Using the Giant Magnet to Search for the Axion
A ten-meter-long magnet, operating at approximately -270 degrees Celsius, that can track the sun for twelve hours a day via a movable platform: Thanks to funding approved by the DFG, the physicists involved in the “BabyIAXO” project can now begin its implementation. “This is the largest dipole magnet ever built for particle physics,” says Prof. Matthias Schott, coordinator of the research proposal and spokesperson for the Transdisciplinary Research Area (TRA) “Matter” at the University of Bonn. “The magnet is the heart of the experiment and is what makes the realization of BabyIAXO possible in the first place.”
The BabyIAXO system is quite a feat: The superconducting magnet must be operated at temperatures near absolute zero to achieve the required magnetic field strengths. In addition, a special design is necessary because the magnet must tilt far upward and downward to track the sun. The system is being built at the German Electron Synchrotron (DESY) in Hamburg.
From “Baby” to a Full-Scale Magnet System
As the name suggests, “BabyIAXO” is an intermediate step on the path to an even larger “full-scale” magnet system: The International Axion Observatory (IAXO) is planned to be twice the size—that is, with a 20-meter-long magnet—making it the largest helioscope experiment planned to date in the search for axions. The telescope is designed to study the Sun with unprecedented sensitivity: about 10,000 times more sensitive than the most powerful helioscope to date. In this way, it is expected to finally provide proof of the axion. “IAXO will have eight measurement stations, each of which can be equipped with different telescopes and detectors,” says IAXO Collaboration Board Chair Prof. Klaus Desch of the University of Bonn. “This will allow us to search for axions with different properties and cover as wide a range of possible axions as possible.”
“We first have to develop the technologies and instruments that IAXO requires ourselves,” adds IAXO Deputy Spokesperson Prof. Julia Vogel of TU Dortmund University. “This requires intensive research and development work as well as extensive experimental testing. BabyIAXO is an important step on this path.”
The Axion: A Solution to a Fundamental Problem of the Standard Model
Some may now ask: Why go to such great lengths to find a hypothetical elementary particle? For physicists, this question doesn’t arise: If they could detect the axion, they would have solved a fundamental problem of the Standard Model of particle physics, the so-called “strong CP problem.”
What this means is the following: According to the known laws of nature, many physical processes should remain unchanged if particles are replaced by their antiparticles and the system is simultaneously spatially reflected. Physicists know that this so-called CP symmetry is violated in the weak interaction. The theory of the strong interaction, which binds quarks into protons and neutrons, also allows for such a CP violation. “Despite decades of experiments, however, physicists have not been able to observe such a violation,” explains Prof. Matthias Schott. To resolve this contradiction, Roberto Peccei and Helen Quinn postulated the existence of the axion in 1977. This is a hypothetical elementary particle with an extremely low mass that interacts only very weakly with ordinary matter. “These properties also make the axion a very good candidate for dark matter,” says IAXO Collaboration Board Chair Klaus Desch. So there are two good reasons why physicists worldwide are searching for experimental evidence of its existence.
Participating Institutions and Funding:
Twenty universities and research institutes worldwide are participating in the International Axion Observatory (IAXO). With this major equipment grant, the DFG has approved the construction of a magnet system for the “BabyIAXO” pilot project at a cost of six million euros: 3 million come from the DFG; 2.4 million euros are provided by the state of North Rhine-Westphalia; the universities of Bonn, Siegen, and Dortmund are contributing a total of 600,000 euros as part of the “Color meets Flavor” Cluster of Excellence.