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Target Systems

Target System efficiently converts the intense proton beam into a focused neutrino beam or muon beam aimed at the detectors. TSD maintains the operation of high-intensity target system facilities, currently NuMI, BNB, and Muon g-2.

NuMI target system

  • The protons are steered into a solid carbon target to produce mesons through hadronic interactions - predominantly pions.
  • The pions are then focused by pulsed toroidal magnets called horns into the decay pipe. A horn is a coaxial, transmission-line magnet with an air gap between the conductors. The inner conductor is hollow and have parabolic profile, such that it allows momentum selection of the pions throgh focusing.
  • The pions decay to muons and muon-neutrinos in the helium filled decay volume.
  • The Hadron Monitor measures the spatial distribution of the uninteracted protons and undecayed pions, after which they are stopped in the Hadron Absorber which is a mass of steel, concrete and aluminum.
  • The muons penetrate the absorber and continue into unexcavated rock, where they range out over a distance. The spatial distributions of muons are measured at Muon Monitor stations.
  • The neutrino beam is largely unaffected by the rock, and propagate in straight lines to the experimental detectors.
​BNB target station

The Booster accelerates protons to 8 GeV, and then sends the protons down the neutrino beamline. The protons hit a beryllium target situated inside a magnetic focusing horn. The mesons are produced. Positively charged mesons are focused, pass through a collimator, and then enter a 50 m long decay volume where they decay to neutrinos or absobed by the beam absorber at the end of the decay volume.

​Muon g-2 target system

The production target station consists of five main devices: the pion production target, the lithium lens, a collimator, a pulsed magnet, and a beam dump.

  • Fermilab's accelerators smash bunches of protons into a fixed Inconel target, creating different types of particles;
  • The shower of secondary particles are focused by a pulsed high current lithium lens that can produce up to 1000 T/m gradient;
  • Downstream of the lens is a pulsed dipole magnet (PMAG), which steers the positive pions into the muon transfer line/delivery ring where the pions decay into muons;
  • Upstream of the pulsed magnet is a Collimator, to provide radiation shielding to the pulsed magnet to improve its longevity;
  • Particles that are not momentum-selected will continue forward and are absorbed into the beam dump.