November 5, 2013
Cutting-Edge Superconductors Assist In Astronomical Observation
Brett Smith for redOrbit.com - Your Universe Online
Having been commercially manufactured since the 1960s, semiconductors are the backbone of modern electronics. However, these materials are slowly being replaced by superconductors – particularly in the field of astrophysics.
Superconductivity is essentially a quantum phenomenon that happens when certain materials are cooled to near absolute zero. This cooling eliminates electrical resistance and magnetic fields, allowing for the detection of the energy and arrival time of individual photons streaming to Earth from outer space.
"What we have made is essentially a hyperspectral video camera with no intrinsic noise," said Ben Mazin, assistant professor of physics at the University of California, Santa Barbara. "On a pixel-per-pixel basis, it's a quantum leap from semiconductor detectors; it's as big a leap going from film to semiconductors as it is going from semiconductors to these superconductors. This allows all kinds of really interesting instruments based on this technology."
The new Array Camera for Optical to Near-infrared (IR) Spectrophotometry (ARCONS) is the first ground-based instrument, optical through near-IR wavelengths, using the superconductor-based Microwave Kinetic Inductance Detectors (MKIDs).
First developed a decade ago, MKIDs are used in astronomy for detecting light across the electromagnetic spectrum. In his lab, Mazin has calibrated these detectors for the ultraviolet, optical and near-IR regions of the spectrum.
"Forty years ago we were doing optical astronomy with photographic plates, which use light to change a chemical emulsion," Mazin explained. "When we switched from photographic plates to the charge couple devices (CCDs) contained in today's electronics, per-pixel performance of the detectors went up by a factor of 20.”
"In the last decade, CCDs and other semiconductor-based detectors for the optical and near-IR have started to hit fundamental limits in their per-pixel performance," he added. "They've gotten about as good as they can get in a given pixel. The way they continue to improve is by making huge pixel mosaics, which is appropriate for many but not all applications."
ARCONS' small field of view – 20 inches by 20 inches – is not a drawback for seeing distant objects in the universe, the astrophysicists noted. The modest size actually improves efficiency as compared to conventional methods. MKIDs capacity for time resolution, or the ability to sense the arrival of each and every photon, allows astronomers to see quickly changing events in the cosmos.
For their test observations, Mazin and his team attached several lenses to ARCONS for 24 observing nights, allowing them to gather data on optical pulsars, high redshift galaxies and planetary transits.
"ARCONS is very sensitive but it's been coupled with 5-meter telescopes," Mazin said. "The 8- to 10-meter telescopes, such as Keck, are at better sites with four times the collecting area.”
“We hope to deploy MKID instruments in the next several years at Keck and other telescopes to make fascinating new observations, including using MKIDs coupled to a coronagraph to directly discover and take spectra of planets around nearby stars,” he added.