When ultrafast electrons are deflected, they emit light—synchrotron radiation. This light, while brilliant, is longitudinally incoherent and consists of a broad spectrum of wavelengths, making it less efficient for certain types of materials research. Monochromators have been used to select individual wavelengths from this spectrum, but at the cost of reducing radiant power significantly. Physicist Alexander Chao and his team discovered a way to overcome this limitation in 2010 by creating monochromatic, coherent light with outputs of several kilowatts, akin to high-power lasers.
Chao’s research revealed that by shortening the electron bunches orbiting in a storage ring to be smaller than the wavelength of the emitted light, the radiation becomes coherent and significantly more powerful. This breakthrough led to the potential for a new type of radiation source with unprecedented capabilities for materials research. Arnold Kruschinski, a Ph.D. student at HZB and lead author of a related study, emphasized how crucial this realization was in advancing the field of synchrotron radiation research.
The Steady-State Micro-Bunching project, spearheaded by Chinese theorist Xiujie Deng, focuses on utilizing specific settings for low-alpha rings in circular accelerators to generate short particle bunches only one micrometer in length. A recent experiment conducted by a collaborative team from HZB, Tsinghua University, and PTB demonstrated the viability of this approach by utilizing the Metrology Light Source in Adlershof. This pivotal experiment validated Deng’s theory and showcased the potential for a new era of coherent light sources in materials research.
While the success of the SSMB project marks a significant milestone in the journey towards coherent light sources, HZB project manager Jörg Feikes cautions that further development and refinement are necessary before widespread implementation. Drawing parallels to the evolution of free-electron lasers, Feikes highlights the lengthy and meticulous process involved in transitioning from initial experiments to fully operational, large-scale accelerators. This long-term perspective underscores the complexity and potential impact of harnessing coherent light for advanced materials research.
The exploration of coherent light sources represents a transformative shift in the realm of materials research. By harnessing the power of ultrafast electrons and optimizing their behavior within storage rings, researchers are unlocking new possibilities for studying and manipulating matter at the atomic and molecular levels. As advancements continue to unfold, the future holds immense promise for the intersection of physics, engineering, and materials science in the quest for groundbreaking discoveries.
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