Reverse the Polarity

Thanks to rpfreeman on Outpost Gallifrey for this:

"I just saw on Economist.com an article about a new precision approach to radiotherapy that included the following "The dielectric-wall accelerator (DWA) that lies at the heart of Dr Mackie's machine was designed in the 1990s at the Lawrence Livermore National Laboratory in California as a portable X-ray source. At first, it was used to accelerate electrons rather than protons. Those electrons were crashed into a metal target to generate the high-energy X-rays that Livermore's physicists needed to peek inside ageing bombs and check that they were still in working order. All of which was fine and dandy for the weapons scientists, but not much use to anybody else. Fortunately Dennis Matthews, one of Livermore's more medically minded programme directors, realised that by changing the polarity of the machine it could be used to accelerate positively charged protons, rather than negatively charged electrons. He then teamed up with the cancer centre at the University of California, Davis, to investigate the possibility of using a DWA for proton therapy. "
Wonder where he got that idea?
The full article is http://www.economist.com/research/ar...y_id=953755 3 although I'm not sure if you ned a subscription to get to it."

If you don't watch Dr Who or rather didn't watch Dr Who in the 1970s and 1980s then please ignore this post!