Last month I reported that Agilent ion pumps helped scientists discover gravitational waves after decades of searching. How did we help? These Agilent vacuum products are used in the laboratory where the discovery took place, the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Washington and Louisiana.
The LIGO detectors measured gravitational waves by using two arms of an interferometer placed at 90 degrees. Each arm was housed in a tube kept under near-perfect vacuum. Agilent’s custom ion pumps helped ensure this near-perfect vacuum.
“Detecting gravity waves from an event a billion light years from Earth is only possible by an instrument with exquisite precision that has been isolated from all sources of noise that would mask the tiny signal,” says Agilent’s Jim Hollenhorst. “This requires all of the key components to be placed in a vacuum chamber with a pressure a trillion times smaller than normal air pressure. Agilent’s ion pumps are essential to achieve these ultrahigh vacuum conditions. They work by ionizing any residual molecules, then accelerating them to collide with an electrode and trapping them within the pump.”
A laser beam, split in two, traveled back and forth along each 4-kilometer arm, bouncing off mirrors at each end and recombining where the arms meet. Physicist Albert Einstein predicted that a gravitational wave would change the length of the arms ever so slightly. Any mismatch in the length of the arms is detected when the beams recombine. That is exactly what LIGO detected—a distortion one thousandth the diameter of one atomic nucleus.
“To put this measurement in perspective, the observed signal changed the length of the interferometer arms by one part in a thousand billion billion,” Jim says. (That’s 1 in 1,000,000,000,000,000,000,000.) “This is like measuring the distance to Pluto with a precision smaller than the size of a virus.
“It is gratifying to know that this discovery could not have been achieved without vacuum pumps as capable as ours.”
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