A modulated neutron initiator is a neutron source capable of producing a burst of neutrons on activation. It is a crucial part of some nuclear weapons, as its role is to "kick-start" the chain reaction at the optimal moment when the configuration is prompt critical. It is also known as an internal neutron initiator. The initiator is typically placed in the center of the plutonium pit, and is activated by impact of the converging shock wave.
One of the key elements in the proper operation of a nuclear weapon is initiation of the fission chain reaction at the proper time. To obtain a significant nuclear yield, sufficient neutrons must be present within the supercritical core at the right time. If the chain reaction starts too soon ("predetonation"), the result will be only a 'fizzle yield', well below the design specification. If it occurs too late, the core will have begun to expand and disassemble into a less-dense state, leading to a lowered yield (less of the core material undergoes fission) or no yield at all (the core is no longer a critical mass). Therefore, low spontaneous neutron emission of the pit material is crucial.
For boosted fission weapons, the size of the centrally placed initiator is critical and has to be as small as possible. The use of an external neutron source allows more flexibility, such as variable yields.
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A modulatedneutroninitiator is a neutron source capable of producing a burst of neutrons on activation. It is a crucial part of some nuclear weapons...
reliable. For example, sealed neutron tubes have replaced radioactive modulatedneutroninitiators, in supplying a pulse of neutrons to the imploding core of...
up initiator in Wiktionary, the free dictionary. An initiator can refer to: A person who instigates something. Modulatedneutroninitiator, a neutron source...
was 3.62 inches (92 mm) in diameter and contained an "Urchin" modulatedneutroninitiator that was 0.8 inches (20 mm) in diameter. The depleted uranium...
were ultimately responsible for creating the polonium-based modulatedneutroninitiators that were used to begin the chain reactions in the atomic bombs...
tamper was coated in a thin layer of boron. A polonium-beryllium modulatedneutroninitiator, known as an "urchin" because its shape resembled the inner shell...
tamper was coated in a thin layer of neutron-absorbing boron. A polonium-beryllium modulatedneutroninitiator, known as an "urchin", was developed to...
neutrons and α-particles created from a reaction in the neutron generator. The system records the temporal and spatial displacement of the neutrons and...
products needed to be conserved. Internal initiation, using a modulatedneutroninitiator, required Polonium-210 (210 Po), a highly radioactive element...
bomb's triggering mechanism, the Fuchs–Sherr polonium-beryllium modulatedneutroninitiator. On July 16, 1945, Sherr was present at the Trinity nuclear test...
of the uranium tamper, and in the design and adoption of the modulatedneutroninitiator. His presence boosted morale, and helped improve the administration...
to assemble. The short life of their lead-acid batteries and modulatedneutroninitiators, and the heat generated by the fissile cores, precluded storing...
gave Bohr credit for an important contribution to the work on modulatedneutroninitiators. "This device remained a stubborn puzzle," Oppenheimer noted...
member of the Manhattan Project, co-inventor of Fuchs-Sherr modulatedneutroninitiator. Sir Ian Sinclair, 87, British lawyer. Sabawi Ibrahim al-Tikriti...
radiation; and 4) the neutrons from the primary's nuclear detonation. The interstage is responsible for accurately modulating the transfer of energy...
maximum density, a burst of neutrons must be supplied to start the chain reaction. Early weapons used a modulatedneutron generator codenamed "Urchin"...
assemblies being sets of bomb components without the fissile pit or modulatedneutroninitiators. Uniforms were issued to Project Alberta's civilian personnel...
or particle accelerators during a supernova during the spin-down of a neutron star when cosmic rays or accelerated particle beams strike atoms The majority...
received a doctorate from the University of Vienna in 1971, with a thesis on "Neutron depolarization measurements on a Dy-single crystal" under Helmut Rauch...
molecular motors, etc. by modulating thermal neutrons into beams of slow neutrons. In combination with fissile materials, neutrons produced by ICF can potentially...
gamma radiation and a high efficiency neutron detector based on novel silicon technologies. The gamma and neutron detectors are integrated into a single...
according to their infrared and Raman activity. NEUTRON computes the phonon extinction rules in inelastic neutron scattering. Its results are also relevant...
uranium-235 (U-235) accounting for about 0.7%. U-238 has 146 neutrons and U-235 has 143 neutrons. Different isotopes have different behaviors. For instance...
brachytherapy, low energy X-rays, high-LET and proton therapy, boron capture neutron therapy and tissue inhomogeneities. A significant development in the field...
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