Physics 2000 The Atomic Lab Bose Einstein Condensation

How is BEC made? The Introduction

It took 70 years to realize Einstein's concept of Bose-Einstein condensation in a gas. It was first accomplished by Eric Cornell and Carl Wieman in Boulder, Colorado in 1995. They did it by cooling atoms to a much lower temperature than had been previously achieved. Their technique used laser light to first cool and hold the atoms, and then these atoms were further cooled by something called evaporative cooling.

It looks like a pretty simple piece of equipment for such an important experiment. Is that really all there was?

Not exactly. There is a table full of equipment associated with the lasers, and they needed to produce exactly the right color of light. Also there is a computer and a bunch of other electronic equipment for controlling everything and making measurements. Still, it was a pretty simple and inexpensive apparatus compared to many physics experiments today. It only cost about $50,000-100,000 for the equipment, but that does not include a lot of hard work that went into putting it all together!

So how cold do the atoms have to be to reach BEC?

Less than one millionth of a degree above Absolute Zero, which is millions of times colder than the lowest temperature found in the depths of outer space. (Click here for more information about Temperature)

That sounds pretty cold. How do they do it?

Well it takes two stages. Sort of like taking a pan out of a hot oven and letting it cool off in air first, and then dunking it in ice water. Except the first step here is to shine laser light on the atoms to cool them to about 1/10,000 of a degree above Absolute zero, and the second step is to evaporatively cool them further.

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