A brief history of Particle Accelerators and Future By Nawin Juntong 4 March 2014 A brief history of Particle Accelerators A.W. Chao, W. Chou, Reviews of Accelerator Science and Technology Volume 1, World Scientific DC acceleration 1895 Philipp von Lenard, Electron scattering on gases (Nobel prize 1905 for his work on cathode rays). < 100 keV electrons Three separate roots 1906 Rutherford bombards mica sheet with natural alphas and develops the theory of atomic Betatron mechanism scattering. Natural alpha particles of several 1923 Wideroe, a young Norwegian student, draws MeV Resonant acceleration in his laboratory notebook the design of the betatron with the well-known 2-to-1 rule. Two 1911 Rutherford publishes theory of atomic 1924 Ising proposes time-varying fields across year later he adds the condition for radial structure drift tubes. This is “resonant acceleration”, stability but does not publish. 1913 Franck and Hertz excited electron shells by which can achieve energies above the given 1927 Later in Aachen, Wideroe make a model electron bombardment (proved Niels Bohr's highest voltage in the system. betatron, but it does not work. Discouraged theory, Nobel prize 1925 for their discovery of 1928 Wideroe demonstrates Ising’s principle with he changes course and builds the linear the laws governing the impact of an electron 1 MHz, 25 kV oscillator to make 50 keV acceleration mentioned in Table 2. upon an atom). Wimshurst-type machines potassium ions. 1919 Rutherford induces a nuclear reaction with 1940 Kerst re-invents the betatron and builds the natural alphas 1929 Lawrence, inspired by Wideroe and Ising, first working machine for 2.2 MeV electrons. conceives the cyclotron. …..Rutherford believes he needs a source of many MeV 1950 Kerst builds the world’s largest betatron of to continue research on the nucleus. This is far beyond 1931 Livingston demonstrates the cyclotron by 300 MeV. the electrostatic machines then existing, but…. accelerating hydrogen ions to 80 keV. 1928 Gamov predicts tunneling and perhaps 500 1932 Lawrence’s cyclotron produces 1.25 MeV keV would suffice…. protons and he also splits the atom just a few weeks after Cockcroft and Walton 1928 Cockcroft and Walton start designing an 800 (Lawrence received the Nobel prize in 1939 kV generator encouraged by Rutherford for the invention and development of the 1932 Generator reaches 700 kV and Cockcroft and cyclotron and for results obtained with it, Walton split lithium atom with only 400 keV especially with regard to artificial protons. They received the Nobel prize in radioactive elements) 1951 for their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles P.J. Bryant, A brief history and review of accelerator, CERN 1919 - The birth of an era Ernest Rutherford discovers the nuclear disintegration by bombarding nitrogen with alpha particles from natural radioactive substances. Later he calls for “ a copious supply” of particles more energetic than those from natural sources. The particle accelerator era is born. In this equipment, nitrogen atoms were converted into oxygen atoms, when in collision with alpha particles from a source in inside the horizontal enclosed tube. Protons ejected by nitrogen when forming oxygen were detected at the rectangular window at the end of the tube Rutherford's transmutation apparatus Hunterian Museum & Art Gallery collections, catalogue number GLAHM 113583 Rutherford’s statement in address to the Royal Society (1927) A few years later in 1927 Rutherford, in his presidential address to the Royal Society, made a strong request for higher energy nuclear probes. “ It has long been my ambition to have available for study a copious supply of atoms and electrons which have an individual energy far transcending that of the α and β particles from radioactive bodies. I am hopeful that I may yet have my wish fulfilled.” Rutherford’s statement became a challenge to invent higher energy particle accelerators A race for higher energy particle accelerators involved an early competition between electrostatic machines, but electric breakdown was a fundamental limitation to high voltages. Meanwhile, it had already been realized by a few that another solution that avoided very high voltages was to use time-dependent accelerating fields. 1924 - Gustav Ising published an linear accelerator concept Gustav Ising (1924) published an accelerator concept with voltage waves propagating from a spark discharge to an array of drift tubes Voltage pulses arriving sequentially at the drift tubes produce accelerating fields in the sequence of gaps. But Ising was unable to demonstrate the concept. 1928 - World’s first accelerator 1927 - Rolf Wideroe, Norwegian graduate student at Aachen University discovered Ising’s 1924 publication in the university library 1928 - Four year after Ising’s concept, Rolf Wideroe builds the world’s first linac in an 88-cm long glass tube in Aachen, Germany. Wideroe simplified Ising’s concept by replacing the spark gap with an ac oscillator For his PhD thesis Wideroe built and demonstrated a simple linac, which had one drift tube between two accelerating gaps 1928 - World’s first accelerator Wideroe applied a 25-KV, 1 MHz AC voltage to the drift tube between two grounded electrodes. The beam experienced an accelerating voltage in both gaps. He accelerated Na and K beams to 50 keV kinetic energy equal to twice the applied voltage. This is not possible using electrostatic voltages “My little machine was a primitive precursor of this type of accelerator which today is called a ‘linac’ for short. However, I must now emphasize one important detail. The drift tube was the first accelerating system which had earthed potential on both sides, i.e. at both the particles’ entry and exit, and was still able to accelerate the particles exactly as if a strong electric field was present.“– Rolf Wideroe (From “The Infancy of Particle Accelerators, Life and Work of Rolf Wideroe” ed. Pedro Waloschek ) 1929 –1932 - Van de Graaff generator Robert Van de Graaff invents the Van de Graaff generator at Princeton University. He also constructs the first tandem accelerator (two generators in series) in 1959 at Chalk River. 1931, the large Van de Graaff generator was constructed 1930 - Cyclotron Inspired by Rolf Wideroe's linac in a vacuum tube, Ernest Lawrence invents the cyclotron at the University of California, Berkeley. He and his student Stanley Livingston build a cyclotron only 4 inches in diameter. 1932 - Lawrence’s cyclotron produces 1.25 MeV protons and he also splits the atom just a few weeks after Cockcroft and Walton 1932- Cockcroft-Walton accelerator John Cockcroft and Ernest Walton invent the Cockcroft-Walton electrostatic accelerator at the Cavendish Laboratory. This accelerator produces the first man-made nuclear reaction. Cockcroft, Rutherford, and Walton in 1932, shortly after they accelerated protons against a lithium target, splitting the lithium nucleus into two alpha particles, i.e., helium nuclei. This demonstrated not only the “transmutation” of elements, but also Einstein's formula E=mc2, since a slight loss of mass produced energetic alpha particles 1937 - Klystron Russell and Sigurd Varian and William Hasen invent the kystron, a high- frequency amplifier for generating microwaves, at Stanford University. A similar device is proposed by Agnesa Arsenjewa-Heil and Oskar Heil in 1935. In 1948 they founded Varian Associates (along with Hansen and Ginzton) to market the klystron and other inventions Varian Semiconductor Equipment Associates Varian Medical Systems Varian, Inc Sold the Electron Device acquired by Agilent Technologies Business and formed Communications & Power Industries, Inc (CPI) 1940 - Betatron Donald Kerst at the University of Illinois constructs the first betatron, proposed by Joseph Slepian and others in the 1920s. 1950 - Kerst builds the world’s largest betatron of 300 MeV. 2nd – 25 MeV 300 MeV 1st – 2.3 MeV 1943 – Synchrotron 1944 – Phase stability 1943- Marcus Oliphant develops the concept for a new type of accelerator, later named the synchrotron by Edwin McMillan. 1944- Vladimir Veksler at the Lebedev Institute of Physics and later Edwin McMillan at the University of California, Berkeley, independently discover the principle of phase stability, a cornerstone of modern accelerators. The principle is first demonstrated on a modified cyclotron in 1946 at Berkeley. Technical difficulty Ising and Wideroe established principle of resonance acceleration Particles can gain arbitrarily high kinetic energy from successive traversals through the same accelerating fields with moderate voltages. Particles acquire a small energy increment with each traversal No basic limit to maximum kinetic energy. Method can be applied to linear accelerators (linac) or to circular accelerators (cyclotron or synchrotron). But with low (1-MHz) frequencies available at that time, linacs for faster protons and electrons had impractically large gap-to-gap spacings. The gap-to-gap spacing is v/2f so high-velocity particles require high oscillator frequency to obtain satisfactory energy gain per gap. At least a few hundred MHz were wanted, but RF frequencies available then were no more than 10 MHz. Higher frequency microwave sources were unavailable until after WWII, a benefit of radar developments for the war. The first proton and electron linacs were built after WWII 1939 – 1945 - World War II 1946 – Electron linac William Walkinshaw and his team at Malvern in the U.K. build the first traveling wave electron linac powered by a magnetron. William Webster Hansen and his team independently build a similar electron linac at Stanford University a few months later based on klystron and GeV energy. 1946 – Synchrotron radiation Frank Goward constructs the first electron synchrotron in the U.K. This is followed by one built by General Electric in the U.S. where synchrotron radiation is first observed, open a new era of accelerator-based light sources. Langmuir is credited as recognizing it as synchrotron radiation or, as he called it, "Schwinger radiation." Subsequent measurements by the GE group began the experimental establishment of its spectral and polarization properties.