Concise Dictionary Of Physics E-Book

• Herausgeber: V&S Publishers
• Kategorie: Bildung
• Sprache: Englisch
• Veröffentlichungsjahr: 2018

Seitenzahl: 439

Beschreibung

Terms frequently used in Physics and their accurate explanation

Leseprobe

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© Copyright: ISBN 978-935-05733-1-0

DISCLAIMER

While every attempt has been made to provide accurate and timely information in this book, neither the author nor the publisher assumes any responsibility for errors, unintended omissions or commissions detected therein. The author and publisher make no representation or warranty with respect to the comprehensiveness or completeness of the contents provided.

All matters included have been simplified under professional guidance for general information only without any warranty for applicability on an individual. Any mention of an organization or a website in the book by way of citation or as a source of additional information doesn't imply the endorsement of the content either by the author or the publisher. It is possible that websites cited may have changed or removed between the time of editing and publishing the book.

Results from using the expert opinion in this book will be totally dependent on individual circumstances and factors beyond the control of the author and the publisher.

It makes sense to elicit advice from well informed sources before implementing the ideas given in the book. The reader assumes full responsibility for the consequences arising out from reading this book. For proper guidance, it is advisable to read the book under the watchful eyes of parents/guardian. The purchaser of this book assumes all responsibility for the use of given materials and information. The copyright of the entire content of this book rests with the author/publisher. Any infringement/ transmission of the cover design, text or illustrations, in any form, by any means, by any entity will invite legal action and be responsible for consequences thereon.

Contents

Publisher's Note

Introduction

        A

        B

        C

        D

        E

        F

        G

        H

        I

        J

        K

        L

        M

        N

        O

        P

        Q

        R

        S

        T

        U

        V

        W

        X

        Y

        Z

AppendicesAppendix – I

Appendix – II

Appendix – III

Appendix – IV

Appendix – V

Publisher's Note

Innumerable books are available in the market on science and its allied branches, like, physics, chemistry, and biology et al, both as textbook and reference manual. Written for different age-groups and class, quite a number of these books come replete with jargon-filled terms; and just fail to connect with readers’ inclination and curiosity level. On top of that, new words keep finding their way into the books every other day. Every new addition contributes to difficulty in comprehending the matter.

An average reader is interested only in knowing what a specific word means without getting lost with heavy sounding inputs.

Following an open-ended discussion with a cross-section of students and other stakeholders we realised that many books on science (physics, chemistry and biology) take readers’ understanding of scientific terms for granted and make short passing references while alluding to the term in the text. Presentations of this nature in no way assist readers in understanding the subject properly.

You need to suffer no longer.

V&S Publishers has come out with four dictionaries of terms; in science, physics, chemistry and biology. These have been compiled to help readers grasp the meaning of popular scientific terms. For easy reference terms have been arranged alphabetically. Terms that have come into the reckoning even in the early 2012 have been incorporated and suitably explained in such a way that an average secondary and senior secondary student can grasp them easily. High resolution images, illustrations and examples, where appropriate, have been added for reader's convenience. For all readers, who have not made a special study of any science subject, explanations of terms will be found to be easily comprehensible.

An attempt has been made to include important scientific charts, tables, constants, conversion tables as appendices to make this dictionary more useful. A glossary of Nobel Prize winners and their contributions is an added attraction.

We would be happy to have your views and comments about the book.

Introduction

What is Physics?

Physics is the systematic study of the way matters interact. It is really concerned with how things move and what causes things to move. Things can be as large as a star or small as an atom.

Why is study of physics important?

Studying the way things move and interact is fundamentally useful in everyday life. Have you given a thought how our brain functions? It uses an automatic understanding of physics, for example, being able to walk or balancing ourselves requires our brains to make lots of calculations about friction and forces.

Physics is crucial to virtually all of our modern technology, conveniences and infrastructure from computers to cameras and everyday appliances.

It is useful in everyday situations. Having an awareness of physics can help explain:

Significance of apple falling from a tree

Difficulty in walking on sand

How our eyes function

Big bang and the origin of Earth

Why we get tired

How water boils or freezes

How simple machines work

How is Physics Classified?

Typically physics is classified into traditional areas of study. These include:

Atomic/nuclear – The scientific study of the structure of an atom, its energy states, and its interactions with other particles and with electric and magnetic fields. Atomic physics has proved to be a spectacularly successful application of quantum mechanics, which is one of the cornerstones of modern physics.

Mechanics – The scientific study of motion of bodies under the action of forces, including the special case in which a body remains at rest. In the problem of motion are the forces that bodies exert on one another. This leads to the study of such topics as gravitation, electricity, and magnetism, according to the nature of the forces involved. Given the forces, one can seek the manner in which bodies move under the action of forces.

Electromagnetism – The study of charge and of the forces and fields associated with charge. Electricity and magnetism are two aspects of electromagnetism. Electric forces are produced by electric charges either at rest or in motion. Magnetic forces, on the other hand, are produced only by moving charges and act solely on charges in motion. Electricity and magnetism were long thought to be separate forces. It was not until the 19th century that they were finally treated as interrelated phenomena. At a practical level, however, electric and magnetic forces behave quite differently and are described by different equations.

Thermodynamics – The study of relationship between heat, work, temperature, and energy. In broad terms, thermodynamics deals with the transfer of energy from one place to another and from one form to another. The key concept is that heat is a form of energy corresponding to a definite amount of mechanical work.

Quantum physics – The study of scientific principles that explains the behaviour of matter and its interactions with energy on the scale of atoms and atomic particles (small scale). In classical physics, matter and energy at the macroscopic level (large scale) of the scale familiar to human experience is studied.

Optics – The study of science concerning the production and propagation of light, the changes that it undergoes and produces, and other phenomena closely associated with it. There are two major branches of optics – physical and geometrical. Physical optics deals primarily with the nature and properties of light itself. Geometrical optics has to do with the principles that govern the image-forming properties of lenses, mirrors, and other devices that make use of light.

Acoustics – The study of science concerning production, control, transmission, reception, and effects of sound.

How does Physics Work?

One way that physicists currently study things is by measuring the basic forces that exist in the universe. These forces are:

The Strong Force (forces inside the nucleus of atoms) – The forces that operate inside the nucleus are a mixture of those familiar from everyday life and those that operate only inside the atom. Two protons, for example, will repel each other because of their identical electrical force but will be attracted to each other by gravitation. Nevertheless, because the nucleus stays together in spite of the repulsive electrical force between protons, there must exist a counterforce-which physicists have named the strong force-operating at short range within the nucleus.

The Weak Force (relates to how atoms decay) – The weak force operates inside the nucleus. The weak force is responsible for some of the radioactive decays of nuclei. The four fundamental forces-strong, electromagnetic, weak, and gravitational-are responsible for every process in the universe. One of the important strains in modern theoretical physics is the belief that, although they seem very different, they are different aspects of a single underlying force.

The Electromagnetic Force (forces created by moving electrons including light)

The Gravitational Force (how things fall)

Most everyday physics is a result of the electromagnetic force and gravitational force.

How is Physics Studied?

The basic principle of studying physics is to measure things. For example, how fast is it moving and in which direction or angle?

For example, a series of events have certain duration in time. Time is the dimension of the duration. The duration might be expressed as 30 minutes or as half-an-hour. Minutes and hours are among the units in which time may be expressed. One can compare quantities of the same dimensions, even if they are expressed in different units (an hour is longer than a minute). Quantities of different dimensions cannot be compared with one another.

The fundamental dimensions used in physics are time, mass, and length. The study of electromagnetism adds an additional fundamental dimension, electric charge. Other quantities have dimensions compounded of these. Temperature is measured in Kelvin,

Measurement is done using internationally accepted SI units. The seven basic units, from which other units are derived, are defined as follows:

Length – metre, defined as the distance travelled by light in vacuum in 1/299,792,458 second.

Mass – kilogram, which equals to 1,000 grams as defined by the international prototype kilogram of platinum-iridium in the keeping of the International Bureau of Weights and Measures in Sèvres, France.

Time – second, the duration of 9,192,631,770 periods of radiation associated with a specified transition of the cesium-133 atom.

Electric current – ampere, which is the current that, if maintained in two wires placed one metre apart in vacuum, would produce a force of 2 × 10?7 Newton per metre of length.

Luminous intensity – candela, defined as the intensity in a given direction of a source emitting radiation of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

Substance – mole, defined as containing as many elementary entities of a substance as there are atoms in 0.012 kg of carbon-12.

Thermodynamic temperature – kelvin.

Physics is also used in other scientific fields like biology and chemistry. For example: The physics of biology becomes Biophysics, Physics of astronomy becomes Astrophysics and Physics of the earth becomes Geophysics.

Important physicists of all time and their contributions

Archimedes (Greek) – Archimedes discovered the concept of buoyancy; developed formulae for the areas and volumes of spheres, cylinders, parabolas, and several other solids. He worked extensively with levers. He also invented the Archimedes screw to raise water. In warfare he developed several siege engines that served to hamper the Roman invasion of his home city of Syracuse.

Galileo Galilei (Italian) – Galileo discovered the law of uniformly accelerated motion. He improved on the refracting telescope. He also discovered the four largest satellites of Jupiter. He described projectile motion and the concept of weight. He was, however, best known for his championing of the Copernican theory of heliocentricity against church opposition.

Michael Faraday (English) – Faraday showed how a changing magnetic field can be used to generate an electric current. He also described the principles of electrolysis. He is an early pioneer in the field of low temperature study.

Johannes Kepler (German) – Kepler outlined three fundamental laws of planetary motion. He described elliptical motion of planets around the sun. His works served as the precursor to that of Newton's.

Isaac Newton (English) – Newton quantified laws of motion and gravity. He also explained the concept of light dispersion and co-invented the Calculus. He invented the reflecting telescope.

Albert Einstein (German/Swiss/American) – Einstein developed theories of Special and General Relativity. He also worked on the photoelectric effect and deescribed mass-energy equivalence.

Max Planck (German) – He is the father of Quantum mechanics. He showed how the energy of a photon is proportional to its frequency.

Georg Ohm (German) – Ohm determined law in electricity that states that current is equal to the ratio of voltage to resistance.

James Maxwell (Scottish) – Maxwell developed equations for electromagnetism and the kinetic theory of gases. He predicted that there were other types of radiation beyond that of visible light and showed that light was a type of electromagnetic radiation.

Marie Curie (Polish) – Two time Nobel Prize winner, Marie Curie with Henri Becquerel and Pierre discovered radioactivity. She also isolated Plutonium and Radium.

Niels Bohr (Danish) – Bohr used Quantum mechanical model to show how electron energy levels are related to Spectral lines.

Erwin Schrödinger (Austrian) – Erwin Schrödinger is famous for the equation that bears his name. Describes the wave action and behaviour of matter.

Werner Heisenberg (German) – He developed a method to express Quantum mechanics in terms of matrices. Heisenberg is best known for his Uncertainty Principle.

Ernest Rutherford (Kiwi/British) – Rutherford is considered as the father of Nuclear Physics. He showed how the atomic nucleus has a positive charge. Rutherford was the first to change one element into another by an artificial nuclear reaction.

Nicolas Copernicus (Polish Monk) – Copernicus wrote the 400 page treatise ‘On the Revolutions of the Celestial Spheres’ that argued that the Earth revolved around the sun. The book challenged the way the world was viewed leading to much ecclesiastical opposition.

Christiaan Huygens (Dutch) – Huygens developed Wave Theory of Light and discovered polarization.

James Joule (British) – Joule showed that heat is a form of energy and also demonstrated that gas expansion with no work leads to a fall in temperature. His work led to the Theory of Conservation of Energy.

Henry Cavendish (British) – He showed that water is made up of the union of two gases and also determined the Universal Gravitation constant.

William Thomson Kelvin (Scottish) – A major figure in Thermodynamics. Thomson Kelvin helped develop the Law of Conservation of Energy. He studied Wave motion and vortex motion in hydrodynamics and produced a dynamical theory of heat.

Thomas Young (British) – Young furthered the doctrine of wave interference. He is famous for his ‘slit’ experiments.

Enrico Fermi (Italian/American) – Fermi split the nucleus by bombarding it with neutrons and built the first Nuclear reactor in the United States.

Richard Feynman (American) – Known for his work on quantum electrodynamics, as well as for his visual representation of the behaviour patterns of interacting particles (Feynman diagrams).

Alessandro Volta (Italian) – Volta built the first electrical battery. He is the first scientist to do substantial work with Electric currents.

Heinrich Hetrz (German) – Discovered radio waves and determined their velocity.

Benjamin Franklin (American) – Franklin worked with electricity and defined positive and negative charges.

John Bardeen (American) – Bardeen developed the point contact transistor (won Nobel Prize with Walter Brattain and William Shockley in 1956). He won a second Nobel Prize (1972) for his work on Superconductivity (shared with Leon Cooper and John Schrieffer).

Nikolai Tesla (Yugoslavian/American) – Tesla is the champion of alternating current flow (which is the means by which electric power is carried in our modern network). He also improved on the dynamo, transformer and electric bulb and invented the Tesla coil.

Paul Dirac (British) – Dirac developed the theory of the spinning electron and proposed the existence of anti-matter.

Robert Millikan (American) – Millikan determined the charge on an electron and did vital work with Cosmic Rays.

Edwin Hubble (American) – Hubble discovered that the universe is expanding. He established a ratio between the rate of expansion and the distance between galaxies.

Pieter Zeeman (Dutch) – Zeeman discovered the Zeeman effect, whereby a ray of light placed in a magnetic field is split spectroscopically into several components. This has helped physicists investigate atoms, study electromagnetic radiation and for astronomers to measure the magnetic field of stars.

Andre-Marie Ampere (French) – Ampere worked in field of Electrodynamics. He also showed how an electric current produces a magnetic field.

Joseph John Thomson (British) – Thomson showed that Cathode rays were rapidly moving particles. He also worked out that the mass of these individual particles (electrons) was less than 2000 times that of the atom itself.

Henri Becquerel (French) – Discovered the natural radioactivity of uranium.

Louis de Broglie (French) – Discovered the wave nature of electrons and particles.

Charles Coulomb (French) – Determined that positive and negative charges attract one another and showed that the magnitude of the force diminishes with distance.

Georges Lemaître (Belgian) – Proposed the Big Bang Theory of the origin of the Universe.

Christian Doppler (Austrian) – Doppler discovered that a wave's frequency changes when its source and the observer are moving relative to one another (the Doppler Effect).

Lise Meitner (Austrian) – Meitner discovered with Otto Hahn the radioactive element – protactinium. Known for her work in Nuclear Physics she developed, with her nephew Otto Frisch, the concept of Nuclear Fission.

Hans Oersted (Danish) – Discovered magnetic effect of an electric current.

Robert Boyle (Irish) – Boyle showed that the pressure and volume of a mixed mass of gas are inversely proportional. He was highly active as a Chemist as well.

Hendrik Lorentz (Dutch) – Lorentz clarified the Electromagnetic Theory of light, developed concept of local time. His work would influence Albert Einstein.

Joseph von Fraunhofer (German) – First to realise that dark lines in spectra of light can be used to determine the makeup of celestial bodies.

Ludwig Boltzmann (Austrian) – Father of Statistical Mechanics. He worked on the kinetic theory of gases.

Robert Hooke (British) – Hooke formulated the law of elasticity and invented the balance spring, the microscope and the Gregorian telescope.

Evangelista Torrecelli (Italian) – Inventor of the Barometer, Evangelista Torrecelli is considered as the Father of Hydrodynamics.

Wilhelm Weber (German) – Weber invented the electrodynamometer. He is the first to apply the mirror and scale method of reading deflections.

Ernst Mach (Austrian) – Mach showed how airflow is disturbed at the speed of sound.

John Wheeler (American) – Wheeler was a theoretical physicist. He coined the terms black hole and worm hole.

Wilhelm Roentgen (German) – Discovered x-rays.

Stephen Hawking (British) – Hawking is noteworthy for his work in cosmology especially with respect to singularities. He predicts that a Black hole will convert its mass to radiation, and then disappear.

Of course there were many others that have contributed to physics in many different ways.

The Future of Physics

There have been revolutionary developments taking place in medicine, computers, artificial intelligence, nanotechnology, energy production, and astronautics. The way scientists are applying theory to applications, in all likelihood, by 2100 we will control computers via tiny brain sensors and, like magicians, move objects around with the power of our minds. Artificial intelligence will be dispersed throughout the environment, and Internet-enabled contact lenses will allow us to access the world's information base or conjure up any image we desire in the blink of an eye.

Meanwhile, cars will drive themselves using GPS, and if room-temperature superconductors are discovered, vehicles will effortlessly fly on a cushion of air, coasting on powerful magnetic fields and ushering in the age of magnetism.

Using molecular medicine, scientists will be able to grow almost every organ of the body and cure genetic diseases. Millions of tiny DNA sensors and nano-particles patrolling our blood cells will silently scan our bodies for the first sign of illness, while rapid advances in genetic research will enable us to slow down or maybe even reverse the aging process, allowing human life spans to increase dramatically.

In space, radically new ships – needle-sized vessels using laser propulsion – could replace the expensive chemical rockets of today and perhaps visit nearby stars. Advances in nanotechnology may lead to the fabled space elevator, which would propel humans hundreds of miles above the earth's atmosphere at the push of a button.

But these astonishing revelations are only the tip of the iceberg. There would be emotional robots, antimatter rockets, X-ray vision, and the ability to create new life-forms. Physics of the Future is a thrilling, wondrous ride through the next 100 years of breathtaking scientific revolution.

What are the laws of physics yet to be discovered? This is perhaps the age old question for physics. One big future goal in physics is to somehow unify the basic forces of nature.

One of the main future goals in physics is to unify laws of gravity with quantum mechanics.

While studying physics, we come across hundreds of words. Some of them are comprehensible to us while others are not. To facilitate study of physics properly, the first important element is to grasp what a particular word means. Once done, it becomes easy to read the text and understand its meaning.

The dictionary you are about to read will do just that.

A

A/D, adc

Analogue to Digital converter (hardware) or the Analogue readback of a device (software). The hardware is a device which converts an analog voltage presented at its input to a binary digital representation of that voltage for use by the control system. Most A/D's in the control system have a measurement resolution of less than 5 mv and accept input voltages in the range -10.23 to 10.24 volts. In some applications (Linac and MRPS regulation) special units are used which have a resolution of less than 1.25 mv.

Aal

Activation Analysis Laboratory of the ES&H Section

Abort

Terminating the acceleration process prematurely, either by inhibiting the injection mechanism or by removing circulating beam to some sort of dump. This is generally done to prevent injury to some personnel or damage to accelerator components.

Abort concentrator module

A CAMAC 200 module in the Main Ring, Tevatron, and Pbar abort system capable of accepting up to 8 inputs from devices in a given service building. If the permit signal originating from a device disappears, an abort is generated.

Abort link generator module

A C201 card located at the C0 Service Building which generates the 5 MHz permit signal broadcast around the abort loop.

Abort logic/pulse shifter interface

Produces status of Main Ring and Tevatron abort loops. Inputs to Linac Keyswitch Module.

Abort loop

The system of electronics which decides to remove the beam from an accelerator in order to protect personnel and/or equipment.

Abort reset command (tev)

A command sent from the MCR in the form of a TCLK event which clears the latched abort status and restores a beam permit.

Abort system

The Main Ring and Tevatron abort system at Fermilab is designed to dump the beam promptly on a beam dump. During Fixed Target operation both dumps are located near the long straight section C. During Colliding Beams operation the Tevatron abort system is located in the A0 section of the ring to make room for the Tevatron seperators. The abort magnets are triggered by any one of several abnormal accelerator conditions or radiation alarms. It is routinely fired at the end of an acceleration cycle to purge the accelerator of unextracted beam.

Abscissa

The value corresponding to the horizontal distance of a point on a graph from the Y axis and the X coordinate.

Absolute deviation

The difference between a single measured value and the average of several measurements made in the same way.

Absolute error

The actual difference between a measured value and its accepted value.

Absolute humidity

The ratio of water vapour in a sample of air to the volume of the sample.

Absolute pressure

Units to measure gas pressure. Normally referred to as psia (pounds per square inch absolute) with zero being a perfect vacuum.

Absolute zero

The temperature of – 273.16°C or – 459.67°F or 0 K at which molecular motion ceases.

Absorptance

The ratio of the total absorbed radiation to the total incident radiation.

Absorption spectrum

A continuous spectrum interrupted by dark lines or bands that are characteristic of the medium through which the radiation has passed.

Accelerating column

Located in the Pre-Acc pit. Set of seven titanium electrodes (eight gaps) arranged in Pierce geometry to accelerate ions to 750 keV. Situated between -750 kV dome and pit wall.

Acceleration

Time rate of change of velocity.

Acceleration due to gravity

The acceleration imparted to bodies by the attractive force of the earth or any other heavenly body.

Accelerator

Any machine used to impart large kinetic energies to charged particles such as electrons, protons, and atomic nuclei. These accelerated particles are then used to probe nuclear or subnuclear phenomena. There are also many accelerators in industrial and medical applications.

Accelerator studies

Mode of operation of the accelerator where accelerator performance and/or beam dynamics is studied and tested.

Acceptance

The measure of the limiting aperture of a transport line, accelerator, or individual device; it defines how “large” a beam will fit without scraping. More technicaly acceptance is the phase-space volume within which the beam must lie in order to be transmitted through an optical system without losses. From an experimenters point of view acceptance is the phase-space volume intercepted by an experimenter's detector system. The complement of emittance.

Acceptor

An element with three valence electrons per atom which when added to a semiconductor crystal provides electron “holes” in the lattice structure of the crystal.

Accidental rate

The rate of false coincidences in an electronic counter experiment produced by products of the reactions of more than one beam particle within the time resolution of the apparatus.

Accuracy

Closeness of a measurement to the accepted value for a specific physical quantity; expressed in terms of error.

Achromatic

The quality of a transport line or optical system where particle momentum has no effect on its trajectory through the system. An achromatic device or system is that in which the output beam displacement or divergence (or both) is independent of the input beam's momentum. If a system of lenses is achromatic, all particles of the same momentum will have equal path lengths through the system.

Aclkwatcher

A process on the VAX which decodes TCLK events and generates timing information for internal consumption (for such things as the frequency of data acquisition.)

Acnet

Accelerator Control NETwork. A system of computers that monitors and controls the accelerator complex. Interfaced to users through consoles in the MCR and elsewhere.

Acoustics

The science of the production, transmission and effects of sound.

Acoustic shielding

A sound barrier that prevents the transmission of acoustic energy.

Ad

Accelerator Division

Ad/ops

Accelerator Division Operations Department

Adhesion

The force of attraction between unlike molecules.

Adiabatic

Any change in which there is no gain or loss of heat.

Adiabatic cooling

The classical description is a process in which the temperature of a system is reduced without any heat being exchanged between the system and its surroundings. At Fermilab this term is used to describe the process in the Antiproton Source Accumulator storage ring where beam emittances are reduced without affecting beam energy. This process is used in accumulating antiprotons.

Adiabatic invariant

An invariant of a motion is a quantity which does not change as time advances. For instance, the energy of a system is often an invariant (for a swinging pendulum, or a planet and the Sun), and knowing that it stays constant is a great help in calculating the motion.

Adiabatic process

A thermal process in which no heat is added to or removed from a system.

Adsorbent

The material of an adsorber. Silica gel, Alumina, Charcoal. Characterized by high surface/volume ratio.

Adsorber

Attracts and holds (by Van der Waal forces) molecular layers of dense gases (i.e. very near condensation temperatures) on porous high surface/volume ratio materials.

Aeolus

A process on the VAX which collects alarm information from the front-ends, combines that information with appropriate parametres in the database, and sends the package to the console cpus.

Afocal lens

A lens of zero convergent power, whose focal points are infinitely distant.

Aggregate ON/OFF

A command used to control the digital status of a block of devices.

Ags

Alternating Gradient Synchrotron accelerator at Brookhaven National Laboratory on Long Island, New York. It is a 30 GeV combined function proton synchrotron which started operation in 1959.

Air ionization chamber

Devices used by NTF to monitor neutron flux during patient treatment.

Alara

As Low As Reasonably Achievable. A safety acronym used to describe the radiation safety philosophy of minimizing occupational radiation exposure.

Alarm

A message, usually generated by the AEOLUS VAX process, indicating that the digital or analogue status of a device is not within the tolerances set for it.

Alarm display monitor

A colour television display in the upper right-hand corner of each ACNET console which lists devices currently in a state of alarm.

Alarm screen

Same as the Alarm Display Monitor.

Albedo

The fraction of the total light incident on a reflecting surface, especially a celestial body, which is reflected back in all directions.

Alpha function

(ax, ay) A measure of the change of the beta function db/dz; a>0 N converging, a

Alpha particle

A helium-4 nucleus, especially when emitted from the nucleus of a radioactive atom.

Alternating current

An electric current that has one direction during one part of a generating cycle and the opposite direction during the remainder of the cycle.

Ammeter

An electric metre designed to measure current.

Amorphous

Solids which have neither definite form nor structure.

Ampere

The unit of electric current; one coulomb per second.

Amplifier

Any device that amplifies an electronic signal.

Amplitude

The maximum displacement of a vibrating particle from its equilibrium position.

Amplitude control module

Linac low-level RF system component that controls the amplitude of the RF gradient by varying the size of the modulator input pulse.

Analogue

Typically a device or circuit that expresses a signal in direct proportion to a physical measurement.

Angle of contact

The angle between tangents to the liquid surface and the solid surface inside the liquid, both the tangents drawn at the point of contact.

Angle of incidence

The angle between the incident ray and the normal drawn to the point of incidence.

Angle of reflection

The angle between the reflected ray and the normal drawn to the point of incidence.

Angle of refraction

The angle between the refracted ray and the normal drawn to the point of refraction.

Angle of repose

The angle of inclination of a plane with the horizontal such that a body placed on the plane is at the verge of sliding.

Angstrom

A unit of linear measure equal to 10−10 m.

Angular acceleration

The time rate of change of angular velocity.

Angular impulse

The product of a torque and the time interval during which it acts.

Angular momentum

The product of the rotational inertia of a body and its angular velocity.

Angular velocity

The time rate of change of angular displacement.

Annihilation

A process in which a particle and antiparticle combine and release their rest energies in other particles.

Annunciator board

Status panel in Linac primary and secondary microprocessors showing status and interrupt levels.

Anode

(1) The positive electrode of an electric cell.

(2) The positive electrode or plate of an electronic tube.

(3) The electron-poor electrode.

Ansi

American National Standards Institute

Antimatter

A substance composed of antiparticles.

Antineutrino

The antiparticle of neutrino, it has zero mass and spin ½.

Antiparticle

A counterpart of a subatomic particle having opposite properties (except for equal mass).

Antiproton

The antimatter counterpart of the proton. The proton forms the nucleus of the hydrogen atom for example. Antiprotons are routinely produced at Fermilab's Antiproton source by slamming high energy protons from the Main Ring into a target. The resulting nuclear collision includes antiprotons as by-products and the source accumulates them over time. After a large “stack” has been built up, the antiprotons are shot out into the Tevatron where they are brought up to the largest energies. They are also found in cosmic rays but the intensity is much smaller.

Antiproton accumulator

After some time in the debuncher, antiprotons are continuously diverted to the accumulator where they undergo further cooling until a large stack of antiprotons is built. At this point, they are funneled out to the Main Ring and accelerated up to where the Tevatron will use them to collide with protons.

Antiproton debuncher

Protons from the Main Ring are presently diverted into a target where among other products, antiprotons are produced. Only 8 GeV antiprotons are accepted and steered into the Debuncher ring where radio frequency manipulations and various cooling systems shrink the size of the size of the beam in phase space in anticipation of its being stored for long periods of time.

Antiquench

The false appearance of a positive resistive voltage (negative resistance). This is the result of the Quench Protection Monitors's calculation during an actual quench in another cell or due to an instrumentation failure.

AP or APCR

Antiproton Control Room, located in AP10. Now more commonly referred to simply as AP10.

Ap0

Accelerator building situated above the pbar target vault enclosure. The power supplies, electronics and maintenance equipment for the pbar target station and lithium lens are located here.

Ap4

The beamline designed to provide a low intensity beam of 8 GeV protons from the Booster to the Debuncher.

Aperture scan

Process of changing the beam position via 3- bumps in a localized area in order to determine the size of the aperture. The beam is moved until is scrapes the side of the beam pipe or encounters an obstruction.

Apm

Applications Programme Manager. A function on the console computer which coordinates application task scheduling by making sure the PA or SA executes at the proper periodic rate, recognizes the keyboard interrupt, etc. It also performs console data collection tasks, determines the visible cursor position, shaft encoder position, touch panel x, y position, and the status of the interrupt button.

Apparent mean thermal conductivity

The effective thermal conductivity of an assemblage of material (Pearlite, super insulation) between specified temperatures.

Apparent power

The product of the effective values of alternating voltage and current.

Application programmes

Software designed for direct use by a console user. The programmes reside on the ACNET consoles.

Arc degree

A unit of angular measure in which there are 360 arc degrees in a full circle.

Arc second

Abbreviated arcsec. A unit of angular measure in which there are 60 arc seconds in 1 arc minute and therefore 3600 arc seconds in 1 arc degree. One arc second is equal to about 725 km on the Sun.

Arc tangent

The inverse function to the tangent. Symbol: arctan or tan−l. Interpretation: “An angle whose tangent is

Archimedes principle

A body immersed in a fluid experiences an apparent loss in weight which is equal to the weight of the fluid displaced by the body.

Archive

Permanent storage of information regarding a given accelerator system. Magnetic tape is the primary medium. An archive should be distinguished from a “Save,” where information is written onto a disk and is likely to be written over at some future date.

Argus

A process on the VAX which logs off interactive users if the account has been idle for a certain length of time.

Armature

A coil of wire formed around an iron or steel core that rotates in the magnetic field of a generator or motor.

Artifact

A feature which appears in an NMR spectrum of a molecule which should not be present based on the chemical structure and pulse sequence used.

Astronomical unit (AU)

Astrophysics

The science of studying the physical processes occurring in and around astronomical objects such as stars and galaxies.

Atmosphere

A convenient measure of pressure.

Atom

The smallest particle of an element that can exist either alone or in combination with other atoms of the same or other elements.

Atomic mass unit

One-twelfth of the mass of carbon-12, or 1.6605655 x 10−27 kg.

Atomic number

The number of protons in the nucleus of an atom.

Atomic weight

The weighted average of the atomic masses of an element's isotopes based on their relative abundance.

Attitude (of a satellite)

The direction in which the satellite is oriented in space.

Audio signal

The alternating voltage proportional to the sound pressure produced in an electric circuit.

Aurora

A colourful, rapidly varying glow in the sky caused by the collision of charged particles in the magnetosphere with atoms in the Earth's upper atmosphere. Auroras are most often observed at high latitudes and are enhanced during geomagnetic storms.

Aurora (short for polar aurora)

A glow in the sky, seen often in a ring-shaped region around the magnetic poles (“auroral zone”) and occasionally further equatorward. The name comes from an older one, “aurora borealis,” Latin for “northern dawn,” given because an aurora near the northern horizon (its usual location when seen in most of Europe) looks like the glow of the sky preceding sunrise. Also known as “northern lights,” although it occurs both north and south of the equator.

Auroral oval

The region in which aurora can be seen at any single time, as observed (for instance) by satellite cameras. It resembles a circle centred a few hundred kilometres nightward of the magnetic pole, and its size varies with magnetic activity. During large magnetic storms it expands greatly, making auroras visible at regions far from the pole, where they are rarely seen.

Auto quench recovery (aqr)

A computer programme residing in the refrigerator micro-p which automatically performs cooldown after a quench.

Auto-gradient

Feature where the Linac RF gradients are controlled by computer through the Amplitude Control Module. Normally engaged.

Average velocity

Total displacement divided by elapsed time.

Avogadro number

The number of molecules in a gram molecular weight of a substance, it is equal to 6.02 x 1023.

Avogadro's law

Under the same conditions of temperature and pressure, equal volumes of all gases contain equal number of molecules.

B

B clock

Obsolete. A frequency that was transmitted to a module in the MAC-A PDC crate which was proportional to the change in the Main Ring current. The dI/dT was measured in the magnet cage and transmitted over the Main Ring B-clock link via CC42 cards.

B0

A reference point on the Main Ring at which the Collider Detector at Fermilab is located (pronounced “B zero”). Other significant reference points include the D0 collision region, and C0, E0, and F0 regions used for specialized experiments.

B0 collision hall

Also referred to as the Collision Hall. CDF detector at B0 resides in this hall during collider operation.

Back emf

An induced emf in the armature of a motor that opposes the applied voltage.

Back racks

Electronics racks behind the primary working region of the Main Control Room; consists of patch panels, link modules, highpotters, and much more.

Background

Whatever devices are used to make a measurement in an experiment, the measurement is a superposition of events from the target and events from all other sources (background). The background therefore sets a lower limit on the detection of small signals. More generally, background is any unwanted signal.

Balmer lines

Band spectrum

An emission spectrum consisting of fluted bands of colour. The spectrum of a substance in the molecular state.

Bao

Batavia Area Office of the DOE

Bar

A unit of pressure, equal to 105 Pascals.

Barn

Barometre

A device used to measure the pressure of the atmosphere.

Baryon

A subatomic particle with a large rest mass, e.g., the proton.

Basic control

The ability to change the digital status of a device by interrupting on a parameter page. This function is supported by the database.

Basic equation

An equation that relates the unknown quantity with known quantities in a problem.

Basic law of electrostatics

Similarly charged objects repel each other. Oppositely charged objects attract each other.

Batch

A unit of beam corresponding to the output of one Booster cycle. Up to 12 batches of beam can be injected into Main Ring each cycle.

Baud

A unit of signalling speed; defined as the number of code elements (i.e. bits) per second.

Bayonet

A low heat conduction, longitudinally extended connector for cryogenic piping. see Transfer Line.

Bcs theory

This is the successful theory of superconductivity developed in the 1950's and eventually resulting in the Nobel prize for the authors, J. Bardeen, L.N. Cooper, and J.R. Schrieffer, Phys. Rev. 108, 1175 (1957). This is the classic exposition of the BCS theory.

Beacon

Message on Linac serial data link flashed by a secondary microprocessor when the link repeater upstream of it fails.

Beam damper

A device for applying a force on the circulating beam in an accelerator to reduce either the excursions from the equilibrium orbit (betatron oscillations) or from equilibrium phase (synchrotron oscillations)

Beam dump

A massive object used to absorb an unwanted beam and dissipate the resulting heat. Dumps for high intensity beams are usually composed of large water cooled metal blocks. They must be shielded from the surrounding environment due to the extreme radioactivity induced by the absorbed beam.

Beam inhibit light link module

Linac Module through which the H- and I- secondary microprocessors can pull the beam inhibit line.

Beam intensity

The average number of particles in a beam passing a given point during a certain time interval, given, for example, as the number of protons per pulse or protons per second.

Beam line

Beam line is a collective term referring to all the devices used to control, monitor, and produce a beam having particular characteristics. The common elements of a beam line are magnets, intensity monitors, beam position monitors, and collimators.

Beam loading

Phenomenon whereby beam being accelerated by an RF cavity changes the gradient and phase of the RF in the cavity.

Beam loss

Loss of protons from the beam chamber.

Beam roll

A periodic change in horizontal and/or vertical positions during spill. This doesn't include changes caused by humans.

Beam sample pulse (bsp)

Obsolete. A pulse originated in a module of the MAC-A PDC crate which sent a signal around the ring by way of CC42 cards. It was a two-way communication, with each CC42 card echoing back a response to the BSP controller in the PDC crate. The pulse was used in generating the Main Ring sample time, as well as taking voltage-to-ground snapshots if a ramp current fault occured.

Beam stacking

A form of multi-turn injection in which a single turn is injected and then moved by acceleration or deceleration to make room for additional turns. This process, also called momentum space stacking, often appears in storage ring applications.

Beam stop

Linac primary critical device in the 750 keV line that blocks the beam path to prohibit beam in Linac. Controlled by CARESS and the pulse shifter.

Beam switch

Toggle switch to inhibit beam to a particular area of the accelerator on HEP pulses according to the logic in the Beam Switch Sum Box. Eight modules of these switches are found in the MCR.

Beam sync clock

The clocks MRBS and TVBS, for which the basic frequency is directly related to the revolution frequency of the beam. They are derived from their respective LLRF systems. They operate at frequencies of about 7.5 MHz and produce a clock “tick” every 7 bunches. Beam sync clocks are used for all critical timing of beam transfers between accelerators.

Beam toroid

A device used for measuring beam intensities by measuring the magnetic field fluctuations produced by the passing beam. The magnetic field fluctuations produce a current in a coil which is wound around a closed circular ring (torus) through which the beam passes.

Beam turns

The width of the beam pulse going to Booster divided by the revolution period of the Booster at injection.

Beam valve

A pneumatically operated gate valve that closes across the beam pipe to physically isolate one section of beam line from another. Beam valves are commonly used to isolate vacuum allowing the beamline in one sector or house to be brought up to atmosphere for maintenance while keeping adjacent sections under vacuum. In the event of a vacuum burst beam valves are closed automatically to isolate sectors in order to localize the vacuum problem.

Beamline (transport line)

A series of magnets and vacuum pipe which carry the proton beam from one portion of the accelerator to another.

Beamline microcomputer

An NTF computer that monitors beamline devices, dose rates, and communicates with the NTF medical microcomputer as well as the local Linac secondary.

Beat

A phenomenon of the periodic variation in the intensity of sound due to superposition of waves differing slightly in frequency.

Becquerel

The rate of radioactivity equal to one disintegration per second.

Belly pan

A design feature of the Linac tanks that allows leaks in the tank welds to be put under vacuum.

Benelex

A substance similar to G-10 used to hold NTF neutron collimators in position.

Berm

Earth shielding over the top of a radiation enclosure.

Bernoulli's theorem

The total energy per unit volume of a non-viscous, incompressible fluid in a streamline flow remains constant.

Beta (β) particle

An electron or positron emitted from a radioactive source.

Beta function

A measure of beam width. The beta function details how the beam changes around the accelerator. There are separate Beta functions for the x and y planes. The square root of bx is proportional to the beam's x-axis extent in phase space.

Beta matching

Matching of the beam size to the radius of the receiving beam pipe.

Betatron

A device that accelerates electrons by means of the transformer principle.

Betatron oscillations

Stable oscillations about the equilibrium orbit in the horizontal and vertical planes; these oscillations were the first studied in betatron oscillators, hence the name.

Bevatron

A high-energy synchrotron.

Bias pulser

A Linac module that drives the grid of the 7651 tube in the Buncher RF system.

Bias supply

Programmable power supply used to power the ferrite tuners of RF cavities in the Booster and Main Ring.

Bimodal ramp

The Main Ring magnets are pulsed to create two flattops to allow extraction at two different energies.

Binding energy

Energy that must be applied to a nucleus to break it up.

Bipolar supply

A power supply that has an operating voltage range of positive to minus. A unipolar supply has an operating range from zero to some positive value.

Birkeland currents

Electric currents linking the Earth's ionosphere with more distant regions, flowing along magnetic field lines. Named for Kristian Birkeland, a pioneer of auroral research who first proposed such currents around 1900, these currents are often associated with the polar aurora.

Bit

This stands for Binary digit. It may have a value of zero or one and is the smallest unit of measure. See byte and word.

Black body

An ideal body which would absorb all incident radiation and reflect none.

Black hole

The remaining core of a supernova that is so dense that even light cannot escape.

Bleeder resistors

In the Linac application, the resistors placed between the High-Voltage supply for the purpose of discharging energy when the power supply is turned off.

Blind scaler

A scaler made without a display for computer readout only.

Blm

A device used to measure beam loss from the accelerator. The detectors are sealed ionization chambers. BLM stands for Beam Loss Monitor.

Block transfer (btr)

An option for data transfer in the CAMAC links. Although data is transmitted serially, it arrives at the MAC or front-end in a continuous stream rather than in discrete units. The BTR link is on a separate cable from the CAMAC serial link. It is able to transfer information at a 10 Mbit/sec rate in blocks 196 Kbytes in length.

Blow up

A relatively sudden and usually catastrophic increase in beam size generally caused by some magnetic field error driving the beam to resonance.

Blowing up emittances

To try to keep down beam-beam tune shifts the emittances of the proton bunches are increased. This is known as “blowing up the emittances”. Emittances will also blow up unintentionally when the machine is tuned wrong.

Boiling point

Any point on a vapour pressure curve.

Booster

The ring directly behind the south side of Wilson Hall surrounding the cooling pond. Protons are accelerated here to 8 GeV for injection into the Main Ring.

Booster clock

The booster clock was a continuous pulse train of 1 microsecond pulses that was synchronized to the power line. A signal marking a specific time like T1, T4 T8, was indicated by a missing pulse or gap in this continuous pulse train. These times initiated actions which carried the booster through its cycle. It was the primary time standard for all accelerator systems.

Booster pulse

That portion of the beam in the Main Ring resulting from the injection of one booster load, viz., about 1/13 of the Main Ring azimuth.

Booster serial link

This is the CAMAC link to which all Booster CAMAC crates are connected and through which control cards communicate with the Booster Serial (DEC BS) front-end.

Bouncer circuit

Haefely-designed system used to boost Dome voltage to compensate for charge leaving the Dome during the beam pulse. Not installed at FNAL.

Bow shock

A sharp front formed in the solar wind ahead of the magnetosphere, marked with a sudden slowing-down of the flow near Earth. It is quite similar to the shock forming ahead of the wing of a supersonic airplace. After passing near Earth, the slowed-down flow gains speed again, to the same value as the surrounding solar wind.

Boyle's law

The volume of a dry gas varies inversely with the pressure exerted upon it, provided the temperature is constant.

Bpm

A diagnostic device used to measure beam positions. BPM stands for Beam Position Monitor.

Breakover

When a Main Ring or Tevatron power supply SCR shorts and conducts continuously (i.e., while in bypass, etc.).

Breeder reactor

A nuclear reactor in which a fissionable material is produced at a greater rate than the fuel is consumed.

Bremsstrahlung

Radiation that is emitted when a free electron is deflected by an ion, but the free electron is not captured by the ion. Generally, it is a type of radiation emitted when high energy electrons are accelerated. (German for braking radiation).

Bremsstrahlung radiation

Electromagnetic radiation, usually in the x-ray region of the spectrum produced by electrons in a collision with the nucleus of an atom. Bremsstrahlung is German for breaking. Bremsstrahlung radiation is produced in regions of high electric potential such as areas surrounding electrostatic septa and RF cavities.

Brewster's law

States that the refractive index of a material is equal to the tangent of the polarizing angle for the material.

Brownian motion

The continuous random motion of solid microscopic particles when suspended in a fluid medium due to the consequence of ongoing bombardment by atoms and molecules.

Brownian movement

The irregular and random movement of small particles suspended in a fluid, known to be a consequence of the thermal motion of fluid molecules.

BSP link

Obsolete. In a hardware context the link was the physical cable between and including the Main Ring CC42 repeaters. In a software context it was the electrical path which carried the beam sample pulse around the ring.

Bubble chamber

Instrument used for making the paths of ionizing particles visible as a trail of tiny bubbles in a liquid.

Bucker

An air core quadrupole magnet used in the Tevatron to eliminate 4-400 Hz structure in the extracted spill.

Bucket

Stable phase space area where beam may be captured and accelerated.

Bucket (R.F.)