On June 15, workers at CERN start modernizing its largest Synchrotron — the LHC. They aim to generate many more particle collisions and collect considerably more data about Higgs- and other particles.
Image: DW/F.Schmidt
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The European Center for Nuclear Research, CERN, is Europe's larges joint research facility. Here, particle physicists from 85 countries ranging from China to Latin America team up. The facility is located near Geneva. The physicists use huge particle accelerators to generate particle streams for all kinds of basic research projects.
The largest of the synchrotrons is the Large Hadron Collider (LHC) with a circumference of 27 kilometers (16.8 miles). Physicists deal with protons that eventually fall apart into the tiniest of elementary particles. It's here that the existence of the famous Higgs particle was demonstrated in 2012. And it's here where researchers want to find out what happened during the Big Bang, what our universe is made of and what the mysterious dark matter is.
The data center of CERN, which collects and processes all the data from those experiments is unique and connected to all the cooperating institutes and universities in the world. The worldwide web was invented here.
CERN is already a huge facility, and it is getting even bigger. Roughly €1 billion is the price tag on the next big modernization of the LHC over the coming years.
By 2020, the engineers want to upgrade the synchrotron in such a way that it produces considerably more particle collisions than before.
The project is dubbed "High Luminosity." Luminosity is a term from astronomy and means the total energy emitted by a star over a given time in the entire electromagnetic spectrum.
At the LHC, luminosity is roughly the same: It is emitted when particles collide and fall apart into smaller elementary particles. The energy that goes into the synchrotron only partly adds to that luminosity.
So far, the LHC reached collision energies of 13 tera electron volts (TeV). From 2020, the scientists hope to run the LHC with energies of 14 TeV. After modernization completes in 2025, the energy volumes may be even higher, probably reaching more than 16 TeV.
More important for luminosity than the sheer energy, however, is the number of collisions actually taking place, with proton rays crossing.
Engineers are thus implementing several technical improvements to increase the number of collisions, probably resulting in a tenfold increase in luminosity.
Two pipes with proton beams running in opposite direction. The beams crash into each other inside the detectorsImage: DW/F.Schmidt
More precise rays and rotating particle packages
One of these improvements includes upgrading the precision of the particle rays. If they meet in a smaller area, you get more particle collisions. Currently the ray measures 16 micrometers in the collision point. In the future, half of that diameter will be reached.
The luminosity will also increase by changing the shape of the particle packages inside the particle beam just before the collision. So called "crab cavities" — specially built resonators — will make the particle packages rotate. This results in a larger surface of the packages and a higher likeliness of protons actually colliding.
You could compare this to two thin arrows being shot at each other: As long as they face each other in a straight line, they are likely to miss each other. If both are turned sidewise they are likely to collide. And more collisions result in more generated elementary particles.
Theory of Everything
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For example, the researchers expect that the Hi-Lumi LHC will be able to generate as many as 15 million Higgs particles per year. In 2012, when the existence of this particle was first verified, the synchrotron only produced about 1.2 million Higgs particles.
Trying to understand the fabric of our universe
But the physicists are also looking for many other particles that may help them understand the fabric of our universe. While everybody is talking about Higgs particles, those are actually rather rare.
Currently, the LHC produces roughly 1 billion particle collisions per second. With high luminosity in place, it's supposed to be five times higher
The LHC must be able to handle this amount, and that requires a lot of work in the coming months. The engineers are installing new, more powerful superconducting electric magnets. And they completely reconfigure the four huge detectors of the LHC. Those detectors work like digital cameras. In order to handle high luminosity, the sensors must be more robust and be able to process collected data more quickly.
That also goes for the huge CERN data center, in which all the pictures from the collisions get stored like on the memory stick of a digital photo camera. Then the data gets redistributed to other servers all over the world where physicists analyze and interpret it.
Huge digital cameras record tiny particles
In the world’s largest particle collider, the Large Hadron Collider (LHC) ions smash into each other at the speed of light, splitting into even smaller particles. And it is all recorded with massive digital cameras.
Image: DW/F.Schmidt
Pictures of particles
The ALICE detector, owned by the European Organization for Nuclear Research (CERN) - is located more than 90 meters underneath this colorful building in Geneva. ALICE is a huge digital camera capable of photographing even the smallest building blocks of the universe - the components of an atom's nucleus.
Image: DW/F. Schmidt
Helmets required
In addition to ALICE, three other detector cameras, named ATLAS, CMS, and LHCb, keep a record of particle collisions at the LHC. To see them you have to go deep below the rock of the French and Swiss Alps.
Image: DW/F.Schmidt
Did puny particles follow the Big Bang?
When protons or lead ions smash together at the speed of light the smallest elementary particles are released - and this is what it looks like to the CMS detector. Scientists believe our universe was created from such particles in the first billionth of a second after the Big Bang.
Image: 2011 CERN
On track at high speed
This is where lead ions and hydrogen protons are accelerated. They fly through a vacuum tube with the energy of a speeding train and are kept on track by massive electromagnets. The pipe has a circumference of 27 kilometers and can be accessed through the four large detectors where the particle collisions take place.
Image: DW/F.Schmidt
The world’s largest fridge
The electromagnets that keep the particle beam on track are made of superconducting inductors. The cables must be kept at a chilly minus 271.3 degrees Celsius (minus 456 Fahrenheit) so they no longer have any electrical resistance. To cool them down, the collider sends a whole lot of liquid helium through the pipes.
Image: DW/F.Schmidt
Precise magnets
The LHC is not a perfect circle but instead consists of long straight stretches interrupted by curves, where magnets redirect the beam. The electromagnets are extremely precise. Just before a collision they focus the beam in exactly the angle so that the probability of two particles colliding is very high. The clash then happens right in the middle of the detector.
Image: DW/F.Schmidt
Built like a ship in a bottle
The detectors are as big as multi-level houses. But they all had to be brought into the mountain in smaller parts through narrow shafts like this one. Underneath it is a gigantic cavern where ALICE was put together.
Image: DW/F.Schmidt
8,000 photos per second
This is the ALICE detector when it is opened for maintenance. When in operation, ion beams collide in its center. New particles are created, flying off in different directions through several layers of silicon chips, similar to the sensors of a digital camera. The chips and other detectors record the particles' routes. ALICE can capture 1.25 gigabytes of digital data each second.
Image: DW/F. Schmidt
Electromagnets make particles identifiable
This blue chunk is another huge electromagnet, an important part of the ALICE detector. It creates a field making it possible to identify particles that are created during the high-speed collisions. Scientists study the direction the new particles travel. For instance, they can determine whether particles were neutral or positively or negatively charged.
Image: DW/F.Schmidt
Wings to catch a muon
The ATLAS detector has a special gauge, the so-called muon spectrometer, which lies outside the detector’s heart, just like large wings. With these wings a heavy relative of the electrons - the muon - can be caught. Muons are difficult to find because they only exist for two millionths of a second.
Image: DW/F.Schmidt
Watching from a safe distance
All detectors have a control room, just like this one for ATLAS. Once the collider is in operation, no one is allowed to stay inside the underground facilities. An out of control proton beam can melt 500 kilograms of copper and escaped helium could cause frostbite and suffocation. The particle stream could even create radioactivity.
Image: DW/F. Schmidt
What to do with the data?
The detectors deliver data 40 million times per second. But because not all collisions are interesting for scientists, the data has to be filtered. In the end, no more than 100 interesting particle collisions per second remain. That’s still more than 700 megabytes of data per second - about what fits on a commercial CD. All data initially lands here in CERN’s data processing center.
Image: DW/F.Schmidt
A global computer network
CERN produces an amount of data per year that if it were stored on CD, the pile would be 20 kilometers high. Even though such a tape library can hold a lot of data, it is still not enough. So the data are distributed worldwide. More than 200 universities and research institutes have created a worldwide CERN computer network with their data processing centers.
Image: DW/F.Schmidt
Data for everyone
Particle physicists from around the world have access to CERN data. The center sees itself as a service provider for universities and institutes conducting basic research. A common project for everyone's benefit.
