The Special Issue on Z-Pinch Plasmas will focus on the latest advances in the physics understanding of Z-pinches.

Czytaj więcej...

The GOLEM tokamak in Prague is organising GOMTRAIC, the GOlem reMote TRAIning Course. In three months, the participants will learn how to operate and diagnose this small tokamak machine without leaving their nests. All they need is a recommendation message from their tutor and the internet Access

Deadline for applications - end of February 2012.

List of tasks:

• Breakdown studies ...
• Comparison of tokamak discharges in H and He working gas.
• Determination of plasma resistance and electron temperature, variation with different discharge regimes
• First wall conditioning. Baking of the vessel and glow discharge influence on plasma performance.
• Generation of runaway electrons in different discharge regimes by means of hard X ray radiation.
• Plasma MHD Activity Observations via Magnetic Diagnostics
• Plasma position studies
• Radial profile of the floating potential and plasma density (determination of radial electric field and poloidal plasma velocity)
• Role of vertical magnetic field on plasma performance.
• Spectroscopy studies
• Other tasks

For details see: GOMTRAIC Website

in 1752, Scottish physicist Thomas Melvill passed some light through a prism and saw something quite unexpected. He was using light emitted by different substances in flames (e.g. salt) and saw, not the familiar rainbow colours of the spectrum, but thin bands of colour, with dark gaps between them. We now know that these patterns of colours are caused by electrons jumping between energy levels, and are unique to each element. The study of these light patterns, spectroscopy, is an extremely useful tool for identifying even tiny traces of elements. At JET there are dozens of different measurement systems set up to analyse the spectra given off by the plasma, some looking through the middle of the plasma, others at the edge; some at the visible wavelengths, others in the ultraviolet; some making measurements 100 000 times per second, while others collect light for longer to examine fainter emission.

The picture shows the spectrum of tungsten, rendered in knitwear. Although at JET this format is not used, this spectrum has suddenly become very important at JET, with the installation of the ITER-Like Wall. As part of this project tiles in the lower section of the vessel, known as the divertor, have had their carbon-fibre tiles entirely replaced with tungsten tiles. The plasma actually touches the divertor tiles, which leads to tungsten contaminating the plasma, but hopefully in a far less detrimental way than carbon, which was found to bind with the deuterium and tritium fuel all too readily.

Tungsten’s extremely high melting point (3410 degrees Celsius) is its attraction, however it has its drawbacks too. In plasma the more electrons an element has, the more it radiates light, in the process sapping energy from the plasma core – tungsten, with its 74 electrons, is a lot more of a problem than carbon, with only six.

“Tungsten has a very complex spectrum, because of all its electrons” says Dr Costanza Maggi, a physicist working on the spectroscopic systems at JET. ”We are learning how to connect the radiation from tungsten to the power being radiated from the core of the plasma. We also need to study the mechanisms that transport the tungsten away from the divertor, so that we can prevent tungsten contamination of the hot, core plasma.”

Many new spectroscopic systems were installed in the 2010 – 2011 shutdown, including systems that can operate in the extreme ultraviolet wavelengths, where tungsten emits strongly (not shown on scarf). This investment is vital to the future of ITER; the savings for ITER, should the tungsten prove a suitable material, is estimated at 400 million euros.

Source: EFDA

Fusion: the energy of the future - think 50 years

DESLEY BLANCH : Nuclear fusion is what you might call the 'holy grail' of energy. Think back to high school physics class, and you may recall that today's nuclear energy is produced by splitting atoms. It's called nuclear fission, and it produces radioactive waste.

Nuclear fusion, on the other hand, is where the nuclei of two atoms are fused into one. It would produce more energy, and is completely clean. There's no radioactive waste at all.

The problem is that at least until now, no one has figured out how to do it reliably.

So, it's Canberra to the rescue, where over 100 scientists from all over the world gathered in Australia to try to solve the problem.

Professor Boyd Blackwell co-chaired the conference. He's the director of the Australian Plasma Research Facility at the Australian National University, as he explained to ABC Radio's Waleed Aly the big picture of world energy.

WALEED ALY : Thanks to climate change the planet is desperately looking for a clean source of energy. Can you tell us if we could crack this, just how significant a breakthrough nuclear fusion would be?

PROFESSOR BOYD BLACKWELL : Plasma fusion gives you essentially limitless energy from sea water and in the future lithium which is also rather abundant, not as abundant as sea water but there's tens-of-thousands of years in the short term, millions of years of energy with virtually no carbon impact and very little but I wouldn't say no radioactive waste, about 100 times less radioactive waste through incidental processes than nuclear fission.

WALEED ALY : And when you say limitless, you can't really mean that can you. There has to be some kind of limit doesn't there?

PROFESSOR BOYD BLACKWELL : Well, there would be, but I think the world's approaching its capacity for population fairly rapidly, so assuming that the world population live at about the standard that the first world live right now, then we can only consume energy at a reasonable rate and we will be sensible and reduce our energy consumption, it might take a while for people to do that, but already a lot of progress has been made in that direction. So there are limits on how much we use, but the amount of energy available will supply a huge population on the earth beyond its capacity I guess for 10,000 years with the technology that we're working on right now and a million years for the technology of the next generation, that would deuterium, deuterium fusion.

WALEED ALY : So what does that mean? Does it mean we shutdown all the power plants that we've got, all the electricity plants, coal we don't need to worry about, we don't need to worry about nuclear power plants as they currently are that they're reconfigured to fusion. Basically the whole energy debate just goes away?

PROFESSOR BOYD BLACKWELL : That's right, that's right. There's no reason why we should have a mix of renewables and base load. One of the things about fusion power is that say a base load source, it's always there on tap as much as you want when you want it and so it's a good complement to the renewable such as solar and wind.

Now we can't just switch off the coal stations, we can't just switch off the fission reactors because it will take 50 to 100 years to replace all those reactors, because people will expect their investment to be returned and unless someone's willing to put in lots of money to repay the people who've invested in those power stations, they're not going to switch them off straight away and we can't build power stations quickly enough, so talking about a transition time, make a difference in 50 years and make a very big difference in 100 years.

WALEED ALY : If I remember back to my high school project on this and it was a cracker let me tell you Professor Blackwell. But the problem here is that you have -- to try to fuse atoms there's sort of a natural repulsion that exists between the atoms, so you have to overcome that and the way to overcome that is by applying energy, which means lots and lots and lots of heat and we just haven't been able to figure out a way to generate high enough temperatures or at least not do so safely. Am I right so far?

PROFESSOR BOYD BLACKWELL : Well, the main obstacle I think can be simplified to saying that we have to take one gram of plasma which is the fourth state of matter that we discussed and we have to hold it for one second, that sounds easy, but the problem is at 100 million degrees.

WALEED ALY : Yeah, right. So how do you create that sort of temperature? Is the problem just creating it or is the problem creating it safely?

PROFESSOR BOYD BLACKWELL : No, it can be reasonably easily, then there's really no safety aspect, anything like nuclear fission of the old generation, because new generation nuclear fission is a lot safer. 

But it's quite simple. We basically use the principle of a microwave oven, just a very big one, and so we use waves which are invisible to us, but carry energy and then we aim the waves at the plasma. We make the waves resonate with the plasma particles by choosing the right frequency and the trick at least from our point of view, the trick is to create a magic force field which is a magnetic field which holds these particles in place without letting the heat escape. So we launch waves into a magnetic field; so it's like putting a magnet in your microwave oven, but on a very big scale.

WALEED ALY : Okay, you make it sound reasonably simple. What's the hold up?

PROFESSOR BOYD BLACKWELL : Well, one of the problems is chaos. The problem is magnetic fields can break into a chaotic shape, particularly when you try to make them efficiently in a three dimensional reactor. The present program is to make a doughnut-shaped plasma which to our listeners will sound like it's three dimensional. But if it's a perfect doughnut, it actually is from a physics and a mathematical point of view two dimensional, so it's living in a two dimensional world.

When you make a real reactor that's economical and lasts a long time and can be maintained remotely, then you can't keep that doughnut perfectly symmetric in its shape, so it will have lumps in it, where you have connections and access ports and so on. So you know move to a three dimensional world and that's one of the subjects of our conference. How do you make these two dimensional idealised machines work in the three dimensional world?

WALEED ALY : This is obviously a challenge that's before you. I gather you must be making some kind of progress; otherwise this sort of conference wouldn't happen if it was just a pipe dream that was really in the realms of science fiction. How far away do you think we are from developing the kind of technology that might actually solve this problem?

PROFESSOR BOYD BLACKWELL : Well, I guess there are two stages. The first stage which is well underway now in Europe in an international effort is making this doughnut-type machine but a little bit three dimensional, a little bit practical and that will produce results one or the other in less than 20 years. 

So that's 500 million watts which isn't that much, but it's a serious amount of power that will give investors confidence these final demonstration type reactors which are maybe a factor of two to ten times larger in power capacity. They'll all happen in another 20 or 30 years after that. So once a demonstration reactor is done, then the various companies that make them hopefully will start to mass produce them.

WALEED ALY : So 50 years before that point?

PROFESSOR BOYD BLACKWELL : Yes, but as I said before, it's got to be a gradual role in because practically speaking, we have so many power plants. Several each week are being built in China. The world needs so many power plants to support the existing population to a reasonable level of comfort, so it's going to take a long time to turn enough power plants out.

WALEED ALY : But being asked to invest in something that is that long range and may well not bear any fruit. It's got to be hard to raise funds for this, doesn't it?

PROFESSOR BOYD BLACKWELL : Yes, there have been a couple of investors in the US that have pulled out, but there are still some private investors in the US, Tri Alpha Corporation for example who has employed a couple of our students, our graduate students are still going strong. 

I guess the thing that you have to keep in mind is that this is the biggest pay off that you can imagine. The world is really energy hungry and it's willing to pay a lot for that energy. This is more or less free energy from the point of view of power stations in a long term, because the cost of fuel is zero. The energy cost is not zero and it'll be similar in cost to the already escalating price of fossil fuel energy, solar energy and so on.

DESLEY BLANCH: Professor Boyd Blackwell is the Director of the Australian Plasma Research Facility at the Australian National University in Canberra where he has co-chaired a conference there that if it's successful could just change the world. He was speaking with Waleed Aly from ABC Radio.

Source: radioaustralia.net.au

Provcence in southern France, known for its picturesque villas and vineyards, is also home to a vast building site - about the size of 60 soccer pitches.

Before work began in 2007, the dead-flat 42ha platform at Cadarache, about an hour's drive from the French Riviera, was forested. Now it is set to become one of the biggest nuclear research facilities in the world.

In all, says my guide Topher White, 90ha of woods have been cleared, something he suggests has been accomplished with a certain ruthless efficiency.

Czytaj więcej...