New method aims to trap coldest antimatter yet

Washington, Jan 7: Researchers from the US and Canada have developed a new method that could potentially cool trapped antihydrogen atoms to temperatures 25 times colder than already achieved, making them much more stable and a lot easier to experiment on.

The suggested method involves a laser, which is directed at antihydrogen atoms to give them a “kick,” causing them to lose energy and cool down.

Antihydrogen atoms are formed in an ultra-high vacuum trap by injecting antiprotons into positron plasma. An atomic process causes the antiproton to capture a positron which gives an electronically excited antihydrogen atom.

Typically, the antihydrogen atoms have a lot of energy compared to the trapping depth which can distort the measurements of their properties.

As it is only possible to trap very few antihydrogen atoms, the main method for reducing the high energies is to laser cool the atoms to extremely low temperatures.

Co-author of the study, Professor Francis Robicheaux of Auburn University in the USA, said: “By reducing the antihydrogen energy, it should be possible to perform more precise measurements of all of its parameters. Our proposed method could reduce the average energy of trapped antihydrogen by a factor of more than 10.”

“The ultimate goal of antihydrogen experiments is to compare its properties to those of hydrogen. Colder antihydrogen will be an important step for achieving this,” he said.

This process, known as Doppler cooling, is an established method for cooling atoms; however, because of the restricted parameters that are needed to trap antimatter, the researchers need to be absolutely sure that it is possible.

“It is not trivial to make the necessary amount of laser light at a specific wavelength of 121 nm. Even after making the light, it will be difficult to mesh it with an antihydrogen trapping experiment. By doing the calculations, we’ve shown that this effort is worthwhile,” Professor Robicheaux added.

Through a series of computer simulations, they showed that antihydrogen atoms could be cooled to around 20 millikelvin; trapped antihydrogen atoms so far have energies up to 500 millikelvin.

The findings are published in IOP Publishing’s Journal of Physics B: Atomic, Molecular and Optical Physics. (ANI)