With approximately 9600 magnets and a circumference of 16,565 miles, the Large Hadron Collider (LHC) is the largest and most sophisticated accelerator operated by the famous CERN research institute, so far. When the LHC started operations, it marked a turning point in the field of particle physics, as it may help unlock answers to fundamental questions, such as the origin of matter. The Large Hadron Collider beauty (LHCb) experiment, the A Toroidal LHC ApparatuS (ATLAS) experiment, and the Compact Muon Solenoid (CMS) experiment are three of the four experiments currently installed at LHC.
Featured Image: With approximately 9600 magnets and a circumference of 16,565 miles, the Large Hadron Collider or LHC (red circle) is the largest and most sophisticated particle accelerator in the world (photo credit: CERN).
Above: In the Large Hadron Collider beauty (LHCb) experiment, researchers pursue the question of why our universe consists primarily of matter and not antimatter. The system they use weighs 5600 metric tons and contains a variety of detectors that are used to identify particles and examine their properties (photo credit: CERN)
PRECISION IS KEY
In order to achieve precise measurements, silicon detectors are built in close vicinity to the interaction point of all experiments. Carbon dioxide cooling plants cool the innermost layers of the silicon detectors down to temperatures as low as -40 degrees Fahrenheit (-40 degrees Celsius). Two diaphragm metering pumps from Lewa GmbH have been used for the LHCb experiment since 2007. They ensure a uniform flow rate, which is essential for continuous and uniform cooling and disturbance-free operation. Two similar systems operated in redundancy guarantee from the beginning of 2015 the thermal management of the IBL sub-detector of the TALS experiment. For the CMS pixel detector upgrade, to be installed in 2016, a new CO2 cooling system featuring a remote head Lewa metering pump has been built and commissioned. Unlike standard pumps, remote-head pumps can convey the highly compressed CO2 without heat input.
The silicon sensors are a major aspect of the detectors. They must be cooled to approximately -13 degrees Fahrenheit (-25 degrees Celsius) by way of two carbon dioxide loops in order to achieve a good signal-to-noise ratio and minimize radiation damage (photo credit: CERN).
The first cooling system equipped with Lewa pumps was developed and produced by the National Institute for Subatomic Physics Nikhef in Amsterdam for the Large Hadron Collider beauty (LHCb) experiment. The aim of this experiment is to answer the question of why the universe is comprised primarily of matter and not anti-matter. One of the things researchers will look at is the B meson, which contains an elementary particle known as a b quark, also known as a beauty quark, from which the name LHCb is derived. In order to obtain such particles, the LHC must accelerate protons to near the speed of light and induce them into collision. The particles obtained in this way are recorded using special instruments and then analyzed with the assistance of computer programs.
OIL-FREE CO2 COOLING OF DETECTORS FOR PRECISE RESULTS
The LHCb detectors are unlike other recording systems at the LHC, since detection occurs in only one direction. The first sub-detector, called the VeLo (for Vertex Locator) is located directly at the collision point. Others are arranged one after the other along a distance of about 65 feet. Among other things, the VeLo is used to precisely determine the location of decays and for particle reconstruction. In order to reach the highest possible precision, the entire system must be under vacuum. Furthermore, to prevent severe radiation damage on silicon sensors, two carbon dioxide loops cool each half of the VeLo detector to about -13 degrees Fahrenheit (-25 degrees Celsius). Silicon detectors subject to the strong radiation levels of the LHC are subject to two kinds of damages: displacements in the crystalline structure due to Non Ionizing Energy Loss, and accumulation of positive charge in superficial layers due to Ionizing Energy Loss. The most relevant effects of these combined radiation-induced damages are a sharp increase of the voltage required for the sensor depletion, an increase of the leakage current (hence of the signal-to-noise ratio), and a sensitive decrease of the breakdown voltage. While huge R&D efforts are dedicated to new generations of ever more radiation-resistant detectors, it is known that operation at temperatures well below 32 degrees Fahrenheit (0 degrees Celsius) greatly mitigates these damaging effects.
The first CO2 cooling system equipped with Lewa pumps was developed and produced by the National Institute for Subatomic Physics Nikhef in Amsterdam for the Hadron Collider beauty (LHCb) experiment. This approach to cooling removes heat by exploiting the phase change of CO2 from liquid to vapor (photo credit: CERN).
A LOOK AHEAD
CERN chose diaphragm metering pumps from Lewa for a number of reasons, especially because no oil can be tolerated in the detector cooling circuit, because oil can start to solidify under the influence of radiation and may then cause a blockage in the thin cooling lines. In next month’s conclusion, we’ll take a closer look at the metering pumps in action. ◆
For More Information:
LEWA GmbH is the world’s leading manufacturer of metering pumps and process diaphragm pumps as well as complete metering packages for process engineering. LEWA develops technologies and provides solutions for the vast array of applications among its customers. Products are primarily used in the oil and gas industry, in the area of gas odorization, refineries, and petrochemistry, but also in the manufacture of plastics, detergents, and cleaning agents. For more information, visit www.lewa-inc.com.
____________________________________________
MODERN PUMPING TODAY, September 2016
Did you enjoy this article?
Subscribe to the FREE Digital Edition of Modern Pumping Today Magazine!
Tracking the Origins of the Universe: Part 1 of 2
