Paul Trap Laser (image) Max-Planck-Gesellschaft Caption Cooling down an ion crystal: a cloud of magnesium (blue spheres) and magnesium ions (tied blue and green spheres) is confined between the four cylindrical electrodes of a Paul trap. A laser, depicted in this image as a bright transparent strip in the center, cools the ions so that they solidify into a Coulomb crystal. When helium atoms (purple), which flow into the trap, collide with magnesium hydride ions, the rotation of the latter slows down -- the rotation temperature drops. Credit Alexander Gingell/Aarhus University Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.