Particle collider edges forward

The ILC will address fundamental questions in nature

A key decision on the International Linear Collider, one of the grand scientific projects of the 21st Century, has been taken in China.

Physicists told a Beijing conference that the multi-billion-dollar project should use superconducting technology to create its particle collisions.

These would be high-energy impacts inside a 30km-long laboratory.

The experiments should give scientists a deeper understanding of the materials used to construct the Universe.

At the moment, the so-called Standard Model of particles and their interactions provides only a partial picture of the nature of the normal matter we see around us.

Researchers know, however, the cosmos is dominated by other material which is invisible to current detection technologies.

New light

Europe is currently building a Large Hadron Collider (LHC) at its Cern laboratory in Geneva, Switzerland, and this is expected to open up a new research frontier when it becomes operational in 2007.

But scientists believe they will need the ILC to carry forward their studies and expand any discoveries made at the LHC.

The ILC is a giant undertaking that could cost upwards of $5bn. It would accelerate electrons and positrons (the antimatter version of the electron) down two 15-km-long pipes and smash them together at a central point.

In the debris, scientists would hope to see new particles flash into and out of view.

For example, the collider could reveal details about the long sought Higgs boson, the particle said to explain why all others have mass.

It may also shed light on the neutralino, a particle hypothesised to interact only weakly with everything around it but which may account for much of the "dark matter" that pervades the Universe.

Now, after 10 years of investigation and development by several teams, the group charged with pushing the ILC forward has set a major technical parameter for the project.

More efficient

Making its announcement at the International Conference on High Energy Physics, the International Committee for Future Accelerators said the collider should employ niobium superconducting technology in the system it uses to accelerate particles.

This technology, developed by a collaboration centred on the DESY lab in Germany, would operate at -271C, just above absolute zero.

Grand undertaking: The LHC becomes operational in 2007

It has been chosen in preference to a rival "warm" copper technology developed in the US and Japan.

Professor George Kalmus, from the UK's Rutherford Appleton Laboratory, is a member of the International Technology Recommendation Panel, which had suggested the ILC adopt the "cold" approach.

"The transfer of the energy from the power source into the electron beam is very highly efficient in the cold technology.

"In the warm technology, there is a considerable electrical loss and you have to take that out. So, one of the consequences is that you use a lot more power for the warm than for the cold."

No decision has been made yet about where to site the ILC but the US, Japan and Germany would appear to be the leading candidates. However, wherever it is constructed, it will be a challenge.

The tunnels down which the particles race will be underground and that will be very expensive.

Further forward

As with other projects on this scale, such as the space station and the international fusion reactor known as Iter, the ILC can only be built by a global consortium.

And, as with those projects, getting a consensus to move forward can sometimes be difficult.

Michael Witherell, director of US Fermi National Accelerator Laboratory, where scientists have worked on both warm and cold technologies, said: "With the technology decision behind us, the particle physics community can now begin work on a global design for a linear collider.

"At the same time, science funding agencies from nations in Europe and Asia, along with the US and others, must reach agreement on the mechanisms for funding and operating a truly global accelerator somewhere in the world.

"There are many steps ahead of us before an international linear collider becomes a reality, but today's announcement of the technology choice provides an important focus."