PHYSICAL STRUCTURE AND COMPOSITION.

In the late 1960s, a new method of x-ray detection was introduced. The use of a solid-state detection device and its accompanying electronics made elemental identification of areas of interest faster and easier than previously had been possible. A basic Energy Dispersive System (EDS) consists of a detector, a high-voltage bias power supply, an amplifier, and a multichannel anaylzer. When the Si(Li) crystal detector receives an x ray from the specimen, electrons from the silicon atoms are excited. The resulting charge is collected, and a current proportional in amplitude to the energy of the x-ray is stored by the Multichannel Analyzer (MCA). After accumulating for a sufficient length of time, the MCA displays the spectrum of x-rays, thus identifying the elements present in the specimen. This method of x-ray detection is applicable in health study field: air pollution, water pollution, and biological studies.