Terahertz Radiation To Enable Portable Particle Accelerators (www.desy.de)

Zothecula writes with this Gizmag story about an interdisciplinary team of researchers who have built the first prototype of a miniature particle accelerator that uses terahertz radiation. "Researchers at MIT in the US and DESY (Deutsches Elektronen-Synchrotron) in Germany have developed a technology that could shrink particle accelerators by a factor of 100 or more. The basic building block of the accelerator uses high-frequency electromagnetic waves and is just 1.5 cm (0.6 in) long and 1 mm (0.04 in) thick, with this drastic size reduction potentially benefitting the fields of medicine, materials science and particle physics, among others."

Comments

Not so easy

[joe_frisch]

There have been designs for high frequency accelerators for a long time. These range from normal ~few GHz machines like SLAC, to 10s of GHz (CLIC - proposed), to THz to direct optical acceleration. There are also plasma based 2-beam accelerators which have extremely high gradients (10 GeV/M).

There are some general trade-offs:

Higher frequency -> more energy / length, but lower beam charge and tighter tolerances, and usually lower efficiency. Depending on the application this may or may not be a good trade, but very high frequency accelerators have so far found limited practical application. Most applications for high energy also require fairly high beam power and good beam quality.

In particular high energy physics accelerators require very high average beam power (megawatts), which require high wall-plug efficiency, (to keep operating costs down). So far none of the high frequency accelerator designs look practical for this application. In addition for a high energy physics machine the final focus system is kilometers long, so even if the accelerators could shrink, it in no way results in a tiny machine.

There is a lot of interest in high frequency accelerators for medical and other low energy low power applications. This is a case where there are a number of ways to solve the problem and we need to see which technology is ultimately the cheapest / easiest. Here mm-wave is competing with lasers and other types.

For comparison, a conventional (x-band) 20MeV accelerator is 20cm long. The shielding for a 20MeV beam (which can generate neutrons) could easily be a meter of concrete.

I'm not knocking this technology at all, it may be very useful for some applications. I just want to counter the idea that it will transform particle accelerators.

Joe Frisch
SLAC