Shine a powerful laser beam on a small piece of metal, plastic, or a liquid and a burst of intense high-energy ionizing radiation is emitted.

Thanks to a grant of £5m from the EPSRC, researchers at Queen's University Belfast, Central Laser and Central Microstructure Facilities at Rutherford Appleton Laboratory, Imperial College London, and the Universities of Surrey, Birmingham, Paisley, Strathclyde and Southampton along with the National Physical Laboratory aim to exploit this property of laser-irradiated matter to help them develop new radiation sources with such diverse medical, industrial and security applications as the treatment of cancers, improved semiconductor production and the rapid detection of hidden explosives.

The radiation that is emitted is in the form of beams of ions, protons, neutrons, electrons, gamma and X-rays, depending on the energy and duration of the laser and the material being irradiated. An ultra short laser pulse can generate a burst of high energy particles and radiation which lasts only picoseconds (millionths of a millionth of a second). Moreover, if the material is extremely thin - just a few millionths of a millimetre thick - it is possible to control other properties of the bursts, such as their energy content or energy spectrum.

Of the possible radiation beams that can be produced, principal investigator Dr Marco Borghesi (Queen’s University Belfast) and his colleagues have identified protons, ions, and gamma rays specifically as the products of laser-energised sources with the greatest potential. The applications for such ion beams, they envisage lie in many areas.

For instance, laser-energised bursts of proton and light ions have the potential to substantially reduce the high equipment costs of proton and ion radiotherapy of cancer, which have so far precluded their routine use in the treatment of cancers in the UK. Compared to the use of X-rays, ion beam therapy promises more effective cancer control and improved quality of life in cancer patients. This is because the particle beam produces a pronounced dose peak within the cancer, with little or no dose beyond. In this way the radiation exposure of other tissues and organs is only a half to a tenth of that which occurs with conventional X-ray based radiotherapy.

Compact laser-energised sources of ions could potentially be used in all UK Cancer Centres, where linear accelerators are presently used to produce X-ray beams for cancer treatment. Proton and ion beams could also be used in research into the effects of cosmic ray exposure. People are currently exposed to cosmic rays during air travel and in space.

Other applications lie in science and industry. Firing a flash of ions at an object can reveal information about its internal structure, and can be useful in engineering diagnostics and the quality control of semiconductor electronics devices. Flash radiography using these beams can also be used to test satellites destined for earth orbit for resilience to high levels of cosmic rays, or reveal faults in rapidly moving components such as turbine blades.

In fundamental science, the new approach has great potential for the versatile production of intense, synchronised beams from a robust and compact source. Such a source could undertake many of the experiments that the enormous and expensive national synchrotron particle accelerators currently do, but at much lower cost and on a laboratory bench-top scale. This could allow physical scientists to carry out so-called pump-probe experiments on an almost routine basis allowing them to get to the heart of matter, materials, and molecules in biology, nanotechnology, and chemistry.

Additionally, radiation beams could have applications in security. A penetrating beam could be used in rapid imaging detection of hidden materials and explosives in large packages and freight containers using 3D gamma-ray mapping to give better resolution and clarity than currently possible.

According to Borghesi and his colleagues, the project aims to develop the relevant technology for such high-flux, high-repetition beams as well as to devise the diagnostic tests for characterising the beams. At the same time, they aim to achieve a high standard of output beam quality that will be necessary to make any of the above techniques viable. They suggest that this can be achieved through a combination of innovative developments in target production and delivery for generating the beams, detector technology, and beam property optimization and control.

Success will provide ultra-short synchronised bursts of protons, ions and gamma rays for potential use in research, engineering, and medicine. The researchers add that the devices should also be adaptable to delivering X-ray, electron, and neutron beams for even more diverse applications. For example, neutron beams in combination with 3 D gamma-ray mapping could be used to activate materials to rapidly identify suspect materials.

Source: http://www.innovations-report.de/[..]

Story posted: 15th March 2007.