SoundMan
Rocket Science
November.16/ 2008 Filed in: This Just
In
As reported in NewScientist,
Murray hacked his amps to produce a gadget that can hold atoms still while he bashes them with beams of electrons. Until now, it has been possible to hold atoms still, or hit them with such beams, but not both at the same time.
Cooling and trapping atoms at temperatures close to absolute zero has produced many insights into physics, and may be critical to the development of quantum computers.
Unfortunately, the force field of lasers and magnetic fields needed to hold atoms still is not compatible with flying beams of electrons or ions. So the only way to study the effect of blasting atoms with such beams has been to do it when the atoms are moving, and this leads to smeared out collisions and Doppler effects that are hard to interpret.
Hitting atoms with a beam shortly after switching off a trap does help. But it takes up to 20 milliseconds for magnetic fields to stop sloshing around inside an atom trap, Murray says, and by that time the atoms have started moving again.
Finding a way to kill those magnetic fields instantly and hit atoms before they start moving has been troubling physicists for years. One solution, Murray realised, is to use the speaker coil from a high power PA amplifier to produce the magnetic fields inside the trap.
Unlike the coils traditionally used by physicists, which are driven by direct current, an audio speaker voice coil is fed by an alternating current. It smoothly cycles between inducing positive and then negative magnetic currents in the trap. At the end of each complete cycle - which takes five milliseconds to complete - the positive and negative currents cancel each other out and there is no net magnetic current.
So if the researchers cut the power precisely at that point they can entirely avoid magnetic currents rippling through the trap.
To read the entire article click here. Thanks to SoundMan Rick Earl for sending this in.
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