Lasers could rapidly make materials hotter than the Sun

November 13, 2015 by Hayley Dunning, Imperial College London

Lasers could heat materials to temperatures hotter than the centre of the Sun in only 20 quadrillionths of a second, according to new research.

Theoretical physicists from Imperial College London have devised an extremely rapid heating mechanism that they believe could heat certain to ten million degrees in much less than a million millionth of a second.

The method, proposed here for the first time, could be relevant to new avenues of research in thermonuclear fusion energy, where scientists are seeking to replicate the Sun's ability to produce clean energy.

The heating would be about 100 times faster than rates currently seen in fusion experiments using the world's most energetic laser system at the Lawrence Livermore National Laboratory in California. The race is now on for fellow scientists to put the team's method into practice.

Researchers have been using high-power lasers to heat material as part of the effort to create fusion energy for many years. In this new study, the physicists at Imperial were looking for ways to directly heat up – particles which make up the bulk of matter.

When lasers are used to heat most materials, the energy from the laser first heats up the electrons in the target. These in turn heat up the ions, making the process slower than targeting the ions directly.

The Imperial team discovered that when a high-intensity laser is fired at a certain type of material, it will create an electrostatic shockwave that can heat ions directly. Their discovery is published today in the journal Nature Communications.

"It's a completely unexpected result. One of the problems with fusion research has been getting the energy from the laser in the right place at the right time. This method puts energy straight into the ions," said the paper's lead author, Dr Arthur Turrell.

Normally, laser-induced electrostatic shockwaves push ions ahead of them, causing them to accelerate away from the shockwave but not heat up. However, using sophisticated supercomputer modelling, the team discovered that if a material contains special combinations of ions, they will be accelerated by the shockwave at different speeds. This causes friction, which in turn causes them to rapidly heat. They found that the effect would be strongest in solids with two ion types, such as plastics.

"The two types of ions act like matches and a box; you need both," explained study co-author Dr Mark Sherlock from the Department of Physics at Imperial. "A bunch of matches will never light on their own - you need the friction caused by striking them against the box."

"That the actual material used as a target mattered so much was a surprise in itself," added study co-author Professor Steven Rose. "In materials with only one ion type, the effect completely disappears."

The heating is so fast in part because the material targeted is so dense. The ions are squeezed together to almost ten times the usual density of a solid material as the electrostatic shockwave passes, causing the frictional effect to be much stronger than it would be in a less-dense material, such as a gas.

The technique, if proven experimentally, could be the fastest heating rate ever demonstrated in a lab for a significant number of particles.

"Faster temperature changes happen when atoms smash together in accelerators like the Large Hadron Collider, but these collisions are between single pairs of particles," said Dr Turrell. "In contrast the proposed technique could be explored at many laser facilities around the world, and would material at solid density."

Explore further: Testing the thermal tolerance of the fusion reactors of the future

More information: A. E. Turrell et al. Ultrafast collisional ion heating by electrostatic shocks, Nature Communications (2015). DOI: 10.1038/ncomms9905

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4.2 / 5 (5) Nov 13, 2015
"in much less than a million millionth of a second."
Is that seconds, or picoseconds?
3.5 / 5 (8) Nov 13, 2015
"Hotter than the sun" is one of the worst phrases used by science writers to create a false impression. The temperature of the surface- most everything but the corona, is on a par with a standard welding torch, averaging about 5600F. The corona's temperature is one to three million kelvin. That's what we mean when we say the sun's hot, not all the other bits that are much cooler by comparison. It's exploiting the fallacy of the middle term. "Sun" doesn't mean the same thing in the various parts of the syllogism. People naively assume it's uniform and picking the cooler bits to compare to something is clearly just exploiting ignorance for clicks.
4.2 / 5 (5) Nov 13, 2015
Laser fusion has already been done decades ago. It's not efficient, but it has been done. It is fusion. It is as hot as the sun. WHATSYERPOINT?
5 / 5 (1) Nov 13, 2015
People...please read the article! This could be a 'fast track' to fusion, and you can bet the Eagleworks AND LLLabs is working on this right NOW. The Chinese maybe even beat our military to do it. Who knows if our research is in response to leaked Chinese classified research documents. Military secrets are the shortest lived secrets of all except for formula for the original Kentucky Fried Chicken and for Japanese family tempura.

Just look at all the fusion related science here in one place. More than I have seen in over forty years of following fusion research ever since being an engineering major cuz the services would not pay for a physics major. I can smell the blood on the water here that tells me that our holy grail, the heart's desire of every lover of physics, is near. If you can not sense this then tell me the stocks you buy so I can sell them short.
5 / 5 (2) Nov 13, 2015
This could provide a mechanism for thermonuclear fusion bombs that don't create radioactive fallout. We could destroy the world without polluting it! Everyone will be happy!
5 / 5 (6) Nov 13, 2015
When commenting on an article, would it be possible for you to read more than the title? This is the lede:"Lasers could heat materials to temperatures hotter than the centre of the Sun in only 20 quadrillionths of a second, according to new research". Explain to me what you find so confusing with the simple combination of those four words: center of the Sun?
Nov 14, 2015
This comment has been removed by a moderator.
5 / 5 (4) Nov 14, 2015
The temperature of the surface- most everything but the corona, is on a par with a standard welding torch, averaging about 5600F.

The sun's surface temperature is more like ~5600 C than ~5600 F, and thus quite a bit hotter than a welding torch....

5 / 5 (4) Nov 14, 2015
...the temperature of target cannot get higher, than the temperature of light source...

Basically, yes, for thermal (black-body) radiation of energy in equilibrium.

But there are loopholes, for example hours of energy could be stored and released in second to reach a higher temperature.

But which is the effective temperature of common laser pointer?

A laser comes from a non-equilibrium state which in some respects has a negative temperature... it is NOT black-body radiation, so the above rule does not apply.

Has the temperature of target some upper limit, if we would focus the laser to same point? How to calculate it?

A laser has a 'beam quality' that is related to how tightly it can be focused. Take laser power, then apply Stefan–Boltzmann law to tightest focus.

Could we initiate the hot fusion with well focused laser pointer - if not, why not?

Beam quality / power much too low, so can't focus tight enough.
Captain Stumpy
5 / 5 (2) Nov 14, 2015
This could provide a mechanism for thermonuclear fusion bombs that don't create radioactive fallout. We could destroy the world without polluting it! Everyone will be happy!
were you going for sarcasm or hyperbole?

since you can't store enough energy to use said laser, and it's impractical to load a generator with the capacity needed for the electric output for said laser for fusion, then it doesn't make sense to use the laser to activate fusion when it is smaller, lighter and cheaper in the long run to use a fission explosion to activate a fusion detonation

... remember, you really don't want to be at ground zero when the bomb goes boom

5 / 5 (1) Nov 15, 2015
were you going for sarcasm or hyperbole?

... remember, you really don't want to be at ground zero when the bomb goes boom

Actually, a little of both. The sarcasm was about political polarization, while the hyperbole involved the possibility of a "clean" nuclear weapon that didn't contain uranium or plutonium, and how politicians could argue that they aren't really the same thing as a conventional nuke and were therefore "legal" to use in "some cases".

Your argument about energy requirements may well be valid, they don't mention how powerful the laser needs to be, however if the duration need only be "20 quadrillionths of a second", you wouldn't need Hoover Dam. Single use chemical lasers might do the trick for all I know.

And if a worldwide nuclear war was to break out, ground zero is exactly where I'd prefer to be, as then I wouldn't survive long enough to know it happened.

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