A brand-new ultra-sensitive "Radio-ear" on the Universe

• What's new?

This new instrument (called Receiver A3i) is an ultra-sensitive detection system for sub-mm wavelength astronomy, designed and built by staff at the
>National Research Council Canada (NRC) in Victoria (on Little Saanich Mountain). This state-of-the-art equipment is part of Canada's contribution to the international partnership that operates the James Clerk Maxwell Telescope in Hawaii. The extremely demanding sensitivity requirements for such an instrument require custom design and components.

• Frontier technology:

The receiver uses technologies similar to those used in cell-phones but extended to much higher frequencies and with a very much higher sensitivity. This receiver is within a factor of four of the absolute sensitivity limit set by quantum fluctuations of photon noise. The heart of the receiver is a microscopic switch which is capable of turning on and off 250,000 million times a second (about 1000 times faster than those in the fastest personal computers) in response to photons of sub-millimetre radiation captured from space. The switch is a super-conducting Josephson junction which is cooled using liquid helium to a temperature of minus 270 degrees centigrade. The signal produced by the switch is then amplified 10 million times before being sent to the observatory's computers for processing. This "radio ear" is one of the most sensitive in the world today and will be a "workhorse" receiver on the James Clerk Maxwell Telescope in Hawaii.

• What now?

The receiver has just finished laboratory tests at the NRC in Victoria prior to being packed and shipped to Hawaii in December 1998. Once it has been checked out on the telescope, all astronomers at Canadian universities can apply for time to use it. The James Clerk Maxwell Telescope (JCMT) is one of the most powerful telescopes for sub-millimetre astronomy in the world. It is located on the Big Island in Hawaii, near the 4,000-metre peak of the extinct volcano "Mauna Kea". At this altitude the telescope is above much of the atmospheric water vapour and benefits from superb conditions for sub-millimetre observing. The main mirror of the JCMT is fifteen metres across and accurate to better than the thickness of a human hair. Canada has a 25% share of the observing time on the telescope, which we share with the UK and the Netherlands.

• User-Friendly:

The receiver has been designed to be fully automatic and as reliable as possible. Its ability to change frequency (or wavelength) quickly makes it easy to tune from one spectral line to another without losing valuable observing time. Apart from filling it with liquid helium once a week, no operator intervention is required.

• What is it used for?

Receiver A3i operates in a band of frequencies corresponding to wavelengths just longward of 1 mm wavelength. It combines sensitivity with remarkable versatility and ease of operation. It will be used extensively at the James Clerk Maxwell Telescope for studies of star formation and large scale mapping of the vast clouds of cold gas and dark dust that constitute significant portions of the total material in our own Milky Way and in many distant galaxies. Such studies are important for understanding the large scale evolutionary processes that have formed stars in galaxies and in understanding the detailed processes that have given rise to our own Sun and its associated planets. The receiver can detect molecular gas in highly redshifted quasars and galaxies where we are looking back to a time when the universe was a fraction of its current age. This early-universe research is just opening up as a new territory for study at submillimeter wavelengths.

• Outer-Space Chemistry:

The cold clouds that fill the spaces between the stars are not only the sites of new star formation, but are rich chemical laboratories containing more than 100 different gases. Receiver A3i will be the JCMT's best tool for studying the emission given off by such gases as Carbon Monoxide, Hydrogen Cyanide, Methyl Alcohol and many others. Such studies not only indicate the chemical complexity of space, but can also be used to infer the physical conditions and dynamics of these clouds which are too cold to be detected in visible light. This kind of information is essential to our understanding of how such clouds are triggered into collapse to form new stars.

More info from: