A detector named "Alice" is one of the four giant detectors around the circular tunnel of the Large Hadron Collider.
Alice weighs 1.25 metric tons
Atlas is a giant digital camera capable of taking pictures of 600 million proton collisions — the Large Hadron Collider has the ability to make protons collide 600 million times per second.
Installation of the final component of Atlas
Sina Technology News, July 24 message, according to the British Broadcasting Corporation, the Large Hadron Collider (LHC) being built in the tunnels beneath the France-Switzerland border is creating one of the coldest places in the universe, lowering temperatures to 1.9 Kelvin (-271 Celsius or -456 Fahrenheit), and it is now entering the final stage to achieve this goal.
This currently largest collider in the world contains thousands of magnets that use liquid nitrogen to maintain such cold temperatures. These magnets are arranged in a ring and extend along a huge tunnel for 27 kilometers. Once the Large Hadron Collider begins operation, two particle beams (usually composed of highly accelerated protons) will be fired down into tubes passing through these magnets. Then these beams will travel around the main ring at the speed of light in opposite directions.
At specified points in the tunnel, these beams will intersect, colliding with each other through high energy transformations. Scientists hope to discover new particles in the debris produced by these collisions, allowing them to further understand the natural state of the universe and how it was formed. The Large Hadron Collider is the most powerful physical experimental instrument ever created, re-creating the natural environment after the Big Bang. So far, six out of eight parts of the Large Hadron Collider have reached temperatures between 4.5 and 1.9 Kelvin, but eventually all parts of the collider will be cooled below 1.9 Kelvin. In comparison, the distant outer space has a temperature of about 2.7 Kelvin (-270 Celsius or -454 Fahrenheit).
Roberto Sabern led the trial run of the electronic components of the Large Hadron Collider, stating that these magnets must be "superconducting" to obtain high magnetic fields without excessive energy. Some materials exhibit this property at very low temperatures, ensuring current transmission with zero resistance and minimal power loss. Helium exhibits surprising properties at 2.2 Kelvin, becoming a "superfluid." This property allows it to quickly conduct heat, making it an extremely effective coolant. Sabern explained that there has never been a physical device on this scale operating at such low temperatures.
He said: "For the commissioning of this machine, we have a very systematic approach. Our motto is: science takes no shortcuts. Changing the temperature of the currently cooled components of the collider is like bringing it back from the moon to Earth. It takes about 3 to 4 weeks to heat these components. Then another 1 to 2 weeks for transformation. And then another 3 to 6 weeks to cool them again. Therefore, it’s clear that if we make a mistake, we would waste three months."
Currently, two components of the Large Hadron Collider have not yet reached the required low temperature, so the experiment cannot proceed. During the collision period, the electronics controlling the cryogenic system within these components will be transferred to an area shielded from particles to prevent them from being emitted from the machine.
The magnets of the Large Hadron Collider must also undergo electrical testing. Each part of the machine contains approximately 200 circuits. Each circuit may consist of 154 magnets or just one magnet. Researchers will test them to determine their ability to handle very high currents (up to 12,000 amperes). Sabern said: "We energize each circuit to ensure it can operate within the planned current range. But first, we must check whether the protection system around it (used to detect possible quenching phenomena) operates as expected." A quenching phenomenon occurs when some parts of the magnet start heating up, preventing current flow. Engineers have developed a recovery system that can detect these phenomena before they affect the magnetic field changing the direction of particles around the ring and cut off the circulating beam.
The machine's refrigerators will take another two weeks to complete, and no serious problems have been found so far. Current testing of the machine requires an additional two weeks. Before the first "activation" of the Large Hadron Collider, proton beams will reach a high-energy state through a particle accelerator called an injector. Once the machine's temperature drops, operators will fire the beams into the main ring, forcing them through each independent section until the circuit breaks. Researchers use a timing system (or synchronization system) to ensure each section operates like an independent machine. After the Large Hadron Collider is activated, it can operate at a high energy of 5 trillion electron volts. It will be shut down during winter so these magnets can be "trained" to handle beams at a high energy of 7 trillion electron volts. (Xiaowen)
Source: http://tech.sina.com.cn/d/2008-07-24/07342347435.shtml