The trailer-mounted radar is a "phased array" type - it scans the sky with a narrow beam which flicks between thousands of locations each second.

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Walking straight on a narrow beam is frustrating and wrong.

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Moreover, engineers have worked out how to make laser beams more intense by using short lengths of optical fibre to narrow the beam.

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But the safety of beaming it back--proposals call for converting the radiated energy into a narrow microwave beam, which would then be collected and converted into electrical energy on earth--makes many people uncomfortable.

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It works by scanning a laser beam across an object and manipulating the reflected light to produce an extremely narrow focal plane.

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The pump beam had a large effect on the reflectivity of the mirror, but only over a narrow range of temperatures.

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