The ALPHA Project

 

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        In this section you will find answers to the following questions:

  • What is the ALPHA Project?

  • Who works at it?

  • What does it do and how?

  • Where is the research carried out?

 

ALPHA is an international research collaboration whose goal is to produce and trap antihydrogen, the antimatter equivalent of the hydrogen atom, for use in experiments to test fundamental laws of the universe. Presently, groups such as ATHENA (the predecessor to the ALPHA collaboration) and ATRAP (a research group from Harvard University) have succeeded in producing cold antihydrogen. Continuing work by both ALPHA and ATRAP aims to take the next step to trap the antihydrogen long enough to carefully study its properties in detail.

Producing antihydrogen requires a number of steps. First, one needs a source of its constituents: positrons (the antimatter version of electrons) and antiprotons (the antimatter version of protons.) Positrons in the ALPHA experiment are produced from special radioactive sodium. Antiprotons require one of the enormous particle accelerators at CERN to produce and a special machine (the AD) to cool the newborn antiprotons from billions of degrees to temperatures usable in our experiments.

The second step involves storing those antiparticles. Because they are charged, they can be easily trapped with electric and magnetic fields. Once these constituents are trapped, the particles are slowly combined. If conditions are just right, when the antiprotons meet the positrons, they combine and form antihydrogen. However, since antihydrogen is a neutral atom, it is not held by the same magnetic traps that held the positrons and antiprotons. Once produced, the antihydrogen drifts into the wall of the experiment and annihilates (in fact, this is the effect that ATHENA used in order to detect the first production of antihydrogen.) ALPHA is currently developing a trap to contain the antihydrogen.

Once the antihydrogen is stored, ALPHA aims to perform spectroscopy on it (to test CPT symmetry) using high resolution laser light. Spectroscopy, one of the most accurate techniques available in Physics nowadays, consists in this case in the measurement of the antiparticles' energies according to the light spectrum they produce under the influence of the laser. Such spectrum should in principle be the same for them as for the electrons and protons in conventional hydrogen; a difference in the spectrums would suggest the existence of important differences between antimatter and matter (which could be useful to explain why the former hardly exists in our universe). Furthermore, since antihydrogen is an atom with a neutral charge, another of ALPHA's goals is to test the influence of gravity on antimatter. In principle, this should be the same as for matter, but such a hypothesis has never been empirically investigated.

The ALPHA Collaboration brings together researchers of many nationalities from twelve different institutions in Europe, America and Asia. Some parts of the project are carried out in the collaboration members' home institutions. For example, the prototype of the trap that will  eventually store antihydrogen atoms was designed and assembled at the University of California at Berkeley (with the collaboration of the Lawrence Berkeley National Laboratory). The main project is carried out at CERN and it is possible thanks to funding from a number of institutions.