What is a lunar particle?

I think you should specify a minimum energy, otherwise an old-fashioned cathode ray tube would already count and I don't think that's what you have in mind.

@ErwinRossen Good point. Minimum energy or minimum size? Or maybe specify that it needs to be for research purposes?

@IsaacKing I think any of these three would help. It's hard to say upfront what to specify when looking almost 30 years into the future.

@ErwinRossen A low threshold could be if it can be carried at once or if it needs to be built in situ