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We have a problem

13/10/2005

We are on the brink of an era in which technology is the undisputed ruler of all of our destinies. Everything depends on it, from the strings of a guitar (as the singer Jorge Drexler has said) to the placement of a tile that will prevent the space shuttle Discovery burning up on its re-entry into the earth's atmosphere. Our mobile telephones, the exploration of space, the identification of organisms that exist in extreme conditions, and the development of the human race, including the possibility of adapting the temperature to suit us, are all dependent on the progress of technology.

So that is the position we are in, and our situation at the GTC is complicated by our need to lower temperatures to avoid heat producing false data in observations.

We have a telescope, and an instrument that can see objects in the infrared range. Yet we have a problem...and we have to solve it. To do so, we need to start from scratch.

IT'S TIME TO SEE THINGS IN A DIFFERENT COLOUR
There is nothing better than a technological challenge to prompt advances and discoveries and, given how clever we have become, to encourage us to apply these to our everyday lives...or at least to the lives of some people.

EMIR is huge, both in terms of the problems it poses and in terms of its sheer size. Before we can start building it we need to test all of its subsystems. To do this, we need a test cryostat, which has been designed at the Instituto de Astrofísica de Canarias. The instrument as a whole weighs over 1000 kg, which means that it has to be moved with a crane. This is a bit heavy and, to make things more complicated, it is layered like an onion.

The exterior will resist pressure. Inside there are two more layers: a radiation screen to stop heat getting in from the outside, and an adiabatic* screen (you will say that we're using technical terms again), which will keep temperatures stable.

The design was sent to the Valencia company TTM and... now we have EMIR's Multiproposal Cryogenic Test System (EMCTS). Don't get worried by the language! We have talked about the wonderful world of infrared and cryostats before. It is just that sometimes we need to get to the roots of a subject to fully understand it.

UNDER PRESSURE
You could liken the cryostat to an enormous pressure cooker, but in reality it is more like a vacuum flask. It does look like a pressure cooker though. To produce it, we need to fulfil two conditions. First we need to produce the vacuum by removing air with pumps and keeping it out. Second, we need to create and maintain a pre-determined temperature.

To prepare the 'environment', we start by introducing liquid nitrogen in a step known as "precooling". Next we use closed cycle helium compressors to lower temperatures further and, most importantly, to ensure that they remain stable. The compressors compress and decompress helium in a circuit - they are similar to the compressors in a refrigerator but they use helium in place of freon or other elements.

All this has nothing to do with the refrigeration of human bodies or heads in the hope that, through advances, they can be brought back to life in the future. The only product in this process will be the image projected on the screen after it passing through the time machine that is the telescope.

A CRYOSTAT THAT IS "MADE IN SPAIN"
This cryostat was designed at the IAC and built by the Spanish company Telstar Tecnología Mecánica S.L., TTM, which was founded in 2003 and is based in Valencia. TTM produces Ultra High Vacuum (UHV) equipment.

The parent company, Telstar, was set up to manufacture vacuum flasks in 1963 and today has branches in China and the United States. Telstar also manufactures other types of equipment such as sterile rooms and sterilisation equipment for the pharmaceutical industry

This is one of the most advanced cryostats and it has been made in Spain. It will help us to commission EMIR, and to solve the problem we started out with: how to see in infrared.

*adiabatic: a term used to describe an entity in which no heat is exchanged between the interior and the exterior (www.rae.es).

Natalia R. Zelman

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