Our Light

 

What is a synchrotron?

A synchrotron is a particle accelerator—our particles are electrons—that sends them circulating through a vacuum at nearly the speed of light. When their direction of travel is changed by a magnet (this is an acceleration) they emit light with a broad range of energies. This light goes from the infrared, through visible light, to ultraviolet, to the highest energy, which is X-rays.

Why do we need synchrotron light?

We can use the light of all different energies to characterize just about anything of scientific interest, including nanomaterials, environmental contaminants, critical minerals, even artwork. When we shine synchrotron radiation on something, we measure what light gets through and which direction it goes, and what new light is emitted from our sample. We also study the electrons and atoms that are emitted.

Who at LSU uses synchrotron light?

Faculty and students from across the flagship and almost two dozen departments use our light.

How do we get the beam of electrons into the ring?

The electrons are emitted from a hot filament and accelerated by a linear accelerator underneath the synchrotron.

How do we steer electrons?

Moving electrons travel a straight path unless they enter a magnetic field. This magnetic field can come from a permanent magnet or from an electromagnet that uses electric current to generate much larger fields, such as our dipole magnets.

How do we get the beam to go around in a circle?

When our electron beam enters into a dipole magnet field, two things happen. The magnet bends the path of the beam and, when electron are going at relativistic speeds (meaning, near the speed of light), causes the electrons to emit synchrotron radiation. We have eight dipole magnets, and each magnet turns the beam by 45 degrees. Simple multiplication (8 x 45) takes us full circle, 360 degrees.

If the electrons emit synchrotron light, why don’t they slow down?

They do. In order to keep them going, the storage ring has a radio frequency (RF) cavity that resupplies the energy lost in emitting synchrotron radiation.

What are the insertion devices?

We have two insertion devices, a wavelength shifter and a multipole wiggler. Both have superconducting magnets that provide higher energy X-rays and more synchrotron light.

What about safety?

Our accelerator is tucked safely behind a concrete and lead shield wall to protect all users of our facility from the X-rays. All users of our facility must undergo radiation safety training followed by a radiation safety test. Both are required before users can request beamtime.

How do you control the X-rays?

We extract the X-rays with beamlines that bring the synchrotron light to the researchers’ end-stations. These beamlines include a monochromator that selects the specific X-ray energy used by the scientist in their measurements. Each end-station is different, allowing for a wide range of research applications.