Building the world’s most senstive particle detectors calls for special workbench

A workman from a specialty moving company navigates the 25-ton granite tablethrough a hole in the Physics-Astronomy building wall. The table is flat to one quarter of one-thousandth of an inch.

A crew of specialty movers didn’t have to violate the laws of physics to get 25-ton slab of Colorado white granite into the basement of the Physics-Astronomy building last week. They “simply” had to take advantage of the giant holes cut in the laboratory walls, flipping the slab on its long edge, maneuvering it through the openings and flipping it back.

The slab—15 feet long, nearly 10 feet wide and 2 feet thick—now stands as a giant table on which to build precision components of one of the world’s most sensitive particle detectors. The components will be built during the next five years for the Atlas detector in a new particle accelerator, the Large Hadron Collider, under construction at the European Laboratory for Particle Physics (CERN) near Geneva, Switzerland.

Physicists have developed the Standard Model of elementary particles that describes all the information obtained with present accelerators. However, the theory breaks down at higher energies and new phenomena must be added, says physics research professor Paul Mockett. The Atlas detector will explore a higher-energy region for the new phenomena. Many physicists expect to find numerous new particles that complement the known particles. They also hope to find the Higgs boson, a particle theorized in the Standard Model. Interactions involving the Higgs boson could be the very reason objects have mass, and its discovery could bring profound advances in understanding the nature of all matter in the universe.

The UW’s Elementary Particle Experiment Group, part of the international team contributing to the Large Hadron Collider, will track the most penetrating charged particles, called muons, produced in the violent collisions created between two very-high-energy beams of protons. Muons are a major component of the cosmic rays that shower from the upper atmosphere, and are often produced in the types of collisions that interest physicists in the search for new phenomena.

The Atlas detector is shaped roughly like a Coke can on its side—except the ends of the can are as tall as a six-story building. Collisions between the two proton beams take place at the center of the “can” and the spray of particles passes through layers of various detector components designed to track them. The UW group will track charged particles that reach the outer layer—specifically the ends—of the “can” and will build components to detect those particles. Physics and engineering students will assist in construction, and physics graduate students will take part in the assembly and operation of the detectors. The detectors must be built with a precision of one-thousandth of an inch to perform properly, thus the granite slab. It has been carefully ground until the top of the slab is flat to one-quarter of one-thousandth of an inch, providing a precision base upon which to build the components and a reference to ensure their precision. Professor Henry Lubatti is responsible for the tubes that go into the detector components, and is responsible for assembling the components. In addition, mechanical engineering professor Colin Daly and physics research engineer David Forbush are key to the engineering effort. ¶

Vince Strichez, News and Information