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Ernest Rutherford carried out his post-graduate research in the Cavendish Laboratory as one of the first generation of graduate students from outside Cambridge to study for a higher degree by resea...

The Multimessenger GW170817 / GRB170817A discovery of the merger of two neutron stars on 17th August 2017 accompanied by a gamma-ray burst and an optical kilonova event is a triumph of the ideas about the evolution of the baryon component in the Universe. Despite the current uniqueness of this observation, the variety of the experimental data obtained makes it possible right now to draw important theoretical conclusions about the origin of the double neutron star, its merger, and the subsequent flare-up of electromagnetic radiation. We demonstrate that the discovery of the merger at a distance of 40 Mpc is entirely consistent with the very first calculations of the Scenario Machine ( Lipunov et al. 1987 ). In modern terms, the predicted rate is ∼10 000 Gpc−3.

In 1930, Walther Bothe and Herbert Becker performed an experiment, which was further improved by Irene and Frederic Joliot-Curie. These authors, however, misinterpreted their results and believed to have observed γ-rays while they had seen neutrons. After additional experimental verifications, James Chadwick gave the correct interpretation of these experiments in 1932. Immediately, the new particle, the neutron, became an essential actor of nuclear and elementary particle physics, and completely changed the whole research landscape. Enrico Fermi and his group applied it to artificial radioactivity, substituting neutrons to α-rays initially used by Joliot-Curies. They also discovered that slow neutrons were more efficient than fast ones in certain nuclear reactions. A crucial discovery of Otto Hahn, Fritz Strasmann, Lise Meitner, and Otto Frisch, after several misinterpretations of complicated experimental results, was nuclear fission. When Joliot, Halban, and Kowarski demonstrated the possibility of a chain reaction by neutron multiplication due to fission, nuclear physics became a military science, at the very moment when the Second World War was beginning. Later it led to nuclear power applications and use of neutrons as an important tool and object of scientific research at large-scale neutron facilities. The Comptes rendus de l'Academie des sciences were partner of a vivid international debate involving several other journals.

We review the history of neutron star physics in the 1930s that is related to L. Landau. According to recollections of Rosenfeld (1974, Proc. 16th Solvay Conference on Physics, p. 174), Landau improvised the concept of neutron stars in a discussion with Bohr and Rosenfeld just after the news of the discovery of the neutron reached Copenhagen in February 1932. We present arguments that the discussion took place in March 1931, before the discovery of the neutron, and that they in fact discussed the paper written by Landau in Zurich in February 1931 but not published until February 1932 (Phys. Z. Sowjetunion, 1, 285). In his paper Landau mentioned the possible existence of dense stars which look like one giant nucleus; this can be regarded as an early theoretical prediction or anticipation of neutron stars, prior to the discovery of the neutron. The coincidence of the dates of the neutron's discovery and the paper's publication has led to an erroneous association of the paper with the discovery of the neutron. In passing, we outline the contribution of Landau to the theory of white dwarfs and to the hypothesis of stars with neutron cores., Comment: 12 pages, 4 figures

Early neutron diffraction experiments performed in 1944 using the first nuclear reactors are described., Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan’s group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool.

Hal as a would-be research student was first interviewed by Rutherford and his second in command, Professor James Chadwick, who later became Hal’s thesis supervisor and a Nobelist for his discovery of the neutron, one of the constituent particles of the nucleus. Hal learned of his acceptance after publication of his excellent final examination results. As a research student, although his supervisor was Chadwick, the ethos of the Cavendish Laboratory was most strongly influenced by Rutherford (Fig. 7.1). He was always keen to see results and when new equipment was built, he demanded results as soon as possible. Usually the researchers preferred to improve the apparatus before using it for their investigations, but instead Rutherford insisted that the equipment be productive immediately. A typical example occurred when John Cockcroft and Ernest Walton were working on their primitive nuclear accelerator, which they wished to perfect. Rutherford insisted that they “use it now for experiments, before developing it further.” They did so and succeeded in splitting the atom and gaining Nobel Prizes. They also showed experimentally for the first time that Einstein’s famous equation E = mc2 was true. Another of Rutherford’s characteristics was to avoid, at all costs, any traces of routine and stereotype. In spite of Rutherford’s strong desire for results he was far from being a slave-driver and the atmosphere in the Cavendish was surprisingly relaxed. Research students were not allowed to have keys nor to set foot in the laboratory after 6 pm (when the gas and electricity were turned off), for he encouraged them to, “go home in the evening, think and plan the next day’s work.” Also Saturday’s work always ended at midday and there was a compulsory 2-week summer holiday for all. At 4.30 pm the laboratory staff gathered together for tea and ideas were exchanged. All considered this a most valuable institution, when junior researchers could benefit from presenting ideas to, and discussion with, their most senior colleagues in a very informal way. Such discussions could sometimes continue long after the nominal end of the tea-break. One of the graduate students was the tea club secretary and collected subscriptions spent on cakes. However J.J. Thomson, who recognised the tea club’s value, provided a legacy which provided tea and cake and removed any further need for subscriptions.

The discovery by Rutherford in 1919 that \(\alpha \)-particles could induce nuclear reactions and transform isotopes and elements opened up the possibility to produce new isotopes in the laboratory. However, only after the discovery of the neutron by Chadwick in 1932 was the nucleus understood in terms of consisting of neutrons and protons. The chapter describes the discovery of radioactive isotopes in the 1930s produced with neutron and \(\alpha \) sources as well as with the first accelerators. The complicated history of the discovery of fission is also included.

This chapter portrays the lives and works of the following pioneers and Nobel Laureates: Luis W. Alvarez, Murray Gell-Mann, George Zweig, Oscar Wallace Greenberg, Moo-Young Han and Harald Fritzsch, Jerome I. Friedman, Henry W. Kendall and Richard E. Taylor, Sheldon L. Glashow, Abdus Salam and Steven Weinberg, Gerardus 't Hooft and Martinus J.G. Veltman, Carlo Rubbia and Simon van der Meer, Yoichiro Nambu, Makoto Kobayashi and Toshihide Maskawa, Francois Englert and Peter W. Higgs, and Serge Haroche and David J. Wineland. The achievements of these pioneers are described in detail, and include the first observation of electron capture decay and beta-delayed neutron emission; the development and applications of the hydrogen bubble chamber; the assignment of strangeness quantum number and the law of conservation of strangeness; the Eightfold Way; the prediction of the existence of quarks by Zweig and Gell-Mann and their eventual discovery; the quark structure and properties of baryons and mesons; properties of quarks and leptons; quark color charge and quantum chromodynamics; the W± and Z0 bosons in neutrino-charged current and neutral current reactions; the Z0 boson in neutrino-neutral current elastic scattering; the W± boson in beta decay; the theory of electroweak unification; the discovery of the W± and Z0 bosons; the discovery of the origin of broken symmetry; the existence of three families of quarks in nature; the Standard Model of elementary particles; the discovery of a mechanism providing an answer to the origin of various masses of subatomic particles, and the detection of the Higgs boson; and the very first capture of photon particles and their nondestructive detection and measurement.

In the course of Rutherford’s effort to develop a plausible model of the atomic nucleus, he postulated the existence of a particle having the same mass as the hydrogen nucleus but having no electrical charge whatsoever. He conceived of this neutral particle—essentially a bound-state of a proton and an electron—in order to account for isotopes having identical atomic charges but different atomic weights (e.g. helium-3 and helium-4). Just a few years later, Rutherford’s hypothetical particle was discovered by one of his students.

I was appointed an Officer in the Order of Australia award in the Queens birthday honours list for 2015. The citation read “for distinguished service to biomedical physics, particularly to radiation oncology and the development of innovative methods of cancer treatment, and to international professional scientific organisations”. My research experience ranges from the formation of radioisotopes in stars to their use in cancer therapy. Although having only two long term appointments, I was fortunate to have the freedom to allow my self-direction and motivation to develop my research interests. After graduating MSc in nuclear physics at the University of Melbourne, I joined the Australian Atomic Energy Commission (AAEC) at Lucas Heights in 1963. The AAEC was expanding rapidly, developing nuclear based research projects for reactors and accelerators. I began my R&D using the 3 MV Van de Graaff accelerator to produce neutron beams at keV energies for neutron capture gamma ray spectroscopy. Neutron energy was measured by pulsed beam time of flight and gamma ray energy by world first Ge(Li) high resolution gamma spectrometry in three dimensional on-line computer studies. The keV neutron capture gamma ray project was to provide data for fast reactor calculations and to investigate the underlying mechanisms for potential and resonance neutron capture. Man landed on the moon, I married Cynthia and together we landed in Atomic City, Oak Ridge, Tennessee, USA on attachment to the Oak Ridge National Laboratory (ORNL) in 1969. My job was to study high resolution resonance neutron capture reactions in collaboration with Dr. Dick Macklin. The world leading 140 MeV Linear Accelerator (ORELA) was used as a high resolution, pulsed source of time of flight neutrons for a wide range of capture studies on separated isotopes. These studies continued with a later posting to Central Bureau for Nuclear Measurements (CBNM) in Belgium, with the additional task of multilingual communication and extensive vacation. Some 105 collaborative papers were published in these fields. This research was also relevant to the slow neutron capture process of stellar nucleosynthesis, which occurs at a Maxwellian neutron temperature of kT = 30 keV and governs the creation of most of the heavier isotopes across the periodic table (Fig. 1). A highlight of the neutron research program was attending in 1982, the 50th anniversary conference of the discovery of the neutron at Cambridge. The worn sandstone steps and the Bridge of Sighs over the river Cam reflected the long history of scientific excellence. However, it was clear that neutrons were sliding down the totem pole at the AAEC and new directions were needed. & Barry J. Allen bja1940@optusnet.com.au

Since the discovery of the neutron by Chadwick [1] was rewarded by the Nobel Prize in Physics, Neutron science and Nobel awards have been in contact from time to time. Concerning the impact of the ...

Following with the discovery of the electron by J. J. Thomson at the end of the nineteenth century a steady elucidation of the structure of the atom occurred over the next 40 years culminating in the discovery of nuclear fission in 1938–1939. The significant steps after the electron discovery were: discovery of the nuclear atom by Rutherford (Philos Mag 6th Ser 21:669–688, 1911), the transformation of elements by Rutherford (Philos Mag 37:578–587, 1919), discovery of artificial radioactivity by Joliot-Curie and Joliot-Curie (Comptes Rendus Acad Sci Paris 198:254–256, 1934), and the discovery of the neutron by Chadwick (Nature 129:312, 1932a, Proc R Soc Ser A 136:692–708, 1932b; Proc R Soc Lond Ser A 136:744–748, 1932c). The neutron furnished scientists with a particle able to penetrate atomic nuclei without expenditure of large amounts of energy. From 1934 until 1938–1939 investigations of the reaction between a neutron and uranium were carried out by E. Fermi in Rome, O. Hahn, L. Meitner and F. Strassmann in Berlin and I. Curie and P. Savitch in Paris. Results were interpreted as the formation of transuranic elements. After sorting out complex radio-chemistry and radio-physics O. Hahn and F. Strassmann came to the conclusion, beyond their belief, that the uranium nucleus split into smaller fragments, that is nuclear fission. This was soon followed in 1939 by its theoretical interpretation by L. Mietner and O. Frisch.

This paper explores the cross-fertilization between science and literature in the 1930s, at key moments in atomic physics and in the development of the atomic bomb. In 1932, the centenary of Goethe's death, physicists attending an international conference at Niels Bohr's Institute of Theoretical Physics in Copenhagen performed a parody of Goethe's Faust. Goethe's critique of science in the play made this a significant choice at the dawn of nuclear physics. James Chadwick's discovery of the neutron that year was high lighted in the performance. In 1933 while in Bloomsbury, London, the physicist Leo Szilard realized how to use a self-sustaining neutron chain reaction to release the energy of the atom. The previous year Szilard had read H. G. Wells's novel The World Set Free (1914) in which the phrase 'atomic bomb' was coined. As well as considering the Faustian themes in the novel, I explore parallels between Wells's scientist, Holsten, and Leo Szilard himself. I argue that this is a clear example o...

In this book the author charts the developments in nuclear physics since its inception around a century ago by reviewing the key experiments that helped drive and shape our understanding of the field, especially in the context of the wider developments in physics in the early 20th century. In addition to providing a path through the field and the crucial events it looks at how these experiments not only answered key questions at the time but presented new challenges to the contemporary perception of the nuclear and sub-atomic worlds and how they helped develop our present understanding of nuclear physics.

The capsule histories of physics that students learn in their physics courses stem basically, I believe, from a linear view of history – that physicists in making fundamental discoveries follow a Royal Road to them, as Hermann von Helmholtz put it in 1892. The actual routes they follow, however, are generally nonlinear, and when historians display these routes to students, they express surprise. Such historical surprises could constitute one or more units of instruction in physics-education or other courses. As illustrations, I discuss historical surprises that I have uncovered in my own researches on Isaac Newton’s work on diffraction, Robert A. Millikan’s photoelectric-effect experiments, Arthur H. Compton’s X-ray scattering experiments, James Chadwick’s discovery of the neutron, George Gamow’s creation of the liquid-drop model of the nucleus, and Lise Meitner’s and Otto Robert Frisch’s interpretation of nuclear fission. Teachers and students can discover many more historical surprises as provocative as these by exploring the historical literature.

Soon after the discovery of the neutron, by Chadwick in 1932, experiments showed that it, like the electron, had wave as well as particle properties. According to de Broglie's hypothesis, a particl...

LEGEND has it that when word reached Copenhagen of the discovery of the neutron in 1932, Niels Bohr threw a great party at his home. Among his guests was a young Russian named Lev Landau, who is said to have quietly remarked that "stars could be made with this new particle". Astronomers like to think that this was said in earnest – and not under the influence of Danish hospitality – because we now know that neutron stars really do exist.

SLX 1737-282 is a persistent moderately bright X-ray source 1.2 deg from the Galactic center. X-ray observations with the Wide Field Cameras on BeppoSAX have for the first time revealed the true nature of SLX 1737-282: a 15-min long thermonuclear flash was detected exposing the source as a neutron star in a binary system. The flash was Eddington-limited constraining the distance to between 5 and 8 kpc. We analyze BeppoSAX, ROSAT, and RXTE data on SLX 1737-282. The persistent 0.5-200 keV luminosity is close to or less than 1% of the Eddington limit which implies a rarely-seen circumstance for thermonuclear flash activity., Comment: Accepted for publication in A&A Letters

It has at times been indicated that Landau introduced neutron stars in his classic paper of 1932. This is clearly impossible because the discovery of the neutron by Chadwick was submitted more than one month after Landau's work. Therefore, and according to his calculations, what Landau really did was to study white dwarfs, and the critical mass he obtained clearly matched the value derived by Stoner and later by Chandrasekhar. The birth of the concept of a neutron star is still today unclear. Clearly, in 1934, the work of Baade and Zwicky pointed to neutron stars as originating from supernovae. Oppenheimer in 1939 is also well known to have introduced general relativity (GR) in the study of neutron stars. The aim of this note is to point out that the crucial idea for treating the neutron star has been advanced in Newtonian theory by Gamow. However, this pioneering work was plagued by mistakes. The critical mass he should have obtained was $6.9\,M_\odot$, not the one he declared, namely, $1.5\ M_\odot$. Probably, he was taken to this result by the work of Landau on white dwarfs. We revise Gamow's calculation of the critical mass regarding calculational and conceptual aspects and discuss whether it is justified to consider it the first neutron-star critical mass. We compare Gamow's approach to other early and modern approaches to the problem.

What constitutes an element? The ancient Greeks believed in four elements: earth, wind, fire and water. By the l920s, however, physicists were defining elements according to the number of protons within the atomic nucleus. Meanwhile, pioneering work by Frederick Soddy and Kasimir Fajans demonstrated the existence of different isotopes – atoms that have similar chemical properties but different masses. This work culminated in 1932 with James Chadwick's discovery of the neutron, the uncharged particle that effectively damps out the Coulomb repulsion between the charged protons.

Neutron scattering had its origin in 1932, the year that marked the discovery of the neutron by Chadwick, and the first nuclear reactors were successfully operated in Chicago and Oak Ridge, Tenn., in the early 1940s. During its initial stages, neutron scattering was used mainly for the study of “hard” crystalline materials. For example, Shull and Wollan's pioneering research, which led to the 1994 Nobel Prize in physics, began with studies of iron, chromium, and iridium, and was followed by the development of polarization analysis to determine the structure of magnetic materials. Such studies continue to yield important structural information (see the articles on magnetism by Aeppli and Hayden and on crystallography by Radaelli and Jorgensen in this issue of MRS Bulletin), although during the last two decades, the technique has been increasingly used by scientists from other disciplines (chemistry, biology, polymer science), and many of these newer applications have involved “soft” matter such as polymers, colloids, and gels. By definition, these substances are “plastic” or “squishy,” and easy to mold into different shapes; because of this flexibility, they have become some of the most practical and widely used materials today.

There is a story, perhaps apocryphal, that Nobel Laureate physicist I. I. Rabi, upon learning of the discovery of the muon in 1936, exclaimed ‘Who ordered that!’ His surprise came from the belief that, with the discovery of the neutron by James Chadwick just four years earlier, physicists ’ model of the sub-atomic world was satisfactorily complete. At the time of its discovery in 1932, the neutron was precisely what physicists would have ordered to resolve a variety of troubling observations. It accounted for the existence of isotopes, for the neutral non-electromagnetic radiation that emerged from alpha particle bombardment of certain elements like beryllium or boron, for the apparent emergence of electrons from inside a nucleus that underwent beta decay, and for the puzzling fact that nitrogen-14 was a boson when, according to a proton–electron model, it should have been a fermion. However satisfied Chadwick may have been to find that the neutron resolved a host of problems physicists faced in the 1930s, were he alive now I suspect he would be rendered speechless in amazement by Rauch and Werner’s comprehensive and lucid book of the very many ways neutrons have been employed since then to test physical principles and to study the properties of condensed matter. At the core of this versatility is the fact that the neutron participates in all the known fundamental interactions: the strong nuclear interaction (it helps maintain the integrity of a nucleus against the mutual electrostatic repulsion of protons), the weak nuclear interaction (it is itself unstable against beta decay with a free-state half-life of about 10 min), gravity (it not only falls in a gravitational field but responds to a gravitational potential under conditions where there is no classical gravitational force) and electromagnetism (although it is neutral, it has a magnetic moment and therefore can respond to magnetic fields as well as to laboratory electric fields that, by virtue of special relativity, transform to magnetic fields in the neutron’s rest frame). Neutron Interferometry examines the manifold consequences of these interactions through detailed explanations of experiments, executed for the most part within the authors’ own research groups, employing the extraordinarily sensitive perfect silicon crystal neutron interferometer. Although a wide variety of experiments are described in the book, the typical experimental configuration is that of a Mach–Zehnder interferometer of monolithic design, the various reflecting plates of which were cut from a single Si crystal which forms the base. The essential feature of the apparatus, as highlighted by the authors, is that the reflecting planes are arranged undisturbed throughout the entire macroscopic apparatus (enclosed areas up to about 100 cm have been tested) with a precision comparable to the lattice spacing. Although a prospective reader may infer from the book title that the subject is limited to interferometry, one discovers immediately from perusing the contents that, from the perspective of modern physics, this is hardly a limitation at all. Interferometry, whether optical, electron or neutron, has played a key role in elucidating many of the most fundamental physical problems of the 20th century, and I expect that to continue throughout the 21st. Among the numerous issues upon which neutron interferometry has been brought to bear, as discussed by Rauch and Werner, are key questions relating to ISSN 1600-5767

The most important contribution given to science by Fritz Georg Houtermans consists in the work, carried out in Gottingen in 1928–1929 in collaboration with Robert d'Escourt Atkinson (1898-1982), on the formation of light elements and the consequent energy production in the center of stars /6/ /7/ (Chap. 4). These papers, which appeared years before the discovery of the neutron (1932), are quoted in all review articles reporting on the history of the interpretation of stellar energy in terms of nuclear processes. They provided the motivation for the IAU to assign, on occasion of its meeting in Sidney in August 1973, the name of Houtermans to one of the lunar craters located near the eastern edge of the visible disk of the Earth’s satellite (lunar long. + 87.0, lunar lat. −9.3) [1].

Foreword.- Chapter 1. Radioactivity, the First Puzzles.- The "Uranic Rays" of Henri Becquerel.- Polonium and Radium.- Emanation from Thorium.- The Puzzle is Disentangled.- Consecrations and Mourning: the End of an Era.- Chapter 2. A Nucleus at the Heart of the Atom.- Prehistory of the Atom.- 1897: The Electrons Are in the Atom.- The Scattering of alpha Particles Makes It Possible to "See" a Nucleus in the Atom.- A Last Ingredient: Moseley Measures the Charge of the Nucleus in the Atom.- Chapter 3. Quantum Mechanics, the Unavoidable Path.- Branching Off.- An Improbable Beginning.- Niels Bohr: The Quanta Are in the Atom.- 1913-1923: Victories and Setbacks.- 1925: Spin and the Pauli Principle.- Quantum Mechanics.- Chapter 4. A Timid Infancy.- The Atomic Nucleus in 1913.- The Discovery of Isotopes and the Measurement of Masses of Nuclei.- An Enquiry Full of Surprises: ss Radioactivity.- The First Nuclear Reactions.- The Nucleus in 1920 According to Rutherford.- The Rapid Expansion of Experimental Means.- The Atomic Nucleus in 1930.- Chapter 5. 1930-1940: A Dazzling Development.- The Nucleus: A New Boundary.- The Discovery of the Neutron.- Nuclear Theory After the Discovery of the Neutron.- A New Particle: The Positron.- The Birth of Particle Accelerators.- "Charge Independence" of the Nuclear Force.- The Discovery of Artificial Radioactivity.- The School of Rome.- The Great Exodus of Jewish Scientists Under Nazism.- A Proliferation of Theories: Yukawa, Breit and Wigner, Bohr.- The Death of a Giant: Ernest Rutherford.- Hans Bethe Sums Up the Situation in 1936-1937.- The Fission of Uranium.- Chapter 6. The Upheavals of the Second World War.- A Chronology.- The New Face of Physics After the War.- Chapter 7. The Time of Maturity.- New Experimental Means.- Data Accumulate.- The "Shell" Structure of Nuclei.- Elastic Scattering and the "Optical Model".- Direct Nuclear Reactions.- A Collective Behavior.- A Unified Model of the Nucleus.- The Nuclear Force.- Nuclear Matter.- Chapter 8. Where the Narrative Ends.- Glossary.- Bibliography of Cited Books.- Index.

Heinrich Greinacher (1880–1974) had been Professor of Physics and Director of the Institute of Physics at the University of Berne for many decades. He had invented the voltage multiplier [1], that became well known after Cockcroft and Walton, at Cambridge (U.K.) in 1932, reinvented it and applied it to construct the accelerator they used in the discovery of the first nuclear reactions produced by accelerated particles [2]. Greinacher had also constructed the first ionization chamber connected to a linear amplifier capable of detecting the ionization produced in a gas by a single alpha particle or fast recoiling proton [3]. But the full power of this new detection technique was exploited by others, in particular by Chadwick in the discovery of the neutron [4].

Philip Moon was an experimental physicist whose achievements covered a wide field not only in atomic and nuclear physics but also in chemistry. He had a special talent for devising and using simple instrumentation to answer fundamental questions. Soon after the discovery of the neutron he proved that these particles could reach thermal energies in their passage through matter. He discovered the selective absorption of slow neutrons by nuclei and thereby helped to clarify the role of the particle in nuclear reactions. He was a member of the wartime MAUD Committee which advised the government on civil and military uses of atomic energy. He will be remembered for his development of high-speed rotors and for the application of this technique to the kinetics of chemical reactions, to the nuclear resonant scattering of γ radiation and to problems in relativity. Much of his academic life was spent at the University of Birmingham where he was a much loved and inspiring leader and teacher.

This lecture was delivered 10 December 1994, on the occasion of the presentation of the 1994 Nobel Prize in Physics. It describes the historical events beginning with the discovery of the neutron leading to current research in neutron scattering. (AIP)

These lecture notes recall the conceptual developments which led from the discovery of the neutron to our present understanding of strong interaction physics., Comment: Lectures given at the International School of Subnuclear Physics Erice, Italy, 23 June to 2 July 2012

Soon after the discovery of the neutron Heisenberg published a theory of the structure of nuclei based on exchange forces between nucleons which had some very nice features. In January 1933 Majorana came to Leipzig with a fellowship to spend several months in Heisenberg’ s Institute. On arrival Majorana pointed out two weak points in Heisenberg’ s theory. It failed to account for the strong binding of the alpha particle and it required a strongly repulsive core in the nuclear force to avoid nuclear collapse. Majorana proposed a new kind of exchange force which avoided these difficulties and wrote a paper which was published at the beginning of March. His theory was so satisfying aesthetically that it was accepted immediately. This lecture will analyze the origin, motivation and impact of Majorana’ s theory and give some information about his stay in Leipzig.

We reconstruct and analyze the path leading from James Chadwick’s discovery of the neutron in February 1932 through Frederic Joliot and Irene Curie’s discovery of artificial radioactivity in January 1934 to Enrico Fermi’s discovery of neutron-induced artificial radioactivity in March 1934. We show, in particular, that Fermi’s innovative construction and use of radon-beryllium neutron sources permitted him to make his discovery.

Dawning neutron physics was more complex than one might expect. The chance that the neutron comprised a proton and an electron was diffusely taken into account after the discovery of the neutron. Moreover, uncertainties persisted about the composition of beryllium radiation until it was realized that the latter comprised both neutrons and gamma-rays. The interaction of neutrons with matter and nuclei was soon investigated. Both a spatial symmetry, a symmetry of charge, and a symmetry in the nuclear reactions soon emerged. The relation of negative beta-decay to the neutron abundance in nuclei was moreover reviewed. Positive beta-radioactivity induced by alpha-particles was eventually announced, having been foreseen some weeks before. Accelerated deutons and protons shortly afterwards revealed to be efficient in inducing radioactivity. The physics institute in Rome got ready to start research on neutrons, but apparently it only planned to go through alpha-induced radioactivity, at first. If so, it is then plausible that some new results achieved by foreign laboratories eventually bent Fermi to neutrons. Fermi's discovery of neutron-induced radioactivity is reviewed with regard to investigations then current, once more showing simplicity as a distinctive trait of Fermi's way of doing physics., 64 pages, 2 figures. Preliminary version of the paper published on HSPS

This chapter begins by discussing Einstein's theory. It describes how Albert Einstein proposed that mass and energy are equivalent, in a three-page paper. Using simple equations and the application of the laws of conservation of energy and momentum, Einstein argued that the atom left after a radioactive decay event, which had emitted energy in the form of radiation, must be less massive than the original atom. Einstein's deduction is more commonly written as E = mc 2 which is probably the most famous equation in Physics. The next section discusses how Einstein's theory led to the concept of fusion energy. In the 19th century, it became apparent that there were groups of different elements with similar properties. However, it was not clear how these were related to each other until the Periodic Table was proposed by Dmitri Mendeleev. The concepts of atoms, nucleus, electrons, atomic mass, and isotopes are briefly explained in the chapter. The measurement of the mass of individual atoms is also discussed. Aston's work is described in detail, followed by Chadwick's discovery of the neutron. Eddington's work, the role of quantum mechanics, nuclear fission, and finally the building of the first atomic reactor are also discussed in the chapter.

The Australian Journal of Chemistry is pleased to publish a collection of papers commemorating the 100th anniversary of the Nobel Prize in chemistry awarded to Marie Curie (nee Marya (Maria) Sk"odowska) for the discovery of two new radioactive elements, polonium and radium. Her first Nobel Prize, in physics in 1903, was shared with Henri Bequerel and her husband Pierre Curie for their work on the radiation phenomena discovered by Becquerel – the so-called Becquerel rays, which were later determined by Rutherford and Royds in 1907 to be a-particles (He2þ nuclei). It wasMarie Curie who in 1898 coined the term radioactivity for this new property of matter. Although Marie and Pierre had discovered and isolated two new highly radioactive elements, Po and Ra from the uranium mineral pitchblende in 1898, the Nobel physics committee appeared to have reservations about this and made no mention of it, thereby making it possible for the chemistry Nobel committee to award her the second prize in 1911. The Curie story is reviewed herein by Clarence Hardy. It is important to realize that these discoveries were made before the structure of the atom was understood. Neither the proton nor the neutron nor indeed the atomic nucleus were known, and the electron had only just been discovered by J. J. Thomson in 1897. The bestmodel of the daywas J. J. Thomson’s ‘plum pudding model’, in which the corpuscular electrons were sitting like the plums in an ill-defined nuclear fluid. Rutherford’s ‘solar system’ model came in 1911, and Bohr’s now familiar quantummodel of the atom in 1913. The Becquerel rays were at first thought to be similar to Rontgen’s X-rays, i.e. electromagnetic in nature. The a-particles emitted by polonium became crucially important in the discovery of the neutron, which earned Chadwick the Nobel Prize in Physics in 1935, and Irene Curie and her husband Frederic Joliot the Chemistry Nobel, also in 1935, for the discovery of the transmutation of elements by a-particle bombardment of lighter elements, e.g. Alþ a(He)Pþ n. The Joliot-Curies first thought the neutron rays emanating from light elements such as beryllium and aluminium on a-bombardment were a powerful variant of g-rays (high energy electromagnetic radiation), but Chadwick realized their particulate nature. The P isotope formed in the Joliot-Curie experiment is radioactive, emitting positrons with a half-life of 3min. Thus, they discovered artificial radioactivity. Similarly, radioactive isotopes of nitrogen and silicon were produced by a-bombardment of boron and magnesium, respectively. Positrons are nowadays immensely important in positron emission tomography (see paper by Greguric et al. below). The fascinating story of the neutron – the Curie family’s legacy – is reviewed expertly by John and Alsia White. The discoveries of Po, Ra, radioactivity, the atomic nucleus, and the neutron paved the way to our current understanding of the atom and the associated advances in chemistry, physics, and medicine. The development of radiation chemistry since the Curies and till the present day is reviewed briefly by Ronald Cooper. Alison Edwards highlights modern uses of neutron diffraction in structure determination in cases where X-ray diffraction is unable to provide definitive answers. This takes advantage of the different scattering properties of X-rays and neutrons: because the neutrons are electrically neutral, they are diffracted more readily by the nuclei rather than the electrons in a molecule, thereby enabling them to reveal the precise locations of the nuclei of hydrogen and other light elements or to ascertain their absence. While neutron diffraction used to be a technique firmly in the realm of physics because forbiddingly large crystals were needed in order to obtain chemical structures, technical advances using Laue neutron diffractometers have made it possible to undertake such studies on crystals of manageable sizes (fractions of mm). Radioactive elements and isotope labelling are of practical importance in several areas of medicine. Radium and other radionuclides were introduced very early byMarie Curie herself and are still used in radiotherapy to combat malignant tumours. More recently, g-rays from e.g. Co, electron (b-rays), and proton beams from particle accelerators have come into use. The synthesis of radioactively labelled drugs (radiosynthesis) is interesting because it permits the location of the molecule on the target and elsewhere by means of 3D positron emission tomography. Ivan Greguric and coworkers describe a synthesis of positron-emitting F-labelled nicotinamide (half-life of F 110min) designed to target random metastasis of melanoma tumours. Because the ingestion of radionuclides is harmful and potentially lethal, it is of crucial importance to be able to determine their presence in drinking water – not least in Australia with its large deposits of uraniumore.MeganCook andRossKleinsmith describe a method for the simultaneous determination of a-emitting Ra-226 and b-emitting Ra-228 in water by liquid scintillation spectrometry. CSIRO PUBLISHING

The nuclear force has been the heart of nuclear physics ever since the field was born in 1932 with the discovery of the neutron by Chadwick [1.1]. In fact, during the first few decades of nuclear physics, the term nuclear force was often used as synonymous for nuclear physics as a whole. There are fundamental reasons why the nuclear force plays such an outstanding role.

The aim of this work is experimental discovery and research of a rare neutron mode, the radiative beta-decay, where a new particle, the radiative gamma-quantum, is formed along with the expected decay products beta-electron, recoil proton and antineutrino. The discovery of this rare neutron decay mode was conducted through identification of triple coincidences events: simultaneous registration of beta electron, proton and radiative gamma-quantum. The ordinary neutron decay was registered by double coincidences of beta electron and recoil proton. The ratio of triple to double coincidences is connected with relative intensity of radiative neutron decay (branching ratio - B.R.) B.R. = (3.2+1.6)10-3 (with 90 % C.L. and in the gamma energy region greater than 35 keV), which we are the first in the world to measure during the second and third cycles on FRMII (TUM, Germany) in Summer 2005. This value of B.R. is consistent with standard electroweak theory.

Portugal may seem an unlikely place to celebrate the 60th anniversary of the discovery of the neutron, but that was the excuse for a gathering at the University of Coimbra on 27–29 July. The link is actually through Prof. Luiz Alta da Veiga, the organizer of this fine meeting, and his connection as a graduate student 30 years ago with Jane Brown (now at the ILL, France) and Bruce Forsyth (ISIS, Rutherford Lab., UK) at the Cavendish Laboratory, Cambridge.

Nuclear physics is now entering one of the most challenging and interesting periods in the half century since the discovery of the neutron. With the simple picture of the nucleus in terms of the single‐nucleon shell model well understood, nuclear physicists are turning to focus on nuclei as finite, saturating, many‐body systems. The dominant theme promises to be the rich physics generated by the extensive array of nuclear degrees of freedom—from pure nucleonic states, as in the shell model, to mesonic and excited hadronic states, through to quarkgluon degrees of freedom.

Work by Rutherford and his colleagues led to his nuclear model of the atom (1911), although it took a few years more for him to recognize the significance of this insight. With the understanding that radioactivity is a nuclear phenomenon, one may say that nuclear physics became the major pursuit in Rutherford’s Manchester and Cambridge laboratories. The key to this problem was reported in his 1919 papers on transmutations produced by bombarding nitrogen with alpha particles. Soon, a number of other elements yielded to these projectiles of radioactive decay, but recognition that more energetic particles would be needed to disintegrate heavier elements led to the development of accelerating machines. The search for the neutron, cloud chamber photographs of disintegrations, and exploration of the properties of beta and gamma rays also figured greatly in Rutherford’s attack on the nucleus.

The early history of the development of our understanding of neutron stars has been described by others, and we summarize it only briefly here. Following an early speculation by Baade & Zwicky ( 1934) soon after the discovery of the neutron in 1932, Oppenheimer & Volkoff(1939) presented a classic analysis of the theoretical viability of neutron stars, based on the general theory of relativity and the nuclear physics that was then known. A number of further theoretical studies were published during the next three decades, but it seemed that neutron stars might be virtually unobservable and thus remain little more than a theorist's curiosity piece. In a prophetic paper, Pacini (1967) noted that a rotating neutron star with a magnetic field whose axis was misaligned with the rotation axis should emit intense magnetic dipole radiation. Almost immediately thereafter (but quite independently), Hewish et al. (1968a,b) announced the discovery of radio pulsars. For a brief period, several theoretical models for the pulsar phenomenon were in contention. However, the discovery of the pulsar NP 0532 in the Crab Nebula (Staelin & Reifenstein i968, Comella et al. 1 969), followed by a notably straightforward set of observations and theoretical arguments, soon clinched the case for neutron stars (Gold 1969a).1 (For a review of these remarkable developments, see Gold 1969b.)

Reports in May 1930 of an anomaly in the scattering and absorption of gamma rays, known as the Meitner–Hupfeld effect, presaged the New Physics of the 1930s. Scattering from light elements agreed with theoretical predictions based upon quantum electrodynamics and the relativistic electron theory of Dirac, but results on heavy targets pointed to a new nuclear absorption effect that was a harbinger of new particles and new phenomena. The experimental investigations of this anomalous absorption placed constraints on theories of nuclear structure, leading Heisenberg, for example, to insist upon the presence of electrons within nuclei as light as helium, even after Chadwick’s discovery of the neutron and Heisenberg’s proposed neutron–proton nuclear model. The anomalous γ‐ray behavior was eventually ascribed to electron–positron pair production and annihilation.

This review, occasioned by the fiftieth anniversary of the discovery of the neutron, considers the most important papers on fundamental studies of the properties of the neutron. Some of the researches are briefly expounded, and the present values of the fundamental quantities that characterize the neutron as an elementary particle are given.

This paper begins with some recollections of the Cavendish Laboratory of the University of Cambridge in the years 1928–30, which just preceded the discovery of the neutron and other major discoveries there in 1932–33. It then goes on to describe new developments in experimental techniques for accelerating, detecting, and counting charged particles such as protons and α particles in the Cavendish Laboratory which made possible the major discoveries by Chadwick, Blackett, and Cockcroft and Walton in 1932–33. The scintillation method was superseded by the linear amplifier and scale‐of‐two counter. Other experimental techniques described here include the original proportional counter, the cloud chamber triggered by coincident pulses in two Geiger–Muller counters for the detection of cosmic rays, and a 700‐kV voltage multiplier for the first transmutations by artificially accelerated hydrogen ions. Pioneer measurements on pair production of γ rays and annihilation radiation are discussed in terms of Dirac’s relativistic theory of the electron.

There were four main steps in the sequence of events leading to the discovery of fission, made just over 50 years ago. There was the discovery of the neutron by Chadwick in 1932; then two years later the discovery of artificial radioactivity by Irene Curie and Frederic Joliot, quickly followed by Fermi's use of the neutron to induce artificial radioactivity, leading eventually to the discovery of fission in early 1939.

During the last three years several outstanding discoveries have been made in the realm of nuclear physics which must prove of great interest to medical radiologists. Prominent among these are: the production of artificial atomic disintegration by means of fast positive ions by Cockroft and Walton, the discovery of the neutron by Chadwick1 and of the positive electron by Anderson and Blackett; the production of induced radioactivity by M. Joliot and Mme. Curie-Joliot2 using alpha particles, and by Fermi3 with neutrons. An account, by chadwick, of the discovery and some of the properties of the neutron, has already appeared in this Journal.1 Since that time intensive research work has shown the neutron to be a peculiarly suitable agent for transmuting matter. A neutron is an uncharged particle liberated at high speed during the disintegration of certain atomic nuclei. Its mass and size are comparable with those of the proton. Unlike charged particles, neutrons in their passage through matter do not interac...

INTENSIVE research on the interaction between neutrons and nuclei started, both in the U.S.S.R.(l) and abroad,t2) soon after the discovery of the neutron by CHADWICK in 1932.@) The neutron was found to be a very convenient particle for studying nuclear energy levels and for producing nuclear reactions since, because of the absence of the coulomb barrier, even slow neutrons readily penetrate into the nucleus. The properties of the resulting composite nucleus can be studied from the relation between the reaction cross-section and the neutron energy. However, the low intensity of neutron sources available at the time, permitted only overall measurements covering a wide neutron spectrum; and only with the construction of nuclear reactors was it possible to make a detailed study of cross-sections as a function of energy.

A brief review is given of selected highlights in scientific developments from the birth of modern nuclear physics at the end of the 19th century to the discovery of the neutron in 1932. This is followed by some important milestones in neutron and reactor physics that have led to our current understanding and implementation of nuclear technologies. The beginnings can be traced back to the discovery of X-rays by Roentgen, the identification of natural radioactivity by Becquerel and the discovery of the electron by Thomson, towards the end of the 19th Century. Rutherford was a key figure in experimental physics who determined the structure of the atom and who inspired his students at McGill, Manchester and Cambridge Universities (many of whom would become Nobel laureates) in the pursuit of their physics research. One of Rutherford's students, James Chadwick, had studied the work carried out by Bothe and Becker on alpha particle-induced disintegration of light elements which had led to their observation of high energy penetrating radiation that neither they nor the Joliot-Curies could identify. Chadwick knew that the only possible explanation was the emission of a neutron in the nuclear reaction. He carried out tests in the Cavendish Laboratory and submitted his now classical paper identifying the neutron to the periodical Nature in 1932. The discovery of the neutron and of nuclear fission in 1939 opened up new areas for scientific investigation, in, for example, astrophysics, geology, neutron and nuclear physics. The prospects for nuclear power in particular appeared to be unlimited and both civil and military applications have been actively pursued. Many new experimental facilities have been designed and built to provide intense sources of neutrons for research purposes. Work carried out in such centres is included in the programme of the 7th International Topical Meeting on Neutron Radiography, an important forum for discussion of the latest research work of this ever-growing scientific community.

James Chadwick’s discovery of the neutron in 1932 is justifiably viewed as a watershed in the history of nuclear physics.1 It opened the way to all modern neutron-proton theories of nuclear structure and (so the story goes) simultaneously expelled the electron from the nucleus where it had become, through its increasingly contrary behavior, an embarrassing guest — part of a problem not to be thought about, like the new taxes, as Peter Debye put it in 1930.2 Chadwick’s discovery reintroduced order and simplicity into nuclear theory.