Page last updated at 10:20 GMT, Wednesday, 29 April 2009 11:20 UK

Q&A: Alpha Magnetic Spectrometer

Samuel Ting, a Nobel Prize-winning physicist from the Massachusetts Institute of Technology (MIT), is the driving force behind a particle detector that is designed to operate on the International Space Station (ISS).

AMS (Laurent Guiraud)
The AMS is designed to fly aboard the International Space Station

The US space agency (Nasa) is still awaiting funding to fly the mission, which was cut from the space shuttles' manifest following the 2003 Columbia accident and the decision to retire the fleet in 2010 once the station was finished.

Professor Ting spoke with reporter Irene Klotz from Geneva, where he is overseeing the final checkout of the Alpha Magnetic Spectrometer at Cern.

IK: How confident are you that the remaining funds for a shuttle mission to fly AMS to the space station will be forthcoming?

ST: I do not know. I have learned in the 15 years working with space experiments that you should only be confident once you are on the space station taking data. Before that time, anything could happen.

So my main job at this moment is to make sure the final phase of the assembly of the detector that nothing goes wrong. The other things are in the hand of God or the hand of Congress.

It is difficult to have a magnet in space because it tends to rotate in Earth's magnetic field, so if you're not careful, the space shuttle or space station will be a satellite with its own style of rotation
Samuel Ting, MIT

IK: Why have you persisted so hard to get this instrument flown? Why is it so important to you to get this to the station?

ST: One, this is a unique experiment because - as you know - all of the knowledge up until now (about) the cosmos has come from measuring light rays from different telescopes in space and on the ground. But in the cosmos, besides light rays, there are particles which carry charge … antiprotons, protons, helium, antihelium, and so forth.

These have never been measured accurately at high energies. That's because once a particle carries charge, it must have a mass. And once it has a mass, it gets absorbed in Earth's atmosphere, so you have to go to space. Because it carries a charge, you need a magnet. Before (AMS) there's never been a large magnet in space.

It is difficult to have a magnet in space because it tends to rotate in Earth's magnetic field, so if you're not careful, the space shuttle or space station will be a satellite with its own style of rotation. So, in a sense, you walk into new territory in science.

Samuel Ting (BNL)
Samuel Ting says the AMS is a unique experiment

IK: Was this your idea originally to fly a detector in space? Or did Nasa pursue you to propose an experiment for the space station? It's unusual to have a particle physicist involved in the shuttle/station programme.

ST: If you had read the New York Times in, I don't know, 1962 or so, there was an article with the headline "Physicists Discover Antimatter in Complex Form". That was my first experiment. That was the discovery of anti-deutrons which I did together with Leon Lederman, and that is the formation of the anti-proton with the anti-neutron to form complex nuclei.

So, since that time, I have been fascinated about whether there exists a Universe made out of anti-matter. You see, the Universe comes from a Big Bang. Before the Big Bang, it was a vacuum, and nothing exists in a vacuum.

So, at the beginning, if you had an electron, you must also have had a positron (the antimatter counterpart of an electron). If you had a proton, you must have had an anti-proton. In other words, there must have been equal amounts of matter and anti-matter.

It always troubled me: where's the Universe made out of antimatter? That was basically one of the reasons we proposed this experiment - to look at the consequences of the Big Bang.

Another reason, as you know, is that 90% of matter in the world is not observable. And because it cannot be seen, it is called dark matter. So the question is: what is the origin of dark matter?

Those are the two things you can only do on the space station and you need a large magnetic spectrometer to do that. The idea that on the space station you cannot do fundamental science is really not correct. You really can do fundamental science, though… doing experiments in space is somewhat difficult.

IK: Assuming AMS is flown to the space station next year, how long would it take before you would be able to start drawing some conclusions from the experiment?

This doesn't depend on me. This depends on nature. What we will do… the experiment is actually very large. It's a very large magnet, a large detector.

That's why it costs close to $2bn (£1.3bn) to build it. What we want to do is … in three years, if we still do not see antimatter, this means there's no antimatter to the edge of the observable Universe. In other words, this is a somewhat definitive experiment to see whether an antimatter Universe really exists or not.

IK: You mean in our present location in space and time?

ST: Yeah. We know antimatter doesn't exist in our galaxy, because if it existed it would collide with matter and would produce sharp X-rays. The fact that we don't see these sharp X-rays means it doesn't exist in our galaxy. But the Universe has 100 million galaxies, so you really need to do a very sensitive, very careful search for this.



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