ALICE collides beams to achieve a UK X-ray first

Physicists working on an R&D prototype for the next generation of accelerator-based light sources ALICE (Accelerators and Lasers in Combined Experiments) at STFC Daresbury Laboratory are celebrating after successfully colliding electrons and a powerful laser beam to produce short-pulsed X-rays.

This is the first time this has ever been done in the UK and is the first time that the concept of using an accelerator and laser source together has been demonstrated on ALICE, opening up the way to more cutting-edge physics developments on the country’s only such testbed particle accelerator.

The project was funded jointly by the Northwest Regional Development Agency’s North West Science Fund and STFC.

Professor Keith Mason, Chief Executive of STFC added: “All of those involved in this project have worked tremendously hard to demonstrate this capability. The successful interaction of accelerated electron beams with laser pulses takes us one step closer to creating the ultimate stroboscopic light source – something that may be capable of making real-time movies of chemical reactions at the atomic level and contribute greatly to research carried out in the fields of drug development, materials science and 'green' technologies.

“Reaching this milestone has confirmed the UK’s ability to build, develop and demonstrate its scientific skills and techniques in this field and given us some exciting prospects for the future of next generation light sources and particle colliders."

The Compton Back Scattering project saw a team of scientists from the Science and Technology Facilities Council (STFC), the Cockcroft Institute, University of Manchester and the Max Born Institute, accelerate bunches of electrons to near the speed of light and then collide them head-on into a high energy, short-pulse multi-terawatt laser photon beam focusing on a spot about the size of the width of a human hair (100 microns). This technique results in the conversion of optical laser light to X-rays. The electrons transfer energy to the laser beam, causing it to bounce back and turn visible light into a source of extremely short pulse high X-rays.

Susan Smith, Head of the ASTeC Accelerator Physics Group at STFC Daresbury Laboratory explains: “Producing these X-rays required absolute and simultaneous control of both a powerful laser beam and electrons moving at almost the speed of light. We’re delighted to have achieved this important milestone and demonstrated our capability to combine successfully two separate accelerator and laser beam sources. The way is now clear for us to address the further challenges and innovations necessary to develop the next generation of light sources for science.”

Professor Elaine Seddon of Manchester University/the Cockcroft Institute and Principal Investigator on the grant funding this work said: "Overlapping laser and electron pulses that are only microns in size and less than a millionth of a millionth of a second long is a truly world-class achievement. Though it is early days yet, we have a tremendous team with very strong international links and we’re really excited about the potential of this source as a tool for spectroscopic measurements involving atomic rearrangements.”

George Baxter, the NWDA’s Director of Science and Innovation said: "The Daresbury team are to be congratulated in achieving this significant milestone and demonstrating once again the world-leading research being undertaken at Daresbury."

The next stage in ALICE’s development will see scientists at Daresbury work on integrating and demonstrating an incredibly bright source of infra-red radiation to be produced by the first infra-red free electron laser to operate in the UK, another vital step towards world leading source capability.

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Notes

The Compton effect was observed by Arthur Holly Compton in 1923 and further verified by his graduate student Y. H. Woo in the years following. Compton earned the 1927 Nobel Prize in Physics for the discovery that provided further verification of the quantum theory of light.

About ALICE

ALICE is an acronym standing for Accelerators and Lasers In Combined Experiments. Financed by STFC with additional funding from the North West Development Agency, the project is designed to investigate next generation particle accelerator beam technology and also to produce light from both accelerator and advanced lasers that can be used simultaneously in cutting edge demonstration experiments.

ALICE’s design 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 re-used after each circuit of the accelerator for further acceleration of fresh particles. This mode minimises 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 is designed to accelerate beams to 35 million electron volts, electrons will be sent round the accelerator at 99.99% of the speed of light and 99.9% of the power at the final accelerator stage will be recovered, making the power sources for the acceleration drastically smaller and cheaper and therefore economically viable.

The technologies and skills under development on ALICE are needed for the next generation of advanced light sources, such as the New Light Source project. Such sources will include capability of making real-time movies of chemical reactions at the atomic level. This capability will have a major impact in research carried out in the fields of drug development, materials science for energy applications and environmentally friendly technologies.

North West Science Fund

This fund is essential in driving forward the region's science and innovation agenda. It specifically targets support at the area between 'blue skies' research and company R&D, where it is often difficult to attract traditional sources of funding. The NWSF will not only play a pivotal role in ensuring the region remains a global leader in scientific innovation, but will also draw on the expertise of our world-class universities to help create scientific developments that will enthuse and educate the next generation of scientists. Six projects have been successful in receiving awards through this fund.

Images available

Image 1 - ALICE at STFC Daresbury Laboratory

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