Sergey Uchaikin

In the basement of the laboratory, an 8 tesla magnet hums. Inside it, like a bell in a bell tower, hangs a hollow copper cylinder tuned to a single note. If an axion, a dark matter particle, flies by, the cylinder responds with a faint ring. The trouble is that ordinary copper muffles this ring: at high frequencies, current flows only through a thin skin of the metal, and losses grow.

Picture a radio receiver with a single tuning knob that moves all of its internal coils at once, like one living organism. That is exactly how a new instrument for the search for the axion works, a particle that may fill galaxies with invisible mass. Inside a copper cylinder the height of a coffee can sit rods of aluminum oxide.