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How Vacuum Impacts the World's Largest & Most Powerful Particle Collider

By Joshua Miller
CERN

Situated deep beneath the Franco-Swiss border is a massive ring of metal and magnets: the Large Hadron Collider (LHC), the world's largest and most powerful particle collider.

Housed 100 meters underground at CERN (Conseil Européen pour la Recherche Nucléaire), the LHC is made up of a 27-kilometer ring of superconducting magnets. The collider’s accelerator allows two extremely high-energy particle beams to travel in opposite directions at speeds close to that of light before colliding with one another.


Vacuums Inside the Large Hadron Collider

A successful and powerful collision requires that ultra-high vacuum levels be maintained while the LHC is being operated. The following is an overview of the primary vacuum systems employed in the collider.

Beam Vacuum

A collision involves two particles that are "beamed" at high speeds in opposite directions, each particle in its own tube. These two tubes must be kept at extremely high vacuum levels to maximize the duration of the beam and maintain low pressure for the experiments. This is achieved by what is known as the beam vacuum.

Two pumping mechanisms are used to achieve this:

  • Cryogenic pumping: residual gas molecules are physically adsorbed into the cold bore surface at a temperature of 1.9 K
  • Non-evaporable getter (NEG) pumping: residual gas molecules are chemically adsorbed onto the surface of the beam pipes

Insulation Vacuum

The LHC's superconducting magnets are cooled with liquid helium to a temperature of 1.9 K (approx. -271 °C). The LHC employs a powerful vacuum to thermally insulate the magnets and consequently maintain the extremely low temperatures needed for a successful collision.

UHV CTA

Pumps Inside the Large Hadron Collider

The primary pump technologies employed within the collider are:

  • Ion pumps: a type of vacuum pump that operates by sputtering a metal getter
  • Turbomolecular pumps: a pump that operates on the principle that gas molecules can be made to undergo repeated collisions with a moving solid surface to attain momentum in the desired direction

Both of these pump systems must have the ability to tolerate high radiation and magnetic field levels.

Potential Maintenance Challenges

A major challenge faced while assembling the LHC was leak detection. Leak tightness must be ensured to reliably operate large vacuum systems. A leak can cause base pressure to rise above or fall below the required levels, resulting in the need for significant — and expensive — re-working.

Future Upgrades and the High Luminosity Large Hadron Collider

The LHC is currently being upgraded and its successor will be known as the High Luminosity Large Hadron Collider (HL-LHC). The upgrades began in June 2018 and are set to be completed in 2027. The changes are expected to increase the discovery range of new particles by around 20-30% over the current LHC and also extend the LHC's lifetime to 2040.

Is a Perfect Vacuum System Possible?

A perfect vacuum is essentially a region in space that has no particles. In reality, achieving this is impossible — just as achieving absolute zero temperature is impossible. Even the Large Hadron Collider operates at a pressure of 10-10 to 10-11 mbar, which means that there are still about 200,000 molecules per cubic centimeter.

Tags: R&D, Ultra High Vacuum

About Joshua Miller

Joshua Miller
As a vacuum technologist/engineer and entrepreneur, Joshua enjoys applying innovative solutions to diverse customer applications and markets. From the vision at a corporate level, to the technical application and installation of his products, he ensures that customer satisfaction is always the highest priority through customer partnerships. Whether it be through direct communication or through support of the industry challenging online communications, you can be sure to find a like mind friend whose always searching for was to help you drive your business forward. In his free time Joshua is an strong believer in that “Golf is a good walk, spoiled” and spend his summer months hot air ballooning with his family.

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