CERN’s ALPHA experiment measures charge of antihydrogen

(a) A schematic of the antihydrogen production and trapping region of the ALPHA apparatus, showing the cryogenically cooled cylindrical Penning–Malmberg trap electrodes, and the mirror and octupole magnet coils. Our positron source (not shown) is towards the right, and the antiproton decelerator (not shown) is towards the left. (b) The on-axis magnetic field B as a function of z. (c) The on-axis electrostatic potentials V used to establish the Bias-Right (red dashed line) and Bias-Left (blue solid line) configurations. (d) Normalized histograms of the experimental z positions of the annihilations in the Bias-Right (red dashed line) and Bias-Left (blue solid line) configurations. The error bars show the expected deviation of the distribution based on the number of observed antiatoms in each bin.

(a) A schematic of the antihydrogen production and trapping region of the ALPHA apparatus, showing the cryogenically cooled cylindrical Penning–Malmberg trap electrodes, and the mirror and octupole magnet coils. Our positron source (not shown) is towards the right, and the antiproton decelerator (not shown) is towards the left. (b) The on-axis magnetic field B as a function of z. (c) The on-axis electrostatic potentials V used to establish the Bias-Right (red dashed line) and Bias-Left (blue solid line) configurations. (d) Normalized histograms of the experimental z positions of the annihilations in the Bias-Right (red dashed line) and Bias-Left (blue solid line) configurations. The error bars show the expected deviation of the distribution based on the number of observed antiatoms in each bin.

Geneva, 3 June 2014.
In a paper published in the journal Nature Communications today, the ALPHA experiment at CERN’s Antiproton Decelerator (AD) reports a measurement of the electric charge of antihydrogen atoms, finding it to be compatible with zero to eight decimal places. Although this result comes as no surprise, since hydrogen atoms are electrically neutral, it is the first time that the charge of an antiatom has been measured to high precision.
“This is the first time we have been able to study antihydrogen with some precision,” said ALPHA spokesperson Jeffrey Hangst. “We are optimistic that ALPHA’s trapping technique will yield many such insights in the future. We look forward to the restart of the AD program in August, so that we can continue to study antihydrogen with ever increasing accuracy.” Continue reading CERN’s ALPHA experiment measures charge of antihydrogen

The First Measurements Of The Antihydrogen Spectrum

A New Result From ALPHA

Once you’ve trapped antihydrogen what do you do? You measure it! That’s just what we’ve done. Published in Nature, we report the first resonant quantum transitions in antihydrogen atoms. We’ve used microwave radiation to change the internal state of the atom, from one which can be kept in our trap, to one that is kicked out. This process depends on the frequency of the microwave radiation and the magnetic field in the trap, so by changing both of these, we demonstrated that we had enough control and sensitivity to sucessfully carry out the experiment. This is by no means easy, as antihydrogen is not found in nature, but must be prepared in our apparatus from antiprotons made in the Antiproton Decelerator, and positrons from a radioactive source, Even more, it must have low enough energy to remain trapped in the magnetic fields making up our trap. Here’s an animation describing how we do our measurement.


http://youtu.be/dY5Zdqxoc8U

Eventually, we will use this technique to compare the structure of antihydrogen and hydrogen atoms, to search for difference between matter and antimatter, but In this first experiment, we do not yet have enough precision to test these fundamental symmetries. This is important, as the Universe has shown a preference for matter over antimatter as it has evolved, but so far, no measurements can explain why this came about. If matter and antimatter were truely identical, the Universe as we know it could not have come about. The next step at ALPHA is to construct an apparatus that will allow us to make these more precise measurements, using both microwave radiation, and laser light.
We’ve been waiting a long time for this result, so we’re really happy — the CERN People documentary has been following us through the process — check out the first video here.

Read more: alpha-new.web.cern.ch/