ALPS II (“Any Light Particle Search”) is the first experiment world-wide that could produce and detect dark
matter particles in a laboratory. There are indirect evidences from astrophysics for the existence of such
novel elementary particles. They are called axions or axion-like particles.
Dark matter/Such particles created in ALPS II would reveal itself/themselves in apparently transporting
light through a light-tight wall.
ALPS II is installed in an approximately 300-metre-long straight section of the HERA tunnel at DESY in
Hamburg. The experiment combines upcycled accelerator magnets from the HERA accelerator with high-precision
interferometry and the highly sensitive light detectors.
1. Laser beam
Light from a laser gets amplified in an optical cavity – basically a huge
mirror chamber.
2. Transformation of photon into axion
The light passes through a strong magnetic field from twelve superconducting
magnets. According to theory, this is where a photon transforms into an axion with the probability of:
1:1014
3. Wall
Laser light is stopped by the wall. The axion would simply pass through the
wall.
4. Transformation of axions into photon
In the magnetic field on the other side, the axion is transformed back into a
photon.
5. Detector
These transformations are extremly rare. That is why the detector must also be
extremely sensitive. It must be able to detect a few photons per day.
ALPS II main contributions
