Researchers at Stanford University are developing a linear accelerator that is the size of a chip — instead of two miles long — and it could herald a medical breakthrough. Linear accelerators are commonly used for external beam radiation treatments for patients with cancer. However, only a handful have been constructed as they are very expensive to build, maintain and operate. Stanford’s accelerator on a chip could provide every hospital with access to this life-saving technology.
Standford’s SLAC National Accelerator Laboratory houses a linear accelerator that measures 3.2 kilometers in length. Because it emits radiation, it’s buried 25 feet under the hills of northern California. Dubbed LINAC, it relies on klystrons to generate high-energy electron beams. At one end of the line, electrons are generated. They are then accelerated to 99.99999 percent of the speed of light and zip down the 2-mile long instrument.
The setup is expensive, however – which is why scientists in the same lab are working to create an accelerator small enough to fit in a large shoebox. After receiving a $13.5 million grant from the Gordon and Betty Moore Foundation in 2015, the “accelerator on a chip” (ACHIP) project was born. When the project launched in 2013, SLAC physicist Joel England said: “Making them much smaller and cheaper would democratize accelerators, potentially making them available to millions of people. We can’t even imagine the creative applications they would find for this technology.”
The minuscule device would work similarly to the LINAC. However instead of shooting electrons down a copper vacuum tube, they would be pushed along with microwaves. Engadget reports, “The AoaC will shove electrons through a precisely-engineered silica chip, smaller than a grain of rice, and excite them with laser beams.”
By adjusting the width of the ridges in the channel, with respect to the wavelength of the laser, the chip’s acceleration gradient could be tuned to a whopping 700 megavolts per meter (MeV/m). That’s ten times what the LINAC can generate. The inexpensive device could replace multimillion-dollar radiotherapy machines in hospitals – and it could be paired with a simple fiber laser power source to “burn out” tumors faster than traditional radiation therapy — and without the need for anesthesia.
Said Joel England, SLAC’s lead researcher for this program, “Once you get into a million electron volts or more then you’re sort of in the regime of where you can have practical applications; where something like a medical accelerator is more viable. So typically for cancer treatment, you’re using particles with between one and 20 million electron volts of energy.”
He explained in 2013, “We still have a number of challenges before this technology becomes practical for real-world use, but eventually it would substantially reduce the size and cost of future high-energy particle colliders for exploring the world of fundamental particles and forces.”
Images via Stanford University