I love the idea that we believe that we can replicate all of the natural processes involved in getting a tan, and to such a precision that we can then speed up the process 10 fold, and that we can fit it all into a single unit that can be wheeled in and out of the room.
Unless of course our calculations are a bit off, then we accidentally created a bed version of the wrong chalice from raiders of the lost ark, but I think it's fine.
Replicate the natural processes? It's literally just UV light.
UV comes in an huge variety of strengths outdoors.
There are no calculations to be a "bit off". It's just strong UV. You're making it sound a lot more complicated than it is.