The most powerful accelerator in the world is currently the proton accelerator LHC in Geneva. The LHC will take us on a voyage of discovery that will provide the first-ever insights into the uncharted territory of very high energies. The great riddles of the universe, however, will only be solvable with the help of a further precision machine – a linear accelerator in which electrons and positrons will be brought to collision at highest energies. DESY is playing a major role in the development of one such linear accelerator, the International Linear Collider ILC, which will complement the discoveries of the LHC.

Precision tool at highest energies

The global particle physics community agrees that the discoveries made using the Large Hadron Collider LHC, which is located at the research centre CERN in Geneva and is currently the world’s most powerful accelerator, will need to be complemented by an electron-positron accelerator. Thanks to its uniquely precise measurements, such an accelerator would reveal the secrets of the terascale – the energy realm of trillions of electronvolts (teraelectronvolts) in which the physicists expect to make decisive new discoveries – in exquisite detail. The International Linear Collider ILC, in which DESY is also strongly involved, is one such future-oriented project: an approximately 35-kilometre-long linear accelerator colliding electrons and positrons at energies of between 500 and 1000 billion electronvolts (gigaelectronvolts, GeV).

The ILC consists of two opposing linear accelerators in which electrons and their antiparticles rush toward one another at close to the speed of light. Superconducting resonators boost the particles to ever-higher energies, until they smash together with great force in the middle of the “racetrack”. The particle beams collide 14 000 times every second at record electron energies of 500 GeV. Each collision produces numerous new particles, which are recorded by two large detectors. The current baseline design has scope for an upgrade of the ILC to 50 kilometres in length and an energy of 1000 GeV in the second stage of the project.

In contrast to proton accelerators such as the LHC in Geneva, in which composite particles collide with one another, the collisions in the ILC will be between point-like electrons and their antiparticles, positrons, which are also point-like. They annihilate each other to become pure energy, from which new particles are created. Although the energies that can be reached in this way are lower than those attained in collisions involving protons, the results are much easier to interpret than the results from the LHC. This is because the initial conditions of the particle production in the ILC are precisely known and no “fragments” of the colliding particles remain. The ILC is thus a genuine precision machine that ideally complements the LHC proton accelerator, whose real job is to produce new particles in the first place.

Mysterious universe

In the recent past, experiments and observations have revealed a surprising gap in our knowledge. It turns out that we can only account for four per cent of the universe. Scientists believe that the remaining 96 per cent consists of mysterious dark matter and dark energy, revealing a universe far stranger and more diverse than they ever suspected.

Thanks to its high energies and unprecedented precision, the ILC will give physicists a new cosmic doorway to the secrets of the cosmos – a doorway beyond the reach of today’s facilities. Together the LHC and ILC could unlock some of the deepest mysteries of the universe. With the discoveries of the LHC pointing the way, the ILC could come up with the missing pieces of the puzzle – and provide answers to the century’s essential questions about the nature of matter, energy, space and time as well as dark matter, dark energy and the existence of extra dimensions.

DESY in pole position

The ILC is to be constructed and operated as a global project. Worldwide, there were several proposals for such a facility, which differed in their choice of accelerator technology. After a thorough assessment, the committee that represents particle physicists worldwide decided that the future linear accelerator will be realized using the superconducting TESLA technology developed by DESY and its international partners.

The same superconducting technology is also employed in the free-electron laser FLASH at DESY and the European XFEL X-ray laser, which is currently under construction in the Hamburg region – an outstanding example of the successful synergies provided by the multiple use of a completely new technology. In other words, DESY remains excellently qualified to continue playing a leading role in the development of superconducting accelerator technology.

At the same time, the DESY researchers are also involved in the development of further important components for the ILC accelerator – mainly as part of international projects such as the TESLA Technology Collaboration or EU projects. The DESY researchers are also making a major contribution to the design and development of the high-precision detectors that will record the particle collisions in the ILC.