ALPHA is an international collaboration based at CERN, and which is working with trapped antihydrogen atoms, the antimatter counterpart of the simplest atom, hydrogen. By precise comparisons of hydrogen and antihydrogen, the experiment hopes to study fundamental symmetries between matter and antimatter.


A schematic of the ELENA ring, to be built at the CERN AD.

The first construction meeting for the Extra-Low ENergy Antiproton (ELENA) Ring kicks off at CERN today. ELENA, approved by the CERN research board last July, is an additional ring in the Antiproton Decelerator (AD) building, designed to slow the 3.5 MeV beam from the AD to 100keV before delivering the beam to the experiments. What this means for experiments like ALPHA is that we can use much thinner matter foils to slow the antiproton beam down before capturing them in the trap, which in turn can mean a hundredfold increase in capture efficiency.

The meeting involves presentations from the experiments on past achievements, and future goals, from the CERN departments on the technical challenges and plans to meet them, and from external institues, committing financial and technical add to the project.

Read more at the CERN press release.

In a paper published online at Nature Physics, ALPHA announces confinement of antihydrogen atoms for at least 1000s.

Last November, we announced in Nature that we had successfuly trapped 38 antihydrogen atoms for at least 172 ms.  In fact, 172 ms is the shortest time we can trap atoms and be sure that we've removed all of the other particles that can be around. By simply leaving the magnetic atom trap on, we can easily make measurements for longer times.

Our complete data set from last year is made up of 309 annihilation events consistent with antihydrogen annihilation, 19 of which occur after holding the trap for at least 1000s. In the figure here, we show the number of atoms trapped as a function of the confinement time.

These results strongly imply that the antihydrogen atoms have reached their lowest-energy (ground) state while in the trap, which is important for the ground-state spectroscopy that ALPHA plans to perform on the trapped atoms. In addition, the large number of atoms allow us to compare the time and position at which the atoms escape the trap to simulations and shed light on the energy distribution of the trapped atoms.

Read more about the results here or read the full paper. See the news sites reporting on this story.


10 May 2011

The first beam of the 2011 season was delivered to ALPHA from the AD (Antiproton Decelerator) on the night of May 9th.

The image here shows some of the first antiprotons captured in the trap. It's produced by dumping the particles onto an MCP/phosphor -- the bright circular shape is the electron plasma used to cool the antiprotons from a few keV (kiloelectron volts = 1000 electron volts) to a few eV. The more diffuse cloud off to an angle on the left is the antiproton cloud. There are about 30,000 antiprotons here, which is what we get from one shot (cycle) of the AD.

Here's to another great run!


The Low Energy Antiproton Physics Conference, held every two years, is one of the most important conferences for the antihydrogen community. This year, more than fifteen members of the ALPHA Collaboration travelled to TRIUMF, in Vacouver, Canada to present results and discuss with the rest of the community. The conference, which had ALPHA member Makoto Fujiwara as the chairman of the local organising committee was  very successful. You can find more details about LEAP 2011 here, as well as some of the ALPHA presentations in the program.

ALPHA's recently announced achievement of trapping antihydrogen atoms has created quite a stir. Now, a stylised view of the ALPHA apparatus has made it to the front cover of the CERN Courier.

Read more about ALPHA in the CERN Courier here.