Silicon integrated

Circuits and the

Elusive top Quark

A report by:

Comm. R.M. Wey

COSR: SFS/SFC

Physicists from around the world have been in search of the TOP quark. And now, after many years and many blind alleys, the search is over. Using a kind of silicon based microscope [referred to as the Microstrip detector] which required more than fifteen years to develop physicists can now measure particles to within ten microns. Such precision was, until now, unavailable and has opened new possibilities in other scientific fields as well as particle physics. How this device works is a study unto itself, but the device uses diodes [sort of an electronic ‘one way street’], which permit current to flow in only one direction. Thus are experiments conducted using the device free of statistical ‘static.’ Deposited on wafers of silicon, these diodes can be shaped to the required shape and size [depending on the requirements of the experiment]. A charged particle passing through such a wafer [or an x-ray absorbed into it] generates a signal which is detected by the diodes. But transforming a chunk of raw silicon into an instrument of such complexity is one, which requires great care. The process begins with a thin wafer of silicon [approx. 300 microns thick and 10 in diameter] into which an impurity atom [typically phosphorus] is introduced. Once prepared, the diode consists of a P-type and an N-type material, with a fine region between them that is free of charged carriers, but that contains a strong electric field. This region is where particles are detected when the diode is part of the detector. Though useful to other areas of discipline, the microstrip detector was designed and built for but one purpose, to locate the all illusive "charm" [or top] quark. The top quark is but one of six [up, down, charm, strange, top, and bottom], along with six particles known as leptons and their corresponding antiparticles, they form the very matter of the universe. With a life expectancy of only about one picosecond [or 1/1,000,000,000,000 of a second] locating and tracking the vertices are what the detector was designed to do. And having played such a vital role in the successful location of the top quark, plans are being set to use it to search for the most desired of particles in high energy physics...The Higgs Boson. Having withstood detection for more than three decades, the Higgs Boson remains the ‘Holy Grail’ of particle physics. But the detectors work is not limited to particle physics, Astrophysics and x-ray imaging, as well as gamma ray astronomy have turned to the detector as a possible means of solving many of these disciplines' problems. Yet, as wonderful a device as it is, it is far from perfect, and only time will tell whether this device is THE answer.