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LET has therefore no meaning when applied to photons. However, many authors speak of "gamma LET" anyway, [6] where they are actually referring to the LET of the secondary electrons, i.e., mainly Compton electrons, produced by the gamma radiation. [7] The secondary electrons will ionize far more atoms than the primary photon. This gamma LET has ...
Heavy ion therapy (e.g. carbon ions) makes use of the similarly high LET of 12 C 6+ ions. [5] [6] Because of the high LET, the relative radiation damage (relative biological effect or RBE) of fast neutrons is 4 times that of X-rays, [7] [8] meaning 1 rad of fast neutrons is equal to 4 rads of X-rays. The RBE of neutrons is also energy dependent ...
Neutron radiation is a form of ionizing radiation that presents as free neutrons.Typical phenomena are nuclear fission or nuclear fusion causing the release of free neutrons, which then react with nuclei of other atoms to form new nuclides—which, in turn, may trigger further neutron radiation.
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.
2. High-LET protons, produced by the scattering of fast neutrons and from the capture of thermal neutrons by nitrogen atoms [14 N(n,p) 14 C]; and 3. High-LET, heavier charged alpha particles (stripped down helium [4 He] nuclei) and lithium-7 ions, released as products of the thermal neutron capture and decay reactions with 10 B [10 B(n,α) 7 Li].
They are named 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: Nuclear fission: thermal fission of 235 U produces neutrons with a mean energy of 2 MeV (200 TJ/kg, i.e. 20,000 km/s), [11] which qualifies as ...
High-LET radiation at doses that are below 0.5 Gy show greater relative biological effectiveness compared to low-LET radiation. [63] The acute effects on the CNS, which are associated with increases in cytokines and chemokines, may lead to disruption in the proliferation of stem cells or memory loss that may contribute to other degenerative ...
These neutrons are sometimes emitted with a delay, giving them the term delayed neutrons, but the actual delay in their production is a delay waiting for the beta decay of fission products to produce the excited-state nuclear precursors that immediately undergo prompt neutron emission. Thus, the delay in neutron emission is not from the neutron ...