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Physics Group’s 500 terawatt laser focuses on cancer

Courtesy of Vladimir Ovchinnikov

With recent advancements, a group at OSU is taking a commonly known device and with laser focus, using it to fight cancer and utilize fusion.

The High Energy Density Physics Group at OSU in the Department of Physics has been upgrading their previous 40-terawatt laser to have the extreme power of 500 terawatts.

Enam Chowdhury, the senior research associate and laser designer, said the world’s power grid is about 20 terawatts and this laser packs a lot more power than that.

“This laser generates (energy) for a very, very short time; when we talk about an ultra-fast time scale, 500 terawatts,” Chowdhury said. “So it’s like roughly around 20 to 50 times that of the world’s whole power grid, but you don’t see a blackout in Columbus, right?”

Chowdhury said the reason there won’t be a power surge is because it is a short pulse laser, meaning the energy is generated for a short period of time.

“It’s such a small time scale that we talk about if the laser pulse was one second of our time, we would be older than the age of the universe,” Chowdhury said. “It allows us to study these extreme conditions, which will be used in laser fusion up at the National Ignition Facility.”

The overall goal is to study extreme states of matter, which includes studying fusion. Fusion reactions occur in the sun. The laser will not generate that much energy, but it will be close to the amount that are in stars and planets.

Rebecca Daskalova, a research associate, said the amount of time is 30 femtoseconds, which is 30 quadrillionths of a second.

“Think about the amount of time it takes you to blink,” Daskalova said. “It’s 13 orders of magnitude shorter.”

The laser is fired through a maze of contraptions of sapphire crystals, prisms, compressors and other devices. The laser is compressed through a chirped pulse amplification system. Once compressed, it will enter the target chamber where it will be focused through a laser/matter interaction.

They expect to compress the beam during their “first light” Tuesday, but the official public “first light” will be sometime in June.

“We’re always excited about it, but if we were just to fire the laser in there right now, it really wouldn’t do anything that you would be able to see and be like, ‘Oh, that’s amazing!'” Daskalova said. “So we want to set something up so that it actually is visually awesome.”

There are about 40 people involved who work under Richard Freeman, professor of physics and team leader, and everyone plays a role, including undergraduates. They are not tasked with cleanup, but with the production and stability of the laser.

Danielle Kelly, a fourth-year in engineering physics, said she is hopeful about this laser because of the amazing things it can do for research with cancer from proton therapy.

“What lasers can do is that they can accelerate protons to very high energies,” Kelly said. “Basically the way protons distribute energy, as opposed to X-rays, they can deposit a lot less energy before and after at the designated area of the tumor.”

The laser generates protons, and if they are focused down, they could be yielded to cure cancer with them. Protons could be used to go after diseased tissue cells and this could mean wonders for this type of research.

These larger experiments will be worked on after they test the laser with plain copper targets, which are just small pieces of metal.

Though the laser will possibly benefit society, there are certain precautions to take while handling the laser. Daskalova said she doesn’t wear any jewelry because if she is aligning the laser, it could reflect off her ring and hurt someone or herself.

The laser is a Class 4 laser, which is the most dangerous type of laser.

Jim Krygier, the project coordinator, said the laser will “obliterate” whatever it hits.

“So that’s what we ultimately do,” Krygier said. “You end up in this last little chamber here and you’re going to put a piece of material in there, whether it’s metal or something else. Then you’re going to hit it, and then you’re going to study the physics of what happened. … The target is no longer there though.”

Krygier said this project has three main components to it. It involves research about fusion, the scientists becoming experienced in this field and the defense capabilities of this laser.

Eddie McCary, a fourth-year in physics, said he is looking forward to the project’s completion because it lets him do work closer to home.

“I’ve done work on accelerating neutrons for detecting nuclear bombs and things like that,” McCary said. “From what the specs I’ve read (about the laser) it’s going to be a lot better than a lot of other systems, so it will be exciting to work on that in house.”

The NIF in Livermore, Calif. has a laser that can also produce 500 terawatts of energy, which cost the facility $4 billion. At OSU, they received a $6 million grant about four years ago from the U.S. Department of Energy. The main difference between these two facilities besides the cost is how many shots the laser can fire in a day, which is about once a minute. This rapid firing time lets OSU study more reactions.

Other universities in this country are doing the same sort of research, like the University of Texas and the University of Michigan. The researchers said this business can be very competitive, but also collaborative.

“The laser should be completed this month and then it will be the most intense sub-100 femtosecond laser in the U.S.,” Chowdhury said. “This comfortably beats Michigan … Ours is going to be higher in peak power than theirs.”

Chowdhury said they are friendly with Michigan and they even work with them, and that their relationship is a “friendly rivalry.”

The entire project has taken six years to construct including the original model that they upgraded from. There are many specialized parts that all take a lot of time to build. The majority of the laser has been built at OSU.

The laser bay is where this is all contained. Anyone who enters this room must first put on the proper attire, including goggles, a dressing gown, plastic shoe covers and a hair net. Once “dressed,” the next step is the air shower where blasts of air remove any dust from one’s body that can harm the laser.

The laser bay is green because the gain medium, made of titanium-doped sapphire crystals to allow it to change the laser frequency, is pumped with 532-nanometer lasers. The green light spectrum is located at 532 nm.

Chowdhury said this laser makes an explosive noise and it’s not going to be like the “photon torpedo” that fires out of the “Star Trek” starship. The difference between that laser and this one is that “in space, you’re not supposed to hear any sound.”

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