A SUPERCONDUCTING transistor should help astronomers pick up signals from
far-off solar systems that are too faint to be detected.
鈥淭he problem with detecting photons from far out is that their energies are
very low,鈥� says Giampiero Pepe of the University of Naples. To solve the
problem, Pepe teamed up with Norman Booth at the University of Oxford to make a
device called a quasiparticle-trapping transistor, or 鈥渜uatratran鈥�, which works
at a temperature of 4 kelvin.
Incoming photons strike a layer of niobium. Because niobium is
superconducting at this temperature, electrons normally move around it in
couples called Cooper pairs. But energy from an incoming photon splits these
pairs into two excited electrons, or 鈥渜uasiparticles鈥�. These pass through a
barrier into a second niobium layer and then into a layer of aluminium, where
they strike more electrons. This, says Booth, generates a flood of energetic
electrons which produce a measurable current.
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鈥淭his is interesting physics,鈥� says Mark Blamire, who works on
superconducting sensors at the University of Cambridge. 鈥淭hey鈥檝e demonstrated
that it鈥檚 got a high gain, and it should have much lower noise than other
蝉测蝉迟别尘蝉.鈥�