Neutron detection

Neutron detectors serve to demonstrate the measurement of the flux density and the spectroscopy of free neutrons ( radiation monitoring, basic research in nuclear physics and solid state physics (including neutron scattering) ). Since neutrons act itself non-ionizing, it must be proved via scattering on nuclei or nuclear reactions in which ionizing radiation is produced.

Fast neutrons

Slow neutrons

Slow, particularly thermal neutrons are detected by appropriate nuclear reactions with large cross sections, such as 10B ( n ) 7Li, 6Li (n, ) 3H or 3He ( n, p) 3H. The reaction substance can be used in gaseous form or as a wall layer in ionization chambers or counter tubes or as part of a scintillator, such as boron trifluoride counter tubes, boron ionization chambers, scintillators of lithium iodide ( LiI ) or lithium-containing glass with enriched Li -6 Li.

For monitoring the neutron flux in the nuclear reactor, the neutron-induced fission of U235 in the gap chambers ( ionization chambers, in which an electrode is coated with enriched uranium ) is used.

Gap chambers, which permanently remains in the reactor core (such as the power distribution detectors in boiling water reactors ), would be unusable by the combustion within 3-4 years. Therefore, a coating of 234U is used with a low proportion of 235U here now. Thus, the splitting losses are continuously offset by Incubation of new 235U through neutron capture and the detector can be used over 10 years without deterioration of measurement accuracy.

For slow neutrons and the detection of neutron activation of suitable material samples by means of ( n ) reactions is possible, as its cross section is large at low energy neutrons.

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