It should be mentioned that a continuous "thermal trigger" around a phase-change (which is usually required for the NiH reaction to proceed in a robust way) can be controlled by the cold-side (output side) as well as the hot-side (input side) - and this feat is apparently what Rossi has achieved with both the ECat and HotCat.
Even so, a thermal trigger is far more difficult to control on the cold side because the transients are greatly dampened, peak to peak, compared with pulse heating (hot side). Imagine a sine wave where only the top 10% of the wave acts as a trigger. For any wave, electrical or thermal, to work - there must be coherence. When the waveform is suppressed, peak-to-peak, or noisy as happens with thermal waves - then the control parameters are greatly compromised. unless, that is one is able to achieve some level of superradiance in the IR. Without superradiance, control is hopeless, as the signal is too noisy. Thus the preference for reaction control via the input side (electrical input). A few of us believe that Rossi's greatest advance (over the prior art of Mills, Piantelli, etc) which is especially noticeable with the HotCat - is engineered superradiance (semi-coherence) in the IR allowing for accurate control via the cold side. In fact, almost any kind of coherence provides its own built-in control by a simple feedback expedient. Giuliano Preparata described this twenty years ago. From: Jed Rothwell Rossi ran his device in public for ~4 hours without input, far beyond the limits of chemistry. He has run in that mode many times in private tests, according to people I know who witnessed these tests. This is known as "heat after death" (HAD) in cold fusion jargon. That is an inaccurate way to describe it, but anyway, if you look up that term you will see that many other researchers have run without input power. Arata supposedly ran that way for weeks. His calorimetry is not good but I think he probably did as claimed. I do not know whether Defkalion has done this. I am sure that Rossi did. I am also sure it really was in HAD mode because the power was definitely off, the cooling water flow was on, so the reactor should have been at room temperature after 4 hours. Yet the video showed it was hot enough to burn a woman who accidentally brushed against it. Also, several people reported the reactor it was full of boiling hot water when they opened it. Rossi has good reasons to avoid HAD mode in normal tests. In the first Elforsk visit, his steel reactor vessel melted. The reaction is not under control. - Jed
