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Lasers, Electron Beams and New Years Resolutions

March 2, 2011 - 3:43pm


The few folks still keeping their New Year’s resolutions to work out might be the first to appreciate the recent record-breaking lift by the Energy Department’s Jefferson Lab. Take a steel dumbbell. Hoist it up – lift with your legs! – onto a stand. Then add another ...and another ...and another. Keep doing so until dollar signs are flashing before your chiropractor’s eyes, until you’ve got 20 feet of steel standing there ...and at least six months of therapy ahead.

Then quick, BLINK!

In that strobe-like second, the electron beam that powers Jefferson’s Free-Electron Laser (FEL) could have burned through the entire steel stack. Earlier this month, Jefferson Lab's FEL test injector pumped up to a record power output of a sustained 500 kilovolts. That’s a massive lift, considering that the previous record was 320 kilovolts, but it’s also a marker for pumping things up even further. Researchers are hoping to eventually hit a total power package of a sustained 500 kilovolts and 100 megawatts.

Sounds impressive – and it is – but what does it mean and why does it matter? A sufficiently powerful laser could make an effective defensive weapon. After all, a missile may fly fast, but light flies faster, and a beam will always beat a missile when it comes to burning a hole in the sky. In addition to swatting unfriendly in-bounds, such a laser might also be useful for out-bounds like accurate detection and tracking. That’s why the Office of Naval Research is sponsoring the project.

Jefferson’s laser is so super charged because it gives electrons an ultimate workout. It injects them into a long racetrack lined with super-cooled, superconducting radiofrequency cryomodules, the accelerating components which pump the electrons up to incredible speeds. In a sense, it’s a relay race, since through an innovative energy-recovery system, the energy given off by one electron is picked up by another – a light-speed recycler. That allows the energy to be amplified with far less power.

And unlike conventional chemical and solid-state lasers, whose beams are weaker when it comes to pushing through changing atmospheric conditions, the FEL can be tuned to a variety of different wavelengths, breaking through a shifting sky in steady strength.

Reaching that peak point will require additional years of development – in addition to pumped up power, the FEL also has to be shrunken in size so it will fit aboard a ship. But other applications are likely to be found along the way. Jefferson Lab’s tunable laser has been used to find the perfect laser color for everything from micro-machining to medical treatments. And researchers there, or at other labs managed by the Office of Science, may find many more applications.

So using brain rather than brawn, scientists and engineers are strengthening our nation and helping the Navy fulfill its full potential of perfect pumpitude. What Saturday Night Live’s Hans and Franz once said remains true for Jefferson Lab and its FEL, “We just want to ...Pump up!”

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