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Cryogenic Particle Detector
Cryogenic particle detectors operate at very low temperature, typically only a few degrees above absolute zero. These sensors interact with an energetic elementary particle (such as a photon) and deliver a signal that can be related to the type of particle and the nature of the interaction. While many types of particle detectors might be operated with improved performance at cryogenic temperatures, this term generally refers to types that take advantage of special effects or properties occurring only at low temperature. Introduction The most commonly cited reason for operating any sensor at low temperature is the reduction in thermal noise, which is proportional to the square root of the absolute temperature. However, at very low temperature, certain material properties become very sensitive to energy deposited by particles in their passage through the sensor, and the gain from these changes may be even more than that from reduction in thermal noise. Two such commonly used prope ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absolute Zero
Absolute zero is the lowest possible temperature, a state at which a system's internal energy, and in ideal cases entropy, reach their minimum values. The absolute zero is defined as 0 K on the Kelvin scale, equivalent to −273.15 °C on the Celsius, Celsius scale, and −459.67 °F on the Fahrenheit scale. The Kelvin and Rankine temperature scales set their zero points at absolute zero by design. This limit can be estimated by extrapolating the ideal gas law to the temperature at which the volume or pressure of a classical gas becomes zero. At absolute zero, there is no thermal motion. However, due to quantum mechanics, quantum effects, the particles still exhibit minimal motion mandated by the Uncertainty principle, Heisenberg uncertainty principle and, for a system of fermions, the Pauli exclusion principle. Even if absolute zero could be achieved, this residual quantum motion would persist. Although absolute zero can be approached, it cannot be reached. Som ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weakly Interacting Massive Particles
Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter. There exists no formal definition of a WIMP, but broadly, it is an elementary particle which interacts via gravity and any other force (or forces) which is as weak as or weaker than the weak nuclear force, but also non-vanishing in strength. Many WIMP candidates are expected to have been produced thermally in the early Universe, similarly to the particles of the Standard Model according to Big Bang cosmology, and usually will constitute cold dark matter. Obtaining the correct abundance of dark matter today via thermal production requires a self-annihilation Cross section (physics), cross section of \langle \sigma v \rangle ≃ , which is roughly what is expected for a new particle in the 100 GeV/''c''2 mass range that interacts via the electroweak force. Experimental efforts to detect WIMPs include the search for products of WIMP annihilation, inclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superconducting Tunnel Junction
The superconducting tunnel junction (STJ) – also known as a superconductor–insulator–superconductor tunnel junction (SIS) – is an electronics, electronic device consisting of two superconductors separated by a very thin layer of Insulator (electrical), insulating material. Current passes through the junction via the process of quantum tunneling. The STJ is a type of Josephson junction, though not all the properties of the STJ are described by the Josephson effect. These devices have a wide range of applications, including high-sensitivity Cryogenic particle detectors, detectors of electromagnetic radiation, SQUID, magnetometers, RSFQ, high speed digital circuit elements, and superconducting quantum computing, quantum computing circuits. Quantum tunneling All Electrical current, currents flowing through the STJ pass through the insulating layer via the process of quantum tunneling. There are two components to the tunneling current. The first is from the tunneling of C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transition-edge Sensor
A transition-edge sensor (TES) is a type of cryogenic energy sensor or cryogenic particle detector that exploits the strongly temperature-dependent resistance of the superconducting phase transition. History The first demonstrations of the superconducting transition's measurement potential appeared in the 1940s, 30 years after Onnes's discovery of superconductivity. D. H. Andrews demonstrated the first transition-edge bolometer, a current-biased tantalum wire which he used to measure an infrared signal. Subsequently he demonstrated a transition-edge calorimeter made of niobium nitride which was used to measure alpha particles. However, the TES detector did not gain popularity for about 50 years, due primarily to the difficulty in stabilizing the temperature within the narrow superconducting transition region, especially when more than one pixel was operated at the same time, and also due to the difficulty of signal readout from such a low- impedance system. Joule heating in a cur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Johnson Noise
Johnson may refer to: People and fictional characters *Johnson (surname), a common surname in English *Johnson (given name), a list of people * List of people with surname Johnson, including fictional characters *Johnson (composer) (1953–2011), Indian film score composer *Johnson (rapper) (born 1979), Danish rapper * Mr. Johnson (born 1966), Nigerian singer Places * Mount Johnson (other) Canada * Johnson, Ontario, township * Johnson (electoral district), provincial electoral district in Quebec * Johnson Point (British Columbia), a headland on the north side of the entrance to Belize Inlet United States * Johnson, Arizona * Johnson, Arkansas, a town * Johnson, Delaware * Johnson, Indiana, an unincorporated town * Johnson, Kentucky * Johnson, Minnesota * Johnson, Nebraska * Johnson, New York * Johnson, Ohio, an unincorporated community * Johnson, Oklahoma * Johnson, Utah * Johnson, Vermont, a town ** Johnson (village), Vermont * Johnson, Washington * Johnson, Wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resistor
A resistor is a passive two-terminal electronic component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat may be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity. Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors as discrete components can be composed of various compounds and forms. Resisto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Fluctuations
In statistical mechanics, thermal fluctuations are random deviations of an atomic system from its average state, that occur in a system at equilibrium.In statistical mechanics they are often simply referred to as fluctuations. All thermal fluctuations become larger and more frequent as the temperature increases, and likewise they decrease as temperature approaches absolute zero. Thermal fluctuations are a basic manifestation of the temperature of systems: A system at nonzero temperature does not stay in its equilibrium microscopic state, but instead randomly samples all possible states, with probabilities given by the Boltzmann distribution. Thermal fluctuations generally affect all the degrees of freedom of a system: There can be random vibrations (phonons), random rotations ( rotons), random electronic excitations, and so forth. Thermodynamic variables, such as pressure, temperature, or entropy, likewise undergo thermal fluctuations. For example, for a system that has an equ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermistors
A thermistor is a semiconductor type of resistor in which the resistance is strongly dependent on temperature. The word ''thermistor'' is a portmanteau of ''thermal'' and ''resistor''. The varying resistance with temperature allows these devices to be used as temperature sensors, or to control current as a function of temperature. Some thermistors have decreasing resistance with temperature, while other types have increasing resistance with temperature. This allows them to be used for limiting current to cold circuits, e.g. for inrush current protection, or for limiting current to hot circuits, e.g. to prevent thermal runaway. Thermistors are categorized based on their conduction models. ''Negative-temperature-coefficient'' (NTC) thermistors have ''less'' resistance at ''higher'' temperatures, while ''positive-temperature-coefficient'' (PTC) thermistors have ''more'' resistance at ''higher'' temperatures. NTC thermistors are widely used as inrush current limiters and temperature ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicon
Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, lead, and flerovium are below it. It is relatively unreactive. Silicon is a significant element that is essential for several physiological and metabolic processes in plants. Silicon is widely regarded as the predominant semiconductor material due to its versatile applications in various electrical devices such as transistors, solar cells, integrated circuits, and others. These may be due to its significant band gap, expansive optical transmission range, extensive absorption spectrum, surface roughening, and effective anti-reflection coating. Because of its high chemical affinity for oxygen, it was not until 1823 that Jöns Jakob Berzelius was first able to p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dielectric
In electromagnetism, a dielectric (or dielectric medium) is an Insulator (electricity), electrical insulator that can be Polarisability, polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, because they have no loosely bound, or free, electrons that may drift through the material, but instead they shift, only slightly, from their average equilibrium positions, causing dielectric polarisation. Because of Polarisation density, dielectric polarisation, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field. This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly Chemical bond, bonded molecules, those molecules not only become polarised, but also reorient so that their Symmetry axis, symmetry axes a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Debye Temperature
In thermodynamics and solid-state physics, the Debye model is a method developed by Peter Debye in 1912 to estimate phonon contribution to the specific heat (heat capacity) in a solid. It treats the oscillation, vibrations of the Crystal structure#Classification, atomic lattice (heat) as phonons in a box in contrast to the Einstein solid, Einstein photoelectron model, which treats the solid as many individual, non-interacting quantum harmonic oscillators. The Debye model correctly predicts the low-temperature dependence of the heat capacity of solids, which is proportional to the cube of temperature – the Debye ''T'' 3 law. Similarly to the Einstein photoelectron model, it recovers the Dulong–Petit law at high temperatures. Due to simplifying assumptions, its accuracy suffers at intermediate temperatures. Derivation The Debye model treats atomic vibrations as phonons confined in the solid's volume. It is analogous to Planck's law of black body radiation, which treats elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
