The process of invention, according to US patent law, conssts of two steps: conception, and reduction to practice. Conception is coming up with the idea, reduction to practice is actually making the thing. I've conceived of a good many inventions over the years, most of them wildly improbable, my most favorite (because it's the most absurd, yet could in principle be made to work) was the "lighter than vacuum space zeppelin". So far as I can recall, I've actually reduced none of them to practice, although there are several that I might someday, not the LTV obviously. Nor, as it turns out, the doomsday device.
This for several reasons. First off, it probably couldn't be made to work. Never know for sure until you try, but I don't plan to be trying anytime soon.
The second, more important reason, is economic. Even a scaled down version which wouldn't do much more than annoy people would probably take years of time and many thousands of dollars to devolop. A fully functional version would doubtless cost millions. And the nature of the beast is that it really wouldn't be useful to bluff people with, since convincing people that you had one would require revealing enough to allow any bozo with a few million to build one. No, the only reason to buy/build one is if you intend to use it.
Here we come to the immovable stumbling block: The free rider problem. A brief marketing survey came to a devastating conclusion: that anyone with the resources and the will to use such a device would, rather than actually doing it, instead spend his money on drugs and hookers and let some other sucker foot the bill. After all, the world can only end once, and once it has, who cares who paid for it?
True, my marketing survey was pretty much limited to the voices in my head, but experience has shown they tend to be reliable. At least, if consistency is a sign of reliability. They tend to say the same as each other, and that's the only justification I have for believing the news.
Doubtless there's a bigger market for improved drugs and hookers anyway. "More research is required", as we say in the science biz.
The final result is, in the event of the end of the world, you won't be able to blame me. Of course, you wouldn't be able to even if I actually were responsible, since we'd all be dead.