pmt definitions

• Activity

  The rate at which an unstable nucleus decays
• Alpha Particle

  A positively charged particle consisting of two protons and two neutrons
• Atomic Number


  The number of protons found in an atom of a specific element
• Background Radiation


  Radiation that is found in small quantities all around us and originates from natural sources such as rocks and cosmic rays, as well as from man-made sources such as nuclear weapons testing and accidents
• Becquerel


  The unit of radioactive activity
• Beta Particle


  A high speed electron that a nucleus emits when a neutron converts into a proton
• Bohr Model

  A model of the atom that suggested that electrons orbit the nucleus at set distances
• Chain Reaction

  The process of neutrons released by a fission reaction, being absorbed by another unstable, large nuclei, and inducing further fission
• Count-Rate


  The number of decays that a detector measures per second
• Electrons

  A negatively charged constituent of the atom, that are found in different energy levels, around the nucleus
• Energy Levels

  The stable states in which electrons are found in around a nucleus. Electrons can transition to a higher energy level through the absorption of electromagnetic radiation and can transition to a lower energy level through the emission of electromagnetic radiation
• Fission Products


  Fission produces two smaller nuclei, two or three neutrons and gamma rays. All these products are released with kinetic energy
• Gamma Ray


  Electromagnetic radiation emitted from a nucleus
• Geiger-Muller Tube


  A detector that measures the count-rate of a radioactive sample
• Half-Life


  The time it takes for the number of unstable nuclei of an isotope in a sample to halve, or the time it takes for the initial count rate of a sample of the isotope to halve
• Ions

  Atoms with a resultant charge due to the loss or gain of electrons
• Irradiation


  The process of an object being exposed to nuclear radiation. The object doesn't become radioactive
• Isotopes

  Atoms with the same number of protons but different numbers of neutrons. The atomic number is the same, but the mass number is different
• Mass Number


  The number of protons and neutrons in an atom
• Negative Ions

  Atoms that gained electrons and so have a resultant negative charge
• Neutrons


  A neutrally charged constituent of the nucleus
• Nuclear Explosions

  Nuclear explosions in nuclear weapons are caused by an uncontrolled chain reaction which results in vast quantities of energy being produced in a very small period of time
• Nuclear Fission


  The splitting of a large and unstable nucleus into two smaller and more stable nuclei to produce energy
• Nuclear Fusion

  The joining of two small, light nuclei to form a larger, heavier one and release energy
• Nucleus

  The positively charged centre of an atom, containing protons and neutrons
• Plum Pudding Model


  An old model of the atom that represented the atom as a ball of positive charge, with negative charges distributed throughout it
• Positive Ions


  Atoms that have lost electrons and so have a resultant positive charge
• Protons

  A positively charged constituent of the nucleus
• Radioactive Contamination

  The unwanted presence of radioactive atoms on other materials. It is hazardous due to the decay of the contaminating atoms
• Radioactive Decay

  The random process involving unstable nuclei emitting radiation to become more stable
• Sieverts


  The unit used for radiation dosage
• Spontaneous Fission

  Fission that occurs without the absorption of a neutron. Spontaneous fission is rare and in most cases, fission is induced with a neutron