What's Inside Large Hadron Collider?
The Large Hadron Collider (LHC) is the world's largest machine built one hundred meters underground near the border between France and Switzerland, it has a circular geometry and has a circumference of 27Kms as shown in Figure 1. LHC is part of a multi-billion dollar global research project by the European Organization for Nuclear Research, also known as CERN where scientists and engineers from over hundred countries are working together to unravel the mysteries of the universe and the fundamental forces governing it by examining the universe tiniest particles. It houses huge and powerful accelerator that collides beams of protons and ions travelling close to speed of light (99.99%) and recording the resulting events caused by the collision. The purpose is to study the origin of the universe by recreating the situation similar to Big Bang but at a very small scale. A total of four particle accelerator labs namely ALICE, ATLAS, CMS and LHCb collect data and look for new physics in the noted events. Surprisingly, despite this tremendous infrastructure and manpower the practical applications of physics discovered at LHC are quite limited as of today.
Figure 1: LHC location and geometry (Source : Ref [1])
Purpose of LHC
As mentioned earlier, the objective of LHC is to increase our knowledge about the universe. Till date, the most acceptable theory of interactions of elementary particles is provided by the Standard Model of particle physics. It combines three of the four basic forces of the universe: strong nuclear force, weak nuclear force and electromagnetic force, but does not address the effects of gravitational force. Standard model also classify all known elementary particles and provides many successfully predictions about the universe, most of which have been experimentally verified including the existence of the God Particle also known as the Higgs Boson. However some of the phenomena are unexplained by the model like reason for the excess of matter as compared to anti-matter in the universe, also termed as the Baryon Asymmetry problem; nature of Dark Matter (the motion of galaxies and other celestial bodies suggests that there must be much more matter in the universe than we can detect, this undetectable material is called dark matter); Dark Energy, a hypothetical energy that contributes to the expansion of the universe is also one unexplained phenomenon. Scientists hope that LHC will provide explanation for all these phenomena. Interestingly, the LHC could also uncover evidence of Other Dimensions. We know of four dimensions - 3 spatial and 1 time. Many physicists consider the theory of other dimensions, for example String Theory of 10 dimensions, M-Theory of 11 dimensions etc.
Figure 2: Cylindrical Tube of LHC (Source: Ref [1])
How It Works?
The LHC uses around 9,600 superconducting magnets weighing several tons, and cooled to a chilling 1.9 degrees kelvin to control beams of protons as they travel close to speed of light. As shown in Figure 2, the proton beams inside the LHC travel through cylindrical tube like chambers in ultra-high vacuum to avoid entry of any foreign particles that could collide with protons before they reach their actual collision points. Even a single molecule of gas (foreign particle) could cause an experiment to fail. There are about 150 million sensors working in LHC that continuously collect data at a rate of 700 megabytes per second (MB/s) and transmit it to various computing systems. About 15 Petabytes of data is generated in a year and CERN uses grid computing for analyzing this huge chunk of data.
Whether LHC will solve all the mysteries of creation of universe? Scientists or Physicists may dwell on this question for now but one thing is certain that LHC is a perfect example of an engineering marvel that is a combination of science and technology attempting to address unanswered questions about the universe.
By: Dr. Rohit Verma, Associate Professor in Physics, Chitkara University, Himachal Pradesh.
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