Neutrino factories

Neutrinos are produced by many processes in our universe. These elusive particles reach the earth having a certain energy permitting them to react with nuclei in detectors that are specifically designed to probe their properties. However, to get higher intensities and higher energy neutrinos for better statistics and better physics reach, the use of accelerators is necessary to advance in the field of neutrino research. To produce neutrinos with an accelerator, one needs to send a high power beam onto a target to get particles or isotopes that produce neutrinos with the required properties, by decay. The parent particles have to be collected and prepared for injection into an accelerating structure. Accelerator-based experiments can tune the energy of the produced neutrinos by boosting and controlling the energy of the parent particle. The produced neutrinos will travel the distance between the source and the detector, generally through earth; the distance the neutrino travels through earth, the energy of the neutrino as well as the flavor of the neutrino give important information on their interaction with matter. The position of the physics detector is coupled to the energy of the neutrino, since the neutrino oscillation length varies inversely with the energy. The position of the detector is chosen depending on what kind of physics is being explored. “Short Baseline” experiments (a few km between the target and the detector) need beam powers up to a few hundred kW and longer baseline experiments, having detectors at from a few hundred up to thousands of km, need beam power on target reaching the MW range. “Next Generation” facilities will go up to many MW. Longer baseline experiments address physics related to oscillations of active neutrinos, while short baseline facilities do research related to the search for neutrinos not yet observed, so called sterile neutrinos. Getting the sensitivities needed for physics today translates to beampower on target reaching up to 5 MW for some of the proposed facilities. The potential of the neutrino beam can be enhanced by accelerating and storing the parent particles in a decay ring. In the case where muons are used for neutrino production, the pions produced in the target are collected and focused into a decay pipe behind the target, where they decay into muons. Challenging cooling and phase space manipulations of the muons make injection of the muon beam into the accelerator chain possible. Then follows acceleration up to the energy of a storage ring, and the neutrino useful for physics is produced in long straight sections directed to the physics detector. Alternatively, beta active isotopes produced in a target can be collected in an ion source, accelerated and stored in a race track decay ring where beta decay gives neutrinos aimed at the experiment.