A massive, exotic device--part of a larger machine called a particle detector--is taking shape in the basement of the University of Washington Physics-Astronomy Building. It will be the largest single piece of apparatus assembled in the University's history.
The six-story-high device, designed by the UW's Physics and Mechanical Engineering Departments, is being built as part of an international collaboration to assemble the world's most powerful atom smasher at the European Laboratory for Particle Physics (CERN) in Switzerland. The $6 billion atom smasher, due for completion in 2005, is designed to reveal the basic constituents of matter as well as answer esoteric questions about the origin of mass.
"The pure size of this dwarfs anything we have done before."
The U.S. has pledged $531 million in components and services for construction of the atom smasher's accelerator, called the Large Hadron Collider (LHC), and its two particle detectors. The LHC is designed to whirl elementary particles such as protons (a group collectively known as hadrons) around a 16-mile-circumference ring. When the particles collide, the two detectors will track the results.
University of Washington faculty and students are building an apparatus for one of the massive, cylinder-shaped particle detectors. "The pure size of this dwarfs anything we have done before," says Henry Lubatti, professor of physics and the University's liaison with CERN. "In terms of physics experimental apparatus, this is one of the most challenging detectors I have been involved with."
The UW and three other U.S. institutions will be building two cone-shaped sections that will detect particles, called muons, that are ejected from the hadron collisions. Among these muons might be a particle, the Higgs boson, whose existence is currently only conjectured. "The discovery of the Higgs boson is the Holy Grail of modern particle physics," says Lubatti, "because it is theorized to be the particle that confers mass. If its existence can be proven it will usher in a new era in physics."
The muon detector consists largely of aluminum tubes--370,000 of them--each with a hair-thin gold-plated tungsten wire at the center. The tubes, ranging from three to 18 feet in length, are filled with pressurized gas. Each tube must measure the position of any muons passing through by a three-thousandths of an inch.
The UW team will be fabricating 27,000 of the tubes. Then they must glue hundreds of the tubes into a trapezoidal shape to form a chamber. In all, the team will assemble 80 such chambers. "The challenge is not only to build something on an industrial scale," says Lubatti, "but to do so with a precision that is rarely achieved in industry."
The UW is providing space and equipment for the project, which is being funded from an $80 million National Science Foundation grant. A prototype of one chamber has already been built and shipped to Europe, and a dust-free clean room has been erected in the physics-astronomy machine shop. At least 20 researchers and scores of students will be involved in the project. Already several physics undergraduates have designed and tested parts of the assembly apparatus.