If there's 0 helium going in, and >0 coming out, there's fusion, no matter how little. There's no other way to get helium from hydrogen. Also, hydrogen gas wou

If there's 0 helium going in, and >0 coming out, there's fusion, no matter how little. There's no other way to get helium from hydrogen. Also, hydrogen gas would float a balloon even better than helium, so that wouldn't be much of a test.