Scientists behind the world's largest atom smasher have laid out a nearly $40 billion vision to build a new one about four times larger under the Swiss-French border, in the hopes of unlocking even more secrets of the universe.

Officials at CERN hope to build a "Future Circular Collider" (FCC) in a circular tunnel stretching 100 kilometres near Geneva that could start operating in 2040 and take over from the existing 27km Large Hadron Collider (LHC).

Photo: CERN's concept for the Future Circular Collider dwarfs the existing LHC. (Supplied: CERN)

Colliders, also known as particle accelerators, send two high-energy particle beams down tubes in opposite directions at close to the speed of light before smashing the beams together, resulting in the creation of new particles that help explain physics and the make-up of the universe.

CERN has released a concept paper for the FCC that has been five years in the making, in the hopes that the European research agency's 22 member states will make a decision in the next few years about whether to proceed with the project.

Why are they already planning a new one?

It may not seem like it, but it's already been more than 10 years since the Large Hadron Collider was completed and first turned on.

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In that time it has conducted many experiments and made important discoveries — including its best-known work of helping confirm the new subatomic Higgs boson in 2012.

CERN says it is announcing the ambitious FCC project now, despite the LHC still enjoying successes, because the large scale and timeframe of the project mean the window for planning for the future is narrow.

A timeframe of 20 years to design, construct and begin operating a new collider is "appropriate", CERN said on its website.

For comparison, the LHC began operation in 2008 but was first conceived in the 1980s.

"The goal is to ensure the seamless continuation of the world's particle physics program after the LHC era," CERN said.

Photo: The proposed Future Circular Collider would take decades to design and build. (Supplied: CERN)

What can a bigger collider achieve?

The particle collisions in the proposed FCC would be a lot more powerful than what can currently be achieved — reaching 100 tera electron volts of energy compared to 17 TeV in the current collider.

What is the Higgs boson?

• The Higgs boson is a sub-atomic particle that scientists say confers mass.
• It is conceived as existing in an invisible field that stretches across the Universe known as the Higgs Field.
• Higgs bosons "stick" to fundamental particles of matter as they move through the field, dragging on them.
• Some of these particles interact more with the Higgs than others and thus have greater mass. But particles of light, also called photons, are impervious to it and have no mass.
• The Higgs particle was verified in experiments conducted in the Large Hadron particle accelerator (pictured) at CERN.
• Watch the Higgs boson explained in 30 seconds here.

This would open up new avenues for research and new particles that could be created and observed in the collider.

It took the LHC years to create and detect a Higgs boson — a particle that helps confirm the standard model of physics and explain why matter has mass — but the new collider would allow the "precise studies of how a Higgs particle interacts with another Higgs particle", CERN said.

It would be a "Higgs factory" of sorts, CERN said.

"The Higgs boson could be a door into new physics. Detailed studies of its properties are therefore a priority for any future high-energy physics accelerator," the agency said.

"In addition, experimental evidence requires physics beyond the standard model to account for observations such as dark matter and the domination of matter over antimatter.

"The search for new physics, for which a future circular collider would have a vast discovery potential, is therefore of paramount importance to making significant progress in our understanding of the universe."

CERN director-general Fabiola Gianotti called the concept paper "a remarkable achievement" that could help boost understanding of fundamental physics and advance technologies.

It comes with a huge price tag

Photo: The Future Circular Collider (red) is significantly bigger than the Large Hadron Collider (blue) and much more expensive. (Supplied: CERN)

The first step of the FCC would be to build an electron-positron collider at an estimated cost of 9 billion euros ($14.2 billion) — with 5 billion euros of that going towards actually building the 100km tunnel.

A second phase would involve a superconducting proton machine in the same 100km tunnel, at a cost of about 15 billion euros ($23.7 billion). That machine could start operation in the late 2050s.

Together the two phases would contribute to a hefty price tag of about $38 billion — significantly more than the $6.4 billion construction cost of the LHC.

The project is the combined work of 1,500 contributors across 150 universities, research institutions and industrial partners and is yet to be approved.

CERN will spend the next two years updating the physics community on its plans and the agency's 22 member states will have to vote on the proposal.