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THE Nuclear Fusion Thread Pt. 3

Discussions of conventional and alternative energy production technologies.

Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby Sys1 » Sat 10 Mar 2018, 05:58:53

Nuclear fusion is in theory a game changer regarding peak oil/growth/pollution/expansion in solar system and universe.
Fermi paradox : If nuclear fusion were possible, we would have been already visited by out-of-Earth civilisations. At least would we have seen a trace of advanced civilisation in space. As it's not the case, this technology will stay out of reach forever.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby Cog » Sat 10 Mar 2018, 08:09:03

Nuclear fusion would not change the facts of why faster than light travel is impossible. Or even travel at a significant percentage of light speed.

There is also another possibility that I know some here find unpalatable. That life is extremely rare and there is no one out there in the universe except us right here.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby Sys1 » Sat 10 Mar 2018, 10:00:17

We don't need faster than light technology to expand in our 200 000 lightyears diameter's galaxy (I admit that beyond galaxy is impossible because of Universe expansion). It would only take millions of years to expand, especially if we use artificial intelligence and robotic to do it. In case of a business as usual scenario for this century, artificial intelligence will dominate Earth before 2100.
Moreover, millions of years is very fast at geologic scale. That's why either we are extremely rare in the universe, either it's simply impossible to create a sustainable civilisation.
As the current key of our civilisation is hydrocarbon energy, it means that something as extraordinary as fusion energy will stay a dream. Nevertheless, I consider that keeping searching a way to create a thermonuclear plant is still far better than creating thermonuclear weapons.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby diemos » Sat 10 Mar 2018, 14:28:20

There's also the more upbeat possibility that the civilization that controls this part of the galaxy has a non-interference directive and we're living in a "nature reserve" until such time as we attain interstellar capability ... or destroy ourselves ... you know, whichever comes first.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby Outcast_Searcher » Sat 10 Mar 2018, 19:29:14

Sys1 wrote:Moreover, millions of years is very fast at geologic scale. That's why either we are extremely rare in the universe, either it's simply impossible to create a sustainable civilisation.

Or, we arrogantly assume we know what intelligent life would be like (i.e. us -- like the "God looks like us meme"). Or the technological evidence of intelligent races a wee bit more advanced than us (say, a few thousand years) is so different than ours, that we don't even know what to look for. (Shades of Star Trek, when they find an old radio signal and are very surprised).

Maybe we're extremely rare. Or just extremely stupid / undeveloped.

But I know. We're "special". Just ask any major religion (which insists it is the "correct" one), or just the assumption that somehow, we're the center of the universe, at each stage of what we discover is "out there" (no matter how inisgnificant the scale makes us in the scheme of things).

For me, the older I get and the more I see, in perspective, "very stupid" seems to pass the Occam's Razor test far better than "special". And I know -- I'll never be accepted into the local chapter of "The Optimists Club". I'll just have to try and survive, anyway. :roll:
Given the track record of the perma-doomer blogs, I wouldn't bet a fast crash doomer's money on their predictions.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby dissident » Sat 10 Mar 2018, 20:46:26

There is no physical reason why human intelligence would be unique in the universe. The number of Earth-like planets being discovered is stupefying. It means that across the vast cosmic sea of galaxies there are billions of planets nearly identical to the Earth. Even if each one of them has a distinct set of realizations of life, the probability of encountering similar conditions that pushed primates to grow bigger brains on Earth approaches 100% on thousands of these planets.

Of course, there is no reason that mammal-like species will be the only ones to develop intelligence. So the stupid Star Trek universe of humanoids from different roots is not so stupid. But the issue is not what the details are, but that 1) there is guaranteed to be other life and 2) that some fraction of planets with life will have intelligent species.
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The search for clean, abundant energy

Unread postby AdamB » Wed 14 Mar 2018, 21:16:05

Oxford-based energy generation and inertial confinement fusion research organisation, First Light Fusion is investing £3.6 million to build a pulsed power machine to advance the company’s work exploring fusion. The device, labelled Machine 3, is under construction and on track to be commissioned by the end of 2018. It will be the only pulsed power machine of its scale in the world dedicated to researching fusion energy. Once complete, it will be capable of discharging up to 200,000 volts and in excess of 14 million ampere within two microseconds. The Machine will use around 3km of high voltage cables and another 10km of diagnostic cables. Machine 3 will be used to further research First Light Fusion’s technology as the company seeks to achieve first fusion. The next step in the technological development will be to achieve ‘gain’, whereby the amount of


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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby onlooker » Tue 03 Apr 2018, 17:25:15

We have been hearing about Fusion since at least WWII, and it's always we are at the cusp. Never mind it appears to be too complicated, cost prohibited and an EROEI loser
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby lpetrich » Sat 23 Jun 2018, 06:58:31

onlooker wrote:We have been hearing about Fusion since at least WWII, and it's always we are at the cusp. Never mind it appears to be too complicated, cost prohibited and an EROEI loser

As some others here have pointed out, it also has the looming problem of preemption by renewable sources. It is currently so complicated and difficult that even if it can get an EROEI greater than 1, it will take a *lot* of R&D before it can compete with renewable sources.

So where might it be useful? High latitudes? That is because of such locations' limited sunlight, though some such locations have good winds. Outer space? Especially the outer Solar System and interstellar spaceflight. One would need some *very* low-maintenance designs there.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby Subjectivist » Mon 25 Jun 2018, 08:03:52

onlooker wrote:We have been hearing about Fusion since at least WWII, and it's always we are at the cusp. Never mind it appears to be too complicated, cost prohibited and an EROEI loser


Every single peaceful method of releasing fusion energy we have ever tried s a net energy consumer. The only way we have discovered to release abundant fusion energy is witha very large explosion. There was even a suggestion decades ago to use the smallest size fusion explosives suspended in huge underground chambers filled with water. The theory was boom, water is flashed to superheated steam then pipes are used to direct the steam through turbines to generate energy. The list of problems with this method are incredibly long, and yet in all the decades since it was proposed no other attempt has been energy positive. A related scheme was to set off dozen of explosion several thousand feet down to create a magma pocket, then hook that up to water and steam lines and use it as an artificial geothermal heat supply. Every year or so as the artificial magma cooled they would drill down into it with more booms to reheat the magma.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby Tanada » Sat 22 Sep 2018, 13:29:30

The elusive dream, are we searching down a blind path?

Here is the thing the vast majority of people do not know. 40% of the energy released by our sun, Sol, comes from the very first step of the proton-proton fusion chain. That step involves in round numbers 1/10E+27 collisions between 2 protons leading to 1 proton decay into a neutron forming 1 deuterium nucleus and all other cases where the two protons succumb to electrostatic repulsion and split back apart. Pause and consider that fact for a minute, 40% of all the energy released by our sun comes from this 1/10E+27 reaction taking place several billion times each second.

Humans from the 1940's to today have focused nearly all our efforts on fusing higher and easier to accomplish steps in the PP chain that takes place in all low mass stars. For example at an effective temperature 1 million degrees Kelvin Deuterium and Protium (a naked hydrogen nucleus, a proton) fuse to form Helium-3, the lighter stable isotope of Helium. As a result of this reaction radiative bodies with a mass as low as 13 times that of Jupiter can achieve the threshold temperature to consume all the existing Deuterium in the super-Jovian body to form Helium-3 out of the their accumulated Protium and Deuterium until every Deuterium nucleus is consumed. From 13 times Jupiter to 80 times Jupiter in mass size this is the highest fusion threshold that a radiative body can achieve, but once the Deuterium is all consumed the body contracts further causing higher heating in the core. but not enough heat to pass the threshold for P-P fusion into Deuterium in that 1/10E+27 rate. Instead the body officially becomes a 'brown dwarf' and spend the rest of its undisturbed life cooling.

If the mass is around 81 times that of Jupiter or .075% the mass of Sol the contraction heating after the Deuterium supply is exhausted is just enough to initiate the P-P fusion at that 1/10E+27 rate and the radiative body is officially a 'star' because the second step in the chain is to fuse Deuterium and Protium into Helium-3, which is the definition used for 'fusion'. The very smallest Red Dwarf stars stop at this point. They can make Deuterium and they can make Helium-3 from that Deuterium because doing so is so easy even Brown Dwarves can manage that step, but adding more protons to make Helium-4 by a couple different methods is beyond their temperature/density threshold so over a period of hundreds of billions of years they will slowly convert their Protium primordial Hydrogen into Helium-3 and then simply stop fusing.

For humans trying to do fusion reactions on Earth the temperature/density issue is crucial because we can not manage to make and hold plasma at the same densities of the core region of even the smallest self sustaining red dwarf star. Typically our solution to this conundrum is to use a very low density plasma and heat it to extremely high temperatures compared to those at the core of the core of even a giant star, let alone a medium size dwarf like Sol. Having chosen to go this route we then concluded that fusing higher order nuclei from Deuterium was the best route to follow, however the energy to fuse Deuterium with deuterium is very high at the density we can achieve, on the order of 400 million Kelvin. The very core of Sol is only 13.8 million K in temperature and the core of Proxima Centauri, the closest red dwarf is about 4 million K.

Given that fusing Deuterium and Protium into He-3 is not only easier to accomplish that D*D fusion, D*P fusion yields on average 5.5 MeV of energy while D*D yields on average 3.6 MeV from three possible resulting nuclei. I think it is nuts we are are so committed to D*D or D*Tritium as fusion fuels. In large part this arose because D*D was the first successful Hydrogen Bomb reaction material and all current Hydrogen Bombs are D*T designs based on using Lithium metal as the precursor to Tritium.

Forget about the bombs and go back to fundamentals, a hydrogen plasma confinement system does not need to depend on bomb materials and in point of fact can get a better energy yield without producing excess neutrons by fusing P*D=He-3.

D*D=H-3(Tritium) + Proton + 4.0 MeV about half the time.
D*D=He-3 + Neutron + 3.25 MeV about half the time; Very Rarely D*D=He-4 + 23 MeV.

P*D=He-3 + 5.49 MeV fusion releases no neutrons or protons, just energy and a lot of it.
P*P=D + 1.44 MeV is exceedingly rare to the point that you need billions of collisions to get one successful decay. This isn't practical for human energy production but supplies 40% of our suns energy.


Although its potential to generate electricity at a commercial scale is several decades away, nuclear fusion can become a promising option to replace fossil fuels as the world's primary energy source and could have an important role to play in addressing climate change, participants agreed at an IAEA General Conference side event focused on the status of fusion energy research, with major players in attendance.

Despite the potential benefits to society from fusion, such as the abundance and accessibility of fuel, the carbon free footprint and the absence of high-level radioactive waste, its science remains one of the most challenging areas of experimental physics today: controlling thermonuclear fusion for energy production is a complex and challenging undertaking.

Moderating the discussion, Meera Venkatesh, Director of IAEA Division of Physical and Chemical Sciences, highlighted the difficulties facing fusion technology to make commercially-viable fusion power a reality. She pointed out that finding the right materials to construct the fusion reactor, and developing the mechanism that will be used to extract the enormous energy/heat that is emitted, are among the major tasks ahead. “The realization of fusion power reactors would be a landmark achievement, taking nuclear science and technology to a higher level,” she said.
ITER: Proving fusion technology on Earth

One major step toward reaching this goal is the ITER project, a 35-nation collaboration to design, build and operate an experimental reactor to achieve and sustain a fusion reaction for a short period of time. ITER will be the world’s largest tokamak, a donut-shaped configuration for the containment of the plasma, which is where the reaction — at temperatures hotter than the Sun — will take place.

ITER Director-General, Bernard Bigot, highlighted the extensive progress in manufacturing and construction, which is now more than 50% completed, with the first experiments scheduled by 2025.

“When we prove that fusion is a viable energy source, it will eventually replace burning fossil fuels, which are non-renewable and non-sustainable. Our mission is to provide a new option which is safe, sustainable and economically competitive. Fusion will be complementary with wind, solar and other renewable energies,” he said.

ITER is expected to produce about 500 megawatts of fusion power by the late 2030s, and will enable scientists to observe for the first time a burning plasma, the state when the energy produced by the fusion reaction is almost or completely sufficient to maintain the temperature of the plasma, so that the external heating can be strongly reduced or switched off altogether. Studying the fusion science and technology at ITER’s scale will enable optimization of the plants that follow while leading discoveries in plasma science and technology.
Wendelstein 7-X: A new twist

These efforts are complemented by the world’s largest stellarator — Wendelstein 7-X (W7-X) at Max Planck Institute for Plasma Physics (IPP) in Germany — an alternative to the tokamak as the reactor layout. It is a twisted racetrack-shaped configuration, which is inherently stable and able to operate the plasma in a steady state for greater lengths of time than the tokamak, but it is technically harder to design.

Although W7-X will not produce energy, its designers hope to prove that stellarators are also suitable for application in power plants and to demonstrate their capability to operate continuously. Such continuous mode will be essential for commercial operation of a fusion reactor.

Sibylle Günter, Scientific Director of IPP, highlighted the most recent results from the first high-performance plasma operation of W7-X, which has recently achieved the highest stellarator fusion triple product: the density, confinement time and plasma temperature used by researchers to measure the performance of a fusion plasma.

“This is an excellent value for a device of this size, and it makes us optimistic for our further work. In the future, we expect to run the machine for a longer time,” she said.

The fusion triple product has seen an increase of a factor of 100,000 in the last fifty years of fusion experimentation; another factor of five is needed to arrive at the level of performance required for a power plant. Some of the improvements in this product were the result of experimental fusion reactors becoming larger. Plasma takes longer to diffuse from the centre to the walls in a bigger reactor, and this extends the confinement time.

Günter added: “Size matters in terms of heat insulation. Based on our experience, I believe that ITER will perform even better than planned today.”
Let there be light

While large scale experiments such as ITER and W7-X continue, nearly two dozen start-ups are working on a variety of devices, fuels, and approaches, using new technologies. These start-ups are backed by venture capital funding.

Mila Aung-Thwin, director of the award-winning documentary about the quest for fusion energy, Let There Be Light, which was shown at the event, emphasized that in addition to public investments into fusion research, there is an increase in the number of new players working in the area of nuclear fusion. As an example, the movie shows fusion start-ups in Canada and the USA.

“It’s great that there are more private entities supporting innovation. Perhaps we are at the level of technology now where start-ups can compete with national labs and agencies, as they seem to be in space travel,” he said.

Bigot added: “These companies are trying to develop alternative options to ITER. Their investors want to make fusion a reality, and this demonstrates trust in fusion as a promising energy supply for the world in the middle and long term.”
Fusion Energy at the IAEA

The IAEA has been supporting the research and development work towards future nuclear fusion energy since the beginning, in the 1950s. The IAEA played an important role in the set-up of ITER, and continues to act as a central hub among Member States developing programme plans and initiating new R&D activities leading to various concepts of a demonstration fusion power plant (DEMO) through its DEMO Programme Workshop.

The IAEA is cooperating with the ITER Organization based on the IAEA-ITER Cooperation Agreement, and is playing an important bridging function between the 35 ITER members and the other IAEA Member States through its periodic series of Fusion Energy Conferences, Workshops and Technical Meetings, Coordinated Research Projects, and publishing the leading scientific journal in the field, Nuclear Fusion.


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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby diemos » Sat 22 Sep 2018, 15:56:26

Tanada wrote:In large part this arose because D*D was the first successful Hydrogen Bomb reaction material and all current Hydrogen Bombs are D*T designs based on using Lithium metal as the precursor to Tritium.


You have cause and effect reversed. DT is chosen because it has the highest cross section for interaction at the lowest temperatures. It doesn't occur in the sun because there is no tritium there.

http://www.kayelaby.npl.co.uk/atomic_an ... _7_4b.html
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby Tanada » Sat 22 Sep 2018, 21:41:25

diemos wrote:
Tanada wrote:In large part this arose because D*D was the first successful Hydrogen Bomb reaction material and all current Hydrogen Bombs are D*T designs based on using Lithium metal as the precursor to Tritium.


You have cause and effect reversed. DT is chosen because it has the highest cross section for interaction at the lowest temperatures. It doesn't occur in the sun because there is no tritium there.

http://www.kayelaby.npl.co.uk/atomic_an ... _7_4b.html


First off the P*D reaction does not appear on the graph you posted despite the fact that it is prevalent in the entire spectrum of dwarf class stars from brown dwarves right up through A stellar class objects.

Secondly I never said D*T was difficult to achieve, I said the tritium in modern thermonuclear weapons is mostly generated from Lithium reacting with high energy particles. Manufacturing tritium is a high cost process when you are talking about the kind of volumes you need for large fusion based power reactors instead of the tiny quantities currently used for making radioluminescent rifle sights and compass indicators.

The first Thermonuclear reactions were done with D*D reactions, then D*T were tested, then D*Li-6 and D*Li-7 were tested with the experimenters shocked at the large number of D*Li-7 reactions which took place as they had calculated that Li-7 would remain basically inert during the Castle Bravo test and ended up with a detonation 235% the predicted yield when it turned out to be very reactive indeed. In fact some modern devices were equipped with P*Li-7 fusion fuel because the reaction profile forms ~Be-8~=He-4 + He-4. Beryllium 8 is so inherently unstable it almost instantly splits into two Helium-4 nuclei.

None of these devices however makes use of the D*P=He-3 reaction despite its very low energy of initiation and even your vaunted fusion researchers ignored the reaction when they made the graph you posted.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby diemos » Sat 22 Sep 2018, 22:59:07

Tanada wrote:First off the P*D reaction does not appear on the graph you posted despite the fact that it is prevalent in the entire spectrum of dwarf class stars from brown dwarves right up through A stellar class objects.


It does not appear on that plot because it is too small.

Oddly enough ... the people who do this stuff for a living actually do know what they're doing and are not sitting around waiting for you to show up and set them straight.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby lpetrich » Sun 23 Sep 2018, 00:32:56

There is a certain problem with the first step in the proton-proton process. It involves the weak interaction.

Two protons by themselves cannot be bound. That's because they are the same flavor of elementary particle and thus cannot occupy the same quantum state. Likewise for neutrons. But a proton and a neutron are different flavors, and they can be bound, though not by much.

So to make deuterium from protium, two protons have to collide close enough to touch, and when they do so, one of them has to turn into a neutron by positive beta decay. Though one may object that the Sun is very bright by ordinary standards, it is also very large by ordinary standards, and the two effects cancel out. The Sun's energy generation per unit volume in its core is about 1/4 human resting metabolism (Nuclear fusion - Wikipedia).

So we are stuck with fusion reactions that conserve nucleon flavor. This means the likes of D + D, D + T, and D + He3.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby Tanada » Sun 23 Sep 2018, 05:38:34

lpetrich wrote:There is a certain problem with the first step in the proton-proton process. It involves the weak interaction.

Two protons by themselves cannot be bound. That's because they are the same flavor of elementary particle and thus cannot occupy the same quantum state. Likewise for neutrons. But a proton and a neutron are different flavors, and they can be bound, though not by much.

So to make deuterium from protium, two protons have to collide close enough to touch, and when they do so, one of them has to turn into a neutron by positive beta decay. Though one may object that the Sun is very bright by ordinary standards, it is also very large by ordinary standards, and the two effects cancel out. The Sun's energy generation per unit volume in its core is about 1/4 human resting metabolism (Nuclear fusion - Wikipedia).

So we are stuck with fusion reactions that conserve nucleon flavor. This means the likes of D + D, D + T, and D + He3.


Hence the fact I pointed out that P*P fusion resulting in D is a 1/10E27 event. If you read what I actually wrote instead of playing wikipedia you will see I am referring to P*D reactions not P*P.

P*D=He-3 as does nearly half of D*D=He-3 + P
The difference being
P*D=He-3 + 5.49 MeV while
D*D=He-3 + P + 3.25 MeV
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THE Nuclear Fusion Thread Pt. 3

Unread postby Tanada » Sun 23 Sep 2018, 05:46:03

diemos wrote:
Tanada wrote:First off the P*D reaction does not appear on the graph you posted despite the fact that it is prevalent in the entire spectrum of dwarf class stars from brown dwarves right up through A stellar class objects.


It does not appear on that plot because it is too small.


If that were true it should be exceedingly easy for you to find a reference showing the reaction cross section for Protium*Deuterium fusion being exceedingly small.
Any reference from any physics oriented publication will do, not a random blog please.

Physics reaction cross sections of even rare reactions like Carbon-12*Helium-4=Oxygen-16 get published and those only take place at very high densities and temperatures. So finding references to H-2*H-1=He-3 which takes place in high density moderate temperature bodies should be a piece of cake for an expert like yourself.
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Re: THE Nuclear Fusion Thread Pt. 2(merged)

Unread postby diemos » Sun 23 Sep 2018, 07:40:18

Tanada wrote:If that were true it should be exceedingly easy for you to find a reference showing the reaction cross section for Protium*Deuterium fusion being exceedingly small.
Any reference from any physics oriented publication will do, not a random blog please.


https://www.nndc.bnl.gov/sigma/getInter ... f=3&mt=102

Peaks at about 1e-5 barns at 6e3 keV temperature.

http://www.kayelaby.npl.co.uk/atomic_an ... _7_4a.html

Same graph as before but in units of barns.

The piece that you're missing is that gas composition matters.

In a .5/.5 DT gas the particle interactions will be:
25% DD
50% DT
25% TT
and DT has the largest cross section and so DT fusion will be dominant.

In a .5/.5 PD gas the particle interactions will be:
25% PP
50% PD
25% DD
but DD has a 1000 times larger cross section than PD so almost everything will go through DD

In the sun it's almost all hydrogen with a tiny amount of deuterium, a 1.0/x PD gas. You'll get:
100% PP
x% PD
x^2% DD

As long as x is less than one part in a thousand, PD will dominate even with the larger cross section for DD fusion.

But if you can get a .5/.5 PD gas to fuse on earth (which will all be DD fusion) then you might as well use a 100% DD gas as that will give you 4 times as much fusion. And you might as well use a 100% DT gas as that will give you 10 times as much fusion from the higher cross section for DT fusion as compared to DD.

And that's the reason no one is pursuing PD fusion on earth even if it's the dominant mode in stars.
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Re: THE Nuclear Fusion Thread Pt. 3

Unread postby Tanada » Wed 10 Apr 2019, 16:30:01

Ready, set, go: Scientists evaluate novel technique for firing up fusion-reaction fuel



To capture and control on Earth the fusion reactions that drive the sun and stars, researchers must first turn room-temperature gas into the hot, charged plasma that fuels the reactions. At the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL), scientists have conducted an analysis that confirms the effectiveness of a novel, non-standard way for starting up plasma in future compact fusion facilities.

The innovative technique, known as "transient coaxial helical injection (CHI)," eliminates the central magnet, or solenoid, that launches the plasma inside tokamaks, the most widely used fusion facilities. Such elimination could facilitate constant, or steady state, fusion reactions and also free up valuable space in the center of compact spherical tokamaks, whose cored-apple shape has less room inside than conventional doughnut-shaped tokamaks that are more common.

Providing advantages

The freed-up space could provide advantages: It could be used to strengthen the magnetic field that confines the plasma and thereby improve its performance. Elimination of the solenoid could also simplify the design of compact tokamaks.

Fusion reactions fuse light elements in the form of plasma -- the hot, charged state of matter composed of free electrons and atomic nuclei that occurs naturally throughout the universe -- and thereby generate energy. Scientists are seeking to replicate fusion on Earth for a virtually inexhaustible supply of safe and clean power to generate electricity.

Solenoids run down the center of a tokamak and induce current in the uncharged gas that researchers inject into the facility. The current strips electrons from the atoms in the gas, turning it into a charged plasma -- a process called "ionization," or plasma breakdown. The current also creates a magnetic field that combines with the field produced by magnets that surround the tokamak to bottle up and control the plasma, enabling heating heating to produce fusion reactions.

Eliminating the solenoid

By contrast, the transient CHI process reported in Physics of Plasmas produces the crucial electric current with electrodes placed near the bottom or top of the tokamak, eliminating the space-eating solenoid. "What we primarily focused on was the beginning stage of forming the plasma," said physicist Kenneth Hammond of the Max Planck Institute of Plasma Physics, the lead author of the paper who did research on CHI as a Columbia University graduate student at PPPL and is joining the laboratory this summer. "This helped paint a fuller picture of how CHI discharges work."

Transient CHI -- so-called because the electrodes that produce the plasma-launching current run briefly rather than continuously -- was first developed in experiments on the small Helicity Injection Torus (HIT-II) at the University of Washington and the larger National Spherical Torus Experiment (NSTX) at PPPL prior to its upgrade; the process also had been modeled at PPPL. The experiments, which showed that transient CHI could be scaled up from smaller to larger machines, motivated the recent study, said Roger Raman, a University of Washington physicist on long-term assignment to PPPL and a coauthor of the paper.

The study found that the placement of CHI electrodes in the earlier experiments "could exhibit a severe weakness when scaled up to a reactor," Hammond said. He then analyzed an alternative electrode configuration similar to one presently used in QUEST, a spherical tokamak in Japan. The findings showed that the alternative configuration could scale up well in a future spherical tokamak-based fusion facility designed at PPPL. "The good news from this study is that the projections for startup in large-scale devices look promising," Hammond said.

Valuable potential

The CHI technique has valuable potential, concurred Tom Brown, a principal engineer at PPPL who helped design the concept of the future spherical facility. "If successful, CHI could provide space for interior components that could enhance the performance of spherical devices," Brown said. However, he added, "further engineering details need to be developed at the experimental level that also can work within a higher-level [demonstration] device and also in an eventual fusion power plant."

Researchers have thus far tested the CHI scaling in simulations conducted on the Tokamak Simulation Code, a computer program created by PPPL physicist Stephen Jardin that has modeled plasmas around the world. Jardin, a coauthor of the Physics of Plasmas report, worked with Raman to produce the simulation referred to in the paper. "Although CHI has never been tested on a large reactor-scale device," Hammond said, "we are optimistic that the same relationships will hold on the larger size with stronger magnetic fields."

Future experiments are scheduled on URANIA, a solenoid-free spherical tokamak at the University of Wisconsin-Madison. The new experiments will test the startup of plasma with two independently operated transient CHI electrodes -- a configuration that could produce greater flexibility for optimizing the promising system.


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Re: THE Nuclear Fusion Thread Pt. 3

Unread postby EnergyUnlimited » Wed 10 Apr 2019, 17:28:43

@Tanada,
OK, lats say that they (whoever are "they") got this fusion reactor working.
Now tell me, how they are going to handle these pesky 14 MeV neutrons?

There will be an immense corrosion of reactor walls... very frequent maintenance and associated costs etc.
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