document_title: Neutron

question_text: who discovered that the nuclei of atoms contained neutrons that carries no charge

question_tokens: who discovered that the nuclei of atoms contained neutrons that carries no charge

text: Neutron

text: Description[edit]

text: Atomic nuclei are formed by a number of protons, Z the atomic number, and a number of neutrons, N the neutron number, bound together by the nuclear force. The atomic number defines the chemical properties of the atom, and the neutron number determines the isotope or nuclide.[8] The terms isotope and nuclide are often used synonymously, but they refer to chemical and nuclear properties, respectively. The atomic mass number, symbol A, equals Z+N. The nucleus of the most common isotope of the hydrogen atom (with the chemical symbol 1H) is a lone proton. The nuclei of the heavy hydrogen isotopes deuterium (D or 2H) and tritium (T or 3H) contain one proton bound to one and two neutrons, respectively. All other types of atomic nuclei are composed of two or more protons and various numbers of neutrons. The most common nuclide of the common chemical element lead, 208Pb, has 82 protons and 126 neutrons, for example. The table of nuclides comprises all the known nuclides. Even though it is not a chemical element, the neutron is included in this table.[10]

text: The free neutron has a mass of about 6973167500000000000♠1.675×10−27 kg (equivalent to 7002939600000000000♠939.6 MeV/c2, or 7000100870000000000♠1.0087 u).[3] The neutron has a mean square radius of about 6984800000000000000♠0.8×10−15 m, or 0.8 fm,[11] and it is a spin-½ fermion.[12] The neutron has no measurable electric charge. With its positive electric charge, the proton is directly influenced by electric fields, whereas the neutron is unaffected by electric fields. The neutron has a magnetic moment, however, so the neutron is influenced by magnetic fields. The neutron's magnetic moment has a negative value, because its orientation is opposite to the neutron's spin.[13]

text: A free neutron is unstable, decaying to a proton, electron and antineutrino with a mean lifetime of just under 15 minutes (7002881500000000000♠881.5±1.5 s). This radioactive decay, known as beta decay,[14] is possible because the mass of the neutron is slightly greater than the proton. The free proton is stable (with the possible exception of proton decay). Neutrons or protons bound in a nucleus can be stable or unstable, however, depending on the nuclide. Beta decay, in which neutrons decay to protons, or vice versa, is governed by the weak force, and it requires the emission or absorption of electrons and neutrinos, or their antiparticles.

text: Protons and neutrons behave almost identically under the influence of the nuclear force within the nucleus. The concept of isospin, in which the proton and neutron are viewed as two quantum states of the same particle, is used to model the interactions of nucleons by the nuclear or weak forces. Because of the strength of the nuclear force at short distances, the binding energy of nucleons is more than seven orders of magnitude larger than the electromagnetic energy binding electrons in atoms. Nuclear reactions (such as nuclear fission) therefore have an energy density that is more than ten million times that of chemical reactions. Because of the mass–energy equivalence, nuclear binding energies add or subtract from the mass of nuclei. Ultimately, the ability of the nuclear force to store energy arising from the electromagnetic repulsion of nuclear components is the basis for most of the energy that makes nuclear reactors or bombs possible. In nuclear fission, the absorption of a neutron by a heavy nuclide (e.g., uranium-235) causes the nuclide to become unstable and break into light nuclides and additional neutrons. The positively charged light nuclides then repel, releasing electromagnetic potential energy.

text: The neutron is classified as a generic particle called hadron, because it is made of quarks. The neutron is also classified as a baryon, because it is composed of three quarks.[15] The finite size of the neutron and its magnetic moment indicates that the neutron is a composite particle (in contrast of being an elementary particle). A neutron consists of two down quarks with charge −⅓ e and one up quark with charge +⅔ e.

text: Like protons, the quarks of the neutron are held together by the strong force, mediated by gluons.[16] The nuclear force results from secondary effects of the more fundamental strong force.

text: Discovery[edit]

text: The story of the discovery of the neutron and its properties is central to the extraordinary developments in atomic physics that occurred in the first half of the 20th century, leading ultimately to the atomic bomb in 1945. In the 1911 Rutherford model, the atom consisted of a small positively charged massive nucleus surrounded by a much larger cloud of negatively charged electrons. In 1920, Rutherford suggested that the nucleus consisted of positive protons and neutrally-charged particles, suggested to be a proton and an electron bound in some way.[17] Electrons were assumed to reside within the nucleus because it was known that beta radiation consisted of electrons emitted from the nucleus.[17] Rutherford called these uncharged particles neutrons, by the Latin root for neutralis (neuter) and the Greek suffix -on (a suffix used in the names of subatomic particles, i.e. electron and proton).[18][19] References to the word neutron in connection with the atom can be found in the literature as early as 1899, however.[20]

text: Throughout the 1920s, physicists assumed that the atomic nucleus was composed of protons and "nuclear electrons"[21][22] but there were obvious problems. It was difficult to reconcile the proton–electron model for nuclei with the Heisenberg uncertainty relation of quantum mechanics.[23][24] The Klein paradox,[25] discovered by Oskar Klein in 1928, presented further quantum mechanical objections to the notion of an electron confined within a nucleus.[23] Observed properties of atoms and molecules were inconsistent with the nuclear spin expected from the proton–electron hypothesis. Since both protons and electrons carry an intrinsic spin of ½ ħ, there is no way to arrange an odd number of spins ±½ ħ to give a spin integer multiple of ħ. Nuclei with integer spin are common, e.g., 14N.

text: In 1931, Walther Bothe and Herbert Becker found that if alpha particle radiation from polonium fell on beryllium, boron, or lithium, an unusually penetrating radiation was produced. The radiation was not influenced by an electric field, so Bothe and Becker assumed it was gamma radiation.[26][27] The following year Irène Joliot-Curie and Frédéric Joliot in Paris showed that if this "gamma" radiation fell on paraffin, or any other hydrogen-containing compound, it ejected protons of very high energy.[28] Neither Rutherford nor James Chadwick at the Cavendish Laboratory in Cambridge were convinced by the gamma ray interpretation.[29] Chadwick quickly performed a series of experiments that showed that the new radiation consisted of uncharged particles with about the same mass as the proton.[6][30][31] These particles were neutrons. Chadwick won the Nobel Prize in Physics for this discovery in 1935.[2]

text: Models for atomic nucleus consisting of protons and neutrons were quickly developed by Werner Heisenberg[32][33][34] and others.[35][36] The proton–neutron model explained the puzzle of nuclear spins. The origins of beta radiation were explained by Enrico Fermi in 1934 by the process of beta decay, in which the neutron decays to a proton by creating an electron and a (as yet undiscovered) neutrino.[37] In 1935 Chadwick and his doctoral student Maurice Goldhaber, reported the first accurate measurement of the mass of the neutron.[38][39]

text: By 1934, Fermi had bombarded heavier elements with neutrons to induce radioactivity in elements of high atomic number. In 1938, Fermi received the Nobel Prize in Physics "for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons".[40] In 1938 Otto Hahn, Lise Meitner, and Fritz Strassmann discovered nuclear fission, or the fractionation of uranium nuclei into light elements, induced by neutron bombardment.[41][42][43] In 1945 Hahn received the 1944 Nobel Prize in Chemistry "for his discovery of the fission of heavy atomic nuclei."[44][45][46] The discovery of nuclear fission would lead to the development of nuclear power and the atomic bomb by the end of World War II.

text: Beta decay and the stability of the nucleus[edit]

text: Under the Standard Model of particle physics, the only possible decay mode for the neutron that conserves baryon number is for one of the neutron's quarks to change flavour via the weak interaction. The decay of one of the neutron's down quarks into a lighter up quark can be achieved by the emission of a W boson. By this process, the Standard Model description of beta decay, the neutron decays into a proton (which contains one down and two up quarks), an electron, and an electron antineutrino.

text: Since interacting protons have a mutual electromagnetic repulsion that is stronger than their attractive nuclear interaction, neutrons are a necessary constituent of any atomic nucleus that contains more than one proton (see diproton and neutron–proton ratio).[47] Neutrons bind with protons and one another in the nucleus via the nuclear force, effectively moderating the repulsive forces between the protons and stabilizing the nucleus.

text: Free neutron decay[edit]

text: Outside the nucleus, free neutrons are unstable and have a mean lifetime of 7002881500000000000♠881.5±1.5 s (about 14 minutes, 42 seconds); therefore the half-life for this process (which differs from the mean lifetime by a factor of ln(2) = 0.693) is 7002611000000000000♠611.0±1.0 s (about 10 minutes, 11 seconds).[14] Beta decay of the neutron, described above, can be denoted by the radioactive decay:[48]

text:
where p+, e−, and ν
e denote the proton, electron and electron antineutrino, respectively. For the free neutron the decay energy for this process (based on the masses of the neutron, proton, and electron) is 0.782343 MeV. The maximal energy of the beta decay electron (in the process wherein the neutrino receives a vanishingly small amount of kinetic energy) has been measured at 0.782 ± 0.013 MeV.[49] The latter number is not well-enough measured to determine the comparatively tiny rest mass of the neutrino (which must in theory be subtracted from the maximal electron kinetic energy) as well as neutrino mass is constrained by many other methods.

text: A small fraction (about one in 1000) of free neutrons decay with the same products, but add an extra particle in the form of an emitted gamma ray:

text: This gamma ray may be thought of as a sort of "internal bremsstrahlung" that arises as the emitted beta particle interacts with the charge of the proton in an electromagnetic way. Internal bremsstrahlung gamma ray production is also a minor feature of beta decays of bound neutrons (as discussed below).

text: A very small minority of neutron decays (about four per million) are so-called "two-body (neutron) decays", in which a proton, electron and antineutrino are produced as usual, but the electron fails to gain the 13.6 eV necessary energy to escape the proton (the ionization energy of hydrogen), and therefore simply remains bound to it, as a neutral hydrogen atom (one of the "two bodies"). In this type of free neutron decay, in essence all of the neutron decay energy is carried off by the antineutrino (the other "body").

text: The transformation of a free proton to a neutron (plus a positron and a neutrino) is energetically impossible, since a free neutron has a greater mass than a free proton.

text: Bound neutron decay[edit]

text: While a free neutron has a half life of about 10.2 min, most neutrons within nuclei are stable. According to the nuclear shell model, the protons and neutrons of a nuclide are a quantum mechanical system organized into discrete energy levels with unique quantum numbers. For a neutron to decay, the resulting proton requires an available state at lower energy than the initial neutron state. In stable nuclei the possible lower energy states are all filled, meaning they are each occupied by two protons with spin up and spin down. The Pauli exclusion principle therefore disallows the decay of a neutron to a proton within stable nuclei. The situation is similar to electrons of an atom, where electrons have distinct atomic orbitals and are prevented from decaying to lower energy states, with the emission of a photon, by the exclusion principle.

text: Neutrons in unstable nuclei can decay by beta decay as described above. In this case, an energetically allowed quantum state is available for the proton resulting from the decay. One example of this decay is carbon-14 (6 protons, 8 neutrons) that decays to nitrogen-14 (7 protons, 7 neutrons) with a half-life of about 5,730 years.

text: Inside a nucleus, a proton can transform into a neutron via inverse beta decay, if an energetically allowed quantum state is available for the neutron. This transformation occurs by emission of an antielectron (also called positron) and an electron neutrino:

text: The transformation of a proton to a neutron inside of a nucleus is also possible through electron capture:

text: Positron capture by neutrons in nuclei that contain an excess of neutrons is also possible, but is hindered because positrons are repelled by the positive nucleus, and quickly annihilate when they encounter electrons.

text: Competition of beta decay types[edit]

text: Three types of beta decay in competition are illustrated by the single isotope copper-64 (29 protons, 35 neutrons), which has a half-life of about 12.7 hours. This isotope has one unpaired proton and one unpaired neutron, so either the proton or the neutron can decay. This particular nuclide is almost equally likely to undergo proton decay (by positron emission, 18% or by electron capture, 43%) or neutron decay (by electron emission, 39%).

text: Intrinsic properties[edit]

text: Mass[edit]

text:
The mass of a neutron cannot be directly determined by mass spectrometry due to lack of electric charge. However, since the masses of a proton and of a deuteron can be measured with a mass spectrometer, the mass of a neutron can be deduced by subtracting proton mass from deuteron mass, with the difference being the mass of the neutron plus the binding energy of deuterium (expressed as a positive emitted energy). The latter can be directly measured by measuring the energy (

B

d

{\displaystyle B_{d}}

) of the single 6987125322244813139♠0.7822 MeV gamma photon emitted when neutrons are captured by protons (this is exothermic and happens with zero-energy neutrons), plus the small recoil kinetic energy (

E

r
d

{\displaystyle E_{rd}}

) of the deuteron (about 0.06% of the total energy).

text: The energy of the gamma ray can be measured to high precision by X-ray diffraction techniques, as was first done by Bell and Elliot in 1948. The best modern (1986) values for neutron mass by this technique are provided by Greene, et al.[50] These give a neutron mass of:

text: The value for the neutron mass in MeV is less accurately known, due to less accuracy in the known conversion of u to MeV:[51]

text: Another method to determine the mass of a neutron starts from the beta decay of the neutron, when the momenta of the resulting proton and electron are measured.

text: Electric charge[edit]

text: The total electric charge of the neutron is 5000000000000000000♠0 e. This zero value has been tested experimentally, and the present experimental limit for the charge of the neutron is 3021799999999999999♠−2(8)×10−22 e,[4]   or 3040700000000000000♠−3(13)×10−41 C. This value is consistent with zero, given the experimental uncertainties (indicated in parentheses). By comparison, the charge of the proton is, of course, 7000100000000000000♠+1 e.

text: Magnetic moment[edit]

text: Even though the neutron is a neutral particle, the magnetic moment of a neutron is not zero. The neutron is not affected by electric fields, but it is affected by magnetic fields. The magnetic moment of the neutron is an indication of its quark substructure and internal charge distribution.[52] The value for the neutron's magnetic moment was first directly measured by Luis Alvarez and Felix Bloch at Berkeley, California in 1940,[53] using an extension of the magnetic resonance methods developed by Rabi. Alvarez and Bloch determined the magnetic moment of the neutron to be μn= 2999807000000000000♠−1.93(2) μN, where μN is the nuclear magneton.

text: In the quark model for hadrons, the neutron is composed of one up quark (charge +2/3 e) and two down quarks (charge −1/3 e).[52] The magnetic moment of the neutron can be modeled as a sum of the magnetic moments of the constituent quarks.[54] The calculation assumes that the quarks behave like pointlike Dirac particles, each having their own magnetic moment. Simplistically, the magnetic moment of the neutron can be viewed as resulting from the vector sum of the three quark magnetic moments, plus the orbital magnetic moments caused by the movement of the three charged quarks within the neutron.

text: In one of the early successes of the Standard Model (SU(6) theory, now understood in terms of quark behavior), in 1964 Mirza A. B. Beg, Benjamin W. Lee, and Abraham Pais theoretically calculated the ratio of proton to neutron magnetic moments to be −3/2, which agrees with the experimental value to within 3%.[55][56][57] The measured value for this ratio is 2999854010194000000♠−1.45989806(34).[58] A contradiction of the quantum mechanical basis of this calculation with the Pauli exclusion principle, led to the discovery of the color charge for quarks by Oscar W. Greenberg in 1964.[55]

text: The above treatment compares neutrons with protons, allowing the complex behavior of quarks to be subtracted out between models, and merely exploring what the effects would be of differing quark charges (or quark type). Such calculations are enough to show that the interior of neutrons is very much like that of protons, save for the difference in quark composition with a down quark in the neutron replacing an up quark in the proton.

text: Attempts have been made to quantitatively recover the neutron magnetic moment from first principles. From the nonrelativistic, quantum mechanical wavefunction for baryons composed of three quarks, a straightforward calculation gives fairly accurate estimates for the magnetic moments of neutrons, protons, and other baryons.[54] For a neutron, the end result of this calculation is that the magnetic moment of the neutron is given by μn= 4/3 μd − 1/3 μu, where μd and μu are the magnetic moments for the down and up quarks, respectively. This result combines the intrinsic magnetic moments of the quarks with their orbital magnetic moments, and assumes the three quarks are in a particular, dominant quantum state.

text:
Baryon
Magnetic moment
of quark model
Computed
(

μ

N

{\displaystyle \mu _{\mathrm {N} }}

)
Observed
(

μ

N

{\displaystyle \mu _{\mathrm {N} }}

)

p
4/3 μu − 1/3 μd
2.79
2.793

n
4/3 μd − 1/3 μu
−1.86
−1.913

text: The results of this calculation are encouraging, but the masses of the up or down quarks were assumed to be 1/3 the mass of a nucleon.[54] The masses of the quarks are actually only about 1% that of a nucleon.[59] The discrepancy stems from the complexity of the Standard Model for nucleons, where most of their mass originates in the gluon fields, virtual particles, and their associated energy that are essential aspects of the strong force.[59][60] Furthermore, the complex system of quarks and gluons that constitute a neutron requires a relativistic treatment.[61] The nucleon magnetic moment has been successfully computed numerically from first principles, however, including all the effects mentioned and using more realistic values for the quark masses. The calculation gave results that were in fair agreement with measurement, but it required significant computing resources.[62][63]

text: Spin[edit]

text: The neutron is a spin 1/2 particle, that is, it is a fermion with intrinsic angular momentum equal to 1/2 ħ, where ħ is the reduced Planck constant. For many years after the discovery of the neutron, its exact spin was ambiguous. Although it was assumed to be a spin 1/2 Dirac particle, the possibility that the neutron was a spin 3/2 particle lingered. The interactions of the neutron's magnetic moment with an external magnetic field were exploited to finally determine the spin of the neutron.[64] In 1949, Hughes and Burgy measured neutrons reflected from a ferromagnetic mirror and found that the angular distribution of the reflections was consistent with spin 1/2.[65] In 1954, Sherwood, Stephenson, and Bernstein employed neutrons in a Stern–Gerlach experiment that used a magnetic field to separate the neutron spin states. They recorded two such spin states, consistent with a spin 1/2 particle.[64][66]

text: As a fermion, the neutron is subject to the Pauli exclusion principle; two neutrons cannot have the same quantum numbers. This is the source of the degeneracy pressure which makes neutron stars possible.

text: Structure and geometry of charge distribution[edit]

text: An article published in 2007 featuring a model-independent analysis concluded that the neutron has a negatively charged exterior, a positively charged middle, and a negative core.[67] In a simplified classical view, the negative "skin" of the neutron assists it to be attracted to the protons with which it interacts in the nucleus. (However, the main attraction between neutrons and protons is via the nuclear force, which does not involve charge.)

text: The simplified classical view of the neutron's charge distribution also "explains" the fact that the neutron magnetic dipole points in the opposite direction from its spin angular momentum vector (as compared to the proton). This gives the neutron, in effect, a magnetic moment which resembles a negatively charged particle. This can be reconciled classically with a neutral neutron composed of a charge distribution in which the negative sub-parts of the neutron have a larger average radius of distribution, and therefore contribute more to the particle's magnetic dipole moment, than do the positive parts that are, on average, nearer the core.

text: Electric dipole moment[edit]

text: The Standard Model of particle physics predicts a tiny separation of positive and negative charge within the neutron leading to a permanent electric dipole moment.[68] The predicted value is, however, well below the current sensitivity of experiments. From several unsolved puzzles in particle physics, it is clear that the Standard Model is not the final and full description of all particles and their interactions. New theories going beyond the Standard Model generally lead to much larger predictions for the electric dipole moment of the neutron. Currently, there are at least four experiments trying to measure for the first time a finite neutron electric dipole moment, including:

text:
Cryogenic neutron EDM experiment being set up at the Institut Laue–Langevin[69]
nEDM experiment under construction at the new UCN source at the Paul Scherrer Institute[70]
nEDM experiment being envisaged at the Spallation Neutron Source[71][72]
nEDM experiment being built at the Institut Laue–Langevin[73]

text: Anti-neutron[edit]

text: The antineutron is the antiparticle of the neutron. It was discovered by Bruce Cork in the year 1956, a year after the antiproton was discovered. CPT-symmetry puts strong constraints on the relative properties of particles and antiparticles, so studying antineutrons yields provide stringent tests on CPT-symmetry. The fractional difference in the masses of the neutron and antineutron is 6995900000000000000♠(9±6)×10−5. Since the difference is only about two standard deviations away from zero, this does not give any convincing evidence of CPT-violation.[14]

text: Neutron compounds[edit]

text: Dineutrons and tetraneutrons[edit]

text: The existence of stable clusters of 4 neutrons, or tetraneutrons, has been hypothesised by a team led by Francisco-Miguel Marqués at the CNRS Laboratory for Nuclear Physics based on observations of the disintegration of beryllium-14 nuclei. This is particularly interesting because current theory suggests that these clusters should not be stable.

text: In February 2016, Japanese physicist Susumu Shimoura of the University of Tokyo and co-workers reported they had observed the purported tetraneutrons for the first time experimentally.[74] Nuclear physicists around the world say this discovery, if confirmed, would be a milestone in the field of nuclear physics and certainly would deepen our understanding of the nuclear forces.[75][76]

text: The dineutron is another hypothetical particle. In 2012, Artemis Spyrou from Michigan State University and coworkers reported that they observed, for the first time, the dineutron emission in the decay of 16Be. The dineutron character is evidenced by a small emission angle between the two neutrons. The authors measured the two-neutron separation energy to be 1.35(10) MeV, in good agreement with shell model calculations, using standard interactions for this mass region.[77]

text: Neutronium and neutron stars[edit]

text: At extremely high pressures and temperatures, nucleons and electrons are believed to collapse into bulk neutronic matter, called neutronium. This is presumed to happen in neutron stars.

text: The extreme pressure inside a neutron star may deform the neutrons into a cubic symmetry, allowing tighter packing of neutrons.[78]

text: Detection[edit]

text: The common means of detecting a charged particle by looking for a track of ionization (such as in a cloud chamber) does not work for neutrons directly. Neutrons that elastically scatter off atoms can create an ionization track that is detectable, but the experiments are not as simple to carry out; other means for detecting neutrons, consisting of allowing them to interact with atomic nuclei, are more commonly used. The commonly used methods to detect neutrons can therefore be categorized according to the nuclear processes relied upon, mainly neutron capture or elastic scattering.[79]

text: Neutron detection by neutron capture[edit]

text: A common method for detecting neutrons involves converting the energy released from neutron capture reactions into electrical signals. Certain nuclides have a high neutron capture cross section, which is the probability of absorbing a neutron. Upon neutron capture, the compound nucleus emits more easily detectable radiation, for example an alpha particle, which is then detected. The nuclides 3He, 6Li, 10B, 233U, 235U, 237Np, and 239Pu are useful for this purpose.

text: Neutron detection by elastic scattering[edit]

text: Neutrons can elastically scatter off nuclei, causing the struck nucleus to recoil. Kinematically, a neutron can transfer more energy to a light nucleus such as hydrogen or helium than to a heavier nucleus. Detectors relying on elastic scattering are called fast neutron detectors. Recoiling nuclei can ionize and excite further atoms through collisions. Charge and/or scintillation light produced in this way can be collected to produce a detected signal. A major challenge in fast neutron detection is discerning such signals from erroneous signals produced by gamma radiation in the same detector.

text: Fast neutron detectors have the advantage of not requiring a moderator, and are therefore capable of measuring the neutron's energy, time of arrival, and in certain cases direction of incidence.

text: Sources and production[edit]

text: Free neutrons are unstable, although they have the longest half-life of any unstable subatomic particle by several orders of magnitude. Their half-life is still only about 10 minutes, however, so they can be obtained only from sources that produce them continuously.

text: Natural neutron background. A small natural background flux of free neutrons exists everywhere on Earth. In the atmosphere and deep into the ocean, the "neutron background" is caused by muons produced by cosmic ray interaction with the atmosphere. These high-energy muons are capable of penetration to considerable depths in water and soil. There, in striking atomic nuclei, among other reactions they induce spallation reactions in which a neutron is liberated from the nucleus. Within the Earth's crust a second source is neutrons produced primarily by spontaneous fission of uranium and thorium present in crustal minerals. The neutron background is not strong enough to be a biological hazard, but it is of importance to very high resolution particle detectors that are looking for very rare events, such as (hypothesized) interactions that might be caused by particles of dark matter.[9] Recent research has shown that even thunderstorms can produce neutrons with energies of up to several tens of MeV.[80] Recent research has shown that the fluence of these neutrons lies between 10−9 and 10−13 per ms and per m2 depending on the detection altitude. The energy of most of these neutrons, even with initial energies of 20 MeV, decreases down to the keV range within 1 ms.[81]

text: Even stronger neutron background radiation is produced at the surface of Mars, where the atmosphere is thick enough to generate neutrons from cosmic ray muon production and neutron-spallation, but not thick enough to provide significant protection from the neutrons produced. These neutrons not only produce a Martian surface neutron radiation hazard from direct downward-going neutron radiation but may also produce a significant hazard from reflection of neutrons from the Martian surface, which will produce reflected neutron radiation penetrating upward into a Martian craft or habitat from the floor.[82]

text: Sources of neutrons for research. These include certain types of radioactive decay (spontaneous fission and neutron emission), and from certain nuclear reactions. Convenient nuclear reactions include tabletop reactions such as natural alpha and gamma bombardment of certain nuclides, often beryllium or deuterium, and induced nuclear fission, such as occurs in nuclear reactors. In addition, high-energy nuclear reactions (such as occur in cosmic radiation showers or accelerator collisions) also produce neutrons from disintegration of target nuclei. Small (tabletop) particle accelerators optimized to produce free neutrons in this way, are called neutron generators.

text: In practice, the most commonly used small laboratory sources of neutrons use radioactive decay to power neutron production. One noted neutron-producing radioisotope, californium-252 decays (half-life 2.65 years) by spontaneous fission 3% of the time with production of 3.7 neutrons per fission, and is used alone as a neutron source from this process. Nuclear reaction sources (that involve two materials) powered by radioisotopes use an alpha decay source plus a beryllium target, or else a source of high-energy gamma radiation from a source that undergoes beta decay followed by gamma decay, which produces photoneutrons on interaction of the high-energy gamma ray with ordinary stable beryllium, or else with the deuterium in heavy water. A popular source of the latter type is radioactive antimony-124 plus beryllium, a system with a half-life of 60.9 days, which can be constructed from natural antimony (which is 42.8% stable antimony-123) by activating it with neutrons in a nuclear reactor, then transported to where the neutron source is needed.[83]

text: Nuclear fission reactors naturally produce free neutrons; their role is to sustain the energy-producing chain reaction. The intense neutron radiation can also be used to produce various radioisotopes through the process of neutron activation, which is a type of neutron capture.

text: Experimental nuclear fusion reactors produce free neutrons as a waste product. However, it is these neutrons that possess most of the energy, and converting that energy to a useful form has proved a difficult engineering challenge. Fusion reactors that generate neutrons are likely to create radioactive waste, but the waste is composed of neutron-activated lighter isotopes, which have relatively short (50–100 years) decay periods as compared to typical half-lives of 10,000 years[citation needed] for fission waste, which is long due primarily to the long half-life of alpha-emitting transuranic actinides.[84]

text: Neutron beams and modification of beams after production[edit]

text: Free neutron beams are obtained from neutron sources by neutron transport. For access to intense neutron sources, researchers must go to a specialized neutron facility that operates a research reactor or a spallation source.

text: The neutron's lack of total electric charge makes it difficult to steer or accelerate them. Charged particles can be accelerated, decelerated, or deflected by electric or magnetic fields. These methods have little effect on neutrons. However, some effects may be attained by use of inhomogeneous magnetic fields because of the neutron's magnetic moment. Neutrons can be controlled by methods that include moderation, reflection, and velocity selection. Thermal neutrons can be polarized by transmission through magnetic materials in a method analogous to the Faraday effect for photons. Cold neutrons of wavelengths of 6–7 angstroms can be produced in beams of a high degree of polarization, by use of magnetic mirrors and magnetized interference filters.[85]

text: Applications[edit]

text:
Science with neutrons

Foundations

Neutron temperature
Flux · Radiation · Transport
Cross section · Absorption · Activation

Neutron scattering

Neutron diffraction

Small-angle neutron scattering
GISANS
Reflectometry

Inelastic neutron scattering

Triple-axis spectrometer
Time-of-flight spectrometer
Backscattering spectrometer
Spin-echo spectrometer

Other applications

Neutron tomography
Activation analysis · Prompt gamma activation analysis
Fundamental research with neutrons: Ultracold neutrons · Interferometry
Fast neutron therapy
Neutron capture therapy

Infrastructure

Neutron sources: Research reactor · Spallation · Neutron moderator
Neutron optics: Guide · Supermirror · Polarizer
Detection

Neutron facilities

America: HFIR · LANSCE · NIST CNR -SNS
Australia: OPAL
Asia: J-PARC · HANARO
Europe: BER II · FRM II · ILL · ISIS · JINR · LLB · PINS · SINQ
Historic: IPNS · HFBR
Under construction: ESS

v
t
e

text: The neutron plays an important role in many nuclear reactions. For example, neutron capture often results in neutron activation, inducing radioactivity. In particular, knowledge of neutrons and their behavior has been important in the development of nuclear reactors and nuclear weapons. The fissioning of elements like uranium-235 and plutonium-239 is caused by their absorption of neutrons.

text: Cold, thermal, and hot neutron radiation is commonly employed in neutron scattering facilities, where the radiation is used in a similar way one uses X-rays for the analysis of condensed matter. Neutrons are complementary to the latter in terms of atomic contrasts by different scattering cross sections; sensitivity to magnetism; energy range for inelastic neutron spectroscopy; and deep penetration into matter.

text: The development of "neutron lenses" based on total internal reflection within hollow glass capillary tubes or by reflection from dimpled aluminum plates has driven ongoing research into neutron microscopy and neutron/gamma ray tomography.[86][87][88]

text: A major use of neutrons is to excite delayed and prompt gamma rays from elements in materials. This forms the basis of neutron activation analysis (NAA) and prompt gamma neutron activation analysis (PGNAA). NAA is most often used to analyze small samples of materials in a nuclear reactor whilst PGNAA is most often used to analyze subterranean rocks around bore holes and industrial bulk materials on conveyor belts.

text: Another use of neutron emitters is the detection of light nuclei, in particular the hydrogen found in water molecules. When a fast neutron collides with a light nucleus, it loses a large fraction of its energy. By measuring the rate at which slow neutrons return to the probe after reflecting off of hydrogen nuclei, a neutron probe may determine the water content in soil.

text: Medical therapies[edit]

text: Because neutron radiation is both penetrating and ionizing, it can be exploited for medical treatments. Neutron radiation can have the unfortunate side-effect of leaving the affected area radioactive, however. Neutron tomography is therefore not a viable medical application.

text: Fast neutron therapy utilizes high-energy neutrons typically greater than 20 MeV to treat cancer. Radiation therapy of cancers is based upon the biological response of cells to ionizing radiation. If radiation is delivered in small sessions to damage cancerous areas, normal tissue will have time to repair itself, while tumor cells often cannot.[89] Neutron radiation can deliver energy to a cancerous region at a rate an order of magnitude larger than gamma radiation[90]

text: Beams of low-energy neutrons are used in boron capture therapy to treat cancer. In boron capture therapy, the patient is given a drug that contains boron and that preferentially accumulates in the tumor to be targeted. The tumor is then bombarded with very low-energy neutrons (although often higher than thermal energy) which are captured by the boron-10 isotope in the boron, which produces an excited state of boron-11 that then decays to produce lithium-7 and an alpha particle that have sufficient energy to kill the malignant cell, but insufficient range to damage nearby cells. For such a therapy to be applied to the treatment of cancer, a neutron source having an intensity of the order of billion (109) neutrons per second per cm2 is preferred. Such fluxes require a research nuclear reactor.

text: Protection[edit]

text: Exposure to free neutrons can be hazardous, since the interaction of neutrons with molecules in the body can cause disruption to molecules and atoms, and can also cause reactions that give rise to other forms of radiation (such as protons). The normal precautions of radiation protection apply: Avoid exposure, stay as far from the source as possible, and keep exposure time to a minimum. Some particular thought must be given to how to protect from neutron exposure, however. For other types of radiation, e.g., alpha particles, beta particles, or gamma rays, material of a high atomic number and with high density make for good shielding; frequently, lead is used. However, this approach will not work with neutrons, since the absorption of neutrons does not increase straightforwardly with atomic number, as it does with alpha, beta, and gamma radiation. Instead one needs to look at the particular interactions neutrons have with matter (see the section on detection above). For example, hydrogen-rich materials are often used to shield against neutrons, since ordinary hydrogen both scatters and slows neutrons. This often means that simple concrete blocks or even paraffin-loaded plastic blocks afford better protection from neutrons than do far more dense materials. After slowing, neutrons may then be absorbed with an isotope that has high affinity for slow neutrons without causing secondary capture radiation, such as lithium-6.

text: Hydrogen-rich ordinary water affects neutron absorption in nuclear fission reactors: Usually, neutrons are so strongly absorbed by normal water that fuel enrichment with fissionable isotope is required.[clarification needed] The deuterium in heavy water has a very much lower absorption affinity for neutrons than does protium (normal light hydrogen). Deuterium is, therefore, used in CANDU-type reactors, in order to slow (moderate) neutron velocity, to increase the probability of nuclear fission compared to neutron capture.

text: Neutron temperature[edit]

text: Thermal neutrons[edit]

text: A thermal neutron is a free neutron that is Boltzmann distributed with kT= 6979405350651211000♠0.0253 eV (6979399999999999999♠4.0×10−21 J) at room temperature. This gives characteristic (not average, or median) speed of 2.2 km/s. The name 'thermal' comes from their energy being that of the room temperature gas or material they are permeating. (see kinetic theory for energies and speeds of molecules). After a number of collisions (often in the range of 10–20) with nuclei, neutrons arrive at this energy level, provided that they are not absorbed.

text: In many substances, thermal neutron reactions show a much larger effective cross-section than reactions involving faster neutrons, and thermal neutrons can therefore be absorbed more readily (i.e., with higher probability) by any atomic nuclei that they collide with, creating a heavier — and often unstable — isotope of the chemical element as a result.

text: Most fission reactors use a neutron moderator to slow down, or thermalize the neutrons that are emitted by nuclear fission so that they are more easily captured, causing further fission. Others, called fast breeder reactors, use fission energy neutrons directly.

text: Cold neutrons[edit]

text: Cold neutrons are thermal neutrons that have been equilibrated in a very cold substance such as liquid deuterium. Such a cold source is placed in the moderator of a research reactor or spallation source. Cold neutrons are particularly valuable for neutron scattering experiments.[citation needed]

text: Ultracold neutrons[edit]

text: Ultracold neutrons are produced by elastically scattering cold neutrons in substances with a temperature of a few kelvins, such as solid deuterium or superfluid helium. An alternative production method is the mechanical deceleration of cold neutrons.

text: Fission energy neutrons[edit]

text: A fast neutron is a free neutron with a kinetic energy level close to 6987160217648700000♠1 MeV (6987160000000000000♠1.6×10−13 J), hence a speed of ~7007140000000000000♠14000 km/s (~ 5% of the speed of light). They are named fission energy or fast neutrons to distinguish them from lower-energy thermal neutrons, and high-energy neutrons produced in cosmic showers or accelerators. Fast neutrons are produced by nuclear processes such as nuclear fission. Neutrons produced in fission, as noted above, have a Maxwell–Boltzmann distribution of kinetic energies from 0 to ~14 MeV, a mean energy of 2 MeV (for U-235 fission neutrons), and a mode of only 0.75 MeV, which means that more than half of them do not qualify as fast (and thus have almost no chance of initiating fission in fertile materials, such as U-238 and Th-232).

text: Fast neutrons can be made into thermal neutrons via a process called moderation. This is done with a neutron moderator. In reactors, typically heavy water, light water, or graphite are used to moderate neutrons.

text: Fusion neutrons[edit]

text: D–T (deuterium–tritium) fusion is the fusion reaction that produces the most energetic neutrons, with 14.1 MeV of kinetic energy and traveling at 17% of the speed of light. D–T fusion is also the easiest fusion reaction to ignite, reaching near-peak rates even when the deuterium and tritium nuclei have only a thousandth as much kinetic energy as the 14.1 MeV that will be produced.

text: 14.1 MeV neutrons have about 10 times as much energy as fission neutrons, and are very effective at fissioning even non-fissile heavy nuclei, and these high-energy fissions produce more neutrons on average than fissions by lower-energy neutrons. This makes D–T fusion neutron sources such as proposed tokamak power reactors useful for transmutation of transuranic waste. 14.1 MeV neutrons can also produce neutrons by knocking them loose from nuclei.

text: On the other hand, these very high-energy neutrons are less likely to simply be captured without causing fission or spallation. For these reasons, nuclear weapon design extensively utilizes D–T fusion 14.1 MeV neutrons to cause more fission. Fusion neutrons are able to cause fission in ordinarily non-fissile materials, such as depleted uranium (uranium-238), and these materials have been used in the jackets of thermonuclear weapons. Fusion neutrons also can cause fission in substances that are unsuitable or difficult to make into primary fission bombs, such as reactor grade plutonium. This physical fact thus causes ordinary non-weapons grade materials to become of concern in certain nuclear proliferation discussions and treaties.

text: Other fusion reactions produce much less energetic neutrons. D–D fusion produces a 2.45 MeV neutron and helium-3 half of the time, and produces tritium and a proton but no neutron the rest of the time. D–3He fusion produces no neutron.

text: Intermediate-energy neutrons[edit]

text: A fission energy neutron that has slowed down but not yet reached thermal energies is called an epithermal neutron.

text: Cross sections for both capture and fission reactions often have multiple resonance peaks at specific energies in the epithermal energy range. These are of less significance in a fast neutron reactor, where most neutrons are absorbed before slowing down to this range, or in a well-moderated thermal reactor, where epithermal neutrons interact mostly with moderator nuclei, not with either fissile or fertile actinide nuclides. However, in a partially moderated reactor with more interactions of epithermal neutrons with heavy metal nuclei, there are greater possibilities for transient changes in reactivity that might make reactor control more difficult.

text: Ratios of capture reactions to fission reactions are also worse (more captures without fission) in most nuclear fuels such as plutonium-239, making epithermal-spectrum reactors using these fuels less desirable, as captures not only waste the one neutron captured but also usually result in a nuclide that is not fissile with thermal or epithermal neutrons, though still fissionable with fast neutrons. The exception is uranium-233 of the thorium cycle, which has good capture-fission ratios at all neutron energies.

text: High-energy neutrons[edit]

text: High-energy neutrons have much more energy than fission energy neutrons and are generated as secondary particles by particle accelerators or in the atmosphere from cosmic rays. These high-energy neutrons are extremely efficient at ionization and far more likely to cause cell death than X-rays or protons.[91][92]


document_title: Saving Private Ryan

question_text: who played private ryan in the action film saving private ryan

root

text: Saving Private Ryan

text: Plot[edit]

text: On the morning of June 6, 1944, American soldiers land on Omaha Beach as part of the Normandy Invasion. They suffer heavy losses in assaulting German positions defended by artillery and machine guns. Captain John H. Miller of the 2nd Ranger Battalion assembles a group to penetrate the German defenses, leading to a breakout from the beach. Elsewhere on the beach, a dead soldier is face down in the bloody surf; his pack is stenciled Ryan, S.

tag: p

text: In Washington, D.C., at the U.S. War Department, General George Marshall learns that three of the four brothers of the Ryan family were killed in action and that the fourth son, James, is missing in action in Normandy. After reading Abraham Lincoln's Bixby letter aloud for his staff, he orders that James Ryan be found and returned home immediately.

text: Three days after D-Day, Miller receives orders to find Ryan and bring him back from the front. He assembles six men from his company—T/Sgt. Mike Horvath, Privates First Class Richard Reiben and Adrian Caparzo, Privates Stanley Mellish and Danny Jackson, medic Irwin Wade—plus T/5 Timothy Upham, a cartographer and interpreter borrowed from another unit. They move out to Neuville, where they meet a squad from the 101st Airborne Division, where Caparzo is killed by a German sniper. They locate a Private James Ryan, but quickly learn he is not their man. They eventually encounter a friend of James Ryan, who tells them that he is defending an important bridge in the town of Ramelle.

text: On the way to Ramelle, Miller decides to neutralize a German machine gun position, despite his men's misgivings; Wade is killed in the skirmish. Miller, at Upham's urging, declines to execute a surviving German (nicknamed "Steamboat Willie") and sets him free on the condition that he surrender to the first Allied unit he encounters. Losing confidence in Miller's leadership, Reiben declares his intention to desert, prompting a confrontation with Horvath, which Miller defuses by disclosing his civilian background as a teacher, about which his men had set up a betting pool. Reiben reluctantly decides to stay.

text: At Ramelle, Miller and the squad find a small group of paratroopers preparing to defend the bridge; one is Ryan. Miller tells Ryan about his brothers and their orders to bring him home and that two men had been lost in finding him. He is distressed at the loss of his brothers, but asks Miller to tell his mother that he intends to stay "with the only brothers [he has] left." Miller decides to join his unit with the paratroopers in defense of the bridge against the imminent German attack. Miller forms ambush positions throughout the ruined town, preparing to attack arriving tanks with Molotov cocktails, detonation cords and "sticky bombs" made from socks filled with Composition B.

text: Elements of the 2nd SS Panzer Division arrive with infantry and armor. Although they inflict heavy casualties on the Germans, most of the paratroopers, along with Jackson, Mellish, and Horvath are killed, while Upham avoids fighting. Miller attempts to blow the bridge, but is shot and mortally wounded by Steamboat Willie, who has rejoined the Germans. Just before a Tiger tank reaches the bridge, an American P-51 Mustang flies overhead and destroys the tank, followed by American armored units which rout the remaining Germans. Witnessing Miller's shooting, Upham confronts Steamboat Willie and his group as they attempt to retreat. Steamboat Willie raises his hands in surrender, believing that Upham will accept because of their earlier encounter. Instead, Upham kills him, but lets the other Germans flee.

text: Reiben and Ryan are with Miller as he dies and says his last words, "James...earn this. Earn it." In the present day, the elderly Ryan and his family visit the Normandy American Cemetery and Memorial and discover Miller's grave. Ryan expresses his appreciation for what Miller and the others did for him. He then asks his wife if he is a "good man" worthy of their sacrifices, to which she tells him he is. Ryan comes to attention and salutes Miller's grave.

text: Cast[edit]

text:
Tom Hanks as Captain John H. Miller, company commander, 2nd Ranger Battalion, U.S. Army
Edward Burns as Private First Class Richard Reiben, a BAR gunner
Tom Sizemore as Technical Sergeant Mike Horvath
Matt Damon as Private First Class James Francis Ryan, a paratrooper
Harrison Young as James Francis Ryan, present day
Barry Pepper as Private Daniel Jackson, a left-handed sniper
Adam Goldberg as Private Stanley "Fish" Mellish, a rifleman
Vin Diesel as Private First Class Adrian Caparzo, a rifleman
Giovanni Ribisi as Technician fourth grade Irwin "Doc" Wade, a medic
Jeremy Davies as Technician fifth grade Timothy E. Upham, a cartographer and interpreter
Ted Danson as Captain Fred Hamill, a pathfinder
Paul Giamatti as Staff Sergeant Hill, a paratrooper
Dennis Farina as Lieutenant Colonel Walter Anderson, battalion commander, 2nd Rangers
Harve Presnell as General George C. Marshall, Chief of Staff of the United States Army
Leland Orser as Second lieutenant DeWindt, pilot of a crashed glider
Bryan Cranston as Colonel I.W. Bryce, an officer at the War Department
Nathan Fillion as Private James Frederick Ryan ("Minnesota Ryan")
Ryan Hurst as Paratrooper Mandelsohn, a soldier whose hearing was damaged by a grenade
Max Martini as Corporal Henderson, ranking paratrooper at Ramelle
Kathleen Byron as James Francis Ryan's wife, present day
Stéphane Cornicard as Jean, a French survivor
Glenn Wrage as Doyle, a soldier of the 2nd Ranger Battalion
Joerg Stadler as "Steamboat Willie", a German soldier
Dale Dye as a War Department Colonel

tag: ul

text: Production[edit]

text: Development[edit]

text: In 1994, Robert Rodat wrote the script for the film. Rodat's script was submitted to producer Mark Gordon, who liked it and in turn passed it along to Spielberg to direct. The film is loosely based on the World War II life stories of the Niland brothers. A shooting date was set for June 27, 1997.[3]

text: Pre-production[edit]

text: In casting the film Spielberg sought to create a cast that "looked" the part, stating in an interview, "You know, the people in World War II actually looked different than people look today", adding to this end that he cast partly based on wanting the cast "to match the faces I saw on the newsreels." [4]

text: Before filming began, several of the film's stars, including Edward Burns, Barry Pepper, Vin Diesel, Adam Goldberg, Giovanni Ribisi, and Tom Hanks, endured ten days of "boot camp" training led by Marine veteran Dale Dye and Warriors, Inc., a California-based company that specializes in training actors for realistic military portrayals.[5] Matt Damon was intentionally not brought into the camp, to make the rest of the group feel resentment towards the character.[6] Spielberg had stated that his main intention in forcing the actors to go through the boot camp was not to learn the proper techniques but rather "because I wanted them to respect what it was like to be a soldier."[4]

text: The film's second scene is a 20+ minute sequence recounting the landing on the beaches of Normandy. Spielberg chose to include this particularly violent sequence in order "to bring the audience onto the stage with me" specifically noting that he did not want the "audience to be spectators" but rather he wanted to "demand them to be participants with those kids who had never seen combat before in real life, and get to the top of Omaha Beach together."[4]

text: Spielberg had already demonstrated his interest in World War II themes with the films 1941, Empire of the Sun, Schindler's List, and the Indiana Jones series. Spielberg later co-produced the World War II themed television miniseries Band of Brothers and its counterpart The Pacific with Tom Hanks. When asked about this by American Cinematographer, Spielberg said, "I think that World War II is the most significant event of the last 100 years; the fate of the baby boomers and even Generation X was linked to the outcome. Beyond that, I've just always been interested in World War II. My earliest films, which I made when I was about 14 years old, were combat pictures that were set both on the ground and in the air. For years now, I've been looking for the right World War II story to shoot, and when Robert Rodat wrote Saving Private Ryan, I found it."[7]

text: Filming[edit]

text: The D-Day scenes were shot in Ballinesker Beach, Curracloe Strand, Ballinesker, just east of Curracloe, County Wexford, Ireland.[8][9][10] Hanks recalled to Roger Ebert that although he realized it was a movie, the experience still hit him hard, stating, "The first day of shooting the D-Day sequences, I was in the back of the landing craft, and that ramp went down and I saw the first 1-2-3-4 rows of guys just getting blown to bits. In my head, of course, I knew it was special effects, but I still wasn't prepared for how tactile it was."[11] Filming began June 27, 1997, and lasted for two months.[12][13][14] Some shooting was done in Normandy, for the Normandy American Cemetery and Memorial in Colleville-sur-Mer and Calvados. Other scenes were filmed in England, such as a former British Aerospace factory in Hatfield, Hertfordshire, Thame Park, Oxfordshire and Wiltshire. Production was due to also take place in Seaham, County Durham, but government restrictions disallowed this.[15]

text: Portrayal of history[edit]

text: Saving Private Ryan has received critical acclaim for its realistic portrayal of World War II combat. In particular, the sequence depicting the Omaha Beach landings was named the "best battle scene of all time" by Empire magazine and was ranked number one on TV Guide's list of the "50 Greatest Movie Moments".[16] The scene cost US$12 million and involved up to 1,500 extras, some of whom were members of the Irish Reserve Defence Forces. Members of local reenactment groups such as the Second Battle Group were cast as extras to play German soldiers.[17] In addition, twenty to thirty actual amputees were used to portray American soldiers maimed during the landing.[18] Spielberg did not storyboard the sequence, as he wanted spontaneous reactions and for "the action to inspire me as to where to put the camera".[19]

text: The historical representation of Charlie Company's actions, led by its commander, Captain Ralph E. Goranson, was well maintained in the opening sequence. The sequence and details of the events are very close to the historical record, including the sea sickness experienced by many of the soldiers as the landing craft moved toward the shoreline, significant casualties among the men as they disembarked from the boats, and difficulty linking up with adjacent units on the shore.

text: The distinctive signature "ping" of the US soldiers' M1 Garand rifles ejecting their ammunition clips is heard throughout the battle sequence. The contextual details of the Company's actions were well maintained, for instance, the correct code names for the sector Charlie Company assaulted, and adjacent sectors, were used. Included in the cinematic depiction of the landing was a follow-on mission of clearing a bunker and trench system at the top of the cliffs which was not part of the original mission objectives for Charlie Company, but which they did undertake after the assault on the beach.[20]

text: The landing craft used included twelve actual World War II examples, 10 LCVPs and 2 LCMs, standing in for the British LCAs that the Ranger Companies rode in to the beach during Operation Overlord.[20][21] The filmmakers used underwater cameras to better depict soldiers being hit by bullets in the water. Forty barrels of fake blood were used to simulate the effect of blood in the seawater.[18] This degree of realism was more difficult to achieve when depicting World War II German armored vehicles, as few examples survive in operating condition. The Tiger I tanks in the film were copies built on the chassis of old, but functional, Soviet T-34 tanks.[22] The two vehicles described in the film as Panzers were meant to portray Marder III tank destroyers. One was created for the film using the chassis of a Czech-built Panzer 38(t) tank[23] similar to the construction of the original Marder III; the other was a cosmetically modified Swedish SAV m/43 assault gun, which also used the 38(t) chassis.[24]

text: There are, however, historical inaccuracies in the film's depiction of the Normandy campaign. At the time of the mission, American forces from the two American beach areas, Utah and Omaha, had not yet linked up.[25] In reality, a Ranger team operating out of the Omaha beach area would have had to move through the heavily enemy-occupied city of Carentan, or swim or boat across the estuary linking Carentan to the channel, or transfer by boat to the Utah landing area. On the other hand, US forces moving out of Utah would have had direct and much shorter routes, relatively unencumbered by enemy positions, and were already in contact with some teams from both US airborne divisions landed in the area.[26]

text: The Utah beach landings, however, were relatively uncontested, with assault units landing on largely unoccupied beaches and experiencing far less action than the landings at Omaha.[27] The filmmakers chose to begin the narrative with a depiction of the more dramatic story of Omaha, despite the strategic inaccuracy of an impossible mission that could easily have been pursued from the other beach area. In addition, one of the most notable of the operational flaws is the depiction of the 2nd SS Panzer Division Das Reich as the adversary during the fictional Battle of Ramelle. The 2nd SS was not engaged in Normandy until July, and then at Caen against the British and Canadians, 100 miles east.[28] Furthermore, the Merderet River bridges were not an objective of the 101st Airborne Division but of the 82nd Airborne Division, part of Mission Boston.[29]

text: Much has also been said about various "tactical errors" made by both the German and American forces in the film's climactic battle. Spielberg responded, saying that in many scenes he opted to replace sound military tactics and strict historical accuracy for dramatic effect.[30] Some other technical errors were also made, often censored, including the mistaken reversed orientation of the beach barriers; the tripod obstructions with a mine at the apex.

text: To achieve a tone and quality that was true to the story as well as reflected the period in which it is set, Spielberg once again collaborated with cinematographer Janusz Kamiński, saying, "Early on, we both knew that we did not want this to look like a Technicolor extravaganza about World War II, but more like color newsreel footage from the 1940s, which is very desaturated and low-tech." Kamiński had the protective coating stripped from the camera lenses, making them closer to those used in the 1940s. He explains that "without the protective coating, the light goes in and starts bouncing around, which makes it slightly more diffused and a bit softer without being out of focus." The cinematographer completed the overall effect by putting the negative through bleach bypass, a process that reduces brightness and color saturation. The shutter timing was set to 90 or 45 degrees for many of the battle sequences, as opposed to the standard of 180-degree timing. Kamiński clarifies, "In this way, we attained a certain staccato in the actors' movements and a certain crispness in the explosions, which makes them slightly more realistic."[31]

text: Reception[edit]

text: Box office[edit]

text: Saving Private Ryan was a critical and commercial success and is credited with contributing to a resurgence in America's interest in World War II. Old and new films, video games, and novels about the war enjoyed renewed popularity after its release.[32] The film's use of desaturated colors, hand-held cameras, and tight angles has profoundly influenced subsequent films and video games.[33][34] Saving Private Ryan was released in 2,463 theaters on July 24, 1998, and grossed $30.5 million on its opening weekend. The film grossed $216.5 million in the US and Canada. and $265.3 million in other territories, bringing its worldwide total to $481.8 million and making it the highest-grossing US film of the year.[1] Box Office Mojo estimates that the film sold over 45.74 million tickets in the United States and Canada.[35]

text: Critical response[edit]

text: The film received critical acclaim and has a 'certified fresh' rating of 92% on Rotten Tomatoes based on 130 reviews with an average score of 8.6 out of 10. The consensus states "Anchored by another winning performance from Hanks, Spielberg's unflinchingly realistic war film virtually redefines the genre."[36] The film also has a score of 90 out of 100 on Metacritic based on 34 reviews indicating "universal acclaim".[37]

text: Much of the praise went for the realistic battle scenes[38] and the actors' performances.[39] However, it did earn some criticism for ignoring the contributions of several other countries to the D-Day landings in general and at Omaha Beach specifically.[40] The most direct example of the latter is that during the actual landing the 2nd Rangers disembarked from British ships and were taken to Omaha Beach by Royal Navy landing craft (LCAs). The film depicts them as being United States Coast Guard-crewed craft (LCVPs and LCMs) from an American ship, the USS Thomas Jefferson (APA-30).[20][41][42] This criticism was far from universal with other critics recognizing the director's intent to make an "American" film.[43] The film was not released in Malaysia after Spielberg refused to cut the violent scenes;[44] however, the film was finally released there on DVD with an 18SG certificate much later in 2005. Many critics associations, such as New York Film Critics Circle and Los Angeles Film Critics Association, chose Saving Private Ryan as Film of the Year.[45] Roger Ebert gave it four stars out of four and called it "a powerful experience".[39]

text: Filmmaker Robert Altman wrote a letter to Spielberg stating, "Private Ryan was awesome -- best I've seen."[46] Filmmaker Quentin Tarantino has expressed admiration for the film and has cited it as an influence on his 2009 film, Inglourious Basterds.[47]

text: Many World War II veterans stated that the film was the most realistic depiction of combat they had ever seen.[48] The film was so realistic that combat veterans of D-Day and Vietnam left theaters rather than finish watching the opening scene depicting the Normandy invasion. Their visits to posttraumatic stress disorder counselors rose in number after the film's release, and many counselors advised "'more psychologically vulnerable'" veterans to avoid watching it.[49] The Department of Veterans Affairs set up a nationwide hotline for veterans who were affected by the film, and less than two weeks after the film was released it had already received over 170 calls.[50]

text: The film has gained criticism and negative reviews from war veterans and film critics. Film director and military veteran Oliver Stone has accused the film of promoting "the worship of World War II as the good war," and has placed it alongside films such as Gladiator and Black Hawk Down that he believes were well-made, but may have inadvertently contributed to Americans' readiness for the 2003 invasion of Iraq.[51] In defense of the film's portrait of warfare, Brian De Palma commented, "The level of violence in something like Saving Private Ryan makes sense because Spielberg is trying to show something about the brutality of what happened."[52] Actor Richard Todd, who performed in The Longest Day and was amongst the first of the Allied soldiers to land in Normandy (Operation Tonga), said the film was "Rubbish. Overdone."[53] American academic Paul Fussell, who saw combat in France during World War II, objected to what he described as, "the way Spielberg's Saving Private Ryan, after an honest, harrowing, 15-minute opening visualizing details of the unbearable bloody mess at Omaha Beach, degenerated into a harmless, uncritical patriotic performance apparently designed to thrill 12-year-old boys during the summer bad-film season. Its genre was pure cowboys and Indians, with the virtuous cowboys of course victorious."[54]

text: Awards[edit]

text: The film was nominated for eleven Academy Awards, and won five including Best Cinematography, Best Sound Mixing, Best Sound Effects Editing, Best Film Editing, and Best Director for Spielberg, but lost the Best Picture award to Shakespeare in Love, being one of a few that have won the Best Director award without also winning Best Picture.[55][56] The Academy's decision to not award the film with the Best Picture Oscar has resulted in much criticism in recent years, with many considering it as one of the biggest snubs in the ceremony's history.[57][58]

text: The film also won the Golden Globes for Best Motion Picture – Drama and Director, the BAFTA Award for Special Effects and Sound, the Directors Guild of America Award, a Grammy Award for Best Film Soundtrack, the Producers Guild of America Golden Laurel Award, and the Saturn Award for Best Action, Adventure, or Thriller Film.[45] The American Film Institute has included Saving Private Ryan in many of its lists, ranking it as the 71st greatest American movie in AFI's 100 Years...100 Movies (10th Anniversary Edition),[59] as well as the 45th most thrilling film in AFI's 100 Years...100 Thrills,[60] the 10th most inspiring in AFI's 100 Years...100 Cheers,[61] and the eighth best epic film in "AFI's 10 Top 10".[62]

text:
List of awards and nominations received by Saving Private Ryan

Award
Category
Nominee
Result

71st Academy Awards
Best Picture
Steven Spielberg, Ian Bryce, Mark Gordon and Gary Levinsohn
Nominated

Best Actor in a Leading Role
Tom Hanks
Nominated

Best Director
Steven Spielberg
Won

Best Original Screenplay
Robert Rodat
Nominated

Best Cinematography
Janusz Kamiński
Won

Best Art Direction
Thomas E. Sanders and Lisa Dean
Nominated

Best Sound Mixing
Gary Rydstrom, Gary Summers, Andy Nelson and Ron Judkins
Won

Best Film Editing
Michael Kahn
Won

Best Sound Effects Editing
Gary Rydstrom and Richard Hymns
Won

Best Makeup
Lois Burwell, Conor O'Sullivan and Daniel C. Striepeke
Nominated

Best Music, Original Dramatic Score
John Williams
Nominated

Academy of Science Fiction, Fantasy & Horror Films
Best Thriller Film

Won

Best Special Effects

Nominated

Amanda Awards
Best Foreign Film
Steven Spielberg
Nominated

American Cinema Editors
Best Edited Feature Film
Michael Kahn
Won

American Society of Cinematographers
Outstanding Achievement in Cinematography in Theatrical Releases
Janusz Kamiński
Nominated

Art Directors Guild
Feature Film

Nominated

Awards of the Japanese Academy
Best Foreign Film

Nominated

BAFTA Awards
Best Sound

Won

Best Special Visual Effects

Won

Best Music
John Williams
Nominated

Best Cinematography
Janusz Kamiński
Nominated

Best Editing
Michael Kahn
Nominated

Best Film

Nominated

Best Makeup & Hair

Nominated

Best Actor
Tom Hanks
Nominated

Best Production Design

Nominated

Best Direction
Steven Spielberg
Nominated

BMI Film Music Award
BMI Film Music Award
John Williams
Won

Blockbuster Entertainment Award
Favorite Actor
Tom Hanks
Won

Favorite Supporting Actor
Jeremy Davies
Nominated

Boston Society of Film Critics Awards
Best Cinematography

Won

British Society of Cinematographers
Best Cinematography

Nominated

Broadcast Film Critics Association Awards
Best Director
Steven Spielberg
Won

Best Picture

Won

Best Score
John Williams
Won

Camerimage
Best Cinematography

Nominated

Casting Society of America
Best Casting

Won

Chicago Film Critics Association Awards
Best Picture

Won

Best Actor
Tom Hanks
Nominated

Best Cinematography

Nominated

Best Director
Steven Spielberg
Nominated

Cinema Audio Society
Best Sound

Won

Czech Lions
Best Foreign Film
Steven Spielberg
Won

César Awards
Best Foreign Film
Steven Spielberg
Nominated

Dallas-Fort Worth Film Critics Association Awards
Best Picture

Won

Best Actor
Tom Hanks
Nominated

Directors Guild of America
Outstanding Directorial Achievement
Steven Spielberg
Won

Empire Awards
Best Actor
Tom Hanks
Won

Best Director
Steven Spielberg
Won

Best Film

Nominated

European Film Award
Screen International Award
Steven Spielberg
Nominated

Film Critics Circle of Australia Awards
Best Foreign Film

Nominated

Florida Film Critics Circle Awards
Best Cinematography

Won

Golden Globes
Best Director
Steven Spielberg
Won

Best Motion Picture – Drama

Won

Best Original Score
John Williams
Nominated

Best Actor
Tom Hanks
Nominated

Best Screenplay

Nominated

Grammy Awards
Best Instrumental Composition Written for a Motion Picture or for Television
John Williams
Won

Huabiao Film Awards
Best Foreign Film

Won

Humanitas Prize
Feature Film Category

Nominated

Italian National Syndicate of Film Journalists
Best Foreign Director
Steven Spielberg
Won

Kansas City Film Critics Circle Awards
Best Film

Won

Best Director
Steven Spielberg
Won

Best Supporting Actor
Jeremy Davies
Won

Key Art Awards
Best of Show – Audiovisual

Won

Las Vegas Film Critics Society Awards
Best Cinematography

Won

Best Director
Steven Spielberg
Won

Best Picture

Won

London Critics Circle Film Awards
Film of the Year

Won

Actor of the Year
Matt Damon
Nominated

Actor of the Year
Tom Hanks
Nominated

Director of the Year
Steven Spielberg
Nominated

Los Angeles Film Critics Association Awards
Best Cinematography

Won

Best Director
Steven Spielberg
Won

Best Picture

Won

MTV Movie Awards
Best Action Sequence
Tom Hanks
Nominated

Best Male Performance
Tom Hanks
Nominated

Best Movie

Nominated

Motion Picture Sound Editors
Best Sound Editing – Dialogue

Won

Best Sound Editing – Sound Effects

Won

Best Sound Editing – Music

Nominated

National Board of Review
Top Ten Films

Won

National Society of Film Critics Awards
Best Film

Nominated

New York Film Critics Circle Awards
Best Film

Won

Online Film Critics Society Awards
Best Cinematography

Won

Best Director
Steven Spielberg
Won

Best Ensemble

Won

Best Film

Won

Best Film Editing
Michael Kahn
Won

Best Actor
Tom Hanks
Nominated

Best Music
John Williams
Nominated

PGA Awards
Motion Picture Producer of the Year Award

Won

Russian Guild of Film Critics
Best Foreign Film
Steven Spielberg
Won

Satellite Awards
Best Editing
Michael Kahn
Won

Best Director
Steven Spielberg
Nominated

Best Film

Nominated

Best Cinematography

Nominated

Best Original Score

Nominated

Best Original Screenplay

Nominated

Best Supporting Actor – Motion Picture
Tom Sizemore
Nominated

Best Visual Effects

Nominated

Saturn Awards
Best Action or Adventure Film

Won

Screen Actors Guild Awards
Best Ensemble

Nominated

Best Actor
Tom Hanks
Nominated

Southeastern Film Critics Association Awards
Best Director
Steven Spielberg
Won

Best Picture

Won

Toronto Film Critics Association Awards
Best Director
Steven Spielberg
Won

Best Picture

Won

Best Male Performance
Tom Hanks
Nominated

Writers Guild of America
Best Original Screenplay
Robert Rodat
Nominated

tag: table

text: Television broadcasts[edit]

text: On Veterans Day from 2001–2004, the American Broadcasting Company aired the film uncut and with limited commercial interruption. The network airings were given a TV-MA rating, as the violent battle scenes and the profanity were left intact. The 2004 airing was marred by pre-emptions in many markets because of the language, in the backlash of Super Bowl XXXVIII's halftime show controversy.[63] However, critics and veterans' groups such as the American Legion and the Veterans of Foreign Wars assailed those stations and their owners, including Hearst-Argyle Television (owner of 12 ABC affiliates); Scripps Howard Broadcasting (owner of six); and Belo (owner of four) for putting profits ahead of programming and honoring those who gave their lives at wartime, saying the stations made more money running their own programming instead of being paid by the network to carry the film, especially during a sweeps period.

text: A total of 65 ABC affiliates—28% of the network—did not clear the available timeslot for the film, even with the offer of The Walt Disney Company, ABC's parent, to pay all fines for language to the Federal Communications Commission.[64] In the end, however, no complaints were lodged against ABC affiliates who showed Ryan, perhaps because even conservative watchdogs like the Parents Television Council supported the unedited rebroadcast of the film.[65] Additionally, some ABC affiliates in other markets that were near affected markets, such as Youngstown, Ohio, ABC affiliate WYTV (which is viewable in parts of the Columbus, Cleveland, and Pittsburgh markets, none of which aired the film) and Gainesville, Florida, ABC affiliate WCJB-TV (which is viewable in parts of the Orlando and Tampa markets), still aired the film and gave those nearby markets the option of viewing the film.[66] TNT and Turner Classic Movies have also broadcast the film.[67][68]

text: Home video[edit]

text: The film was released on home video in May 1999 with a VHS release that earned over $44 million.[69] The DVD release became available in November of the same year,[70] and was one of the best-selling titles of the year, with over 1.5 million units sold.[71] The DVD was released in two separate versions: one with Dolby Digital and the other with DTS 5.1 surround sound. Besides the different 5.1 tracks, the two DVDs are identical. The film was also issued in a very limited 2-disc LaserDisc release in November 1999, making it one of the very last feature films to ever be issued in this format, as LaserDiscs ceased manufacturing and distribution by the year's end, due in part to the growing popularity of DVDs.[72]

text: In 2004, a Saving Private Ryan special edition DVD was released to commemorate the 60th anniversary of D-Day. This two-disc edition was also included in a box set titled World War II Collection, along with two documentaries produced by Spielberg, Price For Peace (about the Pacific War) and Shooting War (about war photographers, narrated by Tom Hanks).[73] The film was released on Blu-ray Disc on April 26, 2010 in the UK and on May 4, 2010 in the US, as part of Paramount Home Video's premium Sapphire Series.[74] However, only weeks after its release, Paramount issued a recall due to audio synchronization problems. The studio issued an official statement acknowledging the problem, which they attributed to an authoring error by Technicolor that escaped the quality control process, and that they had already begun the process of replacing the defective discs.[75]