Nuclear emulsion

In particle and nuclear physics, a nuclear emulsion plate is a photographic plate with a particularly thick emulsion layer and with a very uniform grain size. Like bubble chambers, cloud chambers, and wire chambers nuclear emulsion plates record the tracks of charged particles passing through. They are compact, have high density and produce a cumulative record, but have the disadvantage that the plates must be developed before the tracks can be observed.

Nuclear emulsions can be used to record and investigate fast charged particles like nucleons or mesons. After exposing and developing the plate, single particle tracks can be observed and measured using a microscope.

In 1937, Marietta Blau and Hertha Wambacher discovered nuclear disintegration stars due to spallation in nuclear emulsions that had been exposed to cosmic radiation at a height of 2,300 metres (≈7,500 feet) above sea level.

Using nuclear emulsions exposed on high mountains, Cecil Frank Powell and colleagues discovered the charged pion in 1947.[1] This discovery won them a Nobel Prize in Physics in 1950.

In biology and medicine, nuclear emulsion is used in autoradiography to locate radioactive labels in samples of cells and tissues. Emulsion detectors are still used by some modern particle detectors (for example, the OPERA experiment).

References

  1. ^ G. P. S. Occhialini, C. F. Powell, Nuclear Disintegrations Produced by Slow Charged Particles of Small Mass, Nature 159, 186–190 & 160, 453–456, 1947
  • J. Thewlis (ed.), Encyclopedic Dictionary of Physics, Pergamon Press, Oxford, 1962
  • Robert Rosner, Brigitte Strohmaier (ed.): Marietta Blau, Stars of Disintegration. A biography of a pioneer of modern particle physics. Böhlau, Vienna 2003, ISBN 3-205-77088-9 (in German)

External links

Anomalon

Anomalon is also the type genus of the ichneumon-wasp subfamily Anomaloninae. See Anomalon.In physics, an anomalon is a hypothetical type of nuclear matter that shows an anomalously large reactive cross section. They were first noticed in experimental runs in the early 1980s as short tracks in film emulsions or plastic leaf detectors connected to medium-energy particle accelerators. The direction of the tracks demonstrated that they were the results of reactions taking place within the accelerator targets, but they stopped so quickly in the detectors that no obvious explanation for their behavior could be offered. A flurry of theoretical explanations followed, but over time a series of follow-up experiments failed to find strong evidence for the anomalons, and active study of the topic largely ended by the late 1980s.

Autoradiograph

An autoradiograph is an image on an x-ray film or nuclear emulsion produced by the pattern of decay emissions (e.g., beta particles or gamma rays) from a distribution of a radioactive substance. Alternatively, the autoradiograph is also available as a digital image (digital autoradiography), due to the recent development of scintillation gas detectors or rare earth phosphorimaging systems. The film or emulsion is apposed to the labeled tissue section to obtain the autoradiograph (also called an autoradiogram). The auto- prefix indicates that the radioactive substance is within the sample, as distinguished from the case of historadiography or microradiography, in which the sample is X-rayed using an external source. Some autoradiographs can be examined microscopically for localization of silver grains (such as on the interiors or exteriors of cells or organelles) in which the process is termed micro-autoradiography. For example, micro-autoradiography was used to examine whether atrazine was being metabolized by the hornwort plant or by epiphytic microorganisms in the biofilm layer surrounding the plant.

Cloud chamber

A cloud chamber, also known as a Wilson cloud chamber, is a particle detector used for visualizing the passage of ionizing radiation.

A cloud chamber consists of a sealed environment containing a supersaturated vapor of water or alcohol. An energetic charged particle (for example, an alpha or beta particle) interacts with the gaseous mixture by knocking electrons off gas molecules via electrostatic forces during collisions, resulting in a trail of ionized gas particles. The resulting ions act as condensation centers around which a mist-like trail of small droplets form if the gas mixture is at the point of condensation. These droplets are visible as a "cloud" track that persist for several seconds while the droplets fall through the vapor. These tracks have characteristic shapes. For example, an alpha particle track is thick and straight, while an electron track is wispy and shows more evidence of deflections by collisions.

Cloud chambers played a prominent role in the experimental particle physics from the 1920s to the 1950s, until the advent of the bubble chamber. In particular, the discoveries of the positron in 1932 (see Fig. 1) and the muon in 1936, both by Carl Anderson (awarded a Nobel Prize in Physics in 1936), used cloud chambers. Discovery of the kaon by George Rochester and Clifford Charles Butler in 1947, also was made using a cloud chamber as the detector.. In each case, cosmic rays were the source of ionizing radiation.

César Lattes

Cesare Mansueto Giulio Lattes (11 July 1924 – 8 March 2005), also known as César Lattes, was a Brazilian experimental physicist, one of the discoverers of the pion, a composite subatomic particle made of a quark and an antiquark.

DONUT

DONUT (Direct observation of the nu tau, E872) was an experiment at Fermilab dedicated to the search for tau neutrino interactions. The detector operated during a few months in the summer of 1997, and successfully detected the tau neutrino. It confirmed the existence of the last lepton predicted by the Standard Model. The data from the experiment was also used to put an upper limit on the tau neutrino magnetic moment and measure its interaction cross section.

Gemini 8

Gemini 8 (officially Gemini VIII) was the sixth manned spaceflight in NASA's Gemini program. The mission conducted the first docking of two spacecraft in orbit, but suffered the first critical in-space system failure of a U.S. spacecraft which threatened the lives of the astronauts and required immediate abort of the mission. The crew was returned to Earth safely. The only other time this happened was on the flight of Apollo 13.

It was the twelfth manned American flight and the twenty-second manned spaceflight of all time [including two X-15 flights over 100 kilometers (54 nautical miles)]. Command pilot Neil Armstrong's flight marked the second time a U.S. civilian flew into space (Joe Walker became the first U.S. civilian on X-15 Flight 90). Armstrong had resigned his commission in the United States Naval Reserve in 1960. The Soviet Union had launched the first civilian, Valentina Tereshkova (also the first woman), aboard Vostok 6 on June 16, 1963.

Hypernucleus

A hypernucleus is a nucleus which contains at least one hyperon (a baryon carrying the strangeness quantum number) in addition to the normal protons and neutrons. The first was discovered by Marian Danysz and Jerzy Pniewski in 1952 using the nuclear emulsion technique.

The strangeness quantum number is conserved by the strong and electromagnetic interactions, a variety of reactions give access to depositing one or more units of strangeness in a nucleus. Hypernuclei containing the lightest hyperon, the Lambda, live long enough to have sharp nuclear energy levels. Therefore, they offer opportunities for nuclear spectroscopy, as well as reaction mechanism study and other types of nuclear physics (hypernuclear physics).

Hypernuclear physics differs from that of normal nuclei because a hyperon, having a non-zero strangeness quantum number, can share space and momentum coordinates with the usual four nucleon states that can differ from each other in spin and isospin. That is, they are not restricted by the Pauli Exclusion Principle from any single-particle state in the nucleus. The ground state of helium-5-Lambda, for example, must resemble helium-4 more than it does helium-5 or lithium-5 and must be stable, apart from the eventual weak decay of the Lambda. Sigma hypernuclei have been sought, as have doubly-strange nuclei containing Cascade baryons.

Hypernuclei can be made by a nucleus capturing a Lambda or K meson and boiling off neutrons in a compound nuclear reaction, or, perhaps most easily, by the direct strangeness exchange reaction.

K + nucleus → π + hypernucleusA generalized mass formula developed for both the non-strange normal nuclei and strange hypernuclei can estimate masses of hypernuclei containing Lambda, Lambda-Lambda, Sigma, Cascade and Theta+ hyperon(s). The neutron and proton driplines for hypernuclei are predicted and existence of some exotic hypernuclei beyond the normal neutron and proton driplines are suggested. This generalized mass formula was named as "Samanta Formula" by Botvina and Pochodzalla and used to predict relative yields of hypernuclei in multifragmentation of nuclear spectator matter.Hypernuclei were first observed by their energetic but delayed decay, but have also been studied by measuring the momenta of the K and pi mesons in the direct strangeness exchange reactions.

Ishfaq Ahmad

Ishfaq Ahmad, D.Sc., Minister of State, SI, HI, NI, FPAS (3 November 1930 – 18 January 2018), was a Pakistani nuclear physicist, emeritus professor of high-energy physics at the National Center for Physics, and former science advisor to the Government of Pakistan.A versatile theoretical physicist, Ahmad made significant contributions in the theoretical development of the applications and concepts involving the particle physics, and its relative extension to the quantum electrodynamics, while working as senior research scientist at the CERN in 1960s and 1970s. Joining the PAEC in late 1950s, Ahmad served as the director of the Nuclear Physics Division at the secret Pinstech Institute which developed the first designs of atomic bombs, a clandestine project during the post-1971 war. There, he played an influential role in leading the physics and mathematical calculations in the critical mass of the weapons, and did theoretical work on the implosion method used in the weapons.Since 1960s and onwards, he has been a high-ranking official at the IAEA as part of the Pakistan Government's official mission, working to make the peaceful use of nuclear power for the industrial development. Having chaired the PAEC from 1991 until 2001, he has been affiliated with the Pakistan Government as a Science adviser to the Prime minister on strategic and scientific programs, with the status of Minister of State. A vehement supporter for the peaceful use of nuclear energy, he earned public and international fame in May 1998 when he oversaw and directed PAEC to perform country's first public atomic tests (see Chagai-I and Chagai-II) in a secret weapon-testing laboratories in Balochistan Province of Pakistan. He died on 18 January 2018, aged 87 in Lahore.

KMS Fusion

KMS Fusion was the only private sector company to pursue controlled thermonuclear fusion research using laser technology. Despite limited resources and numerous business problems KMS successfully demonstrated fusion from the Inertial Confinement Fusion (ICF) process. They achieved compression of a deuterium-tritium pellet from laser-energy in December 1973, and on May 1, 1974 carried out the world’s first successful laser-induced fusion. Neutron-sensitive nuclear emulsion detectors, developed by Nobel Prize winner Robert Hofstadter, were used to provide evidence of this discovery.

Lambda baryon

The Lambda baryons are a family of subatomic hadron particles containing one up quark, one down quark, and a third quark from a higher flavour generation, in a combination where the quantum wave function changes sign upon the flavour of any two quarks being swapped (thus differing from a Sigma baryon). They are thus baryons, with total isospin of 0, and have either neutral electric charge or the elementary charge +1.

Lambda baryons are usually represented by the symbols Λ0, Λ+c, Λ0b, and Λ+t. In this notation, the superscript character indicates whether the particle is electrically neutral (0) or caries a positive charge (+). The subscript character, or its absence, indicates whether the third quark is a strange quark (Λ0) (no subscript), a charm quark (Λ+c), a bottom quark (Λ0b), or a top quark (Λ+t). Physicists do not expect to observe a Lambda baryon with a top quark because the Standard Model of particle physics predicts that the mean lifetime of top quarks is roughly 5×10−25 seconds; that is about 1/20 of the mean timescale for strong interactions, which indicates that the top quark would decay before a Lambda baryon could form a hadron.

List of Super Proton Synchrotron experiments

This is a list of past and current experiments at the CERN Super Proton Synchrotron (SPS) facility since its commissioning in 1976. The SPS was used as the main particle collider for many experiments, and has been adapted to various purpose ever since its inception. Four locations were used for experiments, the North Area (NA experiments), West Area (WA experiments), Underground Area (UA experiments), and the Endcap MUon detectors (EMU experiments).

The UA1 and UA2 experiments famously detected the W and Z bosons in the early 1980s. Following this, Carlo Rubbia and Simon van der Meer won the 1984 Nobel Prize in Physics.The list is first compiled from the INSPIRE database, then missing information is retrieved from the online version CERN's Grey Book. The most specific information of the two is kept, e.g. if the INSPIRE database lists November 1974, while the Grey Book lists 22 November 1974, the Grey Book entry is shown. When there is a conflict between the INSPIRE database and the Grey Book, the INSPIRE database information is listed, unless otherwise noted.

List of neutrino experiments

This is a non-exhaustive list of neutrino experiments, neutrino detectors, and neutrino telescopes.

^[a] Accelerator neutrino (AC), Active galactic nuclei neutrino (AGN), Atmospheric neutrino (ATM), Cosmic ray neutrino (CR), Low-energy solar neutrino (LS), Low-energy supernova neutrino (LSN), Pulsar neutrino (PUL), Reactor neutrino (R), Solar neutrino (S), Supernova neutrino (SN), Terrestrial neutrino (T).^[b] Double beta decay (BB), Charged current (CC), Elastic scattering (ES), Neutral current (NC).

Marcello Conversi

Marcello Conversi (August 25, 1917 — September 22, 1988) was an Italian particle physicist. He is best known for his 1946 cosmic ray experiment where he showed that the "mesotron", now known as the muon, was not a strongly interacting particle.Conversi studied under Enrico Fermi at the University of Rome, and received his doctorate in 1940, doing his thesis under Bruno Ferretti. During World War II, Conversi remained in Italy, doing research and teaching at the University of Rome. Together with Oreste Piccioni and Ettore Pancini he conducted the experiment that Luis Walter Alvarez, Nobel Prize laureate of 1968, called the "start of modern particle physics" in his Nobel lecture. In 1946, they showed that the "mesotron", now known as the muon, which had been discovered in 1937 by Seth Neddermeyer and Carl David Anderson, was not the particle predicted by Hideki Yukawa as mediator of the strong force. If the "mesotron", a cosmic ray particle of negative charge, was indeed the meson postulated by Yukawa, it should be captured without decaying.

Conversi, Piccioni and Pancini moved their experiment to a high school to avoid air raids. In their experimental setup negative and positive particles were separated by large pieces of iron on the roof of the high school. The negative particles were absorbed in matter. After switching from iron to graphene absorbers, the 1946 experiment dramatically showed that the negatively charged component of cosmic rays decayed radioactive rather than being captured by the graphite.From 1947 to 1946 Conversi held a position as a post-doctoral fellow at the University of Chicago, before he returned to Italy as a Professor of Experimental Physics and Director of the Physics Institute at the University of Pisa. During his time in Pisa, he founded the Centro Studi Calcolatrici Elettroniche (CSCE), where the first Italian computer was built. For this work he received the gold medal of the President of Italy in 1961. He also developed a new track detector, known as the flash chamber — a precursor to the spark chamber — which went on to become the standard tool in particle and cosmic ray physics.

In 1958 he returned to the University of Rome, as a Professor of Advanced Physics. He had two appointments as director of the institute, one from 1960 to 1962 and the second from 1964 to 1966. His influential school, from 1950 at Pisa and from 1958 at Rome, produced many famous Italian particle physicists, such as Marcello Creti, Carlo Rubbia and Luigi Di Lella.From 1962 to 1964, and again from 1975 to 1977, Conversi was affiliated CERN. At CERN, Conversi was a member of the Scientific Committee from 1969 to 1975, becoming its Vice-President. From 1959, he participated in a series of quests at the Synchro-Cyclotron (CERN) for “forbidden” processes in weak interaction. When the new Super Proton Synchrotron began its operation in 1976 he played a prominent role in searches for short-lived particles using a stack of nuclear emulsion coupled to the BEBC bubble chamber.Conversi was vice president of Italian National Institute of Nuclear Physics from 1967 to 1970.He was a fellow of the American Physical Society since 1950 and a member of the Italian science academy.

Muography

Muography is an imaging technique that produces a projectional image of a target volume by recording elementary particles, called muons, either electronically or chemically with materials that are sensitive to charged particles such as nuclear emulsions. Cosmic rays from outer space generate muons in the Earth’s atmosphere as a result of nuclear reactions between primary cosmic rays and atmospheric nuclei. They are highly penetrative and millions of muons pass through our bodies every day.

Muography utilizes muons by tracking the number of muons that pass through the target volume to determine the density of the inaccessible internal structure. Muography is a technique similar in principle to radiography (imaging with X-rays) but capable of surveying much larger objects. Since muons are less likely to interact, stop and decay in low density matter than high density matter, a larger number of muons will travel through the low density regions of target objects in comparison to higher density regions. The apparatuses record the trajectory of each event to produce a muogram that displays the matrix of the resulting numbers of transmitted muons after they have passed through hectometer to kilometer-sized objects. The internal structure of the object, imaged in terms of density, is displayed by converting muograms to muographs.

OPERA experiment

The Oscillation Project with Emulsion-tRacking Apparatus (OPERA) was an instrument used in a scientific experiment for detecting tau neutrinos from muon neutrino oscillations. The experiment is a collaboration between CERN in Geneva, Switzerland, and the Laboratori Nazionali del Gran Sasso (LNGS) in Gran Sasso, Italy and uses the CERN Neutrinos to Gran Sasso (CNGS) neutrino beam.

The process started with protons from the Super Proton Synchrotron (SPS) at CERN being fired in pulses at a carbon target to produce pions and kaons. These particles decay to produce muons and neutrinos.The beam from CERN was stopped on 3 December 2012, ending data taking, but the analysis of the collected data has continued.

Photographic emulsion

Photographic emulsion is a light-sensitive colloid used in film-based photography. Most commonly, in silver-gelatin photography, it consists of silver halide crystals dispersed in gelatin. The emulsion is usually coated onto a substrate of glass, films (of cellulose nitrate, cellulose acetate or polyester), paper, or fabric.

Photographic emulsion is not a true emulsion, but a suspension of solid particles (silver halide) in a fluid (gelatin in solution). However, the word emulsion is customarily used in a photographic context. Gelatin or gum arabic layers sensitized with dichromate used in the dichromated colloid processes carbon and gum bichromate are sometimes called emulsions. Some processes do not have emulsions, such as platinum, cyanotype, salted paper, or kallitype.

Skyhook balloon

Skyhook balloons were high-altitude balloons developed by Otto C. Winzen and General Mills, Inc. They were used by the United States Navy Office of Naval Research (ONR) in the late 1940s and 1950s for atmospheric research, especially for constant-level meteorological observations at very high altitudes. Instruments like the Cherenkov detector were first used on Skyhook balloons.

Sulamith Goldhaber

Sulamith Goldhaber (November 4, 1923 – December 11, 1965) was a high-energy physicist and molecular spectroscopist. Goldhaber was a world expert on the interactions of K+ mesons with nucleons and made numerous discoveries relating to it.

Tracking (particle physics)

In particle physics, tracking is the process of reconstructing the trajectory (or track) of electrically charged particles in a particle detector known as a tracker. The particles entering such a tracker leave a precise record of their passage through the device, by interaction with suitably constructed components and materials. The presence of a calibrated magnetic field, in all or part of the tracker, allows the local momentum of the charged particle to be directly determined from the reconstructed local curvature of the trajectory for known (or assumed) electric charge of the particle.

Identification and reconstruction of trajectories from the digitised output of a modern tracker can, in the simplest cases, in the absence of a magnetic field and absorbing/scattering material, be achieved via straight-line segment fits. A simple helical model, to determine momentum in the presence of a magnetic field, might be sufficient in less simple cases, through to a complete (e.g.) Kalman Filter process, to provide a detailed reconstructed local model throughout the complete track in the most complex cases.This reconstruction of trajectory plus momentum allows projection to/through other detectors, which measure other important properties of the particle such as energy or particle type (Calorimeter, Cherenkov Detector). These reconstructed charged particles can be used to identify and reconstruct secondary decays, including those arising from 'unseen' neutral particles, as can be done for B-tagging (in experiments like CDF or at the LHC) and to fully reconstruct events (as in many current particle physics experiments, such as ATLAS, BaBar, Belle and CMS).

In particle physics there have been many devices used for tracking. These include cloud chambers (1920–1950), nuclear emulsion plates (1937–), bubble chambers (1952–) , spark chambers (1954-), multi wire proportional chambers (1968–) and drift chambers (1971–), including time projection chambers (1974–). With the advent of semiconductors plus modern photolithography, solid state trackers, also called silicon trackers (1980–), are used in experiments requiring compact, high-precision, fast-readout tracking; for example, close to the primary interaction point in a collider like the LHC.

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