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World's Largest Particle Detector ATLAS Detector is Completing the LHC
:: 11 March, 2008
The ATLAS detector, with its 46 metres long, 25 metres high and 25 metres wide, is the largest particle detector versatile in the world. From a weight of 7000 tons, it consists of 100 million sensors, which measure the particles produced in proton-proton collisions at the Large Hadron Collider at CERN, the LHC. The first element ATLAS was installed in 2003 and, since then, many people have joined at the bottom of the shaft 100 meters underground cavern in the ATLAS.
The final element, called the little wheel moves in the underground experimental hall, 100 metres deep, to complement the muon spectrometer ATLAS. The detector consists of two "small wheel" (small on the scale of ATLAS, of course, because each measuring 9.3 metres in diameter and, with its elements shielding massive, weighing 100 tons). They are covered with sensitive detectors that will define and measure the momentum of the particles will be created in the collisions of the LHC.
If we look at the whole system, the muon spectrometer, which has 1.2 million independent electronic media, is a surface detection equivalent to three football fields. When the particles pass through the magnetic field created by superconducting magnets, the sensitivity of the detector will allow it to determine the trajectories of the particles with an accuracy of the thickness of a hair.
"These detectors are so sensitive the largest measuring instrument ever built for the high-energy physics," says George Mikenberg project manager 'Muon' ATLAS.
The ATLAS collaboration will now concentrate on the activities of commissioned in preparation for the start of LHC this summer. The experiments to be conducted at the LHC will allow physicists to take a big step in a journey that began when Newton began to describe gravity. Gravity is pervasive, as it acts on the estate. But so far, science is unable to explain why the particles have the masses they are experiencing. Experiments such qu'ATLAS may offer an answer to this question. The LHC experiments will also seek to solve the mystery of dark matter and dark energy of the universe and try to explain why matter dominates over antimatter in nature, and they will explore the matter as it was at the very beginning of time and seek extra dimensions of space-time.
Note for ATLAS Experiment
ATLAS is one of the six particle detector experiments (ALICE, ATLAS, CMS, TOTEM, LHCb, and LHCf) currently being constructed at the Large Hadron Collider (LHC), a new particle accelerator at the European Organization for Nuclear Research (CERN) in Switzerland. When completed, ATLAS will be 46 metres long and 25 metres in diameter, and will weigh about 7,000 tonnes. The project involves roughly 2,000 scientists and engineers at 165 institutions in 35 countries. The construction was scheduled to be completed in June 2007, however is now stated to be April or mid-2008. The experiment is designed to observe phenomena that involve highly massive particles which were not observable using earlier lower-energy accelerators and might shed light on new theories of particle physics beyond the Standard Model.
The ATLAS collaboration, the group of physicists building the detector, was formed in 1992 when the proposed EAGLE (Experiment for Accurate Gamma, Lepton and Energy Measurements) and ASCOT (Apparatus with Super COnducting Toroids) collaborations merged their efforts into building a single, general-purpose particle detector for the Large Hadron Collider. The design was a combination of those two previous designs, as well as the detector research and development that had been done for the Superconducting Supercollider. The ATLAS experiment was proposed in its current form in 1994, and officially funded by the CERN member countries beginning in 1995. Additional countries, universities, and laboratories joined in subsequent years, and further institutions and physicists continue to join the collaboration even today. The work of construction began at individual institutions, with detector components shipped to CERN and assembled in the ATLAS experimental pit beginning in 2003.
ATLAS is designed as a general-purpose detector. When the proton beams produced by the Large Hadron Collider interact in the center of the detector, a variety of different particles with a broad range of energies may be produced. Rather than focusing on a particular physical process, ATLAS is designed to measure the broadest possible range of signals. This is intended to ensure that, whatever form any new physical processes or particles might take, ATLAS will be able to detect them and measure their properties. Experiments at earlier colliders, such as the Tevatron and Large Electron-Positron Collider, were designed based on a similar philosophy. However, the unique challenges of the Large Hadron Collider—its unprecedented energy and extremely high rate of collisions—require ATLAS to be larger and more complex than any detector ever built.
The ATLAS detector consists of a series of ever-larger concentric cylinders around the interaction point where the proton beams from the LHC collide. It can be divided into four major parts: the Inner Detector, the calorimeters, the muon spectrometer and the magnet systems. Each of these is in turn made of multiple layers. The detectors are complementary: the Inner Detector tracks particles precisely, the calorimeters measure the energy of easily stopped particles, and the muon system makes additional measurements of highly penetrating muons. The two magnet systems bend charged particles in the Inner Detector and the muon spectrometer, allowing their momenta to be measured.
The only established stable particles that cannot be detected directly are neutrinos; their presence is inferred by noticing a momentum imbalance among detected particles. For this to work, the detector must be "hermetic", and detect all non-neutrinos produced, with no blind spots. Maintaining detector performance in the high radiation areas immediately surrounding the proton beams is a significant engineering challenge.
Note for Particle Detector
In experimental and applied particle physics and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify high-energy particles, such as produced by nuclear decay, cosmic radiation, or reactions in a particle accelerator. Modern detectors are also used as calorimeters to measure energy of the detected radiation. They may also be used to measure other attributes such as momentum, spin, charge etc. of the particles.
Detectors designed for modern accelerators are huge, both in size and in cost. The term "counter" is often used instead of detector, when the detector counts the particles but does not resolve its energy or ionization. Particle detectors usually can also track ionizing radiation (high energy photons or even visible light). If their main purpose is radiation measurement, they are called radiation detector, but as photons can also be seen as (massless) particles, the term particle detector is still correct.
Many of the detectors invented and used so far may are ionization detectors (of which gaseous ionization detectors and semiconductor detectors are most typical) and scintillation detectors; but other, completely different principles have also been applied, like Cherenkov light and transition radiation.
Note for Large Hadron Collider
The Large Hadron Collider (LHC) is a particle accelerator and hadron collider located at CERN, near Geneva, Switzerland (46°14′N, 6°03′E). Currently under construction, the LHC is scheduled to begin operation in May 2008. The LHC is expected to become the world's largest and highest-energy particle accelerator. The LHC is being funded and built in collaboration with over two thousand physicists from thirty-four countries as well as hundreds of universities and laboratories. When activated, it is theorized that the collider will produce the elusive Higgs boson, the observation of which could confirm the predictions and 'missing links' in the Standard Model of physics and could explain how other elementary particles acquire properties such as mass. The verification of the existence of the Higgs boson would be a significant step in the search for a Grand Unified Theory, which seeks to unify three of the four fundamental forces: electromagnetism, the strong force, and the weak force. The Higgs boson may also help to explain why the remaining force, gravitation, is so weak compared to the other three forces. In addition to the Higgs boson, other theorized novel particles that might be produced, and for which searches are planned, include strangelets, micro black holes, magnetic monopoles and supersymmetric particles.
The collider is contained in a circular tunnel with a circumference of 26.659 kilometres (16.5 miles), at a depth ranging from 50 to 175 metres underground. The tunnel, constructed between 1983 and 1988, was formerly used to house the LEP, an electron-positron collider.
The 3.8 metre diameter, concrete-lined tunnel actually crosses the border between Switzerland and France at four points, although the majority of its length is inside France. The collider itself is located underground, with many surface buildings holding ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants.
The collider tunnel contains two pipes enclosed within superconducting magnets cooled by liquid helium, each pipe containing a proton beam. The two beams travel in opposite directions around the ring. Additional magnets are used to direct the beams to four intersection points where interactions between them will take place. In total, over 1600 superconducting magnets are installed, with most weighing over 27 tonnes.
Tags: ATLAS detector , particle detector , Large Hadron Collider , CERN , muon spectrometer ,
