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Operatio

Neutron generators primarily utilize deuterium-tritium (DT) fusion reactions to produce neutrons, which are more efficient than deuterium-deuterium (DD) reactions due to higher yield. The design involves accelerating ions into a hydride target, with the neutron emission being slightly anisotropic due to momentum conservation. Neutron tubes offer higher neutron fluxes and controllable production rates compared to radionuclide sources.

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11 views2 pages

Operatio

Neutron generators primarily utilize deuterium-tritium (DT) fusion reactions to produce neutrons, which are more efficient than deuterium-deuterium (DD) reactions due to higher yield. The design involves accelerating ions into a hydride target, with the neutron emission being slightly anisotropic due to momentum conservation. Neutron tubes offer higher neutron fluxes and controllable production rates compared to radionuclide sources.

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© © All Rights Reserved
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Neutron generator theory and operation

[edit]

Small neutron generators using the deuterium (D, hydrogen-2, 2H) tritium (T, hydrogen-3, 3H) fusion
reactions are the most common accelerator based (as opposed to radioactive isotopes) neutron
sources. In these systems, neutrons are produced by creating ions of deuterium, tritium, or deuterium
and tritium and accelerating these into a hydride target loaded with deuterium, or deuterium and
tritium. The DT reaction is used more than the DD reaction because the yield of the DT reaction is 50–
100 times higher than that of the DD reaction.

2 P + 2 N = 17.7 MeV [19,34 MeV - 1,626 MeV]

D + T → n + 4He En = 14.1 MeV

D + D -> p + Positron + 3 x Gamma = 2.5 MeV

high beginning energy: 11,4 MeV : D + D → p + Positron + 2 Gamma + 3He

En = 13.91 MeV is right. -> sum: ca. 2.5 MeV

Calculation: 6,8 MeV [Proton-> Hypoproton]+ 1,26*1,45 +1,26*0,42 [2,11] MeV [Hyperneutron ->
Neutron] + ~ 2x 2.5 [5] MeV [Hyperneutron-> Hyperproton] 2x HN Deuterium + high energie => 3 He +
Proton + Positron + 2 x Gamma

Neutrons produced by DD and DT reactions are emitted somewhat anisotropically from the target,
slightly biased in the forward (in the axis of the ion beam) direction. The anisotropy of the neutron
emission from DD and DT reactions arises from the fact the reactions are isotropic in the center of
momentum coordinate system (COM) but this isotropy is lost in the transformation from the COM
coordinate system to the laboratory frame of reference. In both frames of reference, the He nuclei
recoil in the opposite direction to the emitted neutron consistent with the law of conservation of
momentum.

The gas pressure in the ion source region of the neutron tubes generally ranges between 0.1 and
0.01 mm Hg. The mean free path of electrons must be shorter than the discharge space to achieve
ionization (lower limit for pressure) while the pressure must be kept low enough to avoid formation of
discharges at the high extraction voltages applied between the electrodes. The pressure in the
accelerating region, however, has to be much lower, as the mean free path of electrons must be longer
to prevent formation of a discharge between the high voltage electrodes.[2]

The ion accelerator usually consists of several electrodes with cylindrical symmetry, acting as an einzel
lens. The ion beam can thus be focused to a small point at the target. The accelerators typically require
power supplies of 100–500 kV. They usually have several stages, with voltage between the stages not
exceeding 200 kV to prevent field emission.[2]

In comparison with radionuclide neutron sources, neutron tubes can produce much higher neutron
fluxes and consistent (monochromatic) neutron energy spectra can be obtained. The neutron
production rate can also be controlled.[2]

Sealed neutron tubes


[edit]

The central part of a neutron generator is the particle accelerator itself,

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