Since 1990, doctors have been regularly treating cancer patients using proton beams, which work similarly to radiation. Proton therapy is more precise, however, causing less harm to healthy surrounding tissues. Unfortunately, generating a proton beam requires a particle-accelerator facility that's the size of an aeroplane hangar and costs more than $US100 million to build.
Thus, proton-beam therapy remains a rarity, with only 37 working facilities worldwide, 10 of which are located in the US. Just 10,000 people were treated last year, less than 5 per cent of suitable patients.
Now scientists at the Compact Particle Acceleration Corporation in Livermore, California, are developing a 13-foot-long particle accelerator that costs about $US30 million. Most accelerators use large magnets to generate the electromagnetic field that pushes charged particles. The magnets require 10-foot-thick concrete shielding and bulky hardware. CPAC's prototype creates the electromagnetic field with electric lines, which don't require massive shielding or large additional equipment. The new accelerator could be commercially available as soon as 2015. (The numbers below will match you up to the location in the picture above.)
1. Proton Beam
Magnets in the kicker pull positively charged protons from hydrogen plasma made by a duoplasmatron. A deflecting magnet collects the stream into proton bundles, which then enter the injector, where a microwave field speeds the particles toward the acceleration chamber at up to five million mph.
At nearly the same time, a laser fires a light pulse, which splits into fibre-optic cables of various lengths.
3. Acceleration Chamber
As a bundle of protons enters the acceleration chamber, a light pulse hits the chamber's first pair of electric lines, triggering the release of electrons. The resulting electromagnetic field propels the proton bundle forward. The light pulse triggers the electric lines in a wave, sequentially accelerating the proton bundle until it's travelling at 335 million mph-or about half the speed of light.
The entire process is controlled by a clock, which directs magnets to turn on or off and the laser to fire.
5. Robotic Chair
Moving a patient is easier than moving a 13-foot-long particle accelerator. A robotic chair manoeuvres a strapped-in patient in front of the proton beam to target a tumour from different angles.
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