A joint Fermilab/SLAC publication

LHC filled with liquid helium

12/17/14

The Large Hadron Collider is now cooled to nearly its operational temperature.

Photo of LHC cool
Maximilien Brice, CERN

The Large Hadron Collider isn’t just a cool particle accelerator. It's the coldest.

Last week the cryogenics team at CERN finished filling the eight curved sections of the LHC with liquid helium. The LHC ring is now cooled to below 4 kelvin (minus 452 degrees Fahrenheit).

This cool-down is an important milestone in preparing the LHC for its spring 2015 restart, after which physicists plan to use it to produce the highest-energy particle collisions ever achieved on Earth.

“We are delighted that the LHC is now cold again,” says Beate Heinemann, the deputy leader of the ATLAS experiment and a physicist with the University of California, Berkeley, and Lawrence Berkeley National Laboratory. “We are getting very excited about the high-energy run starting in spring next year, which will open the possibility of finding new particles which were just out of reach.”

The LHC uses more than 1000 superconducting dipole magnets to bend high-energy particles around its circumference. These superconducting magnets are made from a special material that, when cooled close to absolute zero (minus 460 degrees Fahrenheit), can maintain a high electrical current with zero electrical resistance.

“These magnets have to produce an extremely strong magnetic field to bend the particles, which are moving at very close to the speed of light,” says Mike Lamont, the head of LHC operations. “The magnets are powered with high electrical currents whenever beam is circulating. Room-temperature electromagnets would be unable to support the currents required.”

To get the 16 miles of LHC magnets close to absolute zero, engineers slowly inject helium into a special cryogenic system surrounding the magnets and gradually reduce the temperature over the course of several months at a rate of one sector cooled per month. As the temperature drops, the helium becomes liquid and acts as a cold shell to keep the magnets at their operational temperature.

“Helium is a special element because it only becomes a liquid below 5 kelvin,” says Laurent Tavian, the group leader of the CERN cryogenics team. “It is also the only element which is not solid at very low temperature, and it is naturally inert—meaning we can easily store it and never have to worry about it becoming flammable.”

The first sector cool-down started in May 2014. Engineers first pre-cooled the helium using 9000 metric tons of liquid nitrogen. After the pre-cooling, engineers injected the helium into the accelerator.

“Filling the entire accelerator requires 130 metric tons of helium, which we received from our supplier at a rate of around one truckload every week,” Tavian says.

In January CERN engineers plan to have the entire accelerator cooled to its nominal operating temperature of 1.9 kelvin (minus 456 degrees Fahrenheit), colder than outer space.

 

LHC restart timeline

February 2015
LHC Magnets Cooled

The Large Hadron Collider is now cooled to nearly its operational temperature.

Info-Graphic by Sandbox Studio, Chicago
 

LHC filled with liquid helium

The Large Hadron Collider is now cooled to nearly its operational temperature.
Read more…
LHC Magnets Powered

A first set of superconducting magnets has passed the test and is ready for the Large Hadron Collider to restart in spring.

Info-Graphic by Sandbox Studio, Chicago
 

First LHC magnets prepped for restart

A first set of superconducting magnets has passed the test and is ready for the Large Hadron Collider to restart in spring. Read more…
LHC Experiments Ready

Engineers and technicians have begun to close experiments in preparation for the next run.

Info-Graphic by Sandbox Studio, Chicago
 

LHC experiments prep for restart

Engineers and technicians have begun to close experiments in preparation for the next run.
Read more…
March 2015
LHC accelerator ready

The Large Hadron Collider has overcome a technical hurdle and could restart as early as next week.

Info-Graphic by Sandbox Studio, Chicago
 

LHC restart back on track

The Large Hadron Collider has overcome a technical hurdle and could restart as early as next week. Read more…
April 2015
First beam seen at LHC

The Large Hadron Collider has circulated the first protons, ending a two-year shutdown.

Info-Graphic by Sandbox Studio, Chicago
 

LHC sees first beams

The Large Hadron Collider has circulated the first protons, ending a two-year shutdown. Read more…
energy record broken at LHC

The Large Hadron Collider accelerated protons to the fastest speed ever attained on Earth.

Info-Graphic by Sandbox Studio, Chicago
 

LHC breaks energy record

The Large Hadron Collider accelerated protons to the fastest speed ever attained on Earth.
Read more…
May 2015
Low-Energy Collisions seen at the LHC

LHC sees first low-energy collisions

Info-Graphic by Sandbox Studio, Chicago
 

LHC sees first low-energy collisions

The Large Hadron Collider is back in the business of colliding particles.
Read more…
record-energy collisions achieved at the LHC

The Large Hadron Collider broke its own record again in 13-trillion-electronvolt test collisions.

Info-Graphic by Sandbox Studio, Chicago
 

LHC achieves record-energy collisions

The Large Hadron Collider broke its own record again in 13-trillion-electronvolt test collisions.
Read more…
June 2015
LHC Collisions for Physics

Data collection has officially begun at the Large Hadron Collider.

Info-Graphic by Sandbox Studio, Chicago
 

LHC arrives at the next energy frontier

Data collection has officially begun at the Large Hadron Collider.
Read more…

 

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