Scientists set a record of hottest temperature ever recorded of 2 billion degrees Kelvin or 3.6 billion degrees Fahrenheit using Sandia Lab's Z Machine - and they didn't know how they did it!
Sandia researchers still aren’t sure how the machine achieved the new record. Part of it is probably due to the replacement of the tungsten steel wires with slightly thicker steel wires, which allow the plasma ions to travel faster and thus achieve higher temperatures.
One thing that puzzles scientists is that the high temperature was achieved after the plasma’s ions should have been losing energy and cooling. Also, when the high temperature was achieved, the Z machine was releasing more energy than was originally put in, something that usually occurs only in nuclear reactions.