Science

Argon fluoride laser could lead to practical fusion reactors

Argon fluoride laser could lea...
Matthew Wolford inspects the Electra argon- fluoride (ArF) laser
Matthew Wolford inspects the Electra argon- fluoride (ArF) laser
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In direct-drive laser fusion, an array of laser beams uniformly illuminates a pea-size hollow capsule containing the fusion fuel (mixture of deuterium and tritium)
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In direct-drive laser fusion, an array of laser beams uniformly illuminates a pea-size hollow capsule containing the fusion fuel (mixture of deuterium and tritium)
The Nike laser lens array focusing 44 krypton-fluoride (KrF) laser beams onto targets
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The Nike laser lens array focusing 44 krypton-fluoride (KrF) laser beams onto targets
Mathew Wolford (left), research chemist and Mathew Myers (right), research electrical engineer, stand in front of an argon fluoride (ArF) laser awaits to be tested with new thicker stainless foils at Washington, D.C. June 1, 2020. Wolford and Myers are testing the (ArF) laser that is being outfitted with the new foils in hope to have higher output of the laser. The laser is the world’s largest (ArF) laser that is studying the physics to develop a high efficiency electron-beam pumped (ArF) laser at 193 nanometers. (U.S. Navy photo by Jonathan Steffen)
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Mathew Wolford (left), research chemist and Mathew Myers (right), research electrical engineer, stand in front of an argon fluoride (ArF) laser
Aan overview of the Electra argon fluoride (ArF) laser
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Aan overview of the Electra argon fluoride (ArF) laser
Matthew Wolford inspects the Electra argon- fluoride (ArF) laser
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Matthew Wolford inspects the Electra argon- fluoride (ArF) laser
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The US Naval Research Laboratory (AFL) is developing an Argon Fluoride (ArF) laser that may one day make fusion power a practical commercial technology. The wide-bandwidth ultraviolet laser is designed to have the shortest laser wavelength that can scale up to power a self-sustaining fusion reaction.

To call fusion energy a game changing technology is like saying that fire might one day find a practical application. In fact, the ability to generate clean energy from hydrogen in any desired quantity over any foreseeable timescale would fundamentally alter civilization in ways we can't imagine.

The problem is fusion power is like the proverbial rabbit pie recipe that begins with, "First, catch your rabbit." Though we can recreate the conditions found inside the Sun to produce fusion reactions on Earth, these are relegated to hydrogen bombs and laboratory experiments where it takes more energy to create the fusion reaction than we can get out of it – though recent experiments are getting much closer to turning that around.

The Nike laser lens array focusing 44 krypton-fluoride (KrF) laser beams onto targets
The Nike laser lens array focusing 44 krypton-fluoride (KrF) laser beams onto targets

The goal for the past 75 years has been to produce temperatures in excess of 100 million degrees C (180 million degrees F) and the pressure needed to ignite the fusion reaction and generate enough surplus energy to sustain it. That in itself would be a major achievement, but the technology also has to be able to sustain the reaction indefinitely, while also being cheap enough and the reactor small enough for it to be practical.

The NRL's ArF laser is intended for a test facility based on the principle of Inertial Confinement Fusion (ICF). In this, a bead of deuterium or tritium, which are heavy isotopes of hydrogen, is fired upon by multiple lasers, heating and compressing it in a fraction of a second to such an extent that the hydrogen atoms implode, fuse together, and release enormous amounts of energy.

The new deep ultraviolet laser, also known as a laser driver, is claimed to transfer energy to the fuel bead with greater efficiency and produces much higher temperatures to generate the implosion. Using radiation hydrodynamics simulations the NRL scientists say that performance could be increased a hundredfold with an efficiency of 16 percent, compared to only 12 percent from the next most efficient krypton fluoride laser.

In direct-drive laser fusion, an array of laser beams uniformly illuminates a pea-size hollow capsule containing the fusion fuel (mixture of deuterium and tritium)
In direct-drive laser fusion, an array of laser beams uniformly illuminates a pea-size hollow capsule containing the fusion fuel (mixture of deuterium and tritium)

Because of these improvements, the ArF laser could lead to smaller and less expensive fusion power plants. However, the team stresses that there is still a long way to go before fusion is hooked up to the national grid. The laser will need to provide the required energy, repetition rate, precision, and billion-shot class reliability for a practical plant.

To move towards this, the laboratory is running a three-phase program with the first dedicated to the basic science and technology of the ArF laser. This will be followed by phase two, which will concentrate on building and testing a full-scale high-energy ArF laser, and then phase three where an implosion facility consisting of 20 to 30 lasers will be constructed.

“The advantages could facilitate the development of modest size, less expensive fusion power plant modules operating at laser energies less than one megajoule,” says Steve Obenschain, Ph.D., a research physicist at NRL. “That would drastically change the existing view on laser fusion energy being too expensive and power plants being too large.”

The research was published in the Philosophical Transactions of the Royal Society.

Source: NRL

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16 comments
16 comments
VernonBrechin
Typically, fusion energy advances articles are over-hyped, often by journalists who are not familiar with the field. Many of those journalists don't bother to include critical viewpoints from experts in the field not connected to the experiments. In this case he failed to note that both rare deuterium and extremely rare and expensive radioactive tritium are required in the fuel pellets. Very few experiments actually employ such fuels and they don't produce fusion neutrons, or a fusion reaction. Fusion energy experiments have been conducted since the 1970s and still have major hurdles ahead of them. Most fusion energy physicists agree that the Inertial Confinement Fusion (ICF) approach is highly unlikely to lead to a practical fusion energy electrical generating plant. Readers should always ask how many billionths of a second did the ICF fusion last compared to how many hours lapsed between each shot. Fans of nuclear power solutions continue to assume that we have 20-30 years to scale up their favorite technology to the point where it can displace our addiction to fossil fuel based energy sources. The experimenting labs and commercial firms often generate cleverly crafted press releases in hopes of attracting continuing funding. Typically, fans of such experiments rarely show any interest in the critiques that have appeared such as the following.

ITER is a showcase … for the drawbacks of fusion energy
https://thebulletin.org/2018/02/iter-is-a-showcase-for-the-drawbacks-of-fusion-energy

Fusion Has Major Problems That No One Is Telling You About
https://www.youtube.com/watch?v=FrUWoywZRt8&fbclid=IwAR1D5Xfv5sXGZOeiHo0Vj5aQPa80h7d5Mg4VjfvznH7m7Mx6bmjsZDqx76Y

UN chief: World has less than 2 years to avoid 'runaway climate change'
https://thehill.com/policy/energy-environment/406291-un-chief-the-world-has-less-than-2-years-to-avoid-runaway-climate
Chris__
@VernonBrechin... but what is your point? That pursuing fusion is pointless? That it will take too long? That the money would be better spent on research into other fields? That the research money going into fusion shouldn't even be spent on research? It's very easy to complain about something without actually making any useful suggestion, but if all humanity had done that we'd still be swinging from trees. If you just don't care about fusion but have no further opinion on that field of research, why post in the first place?
Chris Coles
In the UK ZETA was being built in the late 1950's. Same story, same outcome . . . https://en.wikipedia.org/wiki/ZETA_(fusion_reactor)
Philip Argy
Could this laser work with what is being done in Australia with hydrogen boron lasers:
https://hb11.energy/
Frank Kushner
The biggest stumbling block will be thermal transient stress for materials. So far changes in tests have only been minute times. Thick flanges especially are prone to have high thermal stress and leaking bolts from distortion. Use the best program for analysis - ANSYS.
FB36
Some people still may think "Why humanity needs fusion power? Why not just use solar & wind power etc?"

IMHO, humanity definitely/absolutely needs fusion power, because it could really take humanity to a whole new level (which cannot ever be done using solar & wind power etc)!

For example, titanium is an extremely durable & strong & light material & Earth has plenty of it, but AFAIK, it requires so much electricity to mine/process!
Imagine, if we had so much (clean) electricity, we could build all kinds of land/air/sea vehicles, buildings, roads, even whole cities from titanium!

Imagine, we could build a global permanent water pipeline network (& do seawater desalinization) & provide plenty water to everywhere on Earth (for agriculture & forests etc)!

Imagine, very tall poles w/ very powerful infrared heater lamps (etc) on top!
Imagine, using many of them in cities/towns to turn winters to springs/summers!
And/or, using many of them in agricultural fields to grow any hot climate (even tropical) crops/trees, even in coldest places on Earth!

& no doubt, many new techs would become reality, once we have enough electricity power for them!
(For example, consider how computers & internet are used in many ways today, which were pretty much unimaginable to their inventors!)

Also, IMHO, people who think "fusion power will never become reality" are not realizing how long it really took for some other very important tech to become reality!
For example, think about how important computer tech is to humanity today!
& think about how long it really was from Babbage's first computer design/idea to first real/practical computer!
Or, consider how long it took going from first airplane to jet airliners!
Or, going from telegram to telephone to internet, etc!
bwana4swahili
"could lead to practical fusion reactors" Been hearing this for years and years! What is the estimate for commercial Fusion power at present? 50... 100... 500... years!?
Russ Hamilton
Fusion projects are for pensions for engineers and scientists and also for kickbacks to the politicians that vote for them. NIF, JET, ITER and others have distorted their own contribution by telling whoppers about their input/output and so on. We are probably less than 30 years away from another century before we get a useful reactor.
Mark T.
President Kennedy might have added fusion power to his list of things we choose to do not because they are easy, but because they are hard. We need to pursue fusion technology to the maximum extent practicable for reasons both obvious (no CO2 byproduct) and less obvious ("renewable energy" from wind and solar have a very limited range in the galaxy and are ultimately based on fusion power from stars, so travel in deep space will require a deep space power source). Yes it is hard, of course it is hard, so what? Have you noticed that most good things are hard? Kennedy did in 1962. People tend to expect too much in the short term and ignore what is accomplished in the long term.
neutrino23
Fusion power requires electricity to drive it but the result is heat. To change that heat to electricity you will get a little over 30% efficiency at best. If you compare electricity in to electricity out then you need to produce about 3 times the heat energy as is consumed in electric energy just to break even. Getting out 3x more energy than you put in is a dream for fusion today. If you are getting your electricity from wind or solar it would be much cheaper to just add a few more cells or another tower to get more power.

As to what we should do:
1. Aggressively promote conservation and efficiency. It is far better to save a kWh than to find a way to produce it. Insulate our homes better, use LEDs, use more efficient appliances, find others ways to use less energy.
2. Promote distributed wind and solar and batteries. If we have solar panels everywhere and put moderate sized batteries everywhere we can avoid reliance on long distance transmission lines. We'll still have them, they just won't be so critical.
3. Build up solar powered devices that take CO2 out of the air and sequester the CO2.
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