Wednesday, September 25, 2013

Chuanqi Shen: An Accelerator

Visiting SLAC got me excited about physics all over again, so I decided to learn more about the history of SLAC and the different discoveries that were made.

SLAC was a linear accelerator constructed in 1962, dubbed as the longest and straightest structure in the world. In fact, it is so straight that it does not follow the curvature of the Earth. Affectionately called the "Monster", it gave the scientists the ability to accelerate particles to nearly the speed of light, allowing the scientists to observe sub-atomic particles.

The first breakthrough came soon after SLAC reached full operation. A research team was able to use electron beams to discover that protons actually comprised of smaller sub-atomic particles called quarks. This discovery allowed the research team to win the Nobel Prize in Physics in 1990.

A few years later, SLAC was upgraded with the addition of the Stanford Positron Electron Asymmetric Ring (SPEAR). This new technology allowed the scientists to make a breakthrough again. In 1974, in what was called the "November Revolution", a team from SLAC and a team from Brookhaven National Laboratory made independent discoveries of the J/psi particle, which consisted of a paired charm quark and anti-charm quark. This discovery led to the Nobel Prize in Physics in 1976. In 1975, Martin Perl also discovered the tau lepton, and this led to his winning the Nobel Prize in Physics in 1995.

Today, SLAC has diversified from particle physics to applying accelerator science to many other fields ranging from environmental sciences, chemistry to alternative energy research. Application could even be found in art. For example, a few pages of the Archimedes Palimpsest, Archimedes' oldest surviving works, were unreadable, obscured by grime and mold. After discovering that Archimedes used iron-based ink to write the works, SLAC scientist Uwe Bergmann was able to use X-ray florescence imaging to pick up trace of iron on the pages with high precision, thus revealing the text on the pages for the first time in a thousand years. 

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