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87-607: J-PARC includes three main parts: the 400 MeV proton linear accelerator , the 3 GeV Rapid Cycling Synchrotron (RCS), and the 30 GeV Main Ring (MR) synchrotron . There are two main experimental areas: the Materials and Life Science Experimental Facility (MLF), where the proton beam from the RCS is used to create beams of either neutrons or muons for further study, and the Hadron Facility (HD), where

174-491: A Radio-frequency quadrupole (RFQ) stage from injection at 50kVdC to ~5MeV bunches, a Side Coupled Drift Tube Linac (SCDTL) to accelerate from 5Mev to ~ 40MeV and a Cell Coupled Linac (CCL) stage final, taking the output to 200-230MeV. Each stage is optimised to allow close coupling and synchronous operation during the beam energy build-up. The project aim is to make proton therapy a more accessible mainstream medicine as an alternative to existing radio therapy. The higher

261-547: A laser , light is amplified in a cavity resonator that is usually composed of two or more mirrors. Thus an optical cavity , also known as a resonator, is a cavity with walls that reflect electromagnetic waves (i.e. light ). This allows standing wave modes to exist with little loss. Mechanical resonators are used in electronic circuits to generate signals of a precise frequency . For example, piezoelectric resonators , commonly made from quartz , are used as frequency references. Common designs consist of electrodes attached to

348-507: A short circuit or open circuit, connected in series or parallel with a main transmission line. Planar transmission-line resonators are commonly employed for coplanar , stripline , and microstrip transmission lines. Such planar transmission-line resonators can be very compact in size and are widely used elements in microwave circuitry. In cryogenic solid-state research, superconducting transmission-line resonators contribute to solid-state spectroscopy and quantum information science. In

435-545: A Little Linac model kit, containing 82 building blocks, was developed for children undergoing radiotherapy treatment for cancer. The hope is that building the model will alleviate some of the stress experienced by the child before undergoing treatment by helping them to understand what the treatment entails. The kit was developed by Professor David Brettle, Institute of Physics and Engineering in Medicine (IPEM) in collaboration with manufacturers Best-Lock Ltd. The model can be seen at

522-432: A beam line length reduction from some tens of metres to a few cm is quite possible. The LIGHT program (Linac for Image-Guided Hadron Therapy) hopes to create a design capable of accelerating protons to 200MeV or so for medical use over a distance of a few tens of metres, by optimising and nesting existing accelerator techniques The current design (2020) uses the highest practical bunch frequency (currently ~ 3 GHz) for

609-566: A coil of wire, is self-resonant at a certain frequency due to the parasitic capacitance between its turns. This is often an unwanted effect that can cause parasitic oscillations in RF circuits. The self-resonance of inductors is used in a few circuits, such as the Tesla coil . A cavity resonator is a hollow closed conductor such as a metal box or a cavity within a metal block, containing electromagnetic waves (radio waves) reflecting back and forth between

696-418: A device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies , called resonant frequencies , than at other frequencies. The oscillations in a resonator can be either electromagnetic or mechanical (including acoustic ). Resonators are used to either generate waves of specific frequencies or to select specific frequencies from

783-457: A faster speed each time they pass between electrodes; there is little electric field inside the electrodes so the particles travel at a constant speed within each electrode. The particles are injected at the right time so that the oscillating voltage differential between electrodes is maximum as the particles cross each gap. If the peak voltage applied between the electrodes is V p {\displaystyle V_{p}} volts, and

870-419: A few MeV. An advantageous alternative here, however, is a progressive wave, a traveling wave. The phase velocity the traveling wave must be roughly equal to the particle speed. Therefore, this technique is only suitable when the particles are almost at the speed of light, so that their speed only increases very little. The development of high-frequency oscillators and power amplifiers from the 1940s, especially

957-460: A force given by the Lorentz force law: where q {\displaystyle q} is the charge on the particle, E → {\displaystyle {\vec {E}}} is the electric field, v → {\displaystyle {\vec {v}}} is the particle velocity, and B → {\displaystyle {\vec {B}}}

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1044-415: A group of particles into the first electrode once each cycle of the voltage, when the charge on the electrode is opposite to the charge on the particles. Each time the particle bunch passes through an electrode, the oscillating voltage changes polarity, so when the particles reach the gap between electrodes the electric field is in the correct direction to accelerate them. Therefore, the particles accelerate to

1131-488: A horizontal waveguide loaded by a series of discs. The 1947 accelerator had an energy of 6 MeV. Over time, electron acceleration at the SLAC National Accelerator Laboratory would extend to a size of 2 miles (3.2 km) and an output energy of 50 GeV. As linear accelerators were developed with higher beam currents, using magnetic fields to focus proton and heavy ion beams presented difficulties for

1218-502: A linac depends on the type of particle that is being accelerated: electrons , protons or ions. Linacs range in size from a cathode-ray tube (which is a type of linac) to the 3.2-kilometre-long (2.0 mi) linac at the SLAC National Accelerator Laboratory in Menlo Park, California . In 1924, Gustav Ising published the first description of a linear particle accelerator using a series of accelerating gaps. Particles would proceed down

1305-421: A lowest frequency called the fundamental frequency . The above analysis assumes the medium inside the resonator is homogeneous, so the waves travel at a constant speed, and that the shape of the resonator is rectilinear. If the resonator is inhomogeneous or has a nonrectilinear shape, like a circular drumhead or a cylindrical microwave cavity , the resonant frequencies may not occur at equally spaced multiples of

1392-402: A particular engine speed or range of speeds. In many keyboard percussion instruments, below the centre of each note is a tube, which is an acoustic cavity resonator . The length of the tube varies according to the pitch of the note, with higher notes having shorter resonators. The tube is open at the top end and closed at the bottom end, creating a column of air that resonates when the note

1479-407: A piece of quartz, in the shape of a rectangular plate for high frequency applications, or in the shape of a tuning fork for low frequency applications. The high dimensional stability and low temperature coefficient of quartz helps keeps resonant frequency constant. In addition, the quartz's piezoelectric property converts the mechanical vibrations into an oscillating voltage , which is picked up by

1566-439: A precise alignment of their components through the use of servo systems guided by a laser beam. Various new concepts are in development as of 2021. The primary goal is to make linear accelerators cheaper, with better focused beams, higher energy or higher beam current. Induction linear accelerators use the electric field induced by a time-varying magnetic field for acceleration—like the betatron . The particle beam passes through

1653-401: A resonant cavity to produce complex electric fields. These fields provide simultaneous acceleration and focusing to injected particle beams. Beginning in the 1960s, scientists at Stanford and elsewhere began to explore the use of superconducting radio frequency cavities for particle acceleration. Superconducting cavities made of niobium alloys allow for much more efficient acceleration, as

1740-469: A result. The development of the strong focusing principle in the early 1950s led to the installation of focusing quadrupole magnets inside the drift tubes, allowing for longer and thus more powerful linacs. Two of the earliest examples of Alvarez linacs with strong focusing magnets were built at CERN and Brookhaven National Laboratory . In 1947, at about the same time that Alvarez was developing his linac concept for protons, William Hansen constructed

1827-410: A series of ring-shaped ferrite cores standing one behind the other, which are magnetized by high-current pulses, and in turn each generate an electrical field strength pulse along the axis of the beam direction. Induction linear accelerators are considered for short high current pulses from electrons but also from heavy ions. The concept goes back to the work of Nicholas Christofilos . Its realization

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1914-482: A series of tubes. At a regular frequency, an accelerating voltage would be applied across each gap. As the particles gained speed while the frequency remained constant, the gaps would be spaced farther and farther apart, in order to ensure the particle would see a voltage applied as it reached each gap. Ising never successfully implemented this design. Rolf Wideroe discovered Ising's paper in 1927, and as part of his PhD thesis he built an 88-inch long, two gap version of

2001-533: A signal. Musical instruments use acoustic resonators that produce sound waves of specific tones. Another example is quartz crystals used in electronic devices such as radio transmitters and quartz watches to produce oscillations of very precise frequency. A cavity resonator is one in which waves exist in a hollow space inside the device. In electronics and radio, microwave cavities consisting of hollow metal boxes are used in microwave transmitters, receivers and test equipment to control frequency, in place of

2088-453: A specific resistor component, or due to resistance of the inductor windings. Such resonant circuits are also called RLC circuits after the circuit symbols for the components. A distributed-parameter resonator has capacitance, inductance, and resistance that cannot be isolated into separate lumped capacitors, inductors, or resistors. An example of this, much used in filtering , is the helical resonator . An inductor consisting of

2175-415: A spring, pendulums , balance wheels , and LC tuned circuits have one resonant frequency. Systems with two degrees of freedom, such as coupled pendulums and resonant transformers can have two resonant frequencies. A crystal lattice composed of N atoms bound together can have N resonant frequencies. As the number of coupled harmonic oscillators grows, the time it takes to transfer energy from one to

2262-583: A substantially higher fraction of the input power could be applied to the beam rather than lost to heat. Some of the earliest superconducting linacs included the Superconducting Linear Accelerator (for electrons) at Stanford and the Argonne Tandem Linear Accelerator System (for protons and heavy ions) at Argonne National Laboratory . When a charged particle is placed in an electromagnetic field it experiences

2349-401: A transmission line causes reflection of the transmitted signal. Two such reflectors on a transmission line evoke standing waves between them and thus act as a one-dimensional resonator, with the resonance frequencies determined by their distance and the effective dielectric constant of the transmission line. A common form is the resonant stub , a length of transmission line terminated in either

2436-434: Is a stub . You can help Misplaced Pages by expanding it . Linear accelerator A linear particle accelerator (often shortened to linac ) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear beamline . The principles for such machines were proposed by Gustav Ising in 1924, while

2523-501: Is accelerated. A linear particle accelerator consists of the following parts: As shown in the animation, the oscillating voltage applied to alternate cylindrical electrodes has opposite polarity (180° out of phase ), so adjacent electrodes have opposite voltages. This creates an oscillating electric field (E) in the gap between each pair of electrodes, which exerts force on the particles when they pass through, imparting energy to them by accelerating them. The particle source injects

2610-402: Is converted into heat. In an energy recovery linac (ERL), the accelerated in resonators and, for example, in undulators . The electrons used are fed back through the accelerator, out of phase by 180 degrees. They therefore pass through the resonators in the decelerating phase and thus return their remaining energy to the field. The concept is comparable to the hybrid drive of motor vehicles, where

2697-461: Is equal to an integer number of wavelengths λ {\displaystyle \lambda \,} of the wave: If the velocity of a wave is c {\displaystyle c\,} , the frequency is f = c / λ {\displaystyle f=c/\lambda \,} so the resonant frequencies are: So the resonant frequencies of resonators, called normal modes , are equally spaced multiples ( harmonics ) of

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2784-402: Is highly dependent on progress in the development of more suitable ferrite materials. With electrons, pulse currents of up to 5 kiloamps at energies up to 5 MeV and pulse durations in the range of 20 to 300 nanoseconds were achieved. In previous electron linear accelerators, the accelerated particles are used only once and then fed into an absorber (beam dump) , in which their residual energy

2871-482: Is made by cutting a narrow slit along the length of a conducting tube. The slit has an effective capacitance and the bore of the resonator has an effective inductance. Therefore, the LGR can be modeled as an RLC circuit and has a resonant frequency that is typically between 200 MHz and 2 GHz. In the absence of radiation losses, the effective resistance of the LGR is determined by the resistivity and electromagnetic skin depth of

2958-425: Is necessary to use groups of magnets to provide an overall focusing effect in both directions. Focusing along the direction of travel, also known as phase stability , is an inherent property of RF acceleration. If the particles in a bunch all reach the accelerating region during the rising phase of the oscillating field, then particles which arrive early will see slightly less voltage than the "reference" particle at

3045-514: Is struck. This adds depth and volume to the note. In string instruments, the body of the instrument is a resonator. The tremolo effect of a vibraphone is achieved via a mechanism that opens and shuts the resonators. String instruments such as the bluegrass banjo may also have resonators. Many five-string banjos have removable resonators, so players can use the instrument with a resonator in bluegrass style, or without it in folk music style. The term resonator , used by itself, may also refer to

3132-421: Is surrounded by a material with much lower dielectric constant, then this abrupt change in dielectric constant can cause confinement of an electromagnetic wave, which leads to a resonator that acts similarly to a cavity resonator. Transmission lines are structures that allow broadband transmission of electromagnetic waves, e.g. at radio or microwave frequencies. Abrupt change of impedance (e.g. open or short) in

3219-427: Is the magnetic field. The cross product in the magnetic field term means that static magnetic fields cannot be used for particle acceleration, as the magnetic force acts perpendicularly to the direction of particle motion. As electrostatic breakdown limits the maximum constant voltage which can be applied across a gap to produce an electric field, most accelerators use some form of RF acceleration. In RF acceleration,

3306-481: Is used to drive a series of gaps, those gaps must be placed increasingly far apart as the speed of the particle increases. This is to ensure that the particle "sees" the same phase of the oscillator's cycle as it reaches each gap. As particles asymptotically approach the speed of light, the gap separation becomes constant: additional applied force increases the energy of the particles but does not significantly alter their speed. In order to ensure particles do not escape

3393-409: The standing wave is imposed on the beam. This type of system can be used as a sensor to track changes in frequency or phase of the resonance of the fiber. One application is as a measurement device for dimensional metrology . The most familiar examples of acoustic resonators are in musical instruments . Every musical instrument has resonators. Some generate the sound directly, such as

3480-516: The Chalk River Laboratories in Ontario, Canada, which still now produce most Mo-99 from highly enriched uranium could be replaced by this new process. In this way, the sub-critical loading of soluble uranium salts in heavy water with subsequent photo neutron bombardment and extraction of the target product, Mo-99, will be achieved. Resonator#Cavity resonators A resonator is

3567-674: The Jefferson Lab (US), in the Budker Institute of Nuclear Physics (Russia) and at JAEA (Japan). At the University of Mainz , an ERL called MESA is expected to begin operation in 2024. The concept of the Compact Linear Collider (CLIC) (original name CERN Linear Collider, with the same abbreviation) for electrons and positrons provides a traveling wave accelerator for energies of the order of 1 tera-electron volt (TeV). Instead of

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3654-457: The Science Museum, London . The expected shortages of Mo-99 , and the technetium-99m medical isotope obtained from it, have also shed light onto linear accelerator technology to produce Mo-99 from non-enriched Uranium through neutron bombardment. This would enable the medical isotope industry to manufacture this crucial isotope by a sub-critical process. The aging facilities, for example

3741-423: The muffler to reduce noise, by making sound waves "cancel each other out". The "exhaust note" is an important feature for some vehicle owners, so both the original manufacturers and the after-market suppliers use the resonator to enhance the sound. In " tuned exhaust " systems designed for performance, the resonance of the exhaust pipes can also be used to remove combustion products from the combustion chamber at

3828-413: The resonator guitar . The modern ten-string guitar , invented by Narciso Yepes , adds four sympathetic string resonators to the traditional classical guitar. By tuning these resonators in a very specific way (C, B♭, A♭, G♭) and making use of their strongest partials (corresponding to the octaves and fifths of the strings' fundamental tones), the bass strings of the guitar now resonate equally with any of

3915-406: The tuned circuits which are used at lower frequencies. Acoustic cavity resonators, in which sound is produced by air vibrating in a cavity with one opening, are known as Helmholtz resonators . A physical system can have as many resonant frequencies as it has degrees of freedom ; each degree of freedom can vibrate as a harmonic oscillator . Systems with one degree of freedom, such as a mass on

4002-408: The RF power creates a standing wave . Some linacs have short, vertically mounted waveguides, while higher energy machines tend to have a horizontal, longer waveguide and a bending magnet to turn the beam vertically towards the patient. Medical linacs use monoenergetic electron beams between 4 and 25 MeV, giving an X-ray output with a spectrum of energies up to and including the electron energy when

4089-411: The accelerator, it is necessary to provide some form of focusing to redirect particles moving away from the central trajectory back towards the intended path. With the discovery of strong focusing , quadrupole magnets are used to actively redirect particles moving away from the reference path. As quadrupole magnets are focusing in one transverse direction and defocusing in the perpendicular direction, it

4176-417: The attached electrodes. These crystal oscillators are used in quartz clocks and watches, to create the clock signal that runs computers, and to stabilize the output signal from radio transmitters . Mechanical resonators can also be used to induce a standing wave in other media. For example, a multiple degree of freedom system can be created by imposing a base excitation on a cantilever beam. In this case

4263-577: The average output current is still limited.) The high density of the output makes the linac particularly attractive for use in loading storage ring facilities with particles in preparation for particle to particle collisions. The high mass output also makes the device practical for the production of antimatter particles, which are generally difficult to obtain, being only a small fraction of a target's collision products. These may then be stored and further used to study matter-antimatter annihilation. Linac-based radiation therapy for cancer treatment began with

4350-404: The beam after passing through the resonators. The first resonator causes bunching of the particles passing through it. The bunched particles travel in a field-free region where further bunching occurs, then the bunched particles enter the second resonator giving up their energy to excite it into oscillations. It is a particle accelerator that works in conjunction with a specifically tuned cavity by

4437-552: The beam from the main ring is used to create heavy hadronic particles such as pions and kaons . The main ring beam is also used to create neutrino beams for analysis at the Kamioka laboratory, located approximately 300 km to the west. A planned project also allow for research into accelerator-driven nuclear waste transmutation . 36°26′42″N 140°36′22″E  /  36.445°N 140.606°E  / 36.445; 140.606 This accelerator physics -related article

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4524-475: The cavity is conveniently small in size. Due to the low resistance of their conductive walls, cavity resonators have very high Q factors ; that is their bandwidth , the range of frequencies around the resonant frequency at which they will resonate, is very narrow. Thus they can act as narrow bandpass filters . Cavity resonators are widely used as the frequency determining element in microwave oscillators . Their resonant frequency can be tuned by moving one of

4611-467: The cavity's walls. When a source of radio waves at one of the cavity's resonant frequencies is applied, the oppositely-moving waves form standing waves , and the cavity stores electromagnetic energy. Since the cavity's lowest resonant frequency, the fundamental frequency, is that at which the width of the cavity is equal to a half-wavelength (λ/2), cavity resonators are only used at microwave frequencies and above, where wavelengths are short enough that

4698-427: The center of the bunch. Those particles will therefore receive slightly less acceleration and eventually fall behind the reference particle. Correspondingly, particles which arrive after the reference particle will receive slightly more acceleration, and will catch up to the reference as a result. This automatic correction occurs at each accelerating gap, so the bunch is refocused along the direction of travel each time it

4785-427: The charge on each particle is q {\displaystyle q} elementary charges , the particle gains an equal increment of energy of q V p {\displaystyle qV_{p}} electron volts when passing through each gap. Thus the output energy of the particles is electron volts, where N {\displaystyle N} is the number of accelerating electrodes in

4872-439: The conductor used to make the resonator. One key advantage of the LGR is that, at its resonant frequency, its dimensions are small compared to the free-space wavelength of the electromagnetic fields. Therefore, it is possible to use LGRs to construct a compact and high-Q resonator that operates at relatively low frequencies where cavity resonators would be impractically large. If a piece of material with large dielectric constant

4959-412: The configuration of the structures. The reflex klystron is a klystron utilizing only a single apertured cavity resonator through which the beam of charged particles passes, first in one direction. A repeller electrode is provided to repel (or redirect) the beam after passage through the resonator back through the resonator in the other direction and in proper phase to reinforce the oscillations set up in

5046-433: The device. Where Ising had proposed a spark gap as the voltage source, Wideroe used a 25kV vacuum tube oscillator. He successfully demonstrated that he had accelerated sodium and potassium ions to an energy of 50,000 electron volts (50 keV), twice the energy they would have received if accelerated only once by the tube. By successfully accelerating a particle multiple times using the same voltage source, Wideroe demonstrated

5133-598: The dielectric strength limits the maximum acceleration that can be achieved within a certain distance. This limit can be circumvented using accelerated waves in plasma to generate the accelerating field in Kielfeld accelerators : A laser or particle beam excites an oscillation in a plasma , which is associated with very strong electric field strengths. This means that significantly (factors of 100s to 1000s ) more compact linear accelerators can possibly be built. Experiments involving high power lasers in metal vapour plasmas suggest that

5220-438: The electrons are directed at a high-density (such as tungsten ) target. The electrons or X-rays can be used to treat both benign and malignant disease. The LINAC produces a reliable, flexible and accurate radiation beam. The versatility of LINAC is a potential advantage over cobalt therapy as a treatment tool. In addition, the device can simply be powered off when not in use; there is no source requiring heavy shielding – although

5307-410: The extracted RF energy to the load, which may be a cooking chamber in a microwave oven or a high gain antenna in the case of radar. The klystron , tube waveguide, is a beam tube including at least two apertured cavity resonators. The beam of charged particles passes through the apertures of the resonators, often tunable wave reflection grids, in succession. A collector electrode is provided to intercept

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5394-504: The first machine that worked was constructed by Rolf Widerøe in 1928 at the RWTH Aachen University . Linacs have many applications: they generate X-rays and high energy electrons for medicinal purposes in radiation therapy , serve as particle injectors for higher-energy accelerators, and are used directly to achieve the highest kinetic energy for light particles (electrons and positrons) for particle physics . The design of

5481-566: The first patient treated in 1953 in London, UK, at the Hammersmith Hospital , with an 8 MV machine built by Metropolitan-Vickers and installed in 1952, as the first dedicated medical linac. A short while later in 1954, a 6 MV linac was installed in Stanford, USA, which began treatments in 1956. Medical linear accelerators accelerate electrons using a tuned-cavity waveguide, in which

5568-421: The first travelling-wave electron accelerator at Stanford University. Electrons are sufficiently lighter than protons that they achieve speeds close to the speed of light early in the acceleration process. As a result, "accelerating" electrons increase in energy but can be treated as having a constant velocity from an accelerator design standpoint. This allowed Hansen to use an accelerating structure consisting of

5655-489: The frequency of the acceleration voltage selected, the more individual acceleration thrusts per path length a particle of a given speed experiences, and the shorter the accelerator can therefore be overall. That is why accelerator technology developed in the pursuit of higher particle energies, especially towards higher frequencies. The linear accelerator concepts (often called accelerator structures in technical terms) that have been used since around 1950 work with frequencies in

5742-412: The fundamental frequency. They are then called overtones instead of harmonics . There may be several such series of resonant frequencies in a single resonator, corresponding to different modes of vibration. An electrical circuit composed of discrete components can act as a resonator when both an inductor and capacitor are included. Oscillations are limited by the inclusion of resistance, either via

5829-437: The initial stages of the accelerator. Because the magnetic force is dependent on the particle velocity, it was desirable to create a type of accelerator which could simultaneously accelerate and focus low-to-mid energy hadrons . In 1970, Soviet physicists I. M. Kapchinsky and Vladimir Teplyakov proposed the radio-frequency quadrupole (RFQ) type of accelerating structure. RFQs use vanes or rods with precisely designed shapes in

5916-490: The kinetic energy released during braking is made available for the next acceleration by charging a battery. The Brookhaven National Laboratory and the Helmholtz-Zentrum Berlin with the project "bERLinPro" reported on corresponding development work. The Berlin experimental accelerator uses superconducting niobium cavity resonators. In 2014, three free-electron lasers based on ERLs were in operation worldwide: in

6003-538: The klystron, was essential for these two acceleration techniques . The first larger linear accelerator with standing waves - for protons - was built in 1945/46 in the Lawrence Berkeley National Laboratory under the direction of Luis W. Alvarez . The frequency used was 200 MHz .  The first electron accelerator with traveling waves of around 2 GHz was developed a little later at Stanford University by W.W. Hansen and colleagues. In

6090-455: The machine. At speeds near the speed of light, the incremental velocity increase will be small, with the energy appearing as an increase in the mass of the particles. In portions of the accelerator where this occurs, the tubular electrode lengths will be almost constant. Additional magnetic or electrostatic lens elements may be included to ensure that the beam remains in the center of the pipe and its electrodes. Very long accelerators may maintain

6177-409: The maximum power that can be imparted to electrons in a synchrotron of given size. Linacs are also capable of prodigious output, producing a nearly continuous stream of particles, whereas a synchrotron will only periodically raise the particles to sufficient energy to merit a "shot" at the target. (The burst can be held or stored in the ring at energy to give the experimental electronics time to work, but

6264-400: The next becomes significant. The vibrations in them begin to travel through the coupled harmonic oscillators in waves, from one oscillator to the next. The term resonator is most often used for a homogeneous object in which vibrations travel as waves, at an approximately constant velocity, bouncing back and forth between the sides of the resonator. The material of the resonator, through which

6351-485: The other hand, with ions of this energy range, the speed also increases significantly due to further acceleration. The acceleration concepts used today for ions are always based on electromagnetic standing waves that are formed in suitable resonators . Depending on the type of particle, energy range and other parameters, very different types of resonators are used; the following sections only cover some of them. Electrons can also be accelerated with standing waves above

6438-461: The otherwise necessary numerous klystron amplifiers to generate the acceleration power, a second parallel electron linear accelerator of lower energy is to be used, which works with superconducting cavities in which standing waves are formed. High-frequency power is extracted from it at regular intervals and transmitted to the main accelerator. In this way, the very high acceleration field strength of 80 MV / m should be achieved. In cavity resonators,

6525-447: The particle travels, and the central tubes are only used to shield the particles during the decelerating portion of the oscillator's phase. Using this approach to acceleration meant that Alvarez's first linac was able to achieve proton energies of 31.5 MeV in 1947, the highest that had ever been reached at the time. The initial Alvarez type linacs had no strong mechanism for keeping the beam focused and were limited in length and energy as

6612-426: The particle traverses a series of accelerating regions, driven by a source of voltage in such a way that the particle sees an accelerating field as it crosses each region. In this type of acceleration, particles must necessarily travel in "bunches" corresponding to the portion of the oscillator's cycle where the electric field is pointing in the intended direction of acceleration. If a single oscillating voltage source

6699-523: The range from around 100 MHz to a few gigahertz (GHz) and use the electric field component of electromagnetic waves. When it comes to energies of more than a few MeV, accelerators for ions are different from those for electrons. The reason for this is the large mass difference between the particles. Electrons are already close to the speed of light , the absolute speed limit, at a few MeV; with further acceleration, as described by relativistic mechanics , almost only their energy and momentum increase. On

6786-557: The resonator. On the beamline of an accelerator system, there are specific sections that are cavity resonators for radio frequency (RF) radiation. The (charged) particles that are to be accelerated pass through these cavities in such a way that the microwave electric field transfers energy to the particles, thus increasing their kinetic energy and thus accelerating them. Several large accelerator facilities employ superconducting niobium cavities for improved performance compared to metallic (copper) cavities. The loop-gap resonator (LGR)

6873-468: The rim of the chamber are cylindrical cavities. The cavities are open along their length and so they connect with the common cavity space. As electrons sweep past these openings they induce a resonant high frequency radio field in the cavity, which in turn causes the electrons to bunch into groups. A portion of this field is extracted with a short antenna that is connected to a waveguide (a metal tube usually of rectangular cross section). The waveguide directs

6960-421: The sides is d {\displaystyle d\,} , the length of a round trip is 2 d {\displaystyle 2d\,} . To cause resonance, the phase of a sinusoidal wave after a round trip must be equal to the initial phase so the waves self-reinforce. The condition for resonance in a resonator is that the round trip distance, 2 d {\displaystyle 2d\,} ,

7047-423: The treatment room itself requires considerable shielding of the walls, doors, ceiling etc. to prevent escape of scattered radiation. Prolonged use of high powered (>18 MeV) machines can induce a significant amount of radiation within the metal parts of the head of the machine after power to the machine has been removed (i.e. they become an active source and the necessary precautions must be observed). In 2019

7134-576: The two diagrams, the curve and arrows indicate the force acting on the particles. Only at the points with the correct direction of the electric field vector, i.e. the correct direction of force, can particles absorb energy from the wave. (An increase in speed cannot be seen in the scale of these images.) The linear accelerator could produce higher particle energies than the previous electrostatic particle accelerators (the Cockcroft–Walton accelerator and Van de Graaff generator ) that were in use when it

7221-492: The utility of radio frequency (RF) acceleration. This type of linac was limited by the voltage sources that were available at the time, and it was not until after World War II that Luis Alvarez was able to use newly developed high frequency oscillators to design the first resonant cavity drift tube linac. An Alvarez linac differs from the Wideroe type in that the RF power is applied to the entire resonant chamber through which

7308-441: The walls of the cavity in or out, changing its size. The cavity magnetron is a vacuum tube with a filament in the center of an evacuated, lobed, circular cavity resonator. A perpendicular magnetic field is imposed by a permanent magnet. The magnetic field causes the electrons, attracted to the (relatively) positive outer part of the chamber, to spiral outward in a circular path rather than moving directly to this anode. Spaced about

7395-407: The waves flow, can be viewed as being made of millions of coupled moving parts (such as atoms). Therefore, they can have millions of resonant frequencies, although only a few may be used in practical resonators. The oppositely moving waves interfere with each other, and at its resonant frequencies reinforce each other to create a pattern of standing waves in the resonator. If the distance between

7482-468: The wooden bars in a xylophone , the head of a drum , the strings in stringed instruments , and the pipes in an organ . Some modify the sound by enhancing particular frequencies, such as the sound box of a guitar or violin . Organ pipes , the bodies of woodwinds , and the sound boxes of stringed instruments are examples of acoustic cavity resonators. The exhaust pipes in automobile exhaust systems are designed as acoustic resonators that work with

7569-620: Was invented. In these machines, the particles were only accelerated once by the applied voltage, so the particle energy in electron volts was equal to the accelerating voltage on the machine, which was limited to a few million volts by insulation breakdown. In the linac, the particles are accelerated multiple times by the applied voltage, so the particle energy is not limited by the accelerating voltage. High power linacs are also being developed for production of electrons at relativistic speeds, required since fast electrons traveling in an arc will lose energy through synchrotron radiation ; this limits

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