Hi, You might take a look at the work of Dr. Randell Mills (http://brilliantlightpower.com/). A severely shrunken H2 molecule would provide the "constraint" on particle location that you are looking for. Furthermore, the shrunken electrons of the Hydrino molecule can carry away excess energy as fast particles, which then ends up as heat in the fluid. Also, if only one proton (deuteron) of the molecule fuses with the target nucleus, the other proton may carry away the reaction energy.
You may also want to take the following into account:- 1) Water also contains some D. Reactions involving a shrunken HD molecule (or individual shrunken atoms) may avoid the need for weak force reactions. You could see if this is applicable by repeating your experiments with water enriched with heavy water. I wouldn't try using pure heavy water at first, as you wouldn't want the experiment to blow up in your face. 2) The temperatures achieved in a collapsing cavitation bubble, are sufficient to create atomic hydrogen from water, and according to Mills, a water molecule can act as a catalyst for the shrinkage reaction. 3) They say there is nothing new under the Sun, and this isn't the first time that a cavitation based device has been reported to produce excess heat. See https://www.hydrodynamics.com/. This was reported on vortex-l decades ago, and in fact the group was initially set up to discuss this device. 4) You may also want to check out https://lenr-canr.org/ for many related papers. Regards, Robin van Spaandonk <mixent...@aussiebroadband.com.au>