Aus der Serie "Mühsam ernährt sich das Eichhörnchen."

Ich habe mich ja hier verschiedentlich schon äußerst skeptisch geäußert, was die Umsetzbarkeit künstlicher Wasserstofffusion zur Energiegewinnung auf verläßlicher und nutzbarer Basis betrifft; ob nun per Tokamak oder anderweitig. Andererseits wäre es natürlich wunderbar, wenn sich meine Skepsis als unbegründet erweist.

Aus Chronistenpflicht. Es gibt einen weiteren Quantensprung zu berichten. in diesem Fall nicht per Zündung eines 100 Mio. Grad heißen Plasmas, sondern durch Laserbeschuß.

"With explosive new result, laser-powered fusion effort nears ‘ignition’"

Zitat

---

Science Magazine, by Daniel Clery Aug. 17, 2021 , 11:00 AM

Last week, a single laser shot sparked a fusion explosion from a peppercorn-size fuel capsule that produced eight times more energy than the facility had ever achieved: 1.35 megajoules (MJ)—roughly the kinetic energy of a car traveling at 160 kilometers per hour. That was also 70% of the energy of the laser pulse that triggered it, making it tantalizingly close to “ignition”: a fusion shot producing an excess of energy.

“After many years at 3% of ignition, this is superexciting,” says Mark Herrmann, head of the fusion program at Lawrence Livermore National Laboratory, which operates NIF.

NIF’s latest shot “proves that a small amount of energy, imploding a small amount of mass, can get fusion. It’s a wonderful result for the field,” says physicist Michael Campbell, director of the Laboratory for Laser Energetics (LLE) at the University of Rochester.

“It’s a remarkable achievement,” adds plasma physicist Steven Rose, co-director of the Centre for Inertial Fusion Studies at Imperial College London. “It’s made me feel very cheerful. … It feels like a breakthrough.”

And it is none too soon, as years of slow progress have raised questions about whether laser-powered fusion has a practical future.
...
NIF’s approach, known as inertial confinement fusion, uses a giant laser housed in a facility the size of several U.S. football fields to produce 192 beams that are focused on a target in a brief, powerful pulse — 1.9 MJ over about 20 nanoseconds. The aim is to get as much of that energy as possible into the target capsule, a diminutive sphere filled with the hydrogen isotopes deuterium and tritium mounted inside a cylinder of gold the size of a pencil eraser. The gold vaporizes, producing a pulse of x-rays that implodes the capsule, driving the fusion fuel into a tiny ball hot and dense enough to ignite fusion. In theory, if such tiny fusion blasts could be triggered at a rate of about 10 per second, a power plant could harvest energy from the high-speed neutrons produced to generate electricity.

When NIF launched, computer models predicted quick success, but fusion shots in the early years only generated about 1 kilojoule (kJ) each. A long effort to better understand the physics of implosions followed and by last year shots were producing 100 kJ. Key improvements included smoothing out microscopic bumps and pits on the fuel capsule surface, reducing the size of the hole in the capsule used to inject fuel, shrinking the holes in the gold cylinder so less energy escapes, and extending the laser pulse to keep driving the fuel inward for longer. The progress was sorely needed, as NIF’s funder, the National Nuclear Security Administration, was reducing shots devoted to ignition in favor of using its lasers for other experiments simulating the workings of nuclear weapons.

Earlier this year, combining those improvements in various ways, the NIF team produced several shots exceeding 100 kJ, including one of 170 kJ. That result suggested NIF was finally creating a “burning plasma,” in which the fusion reactions themselves provide the heat for more fusion—a runaway reaction that is key to getting higher yields. Then, on 8 August, a shot generated the remarkable 1.35 MJ. “It was a surprise to everyone,” Herrmann says. “This is a whole new regime.”

Exactly which improvements had the greatest impact and what combination will lead to future gains will take a while to unravel, Herrmann says, because several were tweaked at once in the latest shot. “It’s a very nonlinear process. That’s why it’s called ignition: It’s a runaway thing,” he says. But, “This gives us a lot more encouragement that we can go significantly farther.”

---

Der Witz ist nun, die Laser mit der aus dem Fusionsprozess generierten Energie zu betreiben. Bei einem Wirkungsfaktor von 3% ist das ein Zuschußgeschäft; bei Raten >100% gibt es einen Überschuß; eine Steigerung von 3% auf 70% läßt vorerst den Schluß zu, daß da noch "Luft nach oben" sein könnte.