Dec 30, 2009
Dec 18, 2009
Atom smasher preparing 2010 new science restart
GENEVA — The world's largest atom smasher, which exceeded expectations after its comeback from heavy damage, will be ready to begin a groundbreaking research program in February, the operator said Friday.
The European Organization for Nuclear Research, or CERN, has shut down the machine for the planned year-end break. In January, there will be preparation to increase the energy used to smash protons into each other far above previous levels in hopes of revealing secrets of matter and the universe.
The new collisions are expected to shatter the subatomic particles into still smaller fragments and forces than previously achieved on any collider, including the previous record-holder — the Tevatron at Fermilab outside Chicago.
The new $10 billion machine, which has made a nearly flawless comeback after being heavily damaged during a startup failure a year ago, was built to examine suspected phenomena such as dark matter, antimatter and ultimately the creation of the universe billions of years ago, which many theorize occurred as an explosion known as the Big Bang.
Repairs and refinements costing $40 million are being made to the Large Hadron Collider in a 17-mile (27-kilometer) circular tunnel 300 feet (100 meters) under the Swiss-French border at Geneva.
"So far, it is all systems go for the LHC," CERN Director-General Rolf Heuer said.
All of the collider's systems have been tested and more than 1 million proton collisions have provided ample data to the six "experiments" in vast underground rooms so that they can calibrate their huge detectors to work accurately when the research program starts.
"We could not have asked for a better way to bring 2009 to a close," Heuer said.
Last weekend, two beams of circulating particles traveling in opposite directions at 1.18 trillion electron volts, or TeV, produced around 50,000 collisions. The record-breaking energy reached was about 20 percent higher than the previous record set at Fermilab.
After the shutdown and further tests and improvements, CERN will ramp up the energy pushing the beams of protons still higher, to 3 1/2 times the highest levels reached in Chicago. The showers of particles created at the level are expected to reveal still more about the makeup of matter.
The long-term goal, after more modifications, will be to run the proton beams at 7 TeV in each direction.
The particle beams travel at nearly the speed of light, circling the tunnel in pipes 11,000 times a second until powerful, superconducting magnets force the beams to collide to see what will occur.
With the vast amount of data coming off the collisions, CERN has organized a grid of computers at research facilities around the world to analyze what is seen, and the system has been working smoothly, said Torsten Akesson, president of the CERN Council, made up of the 20 European nations that run the organization.
CERN said the operation this year had been carefully prepared in a step-by-step approach to make sure it was safe to go to 1.18 TeV.
Running at higher energy will require higher electrical currents — and further preparation of the protection systems for the collider and its huge superconducting magnets, operating at near absolute zero — colder than outer space — for maximum efficiency.
"Commissioning work for higher energies will be carried out in January, along with necessary adaptations to the hardware and software of the protection systems that have come to light during the 2009 run," CERN said.
Attention to the smallest detail can prove crucial. The LHC circulated its first beams Sept. 10, 2008, with great fanfare. But the machine was sidetracked nine days later when a badly soldered electrical splice overheated and set off a chain of damage to the magnets and other parts of the collider.
Physicists have used smaller, room-temperature colliders for decades to study the atom. They once thought protons and neutrons were the smallest components of the atom's nucleus, but the colliders showed that they are made of quarks and gluons and that there are other forces and particles.
More than 8,000 physicists from labs around the world also have work planned for the Large Hadron Collider. The organization is run by its 20 European member nations, with support from other countries, including observers from Japan, India, Russia and the U.S., which have made big contributions.
Copyright © 2009 The Associated Press. All rights reserved.
What a machine!
After becoming the world’s highest energy particle accelerator, the LHC is now making progress in commissioning stable beams and providing more collisions at the four points for several hours at a time. For the first time, beams have circulated with more than one bunch of protons, thus increasing the intensity.
Nothing is really ordinary when one operates a prototype: ups and downs are possible, adjustments are certainly necessary and a reasonable amount of time is needed to understand the system’s behaviour. The LHC is no exception. With all its achievements since it was switched on a few weeks ago, it has made the headlines in the world’s press several times. The first beams circulated smoothly, the first low-energy collisions happened very quickly, and the first ramp up to record energy was exceptionally good.
Since then the focus has been on increasing the number of protons in the circulating beams. In the first tests, the operators used a ‘pilot’ beam, containing only one bunch of protons, but on the evening of Friday, 4 December, a beam circulated with more than one proton bunch for the first time. Then, in the early hours of Sunday morning, operators succeeded in circulating four bunches in both directions around the LHC and announced stable beams.
During the following days, work focussed on making sure that each step towards higher intensities can be safely handled and that stable conditions can be guaranteed during collisions first at 450 GeV and then at 1.18 TeV per beam. On the evening of Tuesday, 8 December, two bunches per beam circulated for the first time at 1.18 TeV for a short period and ATLAS recorded its first collisions at the record energy of 2.36 TeV (centre of mass).
Over the same period, cryo-experts have intervened a few times to correct some parameters, vacuum experts have quickly repaired some imperfections in the pre-injector chain and operators have injected and dumped the beams to test the behaviour of the various components of the machine and to measure its performance – which is proving to be excellent.
With four bunches per beam and more protons per bunch, the LHC is providing more and more collisions and all six experiments are recording as much data as possible. During the stable beam periods, they can gather a great deal of useful information about their sub-detectors as well as about the whole chain from collisions to data distribution and analysis. On 28 November, the ALICE collaboration submitted its first paper based on the reconstruction and analysis of the 284 collision events at 450 GeV per beam. The results of the ALICE study are consistent with measurements performed by previous experiments, in particular with those at the SPS when it worked as a proton-antiproton collider with the same beam energy as the LHC in this first phase of commissioning.
Over the final few days before the LHC turns off on 16 December, the operators will continue to increase the beam intensity, delivering further good quantities of collision data to the experiments before Christmas.
When the LHC starts up again in 2010, the operators will aim at gently increasing the intensity and energy of the beams until the planned 3.5 TeV for each beam is reached, marking the beginning of the physics programme.
Dec 1, 2009
LHC sets new world record
30 November 2009
Geneva, 30 November 2009. CERN’s Large Hadron Collider has today become the world’s highest energy particle accelerator,having accelerated its twin beams of protons to an energy of 1.18 TeV in the early hours of the morning. This exceeds the previous world record of 0.98 TeV, which had been held by the US Fermi National Accelerator Laboratory’s Tevatron collider since 2001.
It marks another important milestone on the road to first physics at the LHC in 2010.
“We are still coming to terms with just how smoothly the LHC commissioning is going,” said CERN Director General Rolf Heuer.
"It is fantastic. However, we are continuing to take it step by step, and there is still a lot to do before we start physics in 2010. I’m keeping my champagne on ice until then.”
These developments come just 10 days after the LHC restart, demonstrating the excellent performance of the machine. First beams were injected into the LHC on Friday 20 November. Over the following days, the machine’s operators circulated beams around the ring alternately in one direction and then the other at the injection energy of 450 GeV, gradually increasing the beam lifetime to around 10 hours. On Monday 23 November, two beams circulated together for the
first time, and the four big LHC detectors recorded their first collision data.
Last night’s achievement brings further confirmation that the LHC is progressing smoothly towards the objective of first physics early in 2010.The world record energy was first broken yesterday evening, when beam 1 was accelerated from 450 GeV, reaching 1050 GeV (1.05 TeV) at 21:28, Sunday 29 November. Three hours later both LHC beams were successfully accelerated to 1.18 TeV, at 00:44, 30 November.
"I was here 20 years ago when we switched on CERN’s last major particle accelerator, LEP,” said Research and Technology Director Steve Myers. “I thought that was a great machine to operate,
but this is something else. What took us days or weeks with LEP, we’re doing in hours with the LHC. So far, it all augurs well for a great research programme.”
Next on the schedule is a concentrated commissioning phase aimed at increasing the beam intensity before delivering good quantities of collision data to the experiments before Christmas. So far, all the LHC commissioning work has been carried out with a low intensity pilot beam. Higher intensity is needed to provide meaningful proton-proton collision rates. The current commissioning phase aims to make sure that these higher intensities can be safely handled and that stable conditions can be guaranteed for the experiments during collisions.
This phase is estimated to take around a week, after which the LHC will be colliding beams for calibration purposes until the end of the year.
First physics at the LHC is scheduled for the first quarter of 2010, at a collision energy of 7 TeV (3.5 TeV per beam).
Nov 11, 2009
جلسهي اول هندسه و فيزيك
مباني رياضياتي هندسه
«توپولوژي»
خلاصه: در اين جلسه تعاريف لازم را براي جلسات بعدي معرفي كرده و برنامه و هدف از بررسي هندسه در فيزيك را بيان ميكنيم. توپولوژي موضعي- عام، نگاشت، جبرگروه، عملگرهاي پايه در هندسه، تنسورها. تعاريف بسيار پايهاي بوده و تمام دانشجويان در همهي سطوح ميتوانند استفاده نمايند. جلسات بعدي مطابق ليست متن انگليسي كه در پستهاي قبلي آمده برگزار ميشود.
زمان جلسه متعاقباً اعلام ميشود. اين جلسه هفته ي آينده برگزار ميشود.
Oct 28, 2009
هندسه و فيزيك
سري سخنراني هاي فيزيك و هندسه
فرهاد ذكاوت
در اين سري فشرده به دليل محدوديت زماني به موضوعات و اصول هندسه و كاربردهاي هر موضوع در فيزيك ميپردازيم. در سخنراني هاي تخصصي نسبيت عام و فيزيك ذرات به كاربردها و ضرورتهاي هندسه و گرايشهاي مختلف در اين حوزه ميپردازيم. در صورت تمام نشدن اين سري سخنراني در ترم آتي دانشگاهي،ادامهي سخنرانيها در ترم آينده قبل از سال جديد برگزار ميشود. به دليل فقدان اين بخش در واحدهاي فيزيك دانشجويان ارشد و كاشناسي ميتوانند از اين سخنرانيها استفاده كنند.
در صورت امكان از فروردين تا اواخر ارديبهشت مباحث پيشرفته و عام در هر دو سطح برگزار ميشود.
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