A diode is a two-terminal electronic component that conducts current primarily in one direction ; it has low resistance in one direction, and high resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. Semiconductor diodes were the first semiconductor electronic devices. The discovery of asymmetric electrical conduction across the contact between a crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other materials such as gallium arsenide and germanium are used.
Microwaves are a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter; with frequencies between 300 MHz (1 m) and 300 GHz (1 mm). Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF bands. A more common definition in radio engineering is the range between 1 and 100 GHz. In all cases, microwaves include the entire SHF band at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.
A semiconductor material has an electrical conductivity value falling between that of a metal, like copper, gold, etc. and an insulator, such as glass. Their resistance decreases as their temperature increases, which is behaviour opposite to that of a metal. Their conducting properties may be altered in useful ways by the deliberate, controlled introduction of impurities ("doping") into the crystal structure. Where two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers which include electrons, ions and electron holes at these junctions is the basis of diodes, transistors and all modern electronics. Some examples of semiconductors are silicon, germanium, and gallium arsenide. After silicon, gallium arsenide is the second most common semiconductor used in laser diodes, solar cells, microwave frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits.
Semiconductor devices are electronic components that exploit the electronic properties of semiconductor material, principally silicon, germanium, and gallium arsenide, as well as organic semiconductors. Semiconductor devices have replaced thermionic devices in most applications. They use electronic conduction in the solid state as opposed to the gaseous state or thermionic emission in a high vacuum.
A radiation dosimeter is a device that measures exposure to ionizing radiation. As a personal dosimeter it is normally worn by the person being monitored, and is a record of the radiation dose received. Older dosimeters, such as a film badge, require processing after use to reveal the cumulative dose received. Modern electronic personal dosimeters can give a continuous readout of cumulative dose and current dose rate, and can warn the person wearing it when a specified dose rate or a cumulative dose is exceeded.
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a precise frequency. This frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators, but other piezoelectric materials including polycrystalline ceramics are used in similar circuits.
A photodiode is a semiconductor device that converts light into an electrical current. The current is generated when photons are absorbed in the photodiode. Photodiodes may contain optical filters, built-in lenses, and may have large or small surface areas. Photodiodes usually have a slower response time as their surface area increases. The common, traditional solar cell used to generate electric solar power is a large area photodiode.
Optoelectronics is the study and application of electronic devices and systems that source, detect and control light, usually considered a sub-field of photonics. In this context, light often includes invisible forms of radiation such as gamma rays, X-rays, ultraviolet and infrared, in addition to visible light. Optoelectronic devices are electrical-to-optical or optical-to-electrical transducers, or instruments that use such devices in their operation.
Electro-optics is often erroneously used as a synonym, but is a wider branch of physics that concerns all interactions between light and electric fields, whether or not they form part of an electronic device.
A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses.
A synchrotron light source is a source of electromagnetic radiation (EM) usually produced by a storage ring, for scientific and technical purposes. First observed in synchrotrons, synchrotron light is now produced by storage rings and other specialized particle accelerators, typically accelerating electrons. Once the high-energy electron beam has been generated, it is directed into auxiliary components such as bending magnets and insertion devices in storage rings and free electron lasers.
These supply the strong magnetic fields perpendicular to the beam which are needed to convert high energy electrons into photons.
In accelerator physics, a beamline refers to the trajectory of the beam of accelerated particles, including the overall construction of the path segment along a specific path of an accelerator facility. This part is either
Thermoluminescence is a form of luminescence that is exhibited by certain crystalline materials, such as some minerals, when previously absorbed energy from electromagnetic radiation or other ionizing radiation is re-emitted as light upon heating of the material. The phenomenon is distinct from that of black-body radiation.
This article is about ionizing radiation detectors. For information about semiconductor detectors in radio, see Detector (radio), Crystal detector, Diode#Semiconductor diodes, and Rectifier.
Radiation hardening is the act of making electronic components and systems resistant to damage or malfunctions caused by ionizing radiation, such as those encountered in outer space and high-altitude flight, around nuclear reactors and particle accelerators, or during nuclear accidents or nuclear warfare.
A blue laser is a laser that emits electromagnetic radiation with a wavelength between 360 and 480 nanometres, which the human eye sees as blue or violet.
Zinc telluride is a binary chemical compound with the formula ZnTe. This solid is a semiconductor material with a direct band gap of 2.26 eV. It is usually a p-type semiconductor. Its crystal structure is cubic, like that for sphalerite and diamond.
Bismuth germanium oxide or bismuth germanate is an inorganic chemical compound of bismuth, germanium and oxygen. Most commonly the term refers to the compound with chemical formula Bi4Ge3O12 (BGO), with the cubic evlitine crystal structure, used as a scintillator. (The term may also refer to a different compound with formula Bi12GeO20, an electro-optical material with sillenite structure, and Bi2Ge3O9.)
A thermoluminescent dosimeter, or TLD, is a type of radiation dosimeter. A TLD measures ionizing radiation exposure by measuring the intensity of visible light emitted by a crystal inside the detector when the crystal is heated. The intensity of light emitted is dependent upon the radiation exposure. Materials exhibiting thermoluminescence in response to ionizing radiation include calcium fluoride, lithium fluoride, calcium sulfate, lithium borate, calcium borate, potassium bromide, and feldspar. It was invented in 1954 by Professor Farrington Daniels of the University of Wisconsin-Madison.
Sun-free photovoltaics is a photovoltaics technology which does not require sunlight to produce electricity. This technique was developed by research team at Massachusetts Institute of Technology Photovoltaic cells convert light to electricity most efficiently at specific wavelengths. The surface featured of Sun-free photovoltaics is engineered such that it converts heat energy into the specific wavelengths. This increases the efficiency of existing thermophotovoltaic (TPV) systems.
Chipless RFID tags are RFID tags that do not require a microchip in the transponder.
![Neutron monochromator for the ECHIDNA powder diffractometer at OPAL in Australia. It is made by slabs of [113] oriented Germanium crystals which are inclined towards each other in order to focus down the Bragg reflected beam. NeutronMonochromatorBNL.jpg](http://upload.wikimedia.org/wikipedia/commons/thumb/d/d9/NeutronMonochromatorBNL.jpg/200px-NeutronMonochromatorBNL.jpg)
