Number 597 #1, July 9, 2002 by Phil Schewe, James Riordon, and Ben Stein
Nanotube Diagnostic X-Rays
The design of the x-ray sources used in many medical and dental diagnostics
hasn't changed much in a hundred years. A cathode heats up to 1500 C
and then emits lots of electrons, which are pulled across a vacuum tube
toward a target where the ensuing impact kicks up a beam of x rays.
Now a team of physicists and doctors at the University of North Carolina
and the nearby firm of Applied Nanotechnologies, Inc. have created,
for the first time, an x-ray source using a room-temperature array of
carbon nanotubes to create the electrons and deliver a sufficient x-ray
flux for doing practical medical imaging (see figure).
The device is much smaller and cooler and the old models, and the resultant
x-ray pulse is more focused. Also response time is sharper and the pulse
shape can be programmed, which helps in the tracking of moving objects.
(Yue et al.,
Applied Physics Letters, 8 July 2002; contact Otto Zhou, 919-962-3297,