THE UNIVERSE FROM THE CENTER Fusion experiment a breakthrough

DR. GEORGE SPAGNA Special to The Local

The Keeble Observatory at Randolph-Macon College will be resuming a public viewing schedule in the spring. Check their website (www.rmc.edu/Keeble) or call the information line (804-752-3210) for times.

In December we were treated to a breathless announcement that researchers at the Lawrence Livermore Laboratory Had achieved “ignition” in a fusion experiment. In particular, they reported (actually, the Secretary of Energy reported) that a small capsule of deuterium had been imploded by 192 laser beams with a total input of 2.1 megajoules of energy. The resulting fusion reaction released 3.15 megajoules. (A joule is roughly the amount of energy needed to lift a 2-pound bag of sugar to a height of about 4 inches. A megajoule – MJ — is a million times either the sugar or the height reached. Think 1000 metric tons lifted through the same 4 inches or lifting the bag of sugar 160 miles.)

It was considered a “breakthrough” because about 100 previous experiments had only achieved a release of the same or less energy than in the laser beams.

I’ll address two questions here: What is fusion? And why am I skeptical of some of the claims surrounding this announcement?

Einstein’s Special Theory of Relativity (it’s actually more than a theory after almost 129 years of experimental tests) tells us that energy and mass are convertible. The famous equation E = mc² tells us the enormous gain going from mass to energy – the 1.05 MJ gain in this experiment represents the disappearance of only about .00000000000000001 kilograms. This reaction is similar to what posers the sun, where a billion kilo- grams of hydrogen disappear at the core every second.

Under the conditions at the center of the sun (temperature about 15 million kelvins – for all purposes 15 million degrees Celsius – two hydrogen nuclei slamming into one another become a single deuterium nucleus. That’s hydrogen with an extra neutron. Deuterium collides with another hydrogen to make helium-3 (2 protons and a neutron) which then further fuses to form helium-4 and expel 2 hydrogens. The net reaction is then 4 H become 1 He-4. Since the helium is less massive than the 4 hydrogens, energy is released.

Dreams of harnessing this reaction for clean energy have been with us since the 1950s. The promise has been elusive because the difficulties of controlling the fusion have proven very challenging. At best we’ve mastered the uncontrolled fusion of a hydrogen bomb, and that takes a uranium or plutonium fission reaction (“atom bomb”) to set it off. So this contained ignition experiment is a breakthrough. But it will be a long time – probably decades – before this gives us a nearly unlimited source of clean energy.

Why am I skeptical? The main reason is simple bookkeeping. As an example, when you buy a refrigerator or a car you also pay for the factory that made it, the sources of the materials that went into it, and the cost of transporting it to your door. Even discounting the many billions of dollars and decades of effort that built the test facility with its many laser beams, the energy budget for this test doesn’t balance. To produce the 2.1 MJ of laser energy cost an energy input of 300 to 400 MJ!

Yes, it was a breakthrough, and kudos to the teams of researchers and engineers who pulled it off. But the hopedfor promise of practical application is decades away.

Lunar phases for February: Full Moon on the 5th, at 1:29 p.m.; Last Quarter on the 13th, at 11:01 a.m.; New Moon on the 20th at 2:06 a.m.; and First Quarter on the 27th at 3:06 a.m. All times are Eastern Standard.

Mercury is in the predawn sky but it’s low on the horizon. Look to the southeast for a bright “morning star.” Venus is the bright “evening star” which will set around 8 p.m. Mars will be due south (“crosses the meridian”) about 9 p.m., setting before dawn at 4 a.m. Jupiter is already up at sunset; it will set around 9 p.m. Saturn is visible to the southeast at dusk, but it sets early. It will be too close to the sun’s