Discovery Of Neutron Research Articles

Neutron star versus neutral star: On the 90th anniversary of Landau's publication in astrophysics

AbstractIn the late age of developing quantum mechanics, Lev Landau made great efforts to understand the nature of matter, even stellar matter, by applying the quantum theory. Ninety years ago, he published his idea of “neutron” star, which burst upon him during his visit over Europe in the previous year. The key point that motivated Landau to write the paper is to make a state with lower energy for “gigantic nucleus”, avoiding extremely high kinematic energy of electron due to the new Fermi–Dirac statistics at that time. Landau had no alternative but to neutralize by “combining a proton and an electron” before the discovery of neutron. However, our understanding of the nature has fundamentally improved today, and another way (strangeonization) could also embody neutralization and thus a low‐energy state that Landau had in mind, which could further make unprecedented opportunities in this multi‐messenger era of astronomy. Strangeon matter in “old” physics may impact dramatically today's physics, from compact stars initiated by Landau, to cosmic rays and dark matter. In this essay, we are making briefly the origin and development of neutron star concept to reform radically, to remember Landau's substantial contribution to astrophysics and to recall those peculiar memories.

PANCHTATAVAS - MYSTERIOUS WORLD OF MATTER

According to Ancient Indian philospers all matter of this universe is made up of five basic constituents commonly called panch tatavas. Indian philospher Maharishi Kanad around 500 BC postulated that matter is divisible. The smallest indivisible matter were named as parmanu. Greek philosphers named this indivisible particles atoms. In 1808 John Dalton suggest that the atom was indivisible and industructible. After the discovery of electron and proton inside the atom, led to the failure of Daltons theory. In the thirty years between the discovery of neutron in 1932 to the middle of 1962, more than thirty new particles were found, which were thought to be the builders of matter in the universe. Therefore it was established beyond doubt that all the particles discovered are not fundamental but have complex nature. In 1964 Gell-Mann and Zweing proposed that most of these particles called Quarks. Nearly 200 elementary particles were discovered so far. It appears that our search for the ultimate builder is not in a concluding stage but we are reaching towards the goal in stages. In this way we can say that the mysterious world of elementary particles and Quark is still mysterious. The same is written in Vedas and Purana that the search of ultimate particle will go on and on.

Progress and prospect of neutron nuclear data measurement

Neutron nuclear data is the basic data for basic research of nuclear physics, development and utilization of nuclear energy and development of nuclear technology. Its quality is directly related to the effectiveness, safety and economy of nuclear-related products, such as nuclear devices. Since the discovery of neutrons, the research on neutron nuclear data has been carried out for more than 80 years. Developed countries continue to invest a lot of manpower and funding in this field, continuously improve the quality of databases to serve the basic research, national defense science and technology, and national economy development. The research of neutron nuclear data includes three parts: experimental measurement, theoretical evaluation and integral validation. This paper introduces the progress of neutron nuclear data measurement, including measurement platform and method, neutron reaction data and fission data measurement. Finally, the prospect is given.

Neutron therapy--the historical background.

Neutron therapy was first introduced by Stone et al. in 1938, i.e. more than 10 years earlier than electron beam therapy and only 6 years after the discovery of neutrons. In spite of the impressive accomplishment in generating an adequate therapy beam, time was also found for careful radiobiological studies of neutron beams. However, it was not considered that for a certain early reaction the late effects were much greater with neutrons than with x-rays. The severe late sequelae in proportion to the few good results motivated the closure of this therapy. Neutron therapy was again introduced in Hammersmith hospital at the end of the 1960's. The major reason seems to have been to overcome the oxygen effect. Encouraging results were reported. It was argued that the very favourable statistics on local tumour control were obtained at the expense of more frequent and more severe complications. A clinical trial in Edinburgh seemed to indicate this, but it was not proved in the end as the two trials differed regarding fractionation. Today about 16,000 patients have been treated with neutrons. The neutron beams now used differ significantly, both regarding dose distributions and microdosimetrical properties, from those utilized earlier. The advantage of neutrons is still, however, controversial. There are indications that neutron treatment may be favourable for some tumours. A careful cost-benefit study ought to be performed before the creation of a neutron therapy centre in Sweden as the group of patients suitable for neutrons is limited, and there may be new possibilities for improvement of photon and electron treatment with much smaller resources.

Ancient Guest Stars as Harbingers of Neutron Star Formation

It was just after the discovery of neutrons in 1932, Landau suggested the possibility of compact stars composed of neutrons. In 1934 Baade and Zwicky proposed the idea of neutron stars independently and suggested that neutron stars would be formed in supernova explosions.

Source papers in hot atom chemistry

Soon after the discovery of neutrons by J. Chadwick in 1932, a major project was undertaken in the Physics Depar tment of the University of R o m e in which every immediately available element in the Periodic Table was irradiated with neutrons from a strong radium-beryl l ium source. The artificial radioactivity was detected in most of the cases, and the half lives reported. The chemical behaviour of the induced radioactivity was also reported, and it was pointed out that the active elements generated were often chemically different from the bombarded elements. A long paper by E. Fermi et al. At was communicated by Lord Rutherford in the Proceedings of The Royal Society, received on 25 July 1934. Six months later a second paper A2 followed, in which the effect of hydrogenous material in greatly enhancing the activation effects was reported, and attributed to the slowing down of neutrons by light a tom collisions. This was published by the same authors, with B. Pontecorvo added, in February 1935. In between these two papers the short note which is included as the first Source Paper was published in September 1934 in Nature A3. Working in the Physics Depar tment of the Medical College of St Bar tholomew's Hospital in London, Szilard and Chalmers described the separation of radioactive iodine, which they called 'free ' iodine, by the bombardment of its parent iodine in liquid ethyl iodide with neutrons from a radon-beryl l ium source. As a result of this work, the effect by which a nuclear t ransformation releases the radioactive a tom from its parent molecule has been called ' the Szi lard-Chalmers Effect'. In this first paper they note that the effect only occurs when there is no chemical interchange between the free element and its parent compound. Following the pioneer experiment of Fermi, it has been found by Fermi, Amaldi, D'Agostino, Rasetti and Segr(~ that many elements up to the atomic number 30, when bombarded by neutrons from a radon-beryllium source, are transmuted into a radioactive element which is chemically different from the bombarded element. In several cases of this type, they succeeded in separating chemically the active substance from the bulk of the bombarded element, and there is no inherent difficulty in getting any desirable concentration of the radioactive element. They have not observed such chemical changes in elements above the atomic number 30, though many of these heavier elements show strong Fermi effects. For some of these, for example, arsenic, bromine, iodine, iridium and gold, they could show that the activity is carried by the bombarded element, which in the circumstances leads to the conclusion that the radioactive element is an isotope of the bombarded element. In order to separate the radioactive isotope of the bombarded element from the bulk of the bombarded element, one has to find a new principle of separation. We have attempted to apply the following principle. If we irradiate by a neutron source a chemical compound of the element in which we are interested, we might expect those atoms of the element which are struck by a neutron to be removed from the compound. Whether the atoms freed in this way will interchange with their isotopes bound in the irradiated chemical compound will depend on the nature of the chemical compound with which we have to deal. If we work under conditions in which such an interchange does not take place, we obtain the radioactive isotope 'free' and by separating the 'free' element from the compound we can obtain any desirable concentration of the radioactive isotope. We have applied this principle to iodine. Ethyl iodide has been irradiated and a trace of free iodide added to protect the radioactive isotope. By reduction and precipitation as silver iodide in water, it was easy to concentrate the activity so as to get from the precipitate 10 times as many impulses of the Geiger-MiJller /3-ray counter as directly from the irradiated ethyl iodide z. Apparently a large fraction of the active substance could be extracted from the ethyl iodide. The quantity of the active element obtainable in the precipitate will naturally depend on the quantity of the compound subjected to irradiation. This principle of isotopic separation has also been applied to some other elements which, like iodine, are

Contemporary Advances in Physics, XXVII The Nucleus, Second Part*

In this Second Part the major subject is Transmutation: that is to say, the alteration or disintegration of a nucleus, the unique and distinctive part of any atom, by impacts of fast-moving corpuscles. For the last year and a half the pace of progress in this field has been increasingly rapid, and in all likelihood is destined to become yet swifter. This is partly because of the discovery — a discovery due largely to theoretical foresight — that transmutation of some elements is practicable with protons of a relatively modest energy which can be produced in laboratories without any serious difficulty. Partly it is due to the discovery of neutrons and of deutons, particles which apparently possess remarkable ability in effecting certain kinds of transmutation. Partly also it is due to advances and refinements in the methods of working with alpha-particles, the first variety of corpuscle with which disintegration of nuclei was ever achieved. People are already beginning to speak of “nuclear chemistry” as a special branch of science, and this is already almost justified by the number of cases known in which two nuclei interact and produce two others which are recognizable.