Shaffery Among the Immortals, by Frederik Pohl
From what I remember
In fact, Shaffery was not an inventor but mainly an astronomer; he lost most of his prestige when announcing some unexpected phenomena (some planet shifting to red, or blue) which finally does not happen. He ends up in an astronomical observatory that he suspects is used by the Mafia to launder money, and when he dies he is in the process of being sacked for disagreeing with the investor about which would name discoveries made by the observatory. The x-ray idea was just a lateral idea, which did not seem important at the beginning.
I read it a long time ago, and I still remembered in which collection. Since citations needed, here is an extract I found over the web:
A funny yarn about one Jeremy Shaffery, an astronomer who idolizes Einstein and his methods and who wants to achieve immortal fame by doing something just as famous. The problem is that he is not built for this (“The Einstein method, which he had studied assiduously over many years, was to make a pretty theory and then see if, by any chance, observations of events in the real world seemed to confirm it. Shaffery greatly approved of that method. It just didn’t seem to work out for him.”). As his wife says with a bite:
(quoted from Shaffery Among the Immortals)
“Your trouble, Jeremy, is you’re a horse’s ass.” But he knew that wasn’t it. Who was to say Isaac Newton wasn’t a horse’s ass, too, if you looked closely enough at his freaky theology and his nervous breakdowns? And look where he got.”
In a desperate moment, he starts trying to prove Fermat’s Last Theorem (“It was one of those famous mathematical problems that grad students played at for a month or two and amateurs assaulted in vain all their lives. It looked easy enough to deal with.”). A description of the problem with analogy to Pythagoras theorem and the reference to Fermat’s margin note follows. In fact, Shaffery has half a mind to just write a similar margin note but discards the idea for a few reasons (people would not take it seriously, it would be posthumous, etc). He tries out some desperate methods before other events take over. In the end, he achieves non-mathematical fame in an unwitting pandemic he causes which destroys most of the world’s population…
Here is a list of books where it has been published