A key enabling technology of LIGA is the synchrotron, capable of emitting high-power, highly collimated X-rays. This high collimation permits relatively large distances between the mask and the substrate without the penumbral blurring that occurs from other X-ray sources. In the electron storage ring or synchrotron, a magnetic field constrains electrons to follow a circular path and the radial acceleration of the electrons causes electromagnetic radiation to be emitted forward. The radiation is thus strongly collimated in the forward direction and can be assumed to be parallel for lithographic purposes. Because of the much higher flux of usable collimated X-rays, shorter exposure times become possible. Photon energies for a LIGA exposure are approximately distributed between 2.5 and .