Low-power terahertz rays have proven applications in both security devices and medical imaging, but now the effects of Europe’s most intense terahertz light source on human cells is being researched with the hope of triggering advances in cancer diagnosis, including melanomas and esophageal cancers. In conjunction with scientists from the University of Liverpool, the research is being carried out at the Science and Technology Facilities Council's (STFC) Daresbury Laboratory, home to the ALICE accelerator, an R&D prototype for the next generation of accelerator-based light sources. Human stem cell stained to show the nucleus (blue) and internal structure (green). (Image: Dr. Rachel Williams and professor David Edgar, University of Liverpool) Terahertz rays lie between microwaves and infrared light in the electromagnetic spectrum. Terahertz light already is being used to detect hidden explosives, concealed weapons and drugs. Unlike traditional x-rays, terahertz radiation is considered intrinsically safe, in that it is nondestructive and noninvasive to human cells. However, scientists do not yet know what the safe upper limits for human exposure to this radiation are. A deeper understanding of the rays' impact on living tissue will enable a new generation of medical and security imaging devices to be developed and used safely. "Like radio waves and visible light, terahertz rays are not expected to damage tissue like x-rays do," said Peter Weightman, professor and principal investigator from the University of Liverpool. "Our preliminary research at STFC Daresbury Laboratory has indicated that, at low powers, human cells appear to be unaffected by terahertz rays. However, the research carried out in this unique facility is the only way of establishing the safe limits of human exposure to terahertz radiation at high powers and what effect repeated low-level exposure may or may not have on our bodies. "The work will give us invaluable insight into the mechanisms of biological organization and enable us to test a controversial theory of the mechanism by which biological systems organize themselves. Low-power terahertz instruments are already used to analyze tissue removed in surgery because cancerous and healthy tissue respond differently to terahertz radiation. The research on ALICE will enable us to greatly improve these procedures and eventually lead to the development of improved low-cost instruments for cancer diagnosis, although it is expected to be several years before these developments are realized." Professor Peter Weightman. (Image: University of Liverpool) "With ALICE, we have an opportunity to irradiate living cells in a way that has never been done before, combining a high-power source with a tissue culture facility," said Dr. Mark Surman, a research scientist at STFC. "During professor Weightman's research, we expect to see about 70 kW of peak power in short pulses repeated tens of thousands of times every second. This means that the peak power will be thousands of times higher than other laboratory sources. Until now, ultrahigh terahertz power sources have not been available to carry out this kind of research, so it is a major step forward that these trials on tiny samples of human tissue can now be carried out at ALICE." ALICE is based upon an unusual mode of operation for accelerators, known as energy recovery, where the energy used to create its high-energy beam is captured and reused after each circuit of the accelerator for further acceleration of fresh particles. This mode minimizes the power needed to accelerate the beams, which, at maximum level, would otherwise require a small power station to operate. ALICE is the first accelerator in Europe to operate in this way. ALICE accelerates to 26 million electron volts. Electrons are sent round the accelerator at 99.99 percent of the speed of light, and 99.9 percent of the power at the final accelerator stage is recovered, making the power sources for the acceleration drastically smaller and cheaper and, therefore, economically viable. The work is being carried out with funding from the Northwest Regional Development Agency and the Engineering and Physical Sciences Research Council (EPSRC). For more information, visit: www.stfc.ac.uk