A photoelectric tube includes a housing including a light transmitting portion, an electron emitting portion held by a recess provided in the housing, the electron emitting portion including a concave photoelectric surface facing a light transmitting portion side inside the housing, and an electron capturing portion disposed between the light transmitting portion and the photoelectric surface inside the housing. At least a part of the electron capturing portion is located inside a region on an inside of the photoelectric surface.

A system for equalizing a pressure in an ionization chamber of a radiation device is provided. The system may include the ionization chamber including: a chamber housing including one or more chamber walls; a chamber volume inside the chamber housing, the chamber volume being filled with a radiation sensitive material; and a pressure adjustment apparatus operably coupled to the chamber volume via at least one wall of the one or more chamber walls, the pressure adjustment apparatus being configured to equalize a first pressure of the radiation sensitive material inside the chamber volume and a second pressure of ambient air outside the chamber housing.

A system for equalizing a pressure in an ionization chamber of a radiation device is provided. The system may include the ionization chamber including: a chamber housing including one or more chamber walls; a chamber volume inside the chamber housing, the chamber volume being filled with a radiation sensitive material; and a pressure adjustment apparatus operably coupled to the chamber volume via at least one wall of the one or more chamber walls, the pressure adjustment apparatus being configured to equalize a first pressure of the radiation sensitive material inside the chamber volume and a second pressure of ambient air outside the chamber housing.

Methods of detecting high atomic weight materials in a volume such as a truck or cargo container are disclosed. The volume is scanned with an X-ray imaging system and a muon detection system. Using the output data of the muon detection system, the exit momentum and incoming and outgoing tracks of each muon are reconstructed. A muon scattering statistical model is calculated using the muon exit momentum and the incoming and outgoing tracks of the muon. A most likely scattering density map is determined according to the muon-scattering statistical model and an X-ray statistical model. A visual representation of the most likely scattering density map is displayed.

A fissile neutron detection system includes a neutron moderator and a neutron detector disposed proximate such that a majority of the surface area of the neutron moderator is disposed proximate the neutron detector. Fissile neutrons impinge upon and enter the neutron moderator where the energy level of the fissile neutron is reduced to that of a thermal neutron. The thermal neutron may exit the moderator in any direction. Maximizing the surface area of the neutron moderator that is proximate the neutron detector beneficially improves the reliability and accuracy of the fissile neutron detection system by increasing the percentage of thermal neutrons that exit the neutron moderator and enter the neutron detector.

A fissile neutron detection system includes a neutron moderator and a neutron detector disposed proximate such that a majority of the surface area of the neutron moderator is disposed proximate the neutron detector. Fissile neutrons impinge upon and enter the neutron moderator where the energy level of the fissile neutron is reduced to that of a thermal neutron. The thermal neutron may exit the moderator in any direction. Maximizing the surface area of the neutron moderator that is proximate the neutron detector beneficially improves the reliability and accuracy of the fissile neutron detection system by increasing the percentage of thermal neutrons that exit the neutron moderator and enter the neutron detector.

An apparatus for measuring radon and thoron using an ionization chamber is proposed. The apparatus includes: a pump for air inflow suctioning and sending external air to at least one channel; a first sensor module outputting an alpha particle detection signal of an electrical signal by detecting alpha (?) particles discharged from radon and thoron; an air inflow delay module delaying air for a predetermined delay time and then outputting the air; a second sensor module outputting an alpha particle detection signal of an electrical signal by detecting alpha (?) particles discharged from radon and thoron; and a control module discriminating normal or abnormal alpha particle detection signals, counting the normal alpha particle detection signals discriminated for a predetermined measurement time, and calculating radioactive ray concentration values on the basis of the counted number of times of the normal alpha particle detection signals.

A fissile neutron detection system includes a neutron moderator and a neutron detector disposed proximate such that a majority of the surface area of the neutron moderator is disposed proximate the neutron detector. Fissile neutrons impinge upon and enter the neutron moderator where the energy level of the fissile neutron is reduced to that of a thermal neutron. The thermal neutron may exit the moderator in any direction. Maximizing the surface area of the neutron moderator that is proximate the neutron detector beneficially improves the reliability and accuracy of the fissile neutron detection system by increasing the percentage of thermal neutrons that exit the neutron moderator and enter the neutron detector.

A fissile neutron detection system includes a neutron moderator and a neutron detector disposed proximate such that a majority of the surface area of the neutron moderator is disposed proximate the neutron detector. Fissile neutrons impinge upon and enter the neutron moderator where the energy level of the fissile neutron is reduced to that of a thermal neutron. The thermal neutron may exit the moderator in any direction. Maximizing the surface area of the neutron moderator that is proximate the neutron detector beneficially improves the reliability and accuracy of the fissile neutron detection system by increasing the percentage of thermal neutrons that exit the neutron moderator and enter the neutron detector.

A narrow thermal neutron detector includes a slidably receivable ionization thermal neutron detector module within an overall housing body. An active sheet layer of the ionization thermal neutron detector module can be tensioned across its width. The ionization thermal neutron detector module can include module upper major surface extents and module lower surface extents such that, when installed within the housing body, the module upper major surface extents are in a first spaced apart confronting relationship with housing upper major surface extents to define a first clearance and module lower major surface extents are in a second spaced apart confronting relationship with housing lower major surface extents to define a second clearance to accommodate housing flexing due to ambient pressure change. The housing body can be formed with a single opening for receiving the ionization thermal neutron detection module or with opposing first and second opposing end openings.