We think this mainly because 1 L of powder self-heats and there are large heat gradients and flux. You might be able to accomplish the same thing with a smaller sample and the clever use of resistance heaters.
I assume the array of heaters connected to Rossi's control box is producing some sort of gradient or waves of heat, which stimulates the reaction. I expect it is easier to do that with a substantial volume of material. Certainly a lot easier than with, for example, the tiny samples used in the Seebeck calorimeter at the NRL. I can't imagine anyone producing a gradient with that. - Jed
