In order to satisfy the needs of basic research as well as industry, there is currently great interest in coherent, ultrashort-pulse-duration and high-power light sources. In basic research, large (kilometer) x-ray synchrotrons have met some of these needs, but they are extremely expensive, costing hundreds of millions of dollars. Thus, there is a need for an affordable and compact source, having a small enough footprint to fit in a university or industrial research laboratory or factory setting. Additionally, light with shorter pulse durations than are currently produced by synchrotrons are required in order to provide ultrafast time-resolution of transient physical or chemical processes. Perhaps the most important applications of advanced x-ray sources are EUV lithography and protein structural analysis.
University of Michigan researchers have developed an apparatus to generate a beam of coherent light that satisfies all of requirements for uses in lithography and protein analysis, among other applications. It is based on the Thomson scattering of a high-intensity laser pulse with an electron beam that is accelerated by a synchronized laser pulse. In one aspect, a laser-accelerated electron gun is coupled with an electromagnetic wiggler or undulator. A further refinement is the operation of the device in the collective regime by means of the free-electron laser (FEL) mechanism, which increases the coherence of the light as well as increases its power. In order to operate in this collective regime, the invention provides several means by which the output of the laser-driven electron accelerator can be made relatively monoenergetic.
Applications and Advantages
- X-ray and EUV lithography
- Protein structural analysis
- Plasma diagnostics
- X-ray diffraction, crack analysis, non-destructive testing, surface science and ultrafast science.
- Low cost
- Short oulsed, tunable and adjustable degree of coherence