Tuesday, September 18, 2012

SLAC Researchers Explore Terahertz Realm





SLAC's Alan Fisher leads a talk, "Presentation and Future Concepts for Intense Terahertz from SLAC Accelerators," during the Sept. 5-6 "Frontiers of THz Science"... (Photo by Matt Beardsley) September 18, 2012
From detecting concealed weapons and other security threats to manipulating and studying molecules and nanomaterials, potential applications for terahertz (THz) radiation are varied and growing, noted scientists who participated in this month's "Frontiers of THz Science" workshop at SLAC.
The international workshop, held Sept. 5 and 6, drew 130 attendees from as far away as China and Germany for discussions about the latest techniques to generate and use THz radiation, which sits in a largely untapped band of the electromagnetic spectrum between far-infrared and microwave radiation.
In final sessions at the conference, scientists considered the most promising areas for discovery and the types of terahertz research that could best benefit from use of SLAC facilities and expertise.
There was general consensus that experiments using powerful sources of X-ray radiation, including SLAC’s Stanford Synchrotron Radiation Lightsource and Linac Coherent Light Source, could provide insights into how terahertz radiation can drive and control biomechanical, chemical and electrical processes, for example.
Mark Sherwin, a physicist at the University of California, Santa Barbara, who served as a co-chairman for a 2004 conference titled "Opportunities in THz science," said terahertz research since that time has become "a very broad worldwide community." 
Sherwin said SLAC, with its powerful X-ray facilities, is well-positioned to assist this community in exploring some of the previously unreachable areas of terahertz science. 
Because terahertz research is still a fledgling field, "There's a very problem-rich environment" to delve into, Sherwin told SLAC organizers of the 2012 workshop.
Andrea Markelz, a physicist at New York's University at Buffalo, suggested that using terahertz radiation to introduce structural changes, such as controlling a biomolecular function to study its various states, is one promising area of research. 
In a summary presentation, Aaron Lindenberg of SLAC and Stanford concluded that experiments can use terahertz radiation to study a wide range of condensed-matter physics and materials-science problems, from phase transitions to high efficiency, non-contact measurements of electrical properties of nanomaterials. 
And SLAC’s Kelly Gaffney said experiments using terahertz radiation as a "pump" to excite changes in sample materials, followed by X-rays to probe those changes, are perhaps the "most important opportunity to pursue." 
Also, he said, "If terahertz is an important spectral range to measure the properties of materials, it should be an important range to manipulate those properties and how they change over time."
Conference organizers, including SLAC's Chief Scientist Z-X Shen, Norbert Holtkamp, director of the Accelerator Directorate, and Jo Stöhr, LCLS director, will prepare a report based on the discussions and conclusions at the workshop. The report will chart progress in terahertz research since the 2004 conference and plot a course for the future of terahertz science.

Shen will give a summary of this workshop at the LCLS/SSRL Annual Users' Meeting on Oct. 5. The deadline for registration and poster abstracts for LCLS/SSRL 2012 has been extended until Sept. 27.

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