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China Plans Enormous Particle Collider

The country is plotting a separate path to the Large Hadron Collider's successor

3 min read
Photo: Maximilien Brice/CERN

What comes after the Large Hadron Collider?

The main successor concept is the International Linear Collider (ILC), which would smash together electrons with a “center of mass energy” of up to 1 teraelectronvolt. It is currently in an advanced state of discussion between scientists mainly from American, European, and Japanese particle physics institutes. Though the collision energies would be but a fraction of those induced by the LHC, the proposed machine would be a "Higgs factory", performing experiments with large numbers of Higgs bosons, allowing a better understanding of the still enigmatic particle.  

But China may build it’s own successor system. Scientists there have reportedly completed the initial conceptual design for a much larger circular collider that would smash together protons and be housed in a tunnel twice the size of the LHC’s. Particles would ultimately collide with energies of up to 70 TeV—five times as great as those that produced Higgs particles in the LHC. They hope to complete the conceptual design by the end of 2016.

The Super Proton-Proton Collider or SPPC would be an upgraded version of the LHC, and planners at China's Institute of High Energy Physics aim at a completion date in 2040. However, the 54-km long tunnel would be dug out starting in 2020 and would house, in a first step, a much less powerful machine, the Circular Electron-Positron  Collider or CEPC, to be completed in 2025. The tunnel will later be upgraded to house the superconducting magnets of the 70 TeV SPPC.

Just like the ILC, the CEPC will investigate the Higgs particle. The initial phase, which is expected to go online in 2025, and will give electrons and positrons center of mass collision energy approaching 250 gigaelectronvolts. The choice of a circular machine instead of a linear one is  somewhat problematic because electrons and positrons start radiating synchrotron radiation when steered into a circular path. “The synchrotron radiation goes with the fourth power of the energy, and there is a huge scaling loss,” says Lyn Evans, director of the International Linear Collider Organization. “They will be pushed to get to the next level, which will be the top quark, which needs 350 GeV in the center of mass, and that would be an exttreme limit for them,” says Evans.

However, CEPC project director Xinchou Lou says the synchrotron losses will be manageable, because the tunnel will be so large that its magnets will have to pull very little on the electrons and positrons to steer them into a circle. 

According to Evans, the choice of a circular electron-positron collider could be justified because of the long term plans for the 70 TeV proton-proton collider: 

They will build this machine, which will be fairly cheap and the technology is well known, and do the physics with [positrons] and [electrons], but in a second step they will use the same tunnel to make a proton-proton collider, and then you can go to very high energies.  However, the technology will be difficult.  You will need very high field superconducting magnets, and a lot more R&D.

Despite China’s big plans, there’s a chance it will join the ILC project.  “Scientifically, we have support from China, but politically this is another question,” says Evan. “Why would the Chinese government join in in a collaboration for a linear collider while at the same time building a circular machine? That is still a question.”  

Asked the same question, CEPC’s Lou is more positive. “Yes, we plan to collaborate,” he says. “The CEPC and the ILC are complementary to each other and together they can bring the measurement of the Higgs properties to an unprecedented precision.”

This post was updated on 8 December to correct the energy figure for the Super Proton-Proton Collider.

The Conversation (0)
Illustration showing an astronaut performing mechanical repairs to a satellite uses two extra mechanical arms that project from a backpack.

Extra limbs, controlled by wearable electrode patches that read and interpret neural signals from the user, could have innumerable uses, such as assisting on spacewalk missions to repair satellites.

Chris Philpot

What could you do with an extra limb? Consider a surgeon performing a delicate operation, one that needs her expertise and steady hands—all three of them. As her two biological hands manipulate surgical instruments, a third robotic limb that’s attached to her torso plays a supporting role. Or picture a construction worker who is thankful for his extra robotic hand as it braces the heavy beam he’s fastening into place with his other two hands. Imagine wearing an exoskeleton that would let you handle multiple objects simultaneously, like Spiderman’s Dr. Octopus. Or contemplate the out-there music a composer could write for a pianist who has 12 fingers to spread across the keyboard.

Such scenarios may seem like science fiction, but recent progress in robotics and neuroscience makes extra robotic limbs conceivable with today’s technology. Our research groups at Imperial College London and the University of Freiburg, in Germany, together with partners in the European project NIMA, are now working to figure out whether such augmentation can be realized in practice to extend human abilities. The main questions we’re tackling involve both neuroscience and neurotechnology: Is the human brain capable of controlling additional body parts as effectively as it controls biological parts? And if so, what neural signals can be used for this control?

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