CAST - CERN Axion Solar Telescope - X-ray Telescope Group

Copyright © 2005 M. Kuster

Experimental Search for Solar Axions

CAST (CERN Axion Solar Telescope) is a project at the European Organization for Nuclear Research CERN in Geneva, which aims to detect axions. Axions have been proposed 30 years ago to solve the CP problem of Quantum Chromodynamics (the theory of the strong interaction) and are a favorable candidate for dark matter. The strong CP problem describes the fact that Charge-Parity symmetry is broken in weak interactions while in strong interactions CP violation is exceedingly small or even absent. The most persuasive experimental evidence for CP conservation in strong interactions is the experimental limit on the neutron electric dipole moment, which is ten orders of magnitude smaller than the theoretical prediction of quantum chromodynamics. This huge difference between the theoretical prediction by QCD and the experimental upper limit for the neutron electric dipole moment can be resolved by postulating the axion with similar properties as the neutral pion. The strength of the coupling between the axion and "ordinary" matter like to photons, electrons, and nucleons is model dependent. .

The physical detection principle of CAST is based on the inverse Primakoff effect, the fact that axions can be transformed into detectable photons in a strong and transversal magnetic field. The strongest potential axion source is the core plasma of Sun, where axions could be produced via the Primakoff conversion: thermal photons can be converted to axions in the electric field of the solar plasma and leave the Sun like neutrinos due to their very small interaction probability. These free streaming axions could be detected with CAST at Earth. To get a sufficient high detection sensitivity magnetic field intensities of several tesla are required. For CAST a prototype of a superconductive dipole-magnet of the LHC with a length of 9.26 m is used, it provides a magnetic field up to 9 Tesla. The magnet can observe the Sun for 3 hours a day during sunrise and sunset like a conventional astronomic telescope. Our group is responsible for one of the detector systems of CAST, the X-ray telescope.

Collaborating Partners

Max-Planck Institutes

Max-Planck Logo

Max-Planck-Institut for Physics
Max-Planck-Institut for extraterrestrial Physik
Max-Planck Semiconductor Laboratory


Uni Freiburg Logo

University of Freiburg, Institute for Physics

Uni Zaragoza Logo

University of Zaragoza, Nuclear and High Energy Physics Laboratory

Cluster of Excellence

Cluster of Excellence Logo

The Cluster of Excellence for Fundamental Physics: Origin and Structure of the Universe


PN Sensor Logo

PN Sensor GmbH


CAST Collaboration Meeting, CERN
February, 22.-23. 2010

CAST Collaboration Meeting, CERN
February, 24. 2010

CAST in Wikipedia
The article on Wikipedia about CAST has been updated


University of Technology Darmstadt

Dr. Markus Kuster

+49 6151 16-2321
+49 6151 16-4321

Institut für Kernphysik

S2|14 219
Schlossgartenstraße 9
64289 Darmstadt

Max-Planck Institute for Physics

Dr. Rainer Kotthaus

Föringer Ring 6
80805 München

CAST Solar Observation

A solar observation with CAST. To switch to fullscreen mode please press the lower right button.
" " (6.6 MByte)

Copyright © 2009 M. Rosu

CAST Virtual Panorama

Panoramic view of the CAST experiment at CERN. Left click on the image and move your mouse to move the panorama. Requires Quicktime to be installed.

High resolution panorama " " (6 MByte)

Copyright © 2010 M. Kuster

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