Particle accelerators have huge potential for semiconductor applications, medical imaging and therapy, and materials, energy and medical research. However, traditional accelerators require a lot of elbow room (kilometres), are expensive, and are limited to a few national laboratories and universities. A collaborative research team has developed a compact particle accelerator capable of producing high-energy electron beams in a much smaller volume than traditional accelerators. This breakthrough brings new possibilities for medicine, semiconductors and scientific research, with further miniaturization and increased practicality planned.
Researchers at the University of Texas at Austin, multiple national laboratories, universities in Europe and Texas-based TAU Systems have demonstrated a compact particle accelerator less than 20 meters long that can produce an electron beam with energy of 10 billion electron volts (10GeV). Currently, there are only two other accelerators in the United States capable of reaching such high electron energies, but both are about 3 kilometers long.
"We can now achieve these energies within 10 centimeters," said Bjorn "Manuel" Hegelich, associate professor of physics at the University of Texas at Austin and CEO of TAU Systems, referring to the size of the chamber that generates the electron beam. He is the senior author of a paper describing their achievements recently published in the journal Matter and Radiation at Extreme.
Heglich and his team are currently exploring how their accelerator, called the Advanced Wang Field Laser Accelerator, can be used for a variety of purposes. They hope to use it to test the radiation resistance of space electronics, image the three-dimensional internal structure of new semiconductor chip designs, and even develop new cancer treatments and advanced medical imaging techniques.
The accelerator can also be used to drive another device called an X-ray free electron laser, which can film slow-motion processes at the atomic or molecular scale. Examples of such processes include drug-cell interactions, changes inside batteries that can cause them to catch fire, chemical reactions inside solar panels, and the shape changes of viral proteins when they infect cells.
The concept of Wangchang laser accelerator first appeared in 1979. Extremely powerful lasers hit the helium gas, heating it into a plasma and creating waves that knock electrons in the gas out of the high-energy beam. Over the past few decades, different research groups have developed more powerful versions. Heglich and his team's key advance relied on nanoparticles. The auxiliary laser irradiates the metal plate in the gas chamber, and the metal plate injects a flow of metal nanoparticles, thereby enhancing the energy of the electron wave.
The laser is like a boat rowing across the lake, leaving a ripple, and the electrons are like surfers riding this plasma wave.
"It's hard to get into a big wave without getting crushed, so wave surfers are dragged into the wave by jet skis," Heglich said. "The equivalent of jet skis in our accelerator are nanoparticles that release electrons at just the right time and at the right point, so the electrons are in the wave. We get more electrons into the wave when and where we want it, rather than being statistically distributed throughout the interaction, and that's our secret sauce."
For this experiment, the researchers used one of the world's most powerful pulsed lasers, the Texas Petawatt Laser. A single pitawa laser pulse has about 1,000 times the power installed in the United States, but lasts only 150 femtoseconds, less than one billionth of the time of a lightning discharge. The team's long-term goal is to power their system with a laser they are currently developing that could sit on a table and fire repeatedly thousands of times per second, making the entire accelerator more compact and applicable to a wider range of applications than traditional accelerators.