Bose-Einstein Condensate

What is Bose Einstein Condensate?

Bose-Einstein Condesnsate otherwise know as BEC happens at a few billionths of a degree above absolute zero. The atoms are so cold, that they lose their individual identities and all clump into one atom. Cooling a gas this low requires two diffrent types of cooling, laser cooling is used first, and then evaporative cooling is used. Here is a video about Bose-Einstein Condensate.

Bosons and Fermions
To understand BEC, you need to know the diffrence between Bosons and Fermions. Bosons are able to all be in the same quantum state, while fermions can not exist in the same quantum state. Atmos in existing in a certain quantum state can only have a certain amount of energy. Fermions can each individually exist in only one quantum state, while Bosons can all exist in the same quantum state. Bosons all exist in the same quantum state around a few billionths of a degree above zero, which is where BEC is created.

Laser Cooling
The first step in creating a BEC is using laser cooling, a boson like radium is put inside a container, and four lasers are shot into is. For a laser to cool an atom, the laser must it th atom, then bounce of of it. The laser will take energy from the atom, and will slow the atom down. The tricky part of laser cooling, is that every atom wants a diffrent color. So you have to have lasers that can be finely adjusted. To get the faster atoms to slow down, but not the slower atoms, the doppler effect comes into pay. The closer laser light gets to an atom, the more blueish the color looks to the atom. The farther away an atom gets from laser light, the redder the color looks to it. Using this principle you slow down the fasters atoms with light, while leaving the slower atoms alone. Multiple lasers are pointed into the cylinder to create a laser trap, so when cold atoms try to get out of the trap, they get pushed right back in. This effect of getting lots of atoms cold, is called optical molasses. Also to keep the atoms in the trap, they use a magnetic feild. The magnetic feild slightly changes the color of the laser, the atoms want as they get farther away from the center, making them slow down in the middle, becuase that is where the atoms get the color they want. The atoms do not get bumped by other atoms, becuase the container is a vacum. Laser cooling gets atoms 1/10,000 of a degree above absolute zero, which is not cold enough for Bose-Einstein Condensate.

Evaporative Cooling
The second type of cooling is evaporative cooling, this type of cooling allows atoms to get to the tempature neccasarry for BEC. The atoms are contained in a magnetic trap, this magnetic trap keeps the atoms in the center of the continer without need for light. Evaporation cooling happens when the most energetic atoms escape from the trap, and they take more than their share of heat. As the magnetic trap is lowered,more atoms escape, until the only atoms left are on the same quantum level. It also turn out that there has to be a good amount of atoms for BEC to be created.

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