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Topic: Josephson constant

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	Magnetic flux quantum - Wikipedia, the free encyclopedia
		The quantum of magnetic flux is a physical constant, as it is independent of the underlying material as long as it is a superconductor.
		The Josephson constant is the inverse of the quantum of magnetic flux:
		This is remarkable since h is generally associated with the behavior of microscopically small systems, whereas the quantization of magnetic flux in a superconductor and the quantum Hall effect are both collective phenomena associated with thermodynamically large numbers of particles.
	en.wikipedia.org /wiki/Josephson_constant (445 words)

	Josephson effect - Wikipedia, the free encyclopedia
		The Josephson effect is a term given to the phenomenon of current flow across two superconductors separated by a very thin insulating barrier.
		Josephson junctions are also used in Rapid Single Flux Quantum integrated circuits, and some other of their properties can be exploited to build photon or particle detectors.
		Josephson junctions are used as microwave detectors in the giga- and terahertz range.
	en.wikipedia.org /wiki/Josephson_junction (816 words)

	Superconductivity - Wikipedia, the free encyclopedia
		In the same year, Josephson made the important theoretical prediction that a supercurrent can flow between two pieces of superconductor separated by a thin layer of insulator.
		Josephson was awarded the Nobel Prize for this work in 1973.
		Superconductors are used to build Josephson junctions which are the building blocks of SQUIDs (superconducting quantum interference devices), the most sensitive magnetometers known.
	en.wikipedia.org /wiki/Superconductivity (2826 words)

	Physics Today March 2001
		The fine-structure constant in the expression for the electron mass is most precisely determined by comparing theory and experiment for the anomalous magnetic moment of the electron, as discussed in box 2.
		A remarkable aspect of this experiment is that the Planck constant, which is the characteristic unit of quantum phenomena, is measured by a two-story-high apparatus, shown in figure 3, that is described by classical mechanics and classical electromagnetic theory.
		As described in box 2, the value of the fine-structure constant is most strongly determined by comparison of theory and experiment for the electron anomalous magnetic moment, and the theoretical expression, in turn, is determined by high-order QED calculations.
	www.physicstoday.org /pt/vol-54/iss-3/p29.html (3210 words)

	Powering scheme for josephson logic circuits which eliminates disturb signals - Patent 4012646
		A Josephson junction terminated line logic powering scheme is disclosed wherein a logic gate and a regulating gate are utilized in at least a single logic circuit to provide a constant voltage to the logic circuit.
		A Josephson junction array according to claim 12 wherein said pulse transient generating means for reducing cross-talk includes a latching Josephson junction device having a zero voltage state and a voltage state the switching of which into the former state substantially cancels a disturb signal generated by the switching of one of said junctions.
		Josephson junction 12 otherwise characterized as a logic gate, has the usual terminated line logic properties and, for purposes of the present explanation, should be considered to be operable in the latching mode.
	www.freepatentsonline.com /4012646.html (4183 words)

	Physikalisch-Technische Bundesanstalt (PTB)
		Irradiation of this Josephson junction with microwaves (being an electromagnetic wave) creates between the superconductors discrete voltage levels depending only on the ratio of two fundamental constants and the frequency f of the microwaves.
		The Josephson effect is therefore world-wide used as a basis for constant reference voltages in metrological national institutes and in calibration laboratories of industry.
		As the Josephson constant is not known with the needed accuracy, the same agreed value is used everywhere for these purposes, which is named K
	www.ptb.de /en/org/2/Inhalte/Josephson/josephson.htm (374 words)

	[No title]
		For a tension V constant, measured at the boundaries of a Josephson junction, one observes the passage of a sinusoidal current of frequency v = 2 e / h x V. The Josephson effect makes it possible to connect, by the intermediary of the 2 universal constants e and h, the tension to the frequency.
		After the discovery of the Planck's constant h, Einstein put forth the assumption of the corpuscular nature of the photon and stated his famous equation of the photoelectric effect E cin = hv - W where W is the energy of extraction of the electron of material.
		This factor of proportionality is h / e, i.e., in the temporalist model, 2 µ / To, the reverse of the temporalist constant.
	site.voila.fr /nobigbang/mtsixtheconstantt.htm (2767 words)

	SQUID Magnetometer and Josephson Junctions
		If a constant biasing current is maintained in the SQUID device, the measured voltage oscillates with the changes in phase at the two junctions, which depends upon the change in the magnetic flux.
		Parallel Josephson junctions are used in SQUID devices for the detection of minute magnetic fields.
		In the AC Josephson effect, a Josephson junction will oscillate with a characteristic frequency which is proportional to the voltage across the junction.
	hyperphysics.phy-astr.gsu.edu /hbase/solids/squid.html (604 words)

	LNE, Quantum metrology : the josephson effect, Research and Development
		The Josephson effect [1] is one of the notable effects of
		DC Josephson effect: If no voltage is applied to the junction terminals, a direct current - a current of Cooper pairs Ij, - flows through the junction up to a critical value Ic, which depends on the geometry, temperature and magnetic field (Fig.2a).
		The definition of the volt in the International System of Units (SI) is as follows: "The volt is the electromotive force between two points of a conductor carrying a current of 1 ampere when the power dissipated between the two points is 1 watt" [3].
	www.lne.fr /en/r_and_d/electrical_metrology/josephson_effect_ej.shtml (1369 words)

	Physics Today July 2001
		Josephson immediately set to work extending the calculation to a situation in which both sides of the barrier were superconducting.
		As Josephson explained it to me, "Bardeen's basic error was to ignore the non-locality inherent in the Gor'kov theory, and to assume a local connection between the potential and the pairing." There remained, however, a point of contention.
		They succeeded, confirming that it was indeed the Josephson effect by testing, among other things, the magnetic-field dependence of the supercurrent (see figure 2a.) In January 1963, Anderson and Rowell submitted their paper "Probable Observation of the Josephson Superconducting Tunneling Effect" for publication.
	www.aip.org /pt/vol-54/iss-7/p46.html (4120 words)

	Volt - Encyclopedia, History, Geography and Biography
		Josephson junction array chip developed by NIST as a standard volt.
		Since 1990 the volt is maintained internationally for practical measurement using the Josephson effect, where a conventional value is used for the Josephson constant, fixed by the 18th General Conference on Weights and Measures as
		Prior to the development of the Josephson junction voltage standard, the volt was maintained in national laboratories using specially constructed batteries called standard cells.
	www.arikah.net /encyclopedia/Volt (392 words)

	Ultra high accuracy voltage measurement system - Patent 5764048
		The constant voltage difference of the step voltages is proportional to the frequency f while the step number N is dependent of a number of Josephson elements included, a microwave power P emitted to the Josephson junction and a bias current for the Josephson junction.
		A main feedback loop is formed by the Josephson voltage generator 30, the balance detector 21, and the difference feedback circuit 26 to control the Josephson voltage equal to the voltage to be measured, i.e., the voltage of the DUT 10.
		Since the Josephson junction voltage generator employed in the first embodiment is a expensive device, in the second aspect of the present invention, a frequency controlled voltage generator, which is available with a relatively low cost, is used as a precision voltage source.
	www.freepatentsonline.com /5764048.html (6473 words)

	Environmental, Health & Safety (It's my day job): Physical constants
		Constants can take many forms: the Planck length represents a fundamental physical distance; the speed of light in a vacuum signifies a maximum speed limit of the universe; and the fine-structure constant, which characterizes the interaction between electrons and photons, is dimensionless.
		Constants that are independent of systems of units are typically dimensionless numbers, and are known as fundamental physical constants.
		Some believe that if the physical constants had slightly different values, our universe would be so different that intelligent life would probably not have emerged, and that our universe seems to be fine-tuned for intelligent life.
	www.christopherhaase.com /blog/2004/12/physical-constants.html (855 words)

	IEN - Electrical Metrology Department
		We kept constant the width of the lateral idle region and changed the ratio of the longitudinal idle part to the junction length.
		The constant voltage steps generated by a slightly damped Josephson junction driven by short rectangular current pulses are studied within the RSJ model for a broad range of dc and RF bias.
		Josephson junctions, both single and two junctions stacks, have been fabricated using a SNAP process where liquid anodization is used not only for insulation and area patterning, but also for trimming the junction dimensions at a micrometer level.
	www.ien.it /ar96/pub/me.htm (5170 words)

	Physics Today March 2001
		The Planck constant h can be measured by comparing a watt of mechanical power expressed in terms of the meter, kilogram, and second to a watt of electrical power expressed in terms of the Josephson constant K
		Since the voltage U and the voltage and resistance that determine I are calibrated in terms of the Josephson and von Klitzing constants, the constant A is, in principle, exactly known, and f
		are the accurately known frequencies applied to the Josephson junctions in the two phases of the experiment.
	www.physicstoday.org /pt/vol-54/iss-3/captions/p29box3.html (272 words)

	056-058
		Absolute experimental determinations of units are now known as SI realizations, and the uncertainty of the SI values of the electrical units are limited by the uncertainty of their realizations in terms of the kilogram, meter, and second.
		Results from the calcu-lable capacitor experiment and other determinations of the fine-structure constant recently have been combined analytically [7] to yield a value of the von Klitzing constant RK with a relative standard uncertainty of 4.10 Ð9.
		The Josephson constant KJ is based both on its direct measurement by voltage balances and by combining RK with a value of the Planck constant, the latter obtained by realizing the watt in a special way.
	nvl.nist.gov /pub/nistpubs/sp958-lide/html/056-058.html (1682 words)

	metas: Electricity - Electrical Quantum Experiments
		The Josephson effect is a quantum mechanical phenomenon that occurs in a superconducting tunnelling device which is composed of two superconductors separated by a thin insulating barrier (known as a Josephson junction).
		If a Josephson junction is brought to the superconducting state by cooling to 4 K, and exposed to microwave radiation, constant voltage steps are observed in the current-voltage characteristic of the device.
		The combination of the natural constants in the ratio 2e/h is referred to as the Josephson constant K
	www.metas.ch /en/labors/2/21joseph.html (266 words)

	BIPM - principles
		In the moving experiment, the coil is moved at a constant speed v through the magnetic field so that a voltage U is induced:
		The subscript "90" indicates that the measurements of the related quantities are based on the conventional constants, fixed by international agreement in 1990
		The watt balance could therefore contribute to a significant reduction in the uncertainty of the Josephson constant.
	www.bipm.fr /en/scientific/elec/watt_balance/wb_principle.html (292 words)

	Josephson Effect
		If a thin insulating barrier between two superconductors (a Josephson junction) is cooled in liquid helium to 4.2 K and exposed to electromagnetic radiation of frequency, f, then the DC voltage across the junction V
		The Josephson constant is believed to be equal to the ratio h/2e where h is Planck’s constant and e is the electronic charge.
		In January 1990 a value of 483597.9 GHz/V was adopted for the Josephson constant in SI units with a relative 1
	www.npl.co.uk /electromagnetic/dclf/voltres/josephson_effect.html (194 words)

	Liquid Helium Mimics a Superconductor
		Experiments with the Josephson effect are among the few quantum mechanical systems that are accessible by classical measurements, explains J.C. Seamus Davis, of the University of California at Berkeley.
		The Josephson effect is exploited in the superconducting quantum Interference device (SQUID), which is the essential part of ultrasensitive commercial brain scanners, precision position sensors, and advanced magnetic field detectors.
		According to the Josephson effect, each value of the pressure corresponds to a specific "Josephson frequency." They found that the net flow dramatically increased when the pressure corresponded to a Josephson frequency matching a mechanical resonance in the chamber.
	focus.aps.org /story/v2/st9 (726 words)

	Abstract of Ph.D. Theses, Physics (Site not responding. Last check: 2007-10-31)
		Application of Josephson junctions (JJ) as submillimeter sources, detectors or mixer are based on the interaction of large number of JJ in complex arrays.
		It is shown that noise causes the appearance of broad minima and reduction of the maxima in the power dependence of the step amplitude as a consequence of its influence on the dynamical mode of the junction Good agreement of our results with experimental data of Kautz et al.
		In modelling the intrinsic stacked Josephson junction we neglected the coupling between junctions, which is not in real.
	jmi.nic.in /Research/ab2004_physics_jamalakhtar.htm (808 words)

	Constants defining the metric system (Site not responding. Last check: 2007-10-31)
		Constants proposed, or already adopted, for defining the metric SI Speed of light (defines the meter): exactly 299792458 m/s
		A notable step was taken in 1983 when the meter was defined by specifying that the standard speed of light be exactly 299792458 meters per second.
		In 1990 the BIPM established its voltage standard by specifying that Brian Josephson's constant (2e/h, the operating characteristic of modern gauges) be exactly 483597.9 billion cycles per second per volt.
	www.planck.com /adopted.htm (251 words)

	Supraleitung und Hochfrequenzsensoren
		However, in comparison to niobium Josephson junction the spread of parameters of HTS junctions is still very high.
		The application of a Josephson reference voltage based on arrays of HTS junctions for the calibration of Zener diodes permits to retain the small uncertainty of the secondary voltage standard over the whole operating period.
		A link between Josephson standard and Zener reference permits to measure the influence of pressure, temperature and humidity on the output voltage of the electronic standard.
	www.fz-juelich.de /isg/isg2/isg2-sh/jjarrays.htm (1259 words)

	Chemistry International -- Newsmagazine for IUPAC
		In defining the units of the SI upon which this subject is built, we endeavor today to choose definitions that are referenced to quantum properties of atoms or to fundamental constants, a subject known as quantum metrology.
		The second is the X-ray crystal density experiment, in which a perfectly spherical single crystal of silicon (see photo on cover of this issue) is weighed against a kilogram standard, and its lattice spacing is measured by X-ray diffraction, allowing a calculation of the number of atoms in the crystal from its diameter.
		The best estimates of these constants are revised at intervals by the CODATA (Committee on Data for Science and Technology) task group established for this purpose.
	www.iupac.org /publications/ci/2005/2705/3_mills.html (2174 words)

	[No title]
		= 2e/h, which appears in the equations for the alternating-current Josephson effect, where e is the magnitude of the charge of the electron and h is Planck's constant.
		] An equation according to which the Josephson current is a sinusoidally varying function of the applied magnetic field.
		] The law that at constant temperature the internal energy of a gas tends to a finite limit, independent of volume, as the pressure tends to zero.
	www.accessscience.com /Dictionary/J/J3/DictJ3.html (2690 words)

	Physikalisch-Technische Bundesanstalt (PTB)
		If a combination of fundamental constants is required, which has not been included in the table, the correlation of the tabled values must be taken into account when the respective uncertainty is calculated.
		The relevant covariance matrix, its correct use as well as the values of other constants can be found in the following original publication:.
		The actual values of all the fundamental constants can be found in the CODATA database.
	www.ptb.de /en/naturkonstanten/zahlenwerte.html (173 words)

	PowerPedia:Kilogram - PESWiki
		The Watt balance uses the current balance that was formerly used to define the ampere to relate the kilogram to a value for Planck's constant, based on the definitions of the volt and the ohm.
		The levitated superconductor approach relates the kilogram to electrical quantities by levitating a superconducting body in a magnetic field generated by a superconducting coil, and measuring the electrical current required in the coil.
		Since the values of the Josephson (CIPM (1988) Recommendation 1, PV 56; 19) and von Klitzing (CIPM (1988), Recommendation 2, PV 56; 20) constants have been given conventional values, it is possible to combine these values (K
	peswiki.com /index.php/PowerPedia:Kilogram (1047 words)

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