Cornell University, thanks to a major grant from the NSF, is moving forward on building an ultra powerful, ultra fast x-ray machine that promises to capture biomolecular processes happening in full motion video. Using technology developed at the university, called energy-recovery linac (ERL), the plan is to build a mile long linear accelerator on which multiple research projects can operate at the same time.
From the press release:
Moving beyond traditional X-ray crystallography systems–where the arrangement of atoms in crystalline material is revealed by analyzing the way X-ray beams are scattered from electrons in the crystal–the energy-recovery linac offers significant advantages. For one, materials subjected to ultrabright X-ray pulses need not be in crystalline form. And the tightly focused beam allows studies at much smaller scales.
As envisioned and invented by experimental physicists at Cornell, energy-recovery linear accelerators produce high-energy, pulsed X-ray beams by injecting electrons into the electromagnetic fields of a series of superconducting microwave cavities in a linear accelerator. Then, in a return loop, the electron beam is turned into X-rays by passing through undulators, which force the beam to oscillate to the right and left of its mean path with horseshoe magnets of alternating orientations. The pulsed X-rays are now ready for studies in multiple stations at the facility.
While the ERL X-ray beam loses about 0.04 percent of its energy during oscillation, 99.98 percent of its remaining energy is recaptured into the electromagnetic fields when the electrons are re-injected into the linac for deceleration–providing energy to accelerate subsequent bunches of electrons.
Compared to a traditional storage-ring X-ray source, such as CHESS, which recycles electrons billions of times but suffers from a compromised beam size, ERLs send each bunch of electrons through the undulators only once. Again and again, ERLs recover and reuse energy that accelerates electron bunches, while maintaining very small beam size–the key to the brilliance needed to study intimate details at the nano-scale.