473:; a single long glass tube could implode under vacuum or fracture supporting its own weight. Importantly for the physics, these inter-spaced conducting rings help to make a more uniform electric field along the accelerating column. This beam line of glass rings is simply supported by compression at either end of the terminal. As the glass is non-conducting, it could be supported from the ground, but such supports near the terminal could induce a discharge of the terminal, depending on the design. Sometimes the compression is not sufficient, and the entire beam line may collapse and shatter. This idea is especially important to the design of tandems, because they naturally have longer beam lines, and the beam line must run through the terminal.
422:, stripping electrons from the ion beam so that they become cations. As it is difficult to make anions of more than -1 charge state, then the energy of particles emerging from a tandem is E=(q+1)V, where we have added the second acceleration potential from that anion to the positive charge state q emerging from the stripper foil; we are adding these different charge signs together because we are increasing the energy of the nucleus in each phase. In this sense, we can see clearly that a tandem can double the maximum energy of a proton beam, whose maximum charge state is merely +1, but the advantage gained by a tandem has diminishing returns as we go to higher mass, as, for example, one might easily get a 6+ charge state of a
150:
361:
terminal can branch out and be toggled remotely. Omitting practical problems, if the platform is positively charged, it will repel the ions of the same electric polarity, accelerating them. As E=qV, where E is the emerging energy, q is the ionic charge, and V is the terminal voltage, the maximum energy of particles accelerated in this manner is practically limited by the discharge limit of the high voltage platform, about 12 MV under ambient atmospheric conditions. This limit can be increased, for example, by keeping the HV platform in a tank of an
405:
inside the conductor where they will feel no electric force. It turns out to be simple to remove, or strip, electrons from an energetic ion. One of the properties of ion interaction with matter is the exchange of electrons, which is a way the ion can lose energy by depositing it within the matter, something we should intuitively expect of a projectile shot at a solid. However, as the target becomes thinner or the projectile becomes more energetic, the amount of energy deposited in the foil becomes less and less.
36:
133:
349:, is not a particularly uncommon occurrence. The practical difficulty with belts led to a different medium for physically transporting the charges: a chain of pellets. Unlike a normal chain, this one is non-conducting from one end to the other, as both insulators and conductors are used in its construction. These types of accelerators are usually called
800:
is accelerated through a voltage difference of one million volts (1 MV), it will have an energy of two million electron volts, abbreviated 2 MeV. The accelerating voltage on electrostatic machines is in the range 0.1 to 25 MV and the charge on particles is a few elementary charges, so
476:
Most often electrostatic accelerators are arranged in a horizontal line. However, some tandems may have a "U" shape, and in principle the beam can be turned to any direction with a magnetic dipole at the terminal. Some electrostatic accelerators are arranged vertically, where either the ion source
444:
might be extracted as TiH and used to produce a proton beam, because these simple, and often weakly bound chemicals, will be broken apart at the terminal stripper foil. Anion ion beam production was a major subject of study for tandem accelerator application, and one can find recipes and yields for
404:
Conventionally, positively charged ions are accelerated because this is the polarity of the atomic nucleus. However, if one wants to use the same static electric potential twice to accelerate ions, then the polarity of the ions' charge must change from anions to cations or vice versa while they are
219:
The advantages of electrostatic accelerators over oscillating field machines include lower cost, the ability to produce continuous beams, and higher beam currents that make them useful to industry. As such, they are by far the most widely used particle accelerators, with industrial applications such
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places electrons on an insulating sheet, or belt, with a metal comb, and then the sheet physically transports the immobilized electrons to the terminal. Although at high voltage, the terminal is a conductor, and there is a corresponding comb inside the conductor which can pick up the electrons off
144:
built 1937 at the
Westinghouse Research Center in Forest Hills, Pennsylvania. The cutaway shows the fabric belts that carry charge up to the mushroom-shaped high voltage electrode. To improve insulation the machine was enclosed in a 65 ft. pressure vessel which was pressurized to 120 psi during
360:
is placed on the platform at the end of the beam line, which is why it's called the terminal. However, as the ion source is kept at a high potential, one cannot access the ion source for control or maintenance directly. Thus, methods such as plastic rods connected to various levers inside the
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in semiconductor production, and sterilization. Many universities worldwide have electrostatic accelerators for research purposes. High energy oscillating field accelerators usually incorporate an electrostatic machine as their first stage, to accelerate particles to a high enough velocity to
477:
or, in the case of a U-shaped vertical tandem, the terminal, is at the top of a tower. A tower arrangement can be a way to save space, and also the beam line connecting to the terminal made of glass rings can take some advantage of gravity as a natural source of compression.
464:
One trick which has to be considered with electrostatic accelerators is that usually vacuum beam lines are made of steel. However, one cannot very well connect a conducting pipe of steel from the high voltage terminal to the ground. Thus, many rings of a strong glass, like
295:
A special application of electrostatic particle accelerator are dust accelerators in which nanometer to micrometer sized electrically charged dust particles are accelerated to speeds up to 100 km/s. Dust accelerators are used for impact cratering studies, calibration of
848:
Mocker, A.; Bugiel, S.; Auer, S.; Baust, G.; Collette, A.; Drake, K.; Fiege, K.; Grün, E.; Heckmann, F.; Helfert, S.; Hillier, J.; Kempf, S.; Matt, G.; Mellert, T.; Munsat, T.; Otto, K.; Postberg, F.; Röser, H. P.; Shu, A.; Strernovski, Z.; Srama, R. (September 2011).
408:
Tandems locate the ion source outside the terminal, which means that accessing the ion source while the terminal is at high voltage is significantly less difficult, especially if the terminal is inside a gas tank. So then an anion beam from a
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most elements in the
Negative Ion Cookbook. Tandems can also be operated in terminal mode, where they function like a single-ended electrostatic accelerator, which is a more common and practical way to make beams of noble gases.
264:
they are used to produce ion beams for materials modification, including ion implantation and ion beam mixing. There are also a number of materials analysis techniques based on electrostatic acceleration of heavy ions, including
345:, with one major exception: it is seamless. Thus, if the belt is broken, the accelerator must be disassembled to some degree in order to replace the belt, which, owing to its constant rotation and being made typically of a
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Minehara, Eisuke; Abe, Shinichi; Yoshida, Tadashi; Sato, Yutaka; Kanda, Mamoru; Kobayashi, Chiaki; Hanashima, Susumu (1984). "On the production of the KrF- and XeF- Ion beams for the tandem electrostatic accelerators".
448:
The name 'tandem' originates from this dual-use of the same high voltage, although tandems may also be named in the same style of conventional electrostatic accelerators based on the method of charging the terminal.
413:
ion source is injected from a relatively lower voltage platform towards the high voltage terminal. Inside the terminal, the beam impinges on a thin foil (on the order of micrograms per square centimeter), often
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in 1932. The maximum particle energy produced by electrostatic accelerators is limited by the maximum voltage which can be achieved the machine. This is in turn limited by
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In a single-ended electrostatic accelerator the charged particle is accelerated through a single potential difference between two electrodes, so the output particle energy
612:
574:
666:. However, because the charge on elementary particles is so small (the charge on the electron is 1.6x10 coulombs), the energy in joules is a very small number.
437:, although KrF and XeF have been successfully produced and accelerated with a tandem. It is not uncommon to make compounds in order to get anions, however, and
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Electrostatic accelerators have a wide array of applications in science and industry. In the realm of fundamental research, they are used to provide beams of
341:, there is no electric field inside a conductor, so the electrons are not repulsed by the platform once they are inside. The belt is similar in style to a
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the particle energy is in the low MeV range. More powerful accelerators can produce energies in the giga electron volt (GeV) range.
17:
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216:. Oscillating accelerators do not have this limitation, so they can achieve higher particle energies than electrostatic machines.
987:
Thomas, E.; Simolka, J.; DeLuca, M.; Horanyi, M.; Janches, D.; Marshall, R; Munsat, T.; Plane, J.; Sternovski, Z. (March 2017).
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68:
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is a type of Tandem accelerator. Ten of these were installed in the 20th century; six in North
America and four in Europe.
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Owing to their simpler design, electrostatic types were the first particle accelerators. The two most common types are the
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GrĂĽn, E.; Fechtig, H.; Hanner, M.; Kissel, J.; Lindblad, B.A.; Linkert, D.; Maas, D.; Morfill, G.E.; Zook, H. (May 1992).
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for industrial purposes including sterilization of medical instruments, x-ray production, and silicon wafer production.
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the maximum attainable voltage is around 30 MV. There could be other gases with even better insulating powers, but SF
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It is not possible to make every element into an anion easily, so it is very rare for tandems to accelerate any
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724:(eV) which makes it easier to calculate. The electronvolt is equal to the energy a particle with a charge of 1
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accelerator in
Tsukuba, Japan. The high voltage generator is right, the ion source and beam tube is at left
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989:"Experimental setup for the laboratory investigation of micrometeoroid ablation using a dust accelerator"
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In a tandem accelerator the particle is accelerated twice by the same voltage, so the output energy is
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which has dielectric constant roughly 2.5 times that of air. However, even in a tank of SF
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operation. The high pressure air increased the voltage on the machine from 1 MV to 5 MV.
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851:"A 2 MV Van de Graaff accelerator as a tool for planetary and impact physics research"
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gains passing through a potential difference of one volt. In the above equation, if
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coulombs, particle physicists use a different unit to express particle energies, the
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potential. This contrasts with the other major category of particle accelerator,
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Once the platform can be electrically charged by one of the above means, some
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Neukun, G.; Mehl, A.; Fechtig, H.; Zähringer, J. (March 1970).
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Nuclear
Instruments and Methods in Physics Research Section B
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392:. To increase the maximum acceleration energy further, the
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concept was invented to use the same high voltage twice.
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27:Accelerates particles with a static electric field
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284:Although these machines primarily accelerate
177:are accelerated to a high energy by a static
316:can be accelerated. In simple language, an
1166:IAEA database of electrostatic accelerators
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120:Learn how and when to remove this message
816:
303:
148:
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1087:"North-American MP tandem accelerators"
525:multiplied by the accelerating voltage
505:is equal to the charge on the particle
183:oscillating field particle accelerators
14:
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267:Rutherford backscattering spectrometry
1085:Wegner, H.E.; Thieberger, P. (1977).
662:the particle energy will be given in
792:is given in eV. For example, if an
300:dust detectors, and meteor studies.
69:"Electrostatic particle accelerator"
58:adding citations to reliable sources
29:
1142:10.1051/rphysap:0197700120100127900
1103:10.1051/rphysap:0197700120100129100
901:Earth and Planetary Science Letters
24:
748:is measured in elementary charges
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241:inject into the main accelerator.
167:electrostatic particle accelerator
25:
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772:is in volts, the particle energy
993:Review of Scientific Instruments
855:Review of Scientific Instruments
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711:{\displaystyle e=1.6(10^{-19})}
271:particle-induced X-ray emission
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275:accelerator mass spectrometry
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921:10.1016/0012-821X(70)90095-6
819:"Electrostatic Accelerators"
634:is in conventional units of
198:Cockcroft-Walton accelerator
155:Cockcroft-Walton accelerator
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1130:Revue de Physique Appliquée
1091:Revue de Physique Appliquée
943:"The Galileo Dust Detector"
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343:conventional conveyor belt
1126:"The European MP-Tandems"
142:Van de Graaff accelerator
138:Westinghouse Atom Smasher
18:Electrostatic accelerator
279:Elastic recoil detection
1070:A Negative Ion Cookbook
913:1970E&PSL...8...31N
796:which has a charge of 2
358:source of positive ions
318:electrostatic generator
224:production, high power
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607:{\displaystyle (1+q)V}
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569:{\displaystyle E=qV}
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210:insulation breakdown
194:Robert Van de Graaff
171:particle accelerator
54:improve this article
1181:Accelerator physics
1048:1984NIMPB...5..217M
1005:2017RScI...88c4501T
959:1992SSRv...60..317G
867:2011RScI...82i5111M
400:Tandem accelerators
384:is also chemically
367:dielectric constant
281:(ERD), and others.
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817:Hinterberger, F.
785:{\displaystyle E}
765:{\displaystyle V}
741:{\displaystyle q}
673:on the electron,
671:elementary charge
651:{\displaystyle V}
627:{\displaystyle q}
538:{\displaystyle V}
518:{\displaystyle q}
498:{\displaystyle E}
314:charged particles
298:impact ionization
262:materials science
230:radiation therapy
196:in 1929, and the
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220:as plastic
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52:Please help
47:verification
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972:11 February
431:noble gases
339:Gauss's law
222:shrink wrap
140:, an early
1175:Categories
1074:Online pdf
1042:(2): 217.
805:References
411:sputtering
351:Pelletrons
80:newspapers
1150:0035-1687
1111:0035-1687
907:(1): 31.
698:−
420:beryllium
322:capacitor
290:electrons
214:megavolts
212:to a few
173:in which
1018:27 April
926:27 April
880:27 April
636:coulombs
460:Geometry
388:and non-
308:Using a
273:(PIXE),
153:750 keV
1044:Bibcode
1001:Bibcode
955:Bibcode
909:Bibcode
863:Bibcode
452:The MP
424:silicon
277:(AMS),
269:(RBS),
94:scholar
1148:
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833:10 May
664:joules
658:is in
471:gasket
435:helium
426:beam.
416:carbon
394:tandem
347:rubber
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822:(PDF)
660:volts
467:Pyrex
390:toxic
386:inert
169:is a
101:JSTOR
87:books
1146:ISSN
1107:ISSN
1020:2022
974:2022
928:2022
882:2022
835:2022
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