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Reactors as Neutrino source

Neutrinos are produced by $\beta$ decay in fission fragments, so the energy of the neutrinos is below 10 Mev. A good knowledge of the reactor parameters is needed to obtain the neutrino flux emitted by a reactor. The energy spectrum and the flux of the $\nu$ produced by a reactor have been carefully measured above 2 Mev using detectors close to the reactor core. In the inverse $\beta$ decay reaction on proton (threshold 1.8 Mev): $\bar \nu_{e} + p \longrightarrow e^{+} + n $ the neutrino energy is deduced from the e+ energy. The experimental accuracy on the neutrino flux is $ 1.4\%$ to be compared with $2.7\%$ on the expected flux. Below 2 Mev the $\bar\nu_e$ spectrum can only be calculated. Uncertainties from the contribution of the neutron capture in fission fragments have been calculated recently. This is important for experiments searching for neutrino magnetic moment effect in neutrino electron elastic scattering. Many sites have been used around the world, but few are still in operation for neutrino studies. Laboratories which are close to the reactor core are now used to measure very low cross section processes (neutrino electron or neutrino deuteron scattering). In these experiments the value of the $\nu$ flux (reactor power) is more important than the overburden. The search for $\nu$ oscillation imposes now long baseline experiments: the overburden and the reactor power are significant. Comparisons between available sites are shown in table [*].
 
Table:
Parameters of the available neutrino sites near reactors 
 
  Bugey
France
Rovno
Ukraine
Krasnoyarsk
Siberia
Chooz
France
Palo Verde
Arizona
P(Mwth) 2800 1375 1600 8400 10900
$\delta$P(Mwth) 2800 1375 1600 4200 3630
Distance (m) 18 18 18, 34, 300 1100 740-850
overburden (mwe) 40 80 1000 300 46
 
 


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