Particle Detectors

Similar results with much improved energy resolution, the sharpness of the peaks in the pulse height distribution, can be obtained using solid state detectors made from semi-conducting materials such as silicon or germanium. When properly constructed, the electrical charges released in the material by the passage of charged particles can be collected directly producing a short electrical pulse which can be amplified and analyzed. Germanium detectors made for use with gamma rays can have peaks in the pulse height distribution almost 100 times narrower than the peaks from a sodium Mark I detector at the Stanford Linear Accelerator Center (SLAC), California. The orange box-like structure at the left houses magnets that guide beams of electrons and positrons through the accelerator. The large octagonal structure is formed by the detector's magnet. Within it are two rings of photomultiplier tubes that detect light as it passes through the detector. Photograph by Lawrence Berkeley Lab, The National Audubon Society Collection. Photo Researchers, Inc. Reproduced by permission.
iodide detector. To obtain this improved resolution these detectors must be cooled to the temperature of liquid nitrogen 77K (-320.8°F; -196°C).

Smaller solid state detectors, usually made from silicon, are also used for measuring the energy of alpha particles, beta rays (electrons) from radioactive materials and x rays.