the middle ceramic section. These should bring the model to about 10% accurate.
