inverse beta decay
Fissions are taking place inside every nuclear power plant. For each fission, there are approximately 6 anti-neutrinos emitted. The concrete protecting the reactors cannot keep the anti-neutrinos inside. Most of them will travel at almost the speed of light for all directions.
Our detector will be a large tank of liquid organic compound which is proton-rich, to increase the chance of having an anti-neutrino reacting. Hopefully, the anti-neutrino will get tired and spend some time with our proton such that an inverse beta decay will take place. When this process is initiated, a positron and a neutron will come out as the primary products.
The liquid organic compound inside our detector has another two main functions, namely scintillation and neutron capture. For the first one, the compound will emit optical photons when an ionizing particle passes through, giving a prompt signal. The neutron will be captured and again optical photons will be given out by the compound, giving a delayed signal. Because of the characteristic time delay, using this physical process can help to discriminate most of the background. All information are carried by the optical photons which could be detected by a dedicated device, the photomultiplier tubes.
Using our knowledge in Physics and Statistics, the original anti-neutrino event could be reconstructed!