Synchrotron safety data and the hunt for dark matter

A researcher at Tokyo Metropolitan University has discovered that standard synchrotron safety monitoring can be used to hunt for dark matter

By repurposing X-ray beams and simple Geiger counters, this method has set more precise limits on “dark photons” than dedicated, multi-million dollar experiments, all without interrupting daily facility operations.

These hypothetical particles are a leading candidate for dark matter, the mysterious substance that makes up the “missing” mass of the universe.

An accidental dark matter detector

The proposal involves repurposing existing safety equipment and infrastructure already present at synchrotron sites:

• The source:

  • A component called an undulator generates powerful X-rays that pass through magnetic fields, potentially creating dark photons in the process.

• The barrier:

  • Standard safety shielding—walls designed to block dangerous radiation from users—acts as the barrier for a “Light-Shining through a Wall” (LSW) experiment.

• The sensor:

  • A simple Geiger-Muller counter, typically used for routine safety monitoring, serves as the detector.

Reimagining “light-shining through a wall”

Traditional LSW experiments, like the ALPS experiment in Germany, require high-power lasers and dedicated, expensive facilities.

Dr Yin’s method is revolutionary because it:

• Requires no dedicated facility:

  • It utilises the existing X-ray beams at synchrotrons.

• Runs concurrently:

  • The search for dark matter can happen in the background while other scientists use the facility for unrelated research.

• Uses safety data:

  • Because current monitoring shows radiation levels behind the walls are safe, scientists can already calculate the maximum possible strength of dark photon interactions.

Setting new limits

By modelling the passage of hypothetical dark photons through this setup, Dr Yin established a new “mixing parameter” limit—a measurement of how strongly dark and normal photons interact.

• Mass range:

  • The study focused on dark photons with a mass between 1 and 50 electronvolts.

• The result:

  • The interaction limit was found to be less than 0.00001 times the strength of normal photon interactions.

• Greater precision:

  • This limit is significantly more stringent than any other laboratory-based LSW experiment in the same mass range to date.