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Particle accelerators of all shapes and sizes

Is it any coincidence that probably the most famous particle accelerator in the world is also the biggest? The LHC has made headlines in recent years not only because of the potential scientific discoveries it can make but also because of the scale of the engineering. The average member of the public is easy to impress with the 27km tunnel built underground with magnets which are stronger than they can imagine and operating at temperatures comparable with outer space.

There are other new projects which are big as well. The ILC, which is being studied as part of several EuCARD Work Packages is another example. The engineering is again impressive, but what about the engineering required to make things really small? 		ATLAS DetectorThe ATLAS detector at the LHC can be seen to be very big. Image courtesy of CERN. Thumbnail image on main page courtesy of CERN.

A different scale

The concept of a table top accelerator is not new. Accelerators of this size are desirable because they are transportable, and so do not have to remain in the same place for their lifetime. Various types of table top accelerator have been designed. Oxford Instruments designed and built two table top synchrotron radiation sources in the early 90s which were used for X-ray lithography. Many medical accelerators have been designed so that they fit into hospitals. Research is also ongoing into plasma wake field acceleration which can produce accelerating gradients several orders of magnitude better than conventional RF acceleration techniques, which in turn will reduce the size of large particle accelerators.

Making particle accelerators really small

Electrostatic Septum
The microchip sized particle accelerator uses electric fields to steer the ion beam instead of magnets, just like this electrostatic septum shown. Image courtesy of CERN.		 It was reported at the MEMS 2011 conference in January that a particle accelerator the size of a microchip has been created. This accelerator guides argon ions with 1.5keV of energy down a 5mm long channel before taking them through a 90 degree turn. Their energy is boosted by about 30eV in this process. That may sound unimpressive but all this is in a microchip just a few square centimetres in size. No magnets are required to steer the beam; at this energy the beam is simply guided by electric fields. It is hoped that future versions of this accelerator can pass the ions repeatedly through the accelerating channel so they gain more energy. It is also hoped to create a smaller, on-chip ion source. The present source is very big compared to the chip.

 

This technology is in its infancy at the moment. To be useful, the particles would need to have energies of around 1MeV but the potential applications include shoe box size electron microscopes and portable particle accelerators for the treatment of cancer. Such accelerators would be able to target the particle beam more accurately and thus avoid healthy tissue receiving significant doses of radiation. These developments are some time off yet but the potential of this research is significant.

Further details about the microchip particle accelerator can be found here.

- Naomi Wyles, CERN, EuCARD-DCO (WP2)

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