September 27, 2022

Assistant Professor Arijit Bose is a new member of the Department of Physics and Astronomy at the University of Delaware. He has a grant from the Sandia National Lab to study inertial confinement fusion that uses magnetic pressure to produce nuclear fusion. Credit: Jeffrey C. Chase

Imagine trying to summon the sun to your research lab.

Yes, you, great bright star! Bring with you your scorching heat, the drama of your core’s constant fusion, and your unusual energy levels. We want to know how we can make this fusion energy happen here on Earth – at will and efficiently – so that we can delete “energy supply” from our list of concerns forever.

But of course the sun can’t really reach the lab. It lives too far away — some 93 million miles — and it’s way too big (about 864,000 miles in diameter). It’s also way too hot and denser than anything else on Earth. Therefore, it can support the reactions that generate all the energy that powers life on Earth.

Of course, this hasn’t stopped scientists from continuing their quest for nuclear fusion.

Instead, they’ve found extraordinary ways — using intense lasers and hydrogen fuel — to create extreme conditions like those that exist in the sun’s core, producing nuclear fusion in tiny 1-millimeter plastic capsules. This approach is called “inertial confinement fusion”.

The challenge is to create a system that generates more fusion energy than it takes to create it.

This is extremely challenging because it requires extremely precise experiments under extreme conditions, but researchers have made great strides in recent decades in the science and technology needed to produce controlled laboratory fusion.

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Now researcher Arijit Bose of the University of Delaware and his collaborators are pursuing a promising variant of this approach. Their work has recently been published in Physical Assessment Letters.

This animation illustrates inertial confinement fusion, which is achieved by using high-powered lasers to drive a spherical implosion and is a focus of new research by Arijit Bose of the University of Delaware. Credit: University of Delaware/Jeffrey Chase

They applied powerful magnetic fields to the laser-guided implosion, allowing them to direct fusion reactions in ways previously unexplored in experiments.

Bose, an assistant professor in the UD’s Department of Physics and Astronomy, began studying nuclear fusion while in graduate school at the University of Rochester.

After touring the Laboratory for Laser Energetics in Rochester, where lasers are used to implode spherical capsules and create plasmas, known as “inertial confinement fusion,” he found a focus for his own research.

“Fusion is what powers everything on Earth,” he said. “To have a miniature sun on Earth — a millimeter-sized sun — that’s where the fusion reaction would take place. And that surprised me.”

Laser-guided nuclear fusion research has been around for decades, Bose said.

It started at the Lawrence Livermore National Lab in the 1970s. Livermore now houses the largest laser system in the world, the size of three football fields. The fusion research done there uses an indirect approach. Lasers are aimed into a small 100 millimeter can of gold. They hit the inner surface of the can and produce X-rays, which then hit the target — a small sphere made of frozen deuterium and tritium — and heat it to temperatures near the sun’s core.

“Nothing can survive that,” Bose said. “Electrons are stripped from the atoms and the ions move so fast that they collide and fuse.”

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The target implodes within a nanosecond — a billionth of a second — first propelled by the laser and then further compressing on its own inertia. Finally, it expands due to the increasing central pressure caused by the compression.

“Starting a self-heated fusion chain reaction is called inflammation,” Bose said. “We are remarkably close to achieving inflammation.”

Livermore researchers reported: impressive new acquisitions in that attempt on August 8.

Rochester’s OMEGA laser facility is smaller and used to test a direct drive approach. That process doesn’t use a gold can. Instead, lasers hit the target orb directly.

The new piece is the powerful magnetic field – in this case forces up to 50 Tesla – used to control the charged particles. In comparison, typical magnetic resonance imaging (MRI) uses magnets of about 3 Tesla. And the magnetic field shielding Earth from the solar wind is many orders of magnitude smaller than 50T, Bose said.

“You want the nuclei to fuse together,” Bose said. “The magnetic fields trap the charged particles and make them go around the field lines. That helps create collisions and that helps to stimulate fusion. Therefore, adding magnetic fields has benefits for producing fusion energy.”

Fusion requires extreme conditions, but it’s been achieved, Bose said. The challenge is to get more energy output than input and the magnetic fields provide the push that can make this approach transformative.

The experiments published in Physical Assessment Letters were done when Bose was doing postdoctoral research at MIT’s Plasma Science and Fusion Center. That collaboration continues.

Bose said he was attracted to the University of Delaware in part because of its focus on plasma physics in the Department of Physics and Astronomy, which includes William Matthaeus, Michael Shay and Ben Maruca.

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“They’re doing studies and analysis of data coming from the NASA solar program and all of its missions,” he said. “We are conducting laboratory astrophysics experiments that reduce these phenomena in space and time to the laboratory. This gives us a means to unravel some of the complicated physics questions of NASA missions.”

Students are key drivers of this work, Bose said, and their careers can see great progress in this new field.

“It’s a fascinating part of science and students are a very important part of staff development for the national labs,” he said. “Students with experience in this science and technology often end up as scientists and researchers in the national labs.”

There is still a lot more work to be done, he said.

“We won’t have a solution tomorrow. But what we’re doing is contributing to a clean energy solution.”

Magnetize laser-guided inertial fusion implosions

More information:
A. Bose et al, Effect of highly magnetized electrons and ions on heat flux and symmetry of inertial fusion implosions, Physical Assessment Letters (2022). DOI: 10.1103/PhysRevLett.127.195002

Provided by the University of Delaware

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