For more than 50 years, physicists have been eager to achieve controlled fusion, an elusive goal that could potentially offer a boundless and inexpensive source of energy.

To do so, American scientists have built a giant laser, now the size of a football stadium, that takes target practice on specks of fuel smaller than peppercorns. The device has so far cost taxpayers more than $5 billion, making it one of the most expensive federally financed science projects ever. But so far, it has not worked.

Unfortunately, the due date is Sunday, the last day of the fiscal year. And Congress, which would need to allocate more money to keep the project alive, is going to want some explanations.

“We didn’t achieve the goal,” said Donald L. Cook, an official at the National Nuclear Security Administration who oversees the laser project. Rather than predicting when it might succeed, he added in an interview, “we’re going to settle into a serious investigation” of what caused the unforeseen snags.

The failure could have broad repercussions not only for the big laser, which is based at the Lawrence Livermore National Laboratory in California, but also for federally financed science projects in general.

On one hand, the laser’s defenders point out, hard science is by definition risky, and no serious progress is possible without occasional failures. On the other, federal science initiatives seldom disappoint on such a gargantuan scale, and the setback comes in an era of tough fiscal choices and skepticism about science among some lawmakers. The laser team will have to produce a report for Congress about what might have gone wrong and how to fix it if given more time.

“The question is whether you continue to pour money into it or start over,” said Stephen Bodner, a former director of a rival laser effort at the Naval Research Laboratory in Washington. “I think they’re in real trouble and that continuing the funding at the current level makes no sense.”

China is studying the program’s mistakes, Dr. Bodner added, perhaps with a goal of building an improved machine.

“It’s kind of an amazing device,” said William Happer, a physicist at Princeton University who directed federal energy research for the first President George Bush. “Still, it’s not science if you don’t fail now and then. But you do have to have some wins.”

Many science analysts predict that the big laser will survive, because its powerful beams can still squeeze materials to extraordinarily high pressures, temperatures and densities that are useful in safeguarding the nation’s nuclear arms — a goal that attracts bipartisan support. For instance, the laser might help engineers see if a particular metal part that had to be substituted in a class of aging nuclear arms would still work as needed.

Even so, skeptics outside the government have long assailed the laser project, known as the National Ignition Facility, or NIF, as a colossal waste of money. Just operating it, officials concede, costs roughly $290 million a year. Some doubters have ridiculed it as the National Almost Ignition Facility, or NAIF.

Big science projects more costly than the laser include NASA’s newest space telescope, whose price tag now runs to more than $8 billion, and the 17-mile circular accelerator in Europe that recently helped pin down the elusive subatomic particle known as the Higgs boson. It cost about $10 billion.

In interviews, the laser’s architects and supporters at the Livermore lab defended the device as working beautifully and pointed to the challenge of planned breakthroughs as the fundamental problem.

“It’s like having a cure for cancer by a certain date,” said Penrose C. Albright, the laboratory’s director. “I understand why people want to have milestones. But when you’re dealing with science and Mother Nature, all you really can do is agree on whether you’re on the right path.”

The sprawling laser complex, the officials insisted, would one day achieve its advertised goal: fusing the hydrogen atoms in a speck of fuel into helium, and thus creating what physicists liken to a tiny star.

“Contrary to what some people say, this has been a spectacular success,” said Edward Moses, the laser’s director. Even so, he added, “science on schedule is a hard thing to do.”

W Sandia National Laboratories przeprowadzono udane testy berylowych rurek, które mają w przyszłości posłużyć do przeprowadzenia reakcji termojądrowej. Opanowanie tego typu reakcji dałoby dostęp do olbrzymiej ilości czystej energii.

Wspomniane na wstępie berylowe rurki przetrwały w dobrym stanie implozję silnego pola magnetycznego, wywołaną w maszynie Z. To najpotężniejszy na świecie akcelerator impulsowy. Fakt, że rurki przeszły testy oznacza, iż naukowcy z Sandia Labs mogą kontynuować badania nad koncepcją MagLIF (Magnetized Liner Inertial Fusion), która zakłada wykorzystanie pól magnetycznych i laserów do rozpoczęcia reakcji.

Jeśli pojemniki by się nie sprawdziły, oznaczałoby, że nie mogą zostać one wykorzystane do przechowywania deuteru i, ewentualnie, trytu, które miałyby ze sobą reagować.

Wyniki eksperymentów, stopień w jakim rurki zachowały swoją integralność po implozji, zgadza się z wcześniej uzyskanymi wynikami teoretycznych symulacji - powiedział główny autor badań, Ryan McBride.

Symulacje, których wyniki opublikowano w 2010 roku w piśmie Physics of Plasma dowodzą, że zamknięte w berylowym pojemniku deuter i tryt, podgrzane laserem i poddane działaniu olbrzymiego pola magnetycznego wygenerowanemu przez pracującą z natężeniem 25 milionów amperów maszynę Z powinny wyemitować nieco więcej energii niż otrzymały.

Z kolei w styczniu bieżącego roku kolejny artykuł autorstwa naukowców z Sandia Labs. Dowiadujemy się z niego, że jeśli zostanie użyta maszyna generująca wyładowania rzędu 60 milionów amperów, to w wyniku rozpoczętej dzięki niej reakcji uzyskamy ponad 1000-krotnie więcej energii niż włożyliśmy.

Do przeprowadzenia tego typu reakcji są jednak potrzebne wytrzymałe pojemniki na paliwo.

Maszyna Z generuje olbrzymie pole magnetyczne, w wyniku którego prąd przechodzi przez pojemnik, zamieniając jego zewnętrzną warstwę w plazmę. Plazma sięga coraz głębiej i pojemnik zaczyna się rozpadać. Trzeba zatem znaleźć taki cylinder, który dotrwa do końca reakcji. Można co prawda zwiększać grubość ścian pojemnika, jednak im są one grubsze tym większą energię trzeba włożyć w reakcję.

Uczeni z Sandia Labs szukali optymalnej konstrukcji, która połączy dobrą grubość ścian z wytrzymałością. Testy wykazały, że wierzchnia warstwa pojemnika uległa rozpuszczeniu, jednak warstwa wewnętrzna pozostała wystarczająco stabilna. Obawy o integralność cylindra były największym zmartwieniem naukowców od czasu powstania koncepcji MagLIF.

W grudniu bieżącego roku rozpoczną się testy dwóch ostatnich elementów systemu. Najpierw zostaną sprawdzone lasery, które mają ogrzać paliwo wewnątrz pojemnika zanim zostanie on poddany magnetycznej kompresji. Następnie zostaną przeprowadzone testy dwóch cewek elektrycznych umieszczonych z obu stron pojemnika. Generowane przez nie pola magnetyczne mają zapobiegać ucieczce z paliwa zbyt dużej ilości naładowanych cząstek. Jeśli uciekłoby ich zbyt wiele, paliwo ulegnie schłodzeniu i reakcja samodzielnie wygaśnie.

Udane testy berylowych pojemników dają nadzieję, że test pełnego systemu MagLIF będzie można przeprowadzić już w przyszłym roku.

Autor: Mariusz Błoński

Więcej informacji na stronie www.sandia.gov

A new chapter in JET’s career is opening, as a significant international collaboration with India gets underway.  The project is to design and build prototype ELM control coils for JET, and is being almost entirely funded and carried out by the Indian ITER partners.

The project leader on the EFDA side is Dr Christopher Lowry: “The coils are vital to demonstrating a fully integrated ITER scenario on JET,” he says, “and such collaboration is the future of JET – as a training ground for all the ITER partners.”

Two teams of Indian scientists and engineers from the Institute for Plasma Reseach (IPR) in Gandhinagar, in the west of India, have arrived at JET in recent times to begin work in earnest.

The six-strong conceptual design team arrived in mid-September for a six month stay. Team leader Ravi Prakash, who also heads the Remote Handling and Robotics Technology Development Division at IPR, is enthusiastic about the project. “It is an exciting project, ELM mitigation and suppression is leading edge technology in tokamaks!” he says. “It’s inspiring to work with the remote handling system.” His team, consisting of analysts Manoah Stephen Manuelraj and Pramit Dutta, CAD designers Vishnubhai Prajapati and Kanubhai Rathod and design engineer Prosenjit Santra, is responsible for the conceptual design of all 32 coils, including support structures, housing, interfacing with other JET subsystems, assembly and integration. Moreover, because the coils will be assembled inside the vessel the team needs to take into consideration any remote handling requirements, such as designing bespoke tooling.

The second team, which has the goal of building a prototype coil, is Subrata Pradhan (team leader), Mahesh Ghate (engineer), Ananya Kundu (analyst) and Kirit Vasava (draughtsman). Although much of the work will be carried out at the IPR in India, the team kickstarted their project with a month long visit to JET, arriving in mid-August.

“The exposure to the JET machine is an important aspect” says Mr Pradhan. His team spent the visit familiarising themselves with the preconceptual design and preparing preliminary models for the prototype coil, which it is scheduled to deliver mid 2013.

Despite the many JET systems that they need to become familiar with the teams have found the information they need easily. “The JET team has done things very systematically. We can reach the top expert very quickly for clarifications and discussions” says Mr Prakash. “Experience that has been gained through the years is available to the next generation through a carefully designed knowledge base – there is no data loss!”

The conceptual design of the ELM coils, associated support structures, in-vessel components and remote handling integration is expected to be completed by March next year.

Source: EFDA

The Madison Symmetric Torus, a leading piece of equipment in plasma physics research for more than 20 years, recently gained a new capability with the installation of a neutral beam injector. 

The addition allows University of Wisconsin-Madison researchers to delve further into the basic properties of plasmas—hot gases of charged particles—which are important in astrophysics research as well as numerous more down-to-Earth applications such as microchip fabrication, plasma TVs and other displays, and development of fusion technology.

A new study published online this week in Physical Review Letters reports the first description of the effects of instabilities generated by injecting hot plasmas with beams of uncharged particles—generally hydrogen—in a type of plasma confinement device known as a reversed field pinch, or RFP.

The nature of those instabilities can help researchers understand how the beam particles interact with the plasma and their potential beneficial uses, says UW-Madison graduate student Jonathan Koliner, who led the study with UW physics professors Cary Forest and John Sarff. Paper co-authors include other colleagues at UW-Madison, the University of California at Los Angeles, and Oak Ridge National Laboratory.

Neutral beams have sometimes been used to heat plasmas and drive electric currents in another type of plasma device, called a tokamak. Other times, the effects are more problematic.

"Like throwing rocks into a pond generates ripples, these particles come in and generate ripples [in the plasma]. Those ripples can feed back on themselves and start to grow very big, and when the ripples get big enough they'll kick the particles out," says Koliner.

More work is needed to understand and, ultimately, control the bursts to harness the particles' energy rather than losing them from the plasma, he says. In addition, RFPs offer some advantages over tokamaks in studying basic plasma properties due to the way they contain and control plasmas. The beam on the Madison Symmetric Torus is the first on an RFP device and offers the first opportunity to characterize beam-generated instabilities in this type of plasma environment and compare them to those in tokamaks.

"Seeing what neutral beams can do in an RFP is a good way to figure out if you can use them to control [the plasma] in other ways in the future," Koliner says. "It's important first to lock down exactly what they do in all of the different possible plasma equilibria we can make in our machine. Once you figure out what they do, then you can come up with a plan."

Koliner and his colleagues are studying the particle bursts under several plasma conditions and operating modes to form the best possible picture of what the plasma looks like and how it is behaving in the different situations. "The bursts themselves have illuminated a lot of what the beam is doing that has been somewhat mysterious, not perfectly understood up to this point," he says. "Knowing what these bursts do fills in a large piece of the picture."

Source: phys.org

At 54.6 million km away at its closest, the fastest travel to Mars from Earth using current technology (and no small bit of math) takes around 214 days — that’s about 30 weeks, or 7 months. A robotic explorer like Curiosity may not have any issues with that, but it’d be a tough journey for a human crew. Developing a quicker, more efficient method of propulsion for interplanetary voyages is essential for future human exploration missions… and right now a research team at the University of Alabama in Huntsville is doing just that.

This summer, UAHuntsville researchers, partnered with NASA’s Marshall Space Flight Center and Boeing, are laying the groundwork for a propulsion system that uses powerful pulses of nuclear fusion created within hollow 2-inch-wide “pucks” of lithium deuteride. And like hockey pucks, the plan is to “slapshot” them with plasma energy, fusing the lithium and hydrogen atoms inside and releasing enough force to ultimately propel a spacecraft — an effect known as “Z-pinch”.

“If this works,” said Dr. Jason Cassibry, an associate professor of engineering at UAH, “we could reach Mars in six to eight weeks instead of six to eight months.”

The key component to the UAH research is the Decade Module 2 — a massive device used by the Department of Defense for weapons testing in the 90s. Delivered last month to UAH (some assembly required) the DM2 will allow the team to test Z-pinch creation and confinement methods, and then utilize the data to hopefully get to the next step: fusion of lithium-deuterium pellets to create propulsion controlled via an electromagnetic field “nozzle”.

Although a rocket powered by Z-pinch fusion wouldn’t be used to actually leave Earth’s surface — it would run out of fuel within minutes — once in space it could be fired up to efficiently spiral out of orbit, coast at high speed and then slow down at the desired location, just like conventional rockets except… better.

“It’s equivalent to 20 percent of the world’s power output in a tiny bolt of lightning no bigger than your finger. It’s a tremendous amount of energy in a tiny period of time, just a hundred billionths of a second.” – Dr. Jason Cassibry on the Z-pinch effect

In fact, according to a UAHuntsville news release, a pulsed fusion engine is pretty much the same thing as a regular rocket engine: a “flying tea kettle.” Cold material goes in, gets energized and hot gas pushes out. The difference is how much and what kind of cold material is used, and how forceful the push out is.

Everything else is just rocket science.

By Jason Major

Read more on www.uah.edu