Charged Particle

Quantities, Units, and Definitions

Edward Fifty. Alpen , in Radiation Biophysics (Second Edition), 1998

Charged Particle Equilibrium

Charged particle equilibrium (CPE) exists at a point p, centered in a volume, V, if each charged particle carrying a certain energy out of Five is replaced by some other identical charged particle that carries the aforementioned energy into 5. If CPE exists at a point, then D = Thousand (dose equals kerma) at that point, provided that bremsstrahlung (secondary radiation) production past charged particles is negligible. Think that dose is energy absorbed in unit of measurement volume of the medium, whereas kerma is free energy transferred from the original particle or photon in the aforementioned unit of measurement book.

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MECHANISMS

Esam M.A. Hussein , in Radiation Mechanics, 2007

Coulomb elastic scattering

Charged particles can scatter elastically by the force between the electrical fields of an incident particle and a target nucleus. Direct standoff, or contact, between the incident particle and the nucleus is, therefore, not necessary. In this type of collision, the charged particle is deflected without exciting the nucleus and without beingness accompanied with the release of electromagnetic radiation. The incident particle loses only the kinetic energy needed for conservation of momentum. The scattering of ho-hum charged particles past heavy nuclei is called Rutherford scattering 23 . In quantum mechanics, the elastic scattering of an electron with the Coulomb field of the nucleus is chosen Mott handful. When the incident particles and the target are identical, e.yard. a proton on a hydrogen nucleus, the incident and target particles, become indistinguishable, and quantum treatment of the scattering betwixt the 2 particles requires accounting for the interference between their waves. The interaction is then known as Mott scattering between identical particles.

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Radiation Therapy Physics and Treatment Optimization

B. Nilsson , A. Brahme , in Comprehensive Biomedical Physics, 2014

nine.01.2.ane Introduction to Charged Particle Interaction

When charged particles pass through thing, their Coulomb electric field will collaborate with the atomic electrons and the atomic nuclei in the affair. Normally, only a small part of the kinetic free energy is lost in each collision, and the particles will undergo several interactions before they take transferred all their kinetic energy to matter. The interactions will give rise to excitations and ionizations of the atoms and emission of electromagnetic radiation, often called bremsstrahlung. Depending on the blazon of charged particle, different interaction processes are more or less of import, and often, the clarification of the interactions of charged particles is divided into light charged particles (electrons and positrons) and heavy charged particles (ions). The ions are sometimes farther divided into light ions with Z    ten and heavy ions with Z    10. The option of Z is somewhat capricious. Effigy one describes in a simplified way the transport of charged particles in matter for ions and electrons. The mechanisms by which charged particles lose free energy or are scattered tin can be divided into four chief types of interactions:

Figure ane. Schematic diagram of the transport of an ion and an electron through thing.

one.

Inelastic standoff with atomic electrons. This is the ascendant mechanism by which heavy charged particles and light charged particles with low to medium energy volition lose their energy. As a result of such a collision, there will be excitations and ionizations. Often, the free energy transferred to the emitted electron may exist loftier enough to make it possible for the electron to ionize new atoms. If the energy is low, merely a few atoms will exist ionized and there will be a cluster of often three to four ionizations close to each other. If the free energy is higher, this secondary electron is called a δ-electron.

2.

Inelastic collision with a nucleus. When a charged particle passes near a nucleus, it volition exist deflected. In some of the deflections, the charged particle will lose energy and this free energy is emitted equally electromagnetic radiation called bremsstrahlung. This interaction process is, in the free energy region used in medical physics, only of interest for electrons and positrons.

three.

Elastic handful with a nucleus. When the particle is deflected without exciting the nucleus or emitting radiation, at that place will exist elastic scattering. Not only light charged particles merely besides heavy charged particles, in particular depression-energy particles, have a high probability for experiencing elastic scattering.

4.

Rubberband collision with atomic electrons. An incident electron may exist elastically deflected in the field of the atomic electrons. These processes are of interest merely for very-low-energy electrons and volition non be discussed in this chapter.

As indicated in Figure 1 , the tracks of the charged particles will differ from both macroscopic and microscopic points of view. The heavy charged particle will excite and ionize atoms along its path. Equally the particle is heavy compared to the electrons, it volition simply transfer a very pocket-sized amount of its energy in each collision and will merely be deflected in elastic scattering with the nucleus. The runway is then rather straight and dissimilar particles volition accept a like range. The produced δ-particles volition as well have low energies. Notwithstanding, a calorie-free particle can lose a large part of its energy in one collision and can be deflected at large angles. They can too produce high-energy δ-particles and bremsstrahlung. This means that different electron tracks will differ significantly leading to a large energy and range straggling as will be discussed in the following sections.

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Femtosecond Electron Imaging and Spectroscopy

Martin Berz , ... Chong-Yu Ruan , in Advances in Imaging and Electron Physics, 2015

Multi-GeV Electron Radiography for MaRIE

F.Due east. Merrill, Thou.Northward. Borozdin, R.W. Garnett, F.G. Mariam, C.50. Morris, A. Saunders, P.L. Walstrom

Los Alamos National Laboratory, New United mexican states, United states

Charged particle radiography was first investigated in the late 1960s when high-energy proton accelerators (>  100   MeV) provided the kickoff charged particle probes capable of penetrating relatively thick objects. Because of the paradigm deposition that results from scattering processes within the object, this technique was abandoned by the community. In the mid 1990s, even so, Los Alamos National Laboratory developed a magnetic lens imaging technique that has enabled proton radiography for a wide range of applications. Today, there are four proton radiography facilities operating in the globe and two additional facilities are being designed or made. More recently, the technique of charged particle radiography has been extended to utilize high-free energy electron probes (demonstrated with 30   MeV electrons) and Los Alamos National Laboratory is developing this technique for applications at the time to come Materials and Radiation in the Extremes (MaRIE) facility with multi-GeV electrons. The goal for this awarding is to measure fast dynamic materials properties with spatial resolution of less than 1 micron and temporal resolution of less than 1   ps. Through the collection of radiographic movies of dynamic processes a detailed agreement of dynamic materials can be gained. In this presentation, we will draw this method of charged particle radiography, present some examples of proton and electron radiographic measurements, and summarize our predictions for the performance of a 12-GeV electron radiography facility.

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Electromagnetic Radiations

Michael F. L'Annunziata , in Radioactivity (Second Edition), 2016

8.5 Cherenkov Radiation

Charged particles, when they possess sufficient energy, may travel through a transparent medium at a speed greater than the speed of light in that medium. This occurrence causes the emission of photons of low-cal known as Cherenkov radiations. These photons extend over a spectrum of wavelengths from the ultraviolet into the visible portion of the electromagnetic radiation spectrum.

The photon emission is a result of a coherent disturbance of adjacent molecules in thing acquired by the traveling charged particle, which must possess a certain threshold energy. This phenomenon has practical applications in the measurement and detection of radionuclides that emit relatively high-free energy beta particles (50'Annunziata, 2012e). The theory and applications of Cherenkov radiation are discussed in detail in the affiliate entitled "Cherenkov Radiations".

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Electron Optics and Electron Microscopy Conference Proceedings and Abstracts

Peter West. Hawkes , in Advances in Imaging and Electron Physics, 2015

5.1 Charged-Particle Optics (CPO)

The CPO series of meetings was launched by Hermann Wollnik, in collaboration with Karl L. Brown and Peter W. Hawkes, in an attempt to bring together members of the various communities of charged-particle eyes (accelerator optics, electron optics, and spectrometer eyes).

Giessen, 1980. Proceedings of the First Conference on Charged Particle Optics, Giessen, September viii–xi, 1980 (Wollnik, H., Ed.) Nuclear Instruments and Methods in Physics Inquiry, 187 (1981), 1–314.

Albuquerque, NM, 1986. Proceedings of the Second International Briefing on Charged Particle Optics, Albuquerque, NM, May xix–23, 1986 (Schriber, S. O., & Taylor, Fifty. S., Eds.) Nuclear Instruments and Methods in Physics Research A, 258 (1987), 289–598.

Toulouse, France, 1990. Proceedings of the 3rd International Conference on Charged Particle Optics, Toulouse, April 24–27, 1990 (Hawkes, P. W., Ed.) Nuclear Instruments and Methods in Physics Research A, 298 (1990), 1–508.

Tsukuba, Nihon, 1994. Proceedings of the Fourth International Conference on Charged Particle Optics, Tsukuba, October 3–6, 1994 (Ura, 1000., Hibino, K., Komuro, Thou., Kurashige, K., Kurokawa, Due south., Matsuo, T., Okayama, S., Shimoyama, H., & Tsuno, G., Eds.) Nuclear Instruments and Methods in Physics Research A 363 (1995), 1–496.

Delft, the Netherlands, 1998. Proceedings of the 5th International Briefing on Charged Particle Optics, Delft, Apr 14–17, 1998 (Kruit, P., & Amersfoort, van, P. W. Eds.). Nuclear Instruments and Methods in Physics Research A, 427 (1999), one–422.

College Park, MD, 2002. Proceedings of the 6th International Conference on Charged Particle Optics, Marriott Hotel, Greenbelt, MD, October 21–25, 2002 (Dragt, A. & Orloff, J., Eds.). Nuclear Instruments and Methods in Physics Research A, 519 (2004), 1–487.

Cambridge, UK, 2006. Proceedings of the 7th International Conference on Charged Particle Optics, Trinity Higher, Cambridge, July 24–28, 2006 (Munro, E., & Rouse, J., Eds.). Physics Procedia ane (2008), ane–572.

Singapore, 2010. Proceedings of the 8th International Conference on Charged Particle Optics, Suntec Convention Eye, Singapore, July 12–xvi, 2010 (Khursheed, A., Hawkes, P. W., & Osterberg, Grand. B., Eds.). Nuclear Instruments and Methods in Physics Enquiry A, 645 (2011), one–354.

Brno, Czechia, 2014. Proceedings of the 9th International Briefing on Charged Particle Optics, Brno, August 31–September 5, 2014. (Frank, Fifty., Hawkes, P.West., & Radlička, T., Eds.). Microscopy and Microanalysis, 21 (2015) Suppl.

Cardinal West 2018

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MAGNETIC FIELD OF ELECTRIC CURRENT

George B. Arfken , ... Joseph Priest , in University Physics, 1984

Instance three Van Allen Belt Current Loop

Charged particles (mostly electrons and protons) trapped in the earth's magnetic field make upwardly what we call the Van Allen belts (Figure 33.15; run across Section 32.5). Considering of nonuniformities in the magnetic field, the charged particles migrate—the protons motility westward and the electrons move east. This migration of charges constitutes a tremendous electric current encircling the earth. Let united states approximate the very complex electron and proton distributions by a electric current of 100,000 A at an distance of 1600 km encircling the earth w higher up the geomagnetic equator. Despite the size of this current, we tin demonstrate that the resulting magnetic field is small-scale compared to the earth'south magnetic field. For example, we tin can calculate the magnetic field that this Van Allen current produces at the earth's heart.

Figure 33.15. The Van Allen radiation belts.

From Eq. 33.15

B x = μ o I 2 a = 4 π × x 7 × ten 5 2 × eight × ten half-dozen

taking a, the distance to the world'southward center, to be 8 × 10half-dozen grand. The result is

B ten = 0.viii × ten eight T = 0.8 × ten four G

By comparing, the earth's magnetic field is a few tenths of a gauss in magnitude. Thus, although the electric current produced by the Van Allen belts is tremendous when compared with ordinary household or laboratory currents, the resulting magnetic field is only a small disturbance in the earth'south magnetic field.

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Proton Microprobe (Method and Background)*

Geoff W. Grime , in Encyclopedia of Spectroscopy and Spectrometry (2nd Edition), 1999

Ion beam induced charge (IBIC)

Charged particles passing through the junctions of active semiconductor devices create electron–pigsty pairs which can be detected every bit accuse pulses on the electrodes of the device. Thus scanning a semiconductor device using a microbeam gives the possibility of mapping the agile regions of the device either for fault finding or for investigating sensitivity to radiation. This technique is more unremarkably used with electron beams only the use of  MeV ions gives the advantage of the long range, which means that junctions may exist studied which are covered past metallization or passivation layers. Similar STIM, each particle creates a signal and so it is a high-yield technique with the possibility of high-resolution imaging. Effigy 4 shows IBIC images of a gallium arsenide transistor.

Figure four. Optical (top left) and IBIC images of a gallium arsenide transistor at three different magnifications (length of side of image area indicated on each area). The IBIC images show the intensity of charge collected between the p-type and northward-type contacts, with the highest accuse shown as darker. In the highest magnification image, the arrows indicate a 0.8   μm depletion region, showing the resolution that can be accomplished using this technique. Reproduced from Breese MBH, Crud GW, Watt F, and Blaikie RJ (1993) Vacuum 44: 175, with permission.

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Analytical Methods for the Calculation and Simulation of New Schemes of Static and Time-of-Flight Mass Spectrometers

Igor Spivak-Lavrov , in Advances in Imaging and Electron Physics, 2016

1 Introduction

Charged particle optics, or corpuscular optics (CO), was derived from the analogy between the distribution of low-cal in transparent environments and the movement of charged particles in electrical and magnetic fields. CO deals with problems caused by the formation of charged particle beams and the command of these beams. Start of all, it is possible to highlight the tasks connected with the distribution of charged particle beams according to their mass and energy, which are solved via mass- and power-analysis, as well as problems of transportation and focusing of beams that arise in electronic and ionic microscopy and lithography. To solve these tasks, the theoretical methods borrowed from light optics are usually used in CO; namely, at first, the solution of a linear chore or paraxial approximation is found, then the theory of aberrations is formulated. Hither, the aberrational theory is traditionally devised by means of asymptotic series in small parameters characterizing an ion axle. The method of consecutive approximations used for finding aberrational coefficients leads to very beefy expressions for high-order coefficients. At that, information technology is impossible to define within the aberrational theory itself, for what values of small parameters characterizing a beam, the chosen approximation withal works rather well.

At present, information technology is possible to observe the departure from the classical tradition when attempts are made to solve problems of charged particle optics in a straightforward manner (straight, using the known equations of electrodynamics and mechanics) by using the power of modern computers. Now, many packages of applied software programs that allow the simulation of the beliefs of charged particle beams in diverse rather difficult corpuscular optical systems (COS) accept been created. One of the best-known packages is the SIMION plan (Scientific Instrument Services, Ringoes, NJ), which is used by many researchers. However, the complete rejection of belittling methods has not resulted in meaning progress in the creation of new highly effective COS.

Past feel shows that usually the most fruitful ideas in CO began from original theoretical works. Hither, for instance, the prismatic direction in mass- and energy-assay, which has led to the creation of mass spectrometers and energy analyzers that are like according to the scheme to prismatic light optical devices, is worth noting (Kel'man et al., 1979, 1985). Also, annotation other enquiry (e.g., Golikov and Krasnova, 2010), continued with the searching of fields with ideal focusing for the distribution of beams according to energy and analytical works that are the cornerstone of the Orbitrap mass analyzer (Gall et al., 1986; Makarov and Denisov, 2009).

We volition especially notation a couple of studies (Wollnik, 1987) in which information technology was shown that in the case of a circular trajectory of ions in a magnetic field, the Q-parameter defining the quality of static mass analyzers is proportional to a flux of a magnetic field through the section of an ion beam (i.e., the magnetic flux theorem). In addition, an idea was proposed of a beam expansion earlier inbound the magnetic sector with the help of quadrupole lenses, which was realized in a desktop device (Ishihara et al., 1995).

In one of our studies (eastward.thousand., Glikman and Spivak-Lavrov, 1990), the magnetic flux theorem was proved for any form of an axial trajectory and a combined electric and magnetic field. (The proof of this theorem tin can be found in section 2.two, afterward in this chapter.) In Baisanov et al. (2006, 2008b, 2011b), the idea of expanding a beam before it enters a magnet due to the refraction in the prismatic electric field was proposed. Unlike the field of quadrupole lenses, such a field not but expands the beam before it enters a magnet, information technology too allows energy focusing to occur. In this context, the unique design is the cone-shaped achromatic prism (CSAP) possessing a record angular mass dispersion equal to about 50 rads per 100% of mass variation (Spivak-Lavrov, 1979, 1995a; Glikman and Spivak-Lavrov, 1985; Baisanov et al., 2011b). The CSAP scheme projected to the hateful plane (the horizontal management) is presented in Effigy i. Every bit that shows, the parallel ion beam coming into CSAP beginning expands due to the refraction in the electric field, and then boosted expansion in a nonhomogeneous CSAP magnetic field takes place. Since the sector of a magnetic field γ H in CSAP is greater than 180°, the stream of a magnetic field penetrating an ion beam is very big.

Figure 1. Schematic image of CSAP; 1—magnetic poles of a prism; 2, 3—electrodes and magnetic screens; 4—axial trajectory of an ion beam; five—source of ions; 6—detector; 5 0, 5 1, V 2—potentials of electrodes; ψ 0– angle of beam entry in a prism.

Electric and magnetic fields of the 1/r type whose potentials in the spherical system of coordinates r, ϑ, and ψ depend just on angular variables ϑ and ψ are realized in CSAP (Glikman et al., 1973, 1977). It leads to the fact that all trajectories of particles of the homogeneous flat parallel beam entering the CSAP move in the mean aeroplane past like trajectories and proceed parallel at the get out from the CSAP equally well, as shown in Effigy 1. Moreover, this property does not depend on the beam width in the hateful aeroplane; therefore, the increase in the width of a beam in the CSAP does not atomic number 82 to the emergence of boosted aberrations. The latter property is specially of import when using CSAP in prismatic devices supplied with the collimator and focusing lenses. We will note that in CSAP free energy, focusing is carried out, and parallelism of a volumetric beam is preserved owing to its vertical telescoping.

In the present work, we develop numerical and belittling methods of COS research. Section 2 is devoted to the development of methods of calculating wide beams of charged particles. Here, the differential equations describing the deflection of particles of the beam from an axial trajectory for unspecified COS whose axial trajectory possesses torsion, as well as for COS with a flat axial trajectory lying in the mean plane, accept been obtained. In the calculations, these equations are integrated numerically together with differential equations for an centric trajectory, which allows 1 to achieve high accurateness of calculations. In subsection 2.2, general focusing and dispersive backdrop of COS possessing the hateful aeroplane are considered, and in particular, the proof of the magnetic flux theorem is provided.

It is known that in the calculation of electronic mirrors, in that location are mathematical difficulties connected with the fact that most the turning points, the radius of curvature of particle trajectories approach zero, and the inclinations of trajectories to an optical axis and the relative energy spread of particles approach infinity. All these difficulties are put bated if Newton's equations on the fourth dimension of the movement of particles are integrated rather than the trajectory equations. In subsection 2.three, the dimensionless Newton'south equations that are used in section four to calculate the fourth dimension-of-flying (TOF) mirror electrostatic systems are obtained.

All the motion and trajectory equations obtained in department two tin be used nigh effectively when there are belittling expressions for the potentials describing COS electrical and magnetic fields. In section iii, COS, whose electric and magnetic fields are found analytically via considering methods of the theory of functions of a complex variable (TFCV), and trajectories of charged particles in them are calculated numerically by integrating motion and trajectory equations. Hither, nosotros volition peculiarly note the method of calculation of potentials of a transaxial COS and a system with axial symmetry that nosotros adult in harmonic approximation. Subsection iii.iv, in which the original method of calculation of trajectories of the movement of charged particles in the fringe fields of flat and cylindrical capacitors is developed, stands a bit apart in department three.

Section four is devoted to the calculation of instrument characteristics of static and TOF mass analyzers. Here, the results obtained in the previous sections are used to clarify the behavior of beams of charged particles in COS, and the Monte Carlo method is also applied. Past means of a random number generator, the entry conditions for a large number of particles emerging from an ionic source are fake. At that signal, distribution of ions in the source according to coordinates, emergence angles, free energy, and mass is taken into business relationship. For all these particles, the motion equations or trajectory equations are integrated numerically, and the distribution of particles upon the leave from COS in the detector plane is found. Thus, a computer model of a real experiment appears. Changing geometrical and electrical parameters of the model, it is possible to achieve the optimization of instrument characteristics of COS.

In subsection iv.1, a new scheme of a static mass spectrometer with a sector magnet, an electrostatic prism, and a transaxial lens that competes with the desktop device in its theoretical performance is calculated (Baisanov et al., 2008a, 2008b, 2011b). In subsection 4.two, CSAP is calculated, and it is shown that cosmos of the prismatic device on its basis will let one to surpass the desktop device in sensitivity and resolution. In subsection 4.3, TOF mass analyzers on the basis of a wedge-shaped mirror with a two-dimensional (2nd) field are calculated, and systems with loftier-quality spatial temporal focusing are selected. Some other feature of this chapter is the use of dimensionless variables, which facilitates numerical calculation and makes results more versatile.

Thus, in this chapter, we show the fruitfulness of a reasonable combination of analytical and numerical methods to solve problems of CO.

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Advances in Imaging and Electron Physics

Jay Theodore CremerJr., in Advances in Imaging and Electron Physics, 2012

16 Bremsstrahlung from Charged Particle Passage in Matter

Charged particles emit bremstahlung radiation equally they decelerate via their decreasing speed and change of direction due to Coulomb scatter. These accelerated charges emit electromagnetic radiation (or bremsstrahlung) every bit they are slowed and scattered by the electric fields of the atomic electrons and nuclei. However, standoff free energy loss predominates over the free energy loss by bremsstrahlung for the massive charged particles such as protons and alphas, and for the less energetic electrons and positrons. Even so, high-energy electrons and positrons are strong emitters of bremsstrahlung. The ratio of the energy loss Δ Due eastrad due to bremsstrahlung divided by the free energy loss ΔDue eastcol due to collisions is not derived here, simply is stated as

(207) Δ E r a d Δ Due east c o l = T Z + ane . 2 7 0 0 .

The incident charged particle kinetic energy is T[MeV], Z is the atomic number of the scattering material, and the 700 is given in MeV. For tungsten with Z = 74, an ion beam of protons or electrons accelerated to ten MeV that strike tungsten lose almost 50% of its energy by bremstrahlung and 50% by collisions, whereas a deuteron ion or electron accelerated to 100 keV loses 99% of its energy due to collisions and 1% by bremsstrahlung.

The number Due northbr (East 0, E) of bremsstrahlung photons of free energy Due east, per unit energy and per incident electron, emitted when an electron of incident free energy E 0 is completely slowed down, can be approximated by the distribution

(208) Northward b r ( E 0 , E ) = 2 m Z [ ( E 0 E one ) 3 4 L Due north ( E 0 Due east ) ] for Eastward < E 0 .

The units of Due northbr are given in photons per electron per MeV. The normalization constant k is independent of the emitted photon energy Eastward. The fraction of the incident electron's kinetic energy that is later on emitted as bremsstrahlung Y(East 0) is constitute by integrating Eq. (208) with respect to emitted photon energy E to become

(209) Y ( East 0 ) = 1 3 1 6 g Z E 0 .

Solving for normalization constant yard in the expression for Y(E 0) yields

(210) yard = ane 6 one iii Y East 0 Z E 0 .

Substitution of the k expression in Eq. 210 into Eq. 208 for the bremsstrahlung photon energy distribution Nbr gives

(211) N b r ( E 0 , E ) = ( 32 Y ( E 0 ) 13 E 0 ) [ ( E 0 Eastward one ) 3 4 L North ( East 0 Eastward ) ] for Eastward < Due east 0 .

The fraction Y(East 0) of incident electron kinetic energy emitted equally bremsstrahlung photons asymptotically increases from 0 to ane as Due east 0 increases relative to the emitted photon energy Eastward.

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