Experiment on DC Inductive Arcs Driven by Axial and Transverse Magnetic Fields

中英文对照外文翻译文献(文档含英文原文和中文翻译)外文文献：DC Motor CalculationsOverviewNow that we have a good understanding of dc generators, we can begin our study of dc motors. Direct-current motors transform electrical energy into mechanical energy. They drive devices such as hoists, fans, pumps, calendars, punch-presses, and cars. These devices may have a definite torque-speed characteristic (such as a pump or fan) or a highly variable one (such as a hoist or automobile). The torque-speed characteristic of the motor must be adapted to the type of the load it has to drive, and this requirement has given rise to three basic types of motors: 1.Shunt motors 2. Series motors 3. Compound motors Direct-current motors are seldom used in ordinary industrial applications because all electric utility systems furnish alternating current. However, for special applications such as in steel mills, mines, and electric trains, it is sometimes advantageous to transform the alternating current into direct current in order to use dc motors. The reason is that the torque-speed characteristics of dc motors can be varied over a wide range while retaining high efficiency. Today, this general statement can be challenged because the availability of sophisticated electronic drives has made it possible to use alternating current motors for variable speed applications. Nevertheless, there are millions of dc motors still in service and thousands more are being produced every year.Counter-electromotive force (cemf)Direct-current motors are built the same way as generators are; consequently, a dc machine can operate either as a motor or as a generator. To illustrate, consider a dc generator in which the armature, initially at rest, is connected to a dc source E s by means of a switch (Fig. 5.1). The armature has a resistance R, and the magnetic field is created by a set of permanent magnets.As soon as the switch is closed, a large current flows in the armature because its resistance is very low. The individual armature conductors are immediately subjected to a force because they are immersed in the magnetic field created by the permanent magnets. These forces add upto produce a powerful torque, causing the armature to rotate.Figure 5.1 Starting a dc motor across the line.On the other hand, as soon as the armature begins to turn, a second phenomenon takes place: the generator effect. We know that a voltage E o is induced in the armature conductors as soon as they cut a magnetic field (Fig. 5.2). This is always true, no matter what causes the rotation. The value and polarity of the induced voltage are the same as those obtained when the machine operates as a generator. The induced voltage E o is therefore proportional to the speed of rotation n of the motor and to the flux F per pole, as previously given by Eq. 5.1:E o = Zn F/60 (5.1)As in the case of a generator, Z is a constant that depends upon the number of turns on the armature and the type of winding. For lap windings Z is equal to the number of armature conductors.In the case of a motor, the induced voltage E o is called counter-electromotive force (cemf) because its polarity always acts against the source voltage E s. It acts against the voltage in the sense that the net voltage acting in the series circuit of Fig. 5.2 is equal to (E s - Eo) volts and not (E s + E o) volts.Figure 5.2 Counter-electromotive force (cemf) in a dc motor.Acceleration of the motorThe net voltage acting in the armature circuit in Fig. 5.2 is (E s- E o) volts. The resulting armature current /is limited only by the armature resistance R, and soI = (E s- E o)IR (5.2)When the motor is at rest, the induced voltage E o= 0, and so the starting current isI = E s/RThe starting current may be 20 to 30 times greater than the nominal full-load current of the motor. In practice, this would cause the fuses to blow or the circuit-breakers to trip. However, if they are absent, the large forces acting on the armature conductors produce a powerful starting torque and a consequent rapid acceleration of the armature.As the speed increases, the counter-emf E o increases, with the result that the value of (E s—E o)diminishes. It follows from Eq. 5.1 that the armature current / drops progressively as the speed increases.Although the armature current decreases, the motor continues to accelerate until it reaches a definite, maximum speed. At no-load this speed produces a counter-emf E o slightly less than the source voltage E s. In effect, if E o were equal to E s the net voltage (E s—E o) would become zero and so, too, would the current /. The driving forces would cease to act on the armature conductors, and the mechanical drag imposed by the fan and the bearings would immediately cause the motor to slow down. As the speed decreases the net voltage (E s—E o) increases and so does the current /. The speed will cease to fall as soon as the torque developed by the armature current is equal to the load torque. Thus, when a motor runs at no-load, the counter-emf must be slightly less than E s so as to enable a small current to flow, sufficient to produce the required torque.Mechanical power and torqueThe power and torque of a dc motor are two of its most important properties. We now derive two simple equations that enable us to calculate them.1. According to Eq. 5.1 the cemf induced in a lap-wound armature is given byE o = Zn F/60Referring to Fig. 5.2, the electrical power P a supplied to the armature is equal to the supply voltage E s multiplied by the armature current I:P a = E s I (5.3)However, E s is equal to the sum of E o plus the IR drop in the armature:E s = E o + IR (5.4)It follows thatP a= E s I= (E o + IR)I=E o I + I2R (5.5)The I2R term represents heat dissipated in the armature, but the very important term E o I is the electrical power that is converted into mechanical power. The mechanical power of the motor is therefore exactly equal to the product of the cemf multiplied by the armature currentP = E o I (5.6)whereP = mechanical power developed by the motor [W]E o= induced voltage in the armature (cemf) [V]I = total current supplied to the armature [A]2. Turning our attention to torque T, we know that the mechanical power P is given by the expressionP = nT/9.55 (5.7)where n is the speed of rotation.Combining Eqs. 5.7,5.1, and 5.6, we obtainnT/9.55 = E o I= ZnFI/60and soT =Z F I/6.28The torque developed by a lap-wound motor is therefore given by the expressionT =Z F I/6.28 (5.8)whereT = torque [N×m]Z = number of conductors on the armatureF = effective flux per pole [Wb]*/ = armature current [A]6.28 = constant, to take care of units[exact value = 2p]Eq. 5.8shows that we can raise the torque of a motor either by raising the armature current or by raising the flux created by the poles.Speed of rotationWhen a dc motor drives a load between no-load and full-load, the IR drop due to armature resistance is always small compared to the supply voltage E s. This means that the counter-emf E s is very nearly equal to E s.On the other hand, we have already seen that Eo may be expressed by the equationE o = Zn F/60Replacing E o by E s we obtainE s = Zn F/60That is,wheren = speed of rotation [r/min]E s = armature voltage [V]Z = total number of armature conductorsThis important equation shows that the speed of the motor is directly proportional to the armature supply voltage and inversely proportional to the flux per pole. We will now study how this equation is applied.Armature speed controlAccording to Eq. 5.8, if the flux per pole F is kept constant (permanent magnet field or field with fixed excitation), the speed depends only upon the armature voltage E s. By raising or lowering E s the motor speed will rise and fall in proportion.In practice, we can vary E s by connecting the motor armature M to a separately excited variable-voltage dc generator G . The field excitation of the motor is kept constant, but the generator excitation I x can be varied from zero to maximum and even reversed. The generator output voltage E s can therefore be varied from zero to maximum, with either positive or negative polarity. Consequently, the motor speed can be varied from zero to maximum in either direction. Note that the generator is driven by an ac motor connected to a 3-phase line. This method of speed control, known as the Ward-Leonard system, is found in steel mills, high-rise elevators, mines, and paper mills.In modem installations the generator is often replaced by a high-power electronic converter that changes the ac power of the electrical utility to dc, by electronic means.What happens to the dc power received by generator G? When G receives electric power, it operates as a motor, driving its own ac motor as an asynchronous generator!* As a result, ac power is fed back into the line that normally feeds the ac motor. The fact that power can be recovered this way makes the Ward-Leonard system very efficient, and constitutes another of its advantages.Rheostat Speed ControlAnother way to control the speed of a dc motor is to place a rheostat in series with the armature . The current in the rheostat produces a voltage drop which subtracts from the fixed source voltage E s, yielding a smaller supply voltage across the armature. This method enables us to reduce the speed below its nominal speed. It is only recommended for small motors because a lot of power and heat is wasted in the rheostat, and the overall efficiency is low. Furthermore, thespeed regulation is poor, even for a fixed setting of the rheostat. In effect, the IR drop across the rheostat increases as the armature current increases. This produces a substantial drop in speed with increasing mechanical load.中文译文：直流电动机的计算概述现在，我们对直流发电机有一个很好的了解，我们可以开始对直流电动机的研究了。

０ 引 言
随着 人们 对 电力开 关设备 中的关键技 术进 行 深入 的研 究 ， 如何 快 速 熄灭 电弧 成 为 电 力设 备 开 关 研究 的主要课 题 ， 其 中对 于 电弧 电流 密 度 分 布 的测量 和分 析至 关重要 。 由于 开关 电弧高 温等 特 性， 故 测量 方法 极 其 复 杂 。常 规 的 直接 测 量 方 式 在 电弧研究 中很 难 得 到精 确 的测 量 值 。 目前 ， 常
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Ｙ Ａ Ｎ Ｇ Ｂ ｏ ｙ ｕ ， Ｚ Ｈ Ａ ＮＧ Ｇ ｕ ｏ ｇ ａ ｎ ｇ， Ｚ Ｈ Ａ ＮＧ Ｐ ｅ ｎ ｇ ｆ ｅ ｉ ， Ｄ Ｏ ＮＧ Ｊ ｉ ｎ ｌ ｏ ｎ ｇ， Ｇ Ｅ Ｎ Ｇ Ｙ ｉ ｎ ｇ ｓ ａ ｎ
ａ ｎｄ ｍａ ｇ ｎｅ ｔ ｉ ｃ ｉｅ ｆ ｌ ｄ， ｔ ｈ ｅ ｏ ｒ ｉ ｇ ｉ ｎ ａ ｌ ｖ ａ ｌ ｕ ｅ ｏ ｆ ｃ ｕｒ ｒ ｅ ｎｔ ｌ ｉ ｎｅ ｄ ｉ ｓ ｔ ｉｂｕ ｒ ｔ ｉ ｏ ｎ ｉ ｓ ｏ ｂ ｔ ａ ｉ ｎ ｅ ｄ ｂ ｙ ｓ ｏ ｌ ｖ ｉ ｎ ｇ ｌ ｉ ｎ ｅ ａ ｒ ｅ ｑ ｕａ ｔ ｉ ｏ ｎ ｓ ． Ａｔ ｌ ａ ｓ ｔ ， ｔ ｈｅ ｉ ｍｐ ｒ ｏ ｖ ｅ ｄ ａ ｎ ｔ ｃ ｏ ｌ ｏ ｎ ｙ ｏ ｐ ｔ ｉ ｍｉ ｚ ａ ｔ ｉ ｏ ｎ ｉ ｓ ｕ ｓ ｅ ｄ ｔ ｏ ａ ｃ ｃ ｕｒ ａ ｔ ｅ ｌ ｙ ｆ ｉ ｔ ｔ ｈｅ ｃ ｏ ｒｅ ｓ ｐ ｏ ｎ ｄｉ ｎｇ ｒ ｅ ｌ ａ ｔ ｉ ｏ ｎ ｂ ｅ ｔ ｗｅ ｅ ｎ ｃ ｕ ｒ ｒ ｅ ｎ ｔ ｌ ｉ ｎｅ ａ ｎ ｄ ｍａ ｇ ｎ ｅ ｔ ｉ ｃ ｉｅ ｆ ｌ ｄ ｔ ｏ ｉ ｎｖ ｅ ｔ ｒ ｔ ｈｅ ２Ｄ ｄ ｉ ｓ ｔ ｉｂ ｒ ｕ ｔ ｉ ｏ ｎ ｏ ｆ ａ ｒ ｃ ｓ ｕｒ ｆ ａ ｃ ｅ ｃ ｕ ｒ ｒ ｅ ｎ ｔ ｄ ｅ ｎ ｓ ｉ ｔ ｙ． Ｋｅ ｙ ｗｏ ｒ ｄ ｓ： ｓ ｗｉ ｔ ｃ ｈ ａｒ ｃ； ｍ ａ ｇ ｎｅ ｔ ｉ ｃ ｆ ｉｌ ｚ ｅ ｄ ｉ ｎｖ ｅ ｒ ｓ ｅ ｐｒ ｏｂ ｌ ｅ ｍ ； ａｎ ｔ ｃ ｏ ｌ ｏ ｎｙ ｏ ｐｔ ｉ ｍｉ ｚ ａ ｔ ｉ ｏ ｎ； ａ ｒ ｃ ｃ ｕｒ ｒ ｅ ｎｔ ｄｉ ｓ ｔ ｒ ｉ ｂｕ ｔ ｉ ｏ ｎ

Brain Josephson 1973 Nobel Prize
Karl Muller & J.Georg Bednorz 1987 Nobel Prize
总结：磁通量量子化实验证实了超导环的 磁通量总是量子化的，并且量子化单位为 hc/2e。
BCS理论简介
BCS理论在1957年由巴丁、库伯、施里弗 三个人共同建立，其名称以三个人姓氏的 第一个字母组成（Bardeen、Cooper、 Schrieffer）。
BCS理论简介
BCS对超导现象的解释为：在低温下，电 子之间依靠与超导物晶格的相互作用，产 生相互吸引力。两电子依靠此吸引力，结 合成一体系，称为库伯对。库伯对中两个 电子的自旋相反，动量相反。一个电子吸 收或发射的声子将被另一个电子获得，从 而维持整体的动量不变，实现超导。
磁通量量子化实验
前图中，纵轴为未撤去外磁场时超导环为保证总 磁通量子化而产生的磁通量，也即在超导环外相 同面积内磁通量与超导环内磁通量的差值。（也 称为净通量） 按磁通量量子化假设，有下式：
其中 0为相同面积内外加场的磁通， s 为净磁 通。
hc 0 s n 2e
………..式（*）
左边由于环路积分同时应满足为波函数相位因此???????????????????cqsdbcqsdacqldacqss???nldaa2???????磁通量量子化理论推导因此有
05级量子力学电子作业 刘鹏翃 0510233 二班 物理学
磁通量量子化实验及超导 BCS理论
内容概要
磁通量量子化实验 超导BCS理论简介及磁通量量子化理论推导 超导BCS理论的困难 高温超导材料展望
磁通量量子化实验
对于1号样品的数据，问题在于，由于测量 系统的误差与噪声，由图中可以看出，其 磁通量的数据分布实际上是连续的，只是 其平均值为量子单位的整数倍，说服性不 强。 而对于2号样品的测量，可看出其单个点的 分布即为量子单位的整数倍。（如下图）

Introduction to Particle Accelerators國家同步輻射研究中心 周炳榮 Ping J. Chou pjchou@.twPHYS467500— 01Last update: 2007-10-22十年樹木，百年樹人Important Notes to Students: The sole purpose of this lecture notes is meant for classroom use only. Some photographs and graphic illustrations are adapted from various reference literatures, which are NOT to be distributed beyond the classroom use. Acknowledgement: The author is greatly in debt to Dr. Andrew Sessler of Lawrence Berkeley National Laboratory for his generous help and offering of invaluable historic notes on the development of particle accelerators. Dr. Andrew Sessler’s book* on the historic review of the development of particle accelerators is HIGHLY recommended to those who is interested in the physics of particle accelerators and the human stories behind it. One can certainly find some inspiration from his book. * Andrew Sessler and Edmund Wilson, Engines of Discovery –- A Century of Particle Acceerators, (World Scientific, Singapore 2007)The years around 1930 can be marked as the starting point of the accelerator era. Lord Ernest Rutherford can be regarded as the first person to push the development of particle accelerators.Laureates Year Main contribution to the physics of particle accelerators---------------------------------------------------------------------------------------------------------------E.O. Lawrence 1939 the invention of cyclotron and the production of artificial radioactive elements J.D. Cockcroft & 1951 the invention of cascade accelerator and the first E.T.S. Walton disintegration of atomic nuclei by artificially accelerated particles E.M. McMillan 1951 the principle of phase stability (transuranium elements) (in chemistry, shared with G.T. Seaborg ) J. Schwinger ( 1965 the fundamental analysis of properties of synchrotron shared with S. radiation (work on quantum electrodynamics) Tomonaga, R.P. Feynman) L.W. Alvarez 1968 drift tube linear accelerator (development of hydrogen bubble chamber) C. Rubbia & 1984 the invention of stochastic cooling for antiprotons S. Van der Meer (discovery of W/Z particles)Mechanism of Particle Acceleration DC voltage acceleration (developed in 1930s) • Voltage multiplier cascade (Cascade accelerators, Cockcroft and Walton) • Electrostatic generator (Van de Graaff accelerators) Resonance acceleration (Gustaf Ising, Sweden, first proposed it in 1924) • Radio-frequency (RF) Linear accelerators (Rolf Wideröe, Norway, built the first linac using an RF accelerating field) • Radio-frequency quadrupole (RFQ) (first proposed by I.M. Kapchinski and V.A. Teplyakov in 1970) • Cyclic accelerators Cyclotron (first one built in 1931) Microtron (first proposed in 1944 by V. Veksler and J. Schwinger) Synchrocyclotron (first proposed in 1945 by E. McMillan and V. Veksler) synchrotron Magnetic induction acceleration • Betatron (invented & built in 1940 by Donald Kerst, but the concept was formulated by R. Wideröe in 1928) • Induction linac (invented by N.C. Christofilos in 1950s)PHYS467500— 01DC voltage acceleration: (DC electric field)+V-VBattery (DC power supply)Magnetic induction acceleration: (Faraday’s Law of Induction)r r ∂B ∇× E = − ∂t r r r r & ∫ E ⋅ d l = − ∫ B ⋅ dSResonance acceleration: (AC electric field)∆W = e∆V ∆V = V0 sin(ωrf t + φ )E z ( r , t ) = E0 J 0 ( Bθ (r , t ) =e.g. the oscillating electromagnetic fields in a pillbox cavity (Maxwell eqs. + boundary conditions)ωcr ) e j ωtE0 ω J 1 ( r ) e j ωt c cExample of resonance acceleration:A pillbox cavity (NSRRC Booster)Electrostatic Acceleratorusing DC electric field to accelerate charged particles, the gain in the kinetic energy is: K= qV Voltage gain ∆V≦ 10 kV Method 1) 10 kV 10 kV 10 kV 10 kV－ ＋－ ＋ － ＋ － ＋ Connecting several accelerating structures in succession each is charged by high voltage power supply (10 kV max.) Method 2)+ _Charging up several high voltage capacitors, each to the maximum voltage available, then we discharge those capacitors all in series Cockcroft-Walton accelerator, it can reach few MeVMethod 3)Van de Graaff accelerator, it can reach ~ 10 MeV, invented in 1930’s deposit charge on a moving belt (insulating material) driven by a motor. The belt carries the charge to a large sphere continuously. A very huge charge (high voltage) is built up on the sphere. The physical size and expense are the limitationCockcroft-Walton Voltage Multiplier (cascade accelerator)The 750 keV Cockcroft-Walton accelerator at Fermi National Accelerator Laboratory (Fermilab), Batavia, USAThe original Cockcroft-Walton generator developed by J. Cockcroft and E. Walton at Cavendish Laboratory in Cambridge, U.K.Ernest T.S. WaltonErnest RutherfordJohn D. Cockcroft(founding father of nuclear physics)•The Cockcroft-Walton generator can convert AC or raise a low DC voltage to a much higher DC voltage level. It is used to provide higher DC electric fields for particle acceleration. •It is based on the principles of voltage multiplying circuit. A voltage multiplier can step up a relatively low voltage to an extremely high value. This technique is different from the transformer. It does not require the heavy core and use only capacitors and rectifiers (diodes). •The voltage potential achieved by the first Cockcroft-Walton voltage multiplier is 700 kV with a voltage variation within few percent. Positive ions of hydrogen with a beam current of the order of 10 µA being obtained (protons of 710 keV). •This is the first accelerator to demonstrate disintegration of atomic nuclei by artificially accelerated particles! They induced the nucear reaction: Li+ p 2HeFirst cycle K1General principle of voltage multiplying circuitX1 K2 E supply E K3 0 2E K2 E In the 1st cycle when X1 and X2 are connected to K2 and K3, capacitor X2 will be charged to voltage E supply E K3 Efloating connectionE X2Second cycle K1 X1 2E X2The voltage multiplier circuit was known and used at lower potentials around 1920.ÆM. Schenkel, Elektrotechnische, 40: 333 (1919)ÆH. Greinacher, Z. Phys.,4: 195 (1921)Cockcroft and Walton adapted the circuit and applied it to a much higher voltage potentials than in the previous applications. Their results are reported in aseries of papers:Proc. Roy. Soc. (London), A129: 477 (1930)Proc. Roy. Soc. (London), A136: 619 (1932)Proc. Roy. Soc. (London), A137: 229 (1932)Proc. Roy. Soc. (London), A144: 704 (1934)J.D. Cockcroft and E.T.S. Walton were awarded the Nobel Prize in Physics for 1951.The steady DC voltage potentials available with the voltage multiplier cascade and its reliability have made it very useful in low-energy nuclear physics, in theenergy range up to 1 MeV. For enclosed systems filled with high pressureinsulating gases, the voltage has been achieved up to 6 MV. It is alsofrequently chosen as the pre-accelerator (injector) for higher energy machines when high-intensity ion beam is desired.Diameter of the sphere: 15 ft. Diameter of the supporting column: 6 ft.The machine was used as a research accelerator at MIT operating at potentials up to 2.75 MV. It was moved to Boston Museum of Science eventually. The effect of pigeons’droppings on the sphere is very dramatic as shown by those sparks.The diagram from E.O. Lawrence’s 1934 patent, found from WikipediaErnest O. Lawrence in 1930The first cyclotron with a diameter of 5 inchesE.O. Lawrence’s idea of using voltages oscillating at radio frequency (RF) toaccelerate charged particles in a circular machine was triggered by Rolf Wideroe’spaper that he came across in the Berkeley University library in 1929.[Ref.]: Photography gallery of Lawrence Berkeley National Laboratory,/photo/gallery/If the frequency of electric oscillator is adjusted to be the same as the cyclotron frequency, i.e. particles always cross the voltage gap at the right timing (resonance condition: continuous accelerationÄenergy gain)The 11-inch cyclotron built by Lawrence and his graduate students, David Sloan and M. Stanley Livingston at the Univ. of California, Berkeley during 1931. They obtained a proton beam of energy 1.22 MeV and a current of 1 nA with a maximum accelerating voltage of only 4 kV.•Phys. Rev., 40: 19 (1932), E.O. Lawrence and M.S. Livingston•Rev. Mod. Phys.,18, 293 (1946), M.S. Livingston; “Ion Sources for Cyclotrons”The principle of vertical focusing in a cyclotron (focusing action of electric field)＋V－VA H＋BBecause of the existence of the curvature of the field lines, most effective for particles at low energy, near the center of gap.PHYS467500— 01At higher beam energy, the increase of speed is getting smaller. Particles can not cross the voltage gap at the right timing. Eventually they are decelerated (not synchronized with the accelerating voltage), i.e. the resonance condition is lost. The maximum energy gain can be obtained from a cyclotron: heavy particles: E ~ 20 MeV (protons) electrons : E ~ few hundred eV, < 1 keV ! The energy limit of cyclotron is set by the effects of relativity Synchronism is lost when v c (why?) What is the limitation to build a cyclotron at higher energy for heavy ions? Is cyclotron a good option for accelerating electrons to higher energy? Why?Homework 1) The correct expression to be used when the relativistic effect is taken into account should be R=P/(qB), instead of Eq.(1.2), where P is the momentum. Derive this result. PHYS467500— 01Homework 2) Using the expression given in Homework 1, derive the circulating frequency of particles when the relativistic effect is taken into account.qB f = 1− v2 c2 2πm0(1.5)Homework 3) Using the relativistic expression of circulating frequency given in Eq.(1.5) of Homework 2, calculate the circulating frequency for electrons with kinetic energy 10 keV and 1 MeV respectively. Assuming a magnetic field B= 500 Gauss. Then, you repeat the calculation using the nonrelativistic expressions given by Eqs.(1.2) and (1.3), compare the circulating frequencies obtained with the nonrelativistic expressions and relativistic expressions. Homework 4) Repeat the calculation you have done in Homework 3, calculate the circulating frequency for protons with kinetic energy 1 MeV and 30 MeV respectively. Assuming a magnetic field B= 500 Gauss. Then, you repeat the calculation with nonrelativistic expressions given by Eqs.(1.2) and (1.3), compare the circulating frequency for both cases.The 184 inch cyclotron built at Univ. of California, Berkeley[Ref.]: Photography Gallery of Lawrence Berkeley National Laboratory, /photo/gallery/Electron Linac (disk loaded structure)[Ref.] High power microwave amplifier[Ref.] Beam Line, Vol.28 (1998), published by SLACStanford Linear Accelerator Center (SLAC)50 ¥ 50 GeV e-e+September 25, 2007 - Wolfgang Panofsky, Renowned Stanford Physicist and Arms Control Advocate, Dead at 88 •born in Berlin April 24, 1919 •graduated from Princenton University in 1938 •received his PhD. From California Institute of Technology in 1942 and served as consultant to the Manhattan Project, helping build the first atomic bomb during World War II. •The founding director of SLAC •member of the President’s Science Advisory Committee in the Eisenhower, Kennedy and Johnson administrations. •a fellow of the American Physical Society and served as its president in 1974. For more details, please refer to /pressreleases/2007/20070925.htmMagnetic induction accelerationBetatronBgBav• • •Donald Kerst and Robert Serber reinvented R. Wideröe’s beam transformer idea and renamed it as betatron. The success is due to their detailed orbit stability analysis and careful magnet design by D. Kerst. In the betatron, a time varying magnetic field produces an electric field that accelerates electrons. Although the betatron has a circular geometry similar to the cyclotron, it’s a pulsed machine and the particle orbit does not spiral out. It’s the first circular accelerator to operate at a constant orbit radiusPhys. Rev., 58: 841 (1940), D.W. Kerst Phys. Rev., 60: 47 (1941), D.W. Kerst Phys. Rev., 60: 53 (1941), D.W. Kerst and R. SerberPrimary coilSecondary coilAC Induced alternating currentChanging magnetic flux The principle of betatron is similar to the action taking place in an electric transformer. The coil of magnet in the betatron acts as the primary winding, the circulating electron beam acts as the secondary winding. the changing magnetic flux acceleration the increasing magnetic field particle guiding In contrast, cyclotrons can be operated continuously ! Betatron operation must be recycled Pulsed operation[Ref.] /history/Timeline/1940s.html[Ref.] /engineering/ind_module_summary.htmlThe Flash X-Ray Facility (FXR),a linear-induction electron beamaccelerator built in 1982, atLawrence Livermore NationalLaboratory, California, USA. Itis used to study the detonationprocess (implosion) of nuclearweapons.[Ref.] /str/April02/April50th.htmlNichola C. Christofilos, theinventor of the inductionlinac (1950s) and theprinciple of strong focusing.[Ref.] http://www.mlahanas.de/Greeks/new/Christofilos.htm國家同步輻射研究中心增能環（新竹科學園區）Synchrotron (higher energy electron)when e-travels at 0.98c Äthe beam energy is only at 2 MeV e-travels at a constant speed above few MeV The operation principles of e-synchrotron combine:•cyclotron method of acceleration•Strength of magnetic guiding field increases as the e-energy increasesThe alternating voltages at the gaps can be kept at constant frequency (f RF = const.)Synchrotron must also be pulsed.•Phys. Rev., 70: 249 (1946), D. Bohm and L. Foldy同步輻射加速器基本構造示意圖The synchrotron radiation emitted by electrons orbiting in the magnetic field was first observed in a 70 MeV electron synchrotron at General Electric Company Research Laboratory in 1947.•J. Appl. Phys.,18: 810 (1947), F.R. Elder, A.M. Gurewitsch, R.V. Langmuir, and H.C. PollockThe 300 MeV electron synchrotron built at General Electric Co. in 1940s.The photograph shows the synchrotron radiation emitted from theaccelerator.PHYS467500—01•Fixed-target machine:¨test particle m B is at rest in the lab frame, E AB E c m E 2*2≅•Colliding-beam machine:SLAC Beam Line , Spring 1997Livingston Plot★Terminated in 1993 SSC: 20 TeVLivingston Plot for Colliders in the Constituent Frame 7 TeV (p-p collider)Replaced by International Linear Collider (ILC)The energy of hardon colliders here has been derated by factors of 6-10. Why?PHYS467500— 01[Ref.]: SLAC Beam Line, Spring 1997Fermi National Accelerator Laboratory (Fermilab), Chicago, U.S.A.Tevatron (1 TeV)Main Injector[Ref.] Visual Media Services, Fermilab /pub/presspass/vismedia/RecyclerMain RingTevatronMain InjectorMain Control RoomLarge Hadron Collider (LHC) at CERN, Geneva, Switzerland (will start up in May 2008)[Ref.] http://www.cern.ch Operating temperature 1.9 KSuperconducting coils cooled down to 1.9 °K, dipole field B= 8 TStanford Linear Accelerator Center (SLAC), Menlo Park, California, U.S.A.[Ref.] Klystron galleryLinac tunnel[Ref.] /exp/e158/pictures/ASSET/tunnel_.jpgSLAC Linear Collider[Ref.] /sldwww/slc/SLAC_AERIAL.GIFForth Generation Light Source ( X-ray FEL ) FEL: free electron laser/lcls/Electron bunch length: 0.023 mm, 15 GeV electron beam X-ray wavelength: 0.15 – 1.5 nm X-ray pulse duration: 100 femtosecond – 100 attosecond。