The LARGE HADRON COLLIDER (LHC) is the world's largest and highest-energy particle accelerator .LHC lies in a tunnel 27 kilometres in circumference, as much as 175 metres (574 ft) beneath the Franco-Swiss border near Geneva, Switzerland.
This synchrotron is designed to collide opposing particle beams of protons at an energy of 7 teraelectronvolts (1.12 microjoules) per particle, or lead nuclei at an energy of 574 TeV (92.0 µJ) per nucleus.
The term HADRON refers to particles composed of quarks . It is expected that it will address the most fundamental questions of physics , advancing our understanding of the deepest laws of nature .
This synchrotron is designed to collide opposing particle beams of protons at an energy of 7 teraelectronvolts (1.12 microjoules) per particle, or lead nuclei at an energy of 574 TeV (92.0 µJ) per nucleus.
The term HADRON refers to particles composed of quarks . It is expected that it will address the most fundamental questions of physics , advancing our understanding of the deepest laws of nature .
The Large Hadron Collider was built by the EUROPEAN ORGANISATION OF NUCLEAR RESEARCH (CERN) with the intention of testing various predictions of high-energy physics , including the existence of the hypothesized Higgs Boson and of the large family of new particles predicted by supersymmetry . It is funded by and built in collaboration with over 10,000 scientists and engineers from over 100 countries as well as hundreds of universities and laboratories. On 10 September 2008, the proton beams were successfully circulated in the main ring of the LHC for the first time, but nine days later, operations were halted due to a serious fault between two super conducting bending magnets . Repairing the resulting damage and installing additional safety features took over a year.
On 20th November the proton beams were successfully calculated again with the first proton–proton collisions being recorded three days later at the injection energy of 450 GeV per beam. The LHC became the world's highest-energy particle accelerator on 30 November 2009, achieving a world record 1.18 TeV per beam and surpassing the record previously held by the Tevatron, at Fermilab in Batavia, Illinois.
After the 2009 winter shutdown, the LHC was restarted and the beam was ramped up to 3.5 TeV per beam, half its designed energy, which is planned for after its 2012 shutdown. On 30 March 2010, the first planned collisions took place between two 3.5 TeV beams, which set a new world record for the highest-energy man-made particle collisions.
THE MAIN PURPOSE OF LHC
On 20th November the proton beams were successfully calculated again with the first proton–proton collisions being recorded three days later at the injection energy of 450 GeV per beam. The LHC became the world's highest-energy particle accelerator on 30 November 2009, achieving a world record 1.18 TeV per beam and surpassing the record previously held by the Tevatron, at Fermilab in Batavia, Illinois.
After the 2009 winter shutdown, the LHC was restarted and the beam was ramped up to 3.5 TeV per beam, half its designed energy, which is planned for after its 2012 shutdown. On 30 March 2010, the first planned collisions took place between two 3.5 TeV beams, which set a new world record for the highest-energy man-made particle collisions.
THE MAIN PURPOSE OF LHC
A Stimulated event in the CMS detector , featuring the appearance of the Higgs Boson.
Physicists hope that the LHC will help answer many of the most fundamental questions in physics: questions concerning the basic laws governing the interactions and forces among the elementary objects , the deep structure of space and time, especially regarding the intersection of Quantum Mechanics and General Relativity , where current theories and knowledge are unclear or break down altogether.
Physicists hope that the LHC will help answer many of the most fundamental questions in physics: questions concerning the basic laws governing the interactions and forces among the elementary objects , the deep structure of space and time, especially regarding the intersection of Quantum Mechanics and General Relativity , where current theories and knowledge are unclear or break down altogether.
DESIGN OF THE LHC
The LHC is the world's largest and highest-energy particle accelator . The collider is contained in a circular tunnel, with a circumference of 27 kilometres (17 mi), at a depth ranging from 50 to 175 metres (160 to 574 ft) underground.
The 3.8-metre (12 ft) wide concrete-lined tunnel, constructed between 1983 and 1988, was formerly used to house the LARGE ELECTRON-POSITRON COLLIDER . It crosses the border between Switzerland and France at four points, with most of it in France. Surface buildings hold ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants.
The collider tunnel contains two adjacent parallel beam pipes that intersect at four points, each containing a proton beam, which travel in opposite directions around the ring. Some 1,232 dipole magnets keep the beams on their circular path, while an additional 392 quadrupole magnets are used to keep the beams focused, in order to maximize the chances of interaction between the particles in the four intersection points, where the two beams will cross. In total, over 1,600 superconducting magnets are installed, with most weighing over 27 tonnes. Approximately 96 tonnes of liquid helium is needed to keep the magnets at their operating temperature of 1.9 K (−271.25 °C), making the LHC the largest cryogenic facility in the world at liquid helium temperature.
The 3.8-metre (12 ft) wide concrete-lined tunnel, constructed between 1983 and 1988, was formerly used to house the LARGE ELECTRON-POSITRON COLLIDER . It crosses the border between Switzerland and France at four points, with most of it in France. Surface buildings hold ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants.
The collider tunnel contains two adjacent parallel beam pipes that intersect at four points, each containing a proton beam, which travel in opposite directions around the ring. Some 1,232 dipole magnets keep the beams on their circular path, while an additional 392 quadrupole magnets are used to keep the beams focused, in order to maximize the chances of interaction between the particles in the four intersection points, where the two beams will cross. In total, over 1,600 superconducting magnets are installed, with most weighing over 27 tonnes. Approximately 96 tonnes of liquid helium is needed to keep the magnets at their operating temperature of 1.9 K (−271.25 °C), making the LHC the largest cryogenic facility in the world at liquid helium temperature.
Superconducting quadrupole electromagnets are used to direct the beams to four intersection points, where interactions between accelerated protons will take place.
Once or twice a day, as the protons are accelerated from 450GEV to 7TEV , the field of the superconducting dipole magnets will be increased from 0.5 to 8.3 TESLAS(T)The protons will each have an energy of 7 TeV, giving a total collision energy of 14 TeV. At this energy the protons have a Lorenz Factor of about 7,500 and move at about 0.999999991 c, or about 3 metres per second slower than of the speed of light (c).It will take less than 90 microseconds (μs) for a proton to travel once around the main ring – a speed of about 11,000 revolutions per second. Rather than continuous beams, the protons will be bunched together, into 2,808 bunches, so that interactions between the two beams will take place at discrete intervals never shorter than 25 nanoseconds (ns) apart. However it will be operated with fewer bunches when it is first commissioned, giving it a bunch crossing interval of 75 ns.
Prior to being injected into the main accelerator, the particles are prepared by a series of systems that successively increase their energy. The first system is the Linear Particle Accelarator (LINAC 2) generating 50-MeV protons, which feeds the Proton Synchrotron Booster (PSB) .There the protons are accelerated to 1.4 GeV and injected into the Proton Synchrotron (PS) where they are accelerated to 26 GeV. Finally the Super Proton Synchrotron (SPS) is used to further increase their energy to 450 GeV before they are at last injected (over a period of 20 minutes) into the main ring. Here the proton bunches are accumulated, accelerated (over a period of 20 minutes) to their peak 7-TeV energy, and finally circulated for 10 to 24 hours while collisions occur at the four intersection points.
Prior to being injected into the main accelerator, the particles are prepared by a series of systems that successively increase their energy. The first system is the Linear Particle Accelarator (LINAC 2) generating 50-MeV protons, which feeds the Proton Synchrotron Booster (PSB) .There the protons are accelerated to 1.4 GeV and injected into the Proton Synchrotron (PS) where they are accelerated to 26 GeV. Finally the Super Proton Synchrotron (SPS) is used to further increase their energy to 450 GeV before they are at last injected (over a period of 20 minutes) into the main ring. Here the proton bunches are accumulated, accelerated (over a period of 20 minutes) to their peak 7-TeV energy, and finally circulated for 10 to 24 hours while collisions occur at the four intersection points.
CMS detector for LHC.
The LHC physics program is mainly based on proton–proton collisions. However, shorter running periods, typically one month per year, with heavy-ion collisions are included in the program. While lighter ions are considered as well, the baseline scheme deals with lead ions. The lead ions will be first accelerated by the Linear Accelerator LINAC 3 , and the Low-Energy Ion Ring (LEIR) will be used as an ion storage and cooler unit. The ions will then be further accelerated by the PS and SPS before being injected into LHC ring, where they will reach an energy of 2.76 TeV per nucleon (or 575 TeV per ion), higher than the energies reached by the Relativistic Heavy Ion Collider . The aim of the heavy-ion program is to investigate Quark-Gluon Plasma ,which existed in the early universe .
DETECTORS
Six detectors have been constructed at the LHC, located underground in large caverns excavated at the LHC's intersection points. Two of them, the ATLAS Experiment and the Compact Muon Sollenoid (CMS) are large, general purpose particle detectors. A Large Ion Collider Experiment (ALICE) and LHCb , have more specific roles and the last two, TOTEM and LHCf , are very much smaller and are for very specialized research.
TEST TIMELINE
The first beam was circulated through the collider on the morning of 10 September 2008. CERN successfully fired the protons around the tunnel in stages, three kilometres at a time. The particles were fired in a clockwise direction into the accelerator and successfully steered around it at 10:28 local time. The LHC successfully completed its first major test: after a series of trial runs, two white dots flashed on a computer screen showing the protons travelled the full length of the collider. It took less than one hour to guide the stream of particles around its inaugural circuit. CERN next successfully sent a beam of protons in a counterclockwise direction, taking slightly longer at one and a half hours due to a problem with the cryogenics, with the full circuit being completed at 14:59.
On 19 September 2008, a quench occurred in about 100 bending magnets in sectors 3 and 4, causing a loss of approximately six tonnes of liquid helium, which was vented into the tunnel, and a temperature rise of about 100 kelvin in some of the affected magnets. Vacuum conditions in the beam pipe were also lost. Shortly after the incident CERN reported that the most likely cause of the problem was a faulty electrical connection between two magnets, and that – due to the time needed to warm up the affected sectors and then cool them back down to operating temperature – it would take at least two months to fix it. Subsequently, CERN released a preliminary analysis of the incident on 16 October 2008, and a more detailed one on 5 December 2008. Both analyses confirmed that the incident was indeed initiated by a faulty electrical connection. A total of 53 magnets were damaged in the incident and were repaired or replaced during the winter shutdown.
In the original timeline of the LHC commissioning, the first "modest" high-energy collisions at a centre-of-mass energy of 900 GeV were expected to take place before the end of September 2008, and the LHC was expected to be operating at 10 TeV by the time of the official inauguration on 21 October 2008. However, due to the delay caused by the above-mentioned incident, the collider was not operational until November 2009. Despite the delay, LHC was officially inaugurated on 21 October 2008, in the presence of political leaders, science ministers from CERN's 20 Member States, CERN officials, and members of the worldwide scientific community.
On 30 March 2010, LHC set a record for high-energy collisions, by colliding proton beams at a combined energy level of 7 TeV. The attempt was the third that day, after two unsuccessful attempts in which the protons had to be "dumped" from the collider and new beams had to be injected. Describing the event, CERN Director General Rolf Heuer said, "It's a great day to be a particle physicist." According to a press release, CERN will run the LHC for 18–24 months with the objective of delivering enough data to the experiments to make significant advances across a wide range of physics channels.
On 19 September 2008, a quench occurred in about 100 bending magnets in sectors 3 and 4, causing a loss of approximately six tonnes of liquid helium, which was vented into the tunnel, and a temperature rise of about 100 kelvin in some of the affected magnets. Vacuum conditions in the beam pipe were also lost. Shortly after the incident CERN reported that the most likely cause of the problem was a faulty electrical connection between two magnets, and that – due to the time needed to warm up the affected sectors and then cool them back down to operating temperature – it would take at least two months to fix it. Subsequently, CERN released a preliminary analysis of the incident on 16 October 2008, and a more detailed one on 5 December 2008. Both analyses confirmed that the incident was indeed initiated by a faulty electrical connection. A total of 53 magnets were damaged in the incident and were repaired or replaced during the winter shutdown.
In the original timeline of the LHC commissioning, the first "modest" high-energy collisions at a centre-of-mass energy of 900 GeV were expected to take place before the end of September 2008, and the LHC was expected to be operating at 10 TeV by the time of the official inauguration on 21 October 2008. However, due to the delay caused by the above-mentioned incident, the collider was not operational until November 2009. Despite the delay, LHC was officially inaugurated on 21 October 2008, in the presence of political leaders, science ministers from CERN's 20 Member States, CERN officials, and members of the worldwide scientific community.
On 30 March 2010, LHC set a record for high-energy collisions, by colliding proton beams at a combined energy level of 7 TeV. The attempt was the third that day, after two unsuccessful attempts in which the protons had to be "dumped" from the collider and new beams had to be injected. Describing the event, CERN Director General Rolf Heuer said, "It's a great day to be a particle physicist." According to a press release, CERN will run the LHC for 18–24 months with the objective of delivering enough data to the experiments to make significant advances across a wide range of physics channels.
RESULTS
Expected Results
CERN scientists estimate that if the Standard Model is correct, a single Higgs Boson may be produced every few hours. At this rate, it may take about two to three years to collect enough data to discover the Higgs boson unambiguously. Similarly, it may take one year or more before sufficient results concerning supersymmetric particles have been gathered to draw meaningful conclusions.
Current results
The results of the first proton–proton collisions at energies higher than Fermilab's Tevatron proton–antiproton collisions have been published, yielding greater-than-predicted charged Hadron production. The CMS paper reports that the increase in the production rate of charged hadrons when the centre-of-mass energy goes from 0.9 TeV to 2.36 TeV exceeds the predictions of the theoretical models used in the analysis, with the excess ranging from 10% to 14%, depending upon which model is used. The charged hadrons were primarily mesons (kaons and pions).
COST OF THE EXPERIMENT
With a budget of 9 billion US dollars (approx. €7.5bn or £6.19bn as of Jun 2010), the LHC is one of the most expensive scientific instruments ever built. The total cost of the project is expected to be of the order of 4.6bn Swiss francs (approx. $4.4bn, €3.1bn, or £2.8bn as of Jan 2010) for the accelerator and SFr 1.16bn (approx. $1.1bn, €0.8bn, or £0.7bn as of Jan 2010) for the CERN contribution to the experiments. The construction of LHC was approved in 1995 with a budget of SFr 2.6bn, with another SFr 210M towards the experiments. However, cost overruns, estimated in a major review in 2001 at around SFr 480M for the accelerator, and SFr 50M for the experiments, along with a reduction in CERN's budget, pushed the completion date from 2005 to April 2007. The superconducting magnets were responsible for SFr 180M of the cost increase. There were also further costs and delays due to engineering difficulties encountered while building the underground cavern for Compact Muon Sollenoid , and also due to faulty parts provided by Fermilab. Due to lower electricity costs during the summer, it is expected that the LHC will normally not operate over the winter months, although an exception was made to make up for the 2008 start-up delays over the 2009/10 winter.
Bibliography
1.Books referred.
(a)“Large Hadron Collider. Thirteen ways to change the world” .
(b)”Manorama Yearbook 2008 &2009” .
2.Sites visited.
(a) Wikipedia.
Bibliography
1.Books referred.
(a)“Large Hadron Collider. Thirteen ways to change the world” .
(b)”Manorama Yearbook 2008 &2009” .
2.Sites visited.
(a) Wikipedia.
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