How do scientists make a neutrino beam? It's a three-step process.
The processs start by extracting a proton beam from an accelerator complex and smashing the protons into a target. The protons' interactions with the protons and neutrons in the target material produce new, short-lived particles such as pions and kaons. These particles travel a short distance (about 200 m) through a "decay pipe," and as they do, a good fraction of them decays into neutrinos that continue on in the same direction, forming a neutrino beam. Of the three known neutrino types, a beam produced in this manner contains mostly muon neutrinos.
Using Fermilab's Main Injector accelerator as a proton source, the proposed Long-Baseline Neutrino Experiment (LBNE) Beamline will be able to make the highest-intensity neutrino beam in the world – i.e., with the highest concentration of neutrinos.
Like the beam of light produced by a flashlight, the beam of neutrinos produced by an accelerator widens over distance. To make sure that a sufficiently large number of neutrinos hits the particle detector, located hundreds of miles away, the beam must be highly concentrated, highly focused and aimed precisely in the right direction. Because neutrinos have no electric charge, there is no way to change the direction of a neutrino once it has been created.
The Proton Improvement Plan-II (PIP-II), a proposed facility for Fermilab that would significantly increase the number of protons the Main Injector could supply, would provide increased intensity for LBNE's neutrino beam. The schedule for building PIP-II is expected to be later than that for LBNE, therefore LBNE will need to undergo an upgrade to higher beam power part-way through its operational lifetime.