Instruments
Status: Operational
Location: S2 vault (Spring 2025)
Contact person: Thomas Baumann
Overview
This pair of detector arrays consists of a total of 288 bars of plastic scintillator. Each of these bars measures 10 cm by 10 cm and 2 m wide. The bars are typically stacked to form two walls that are each 2 m wide and 1.6 m high, but due to its modularity, the array can be configured in other ways as well. The ends of each detector bar are equipped with photo-multipliers that are able to detect the faint scintillation light and amplify it with a gain of one to three million. The detection efficiency for neutrons with energies up to 100 MeV is about 70 percent. These photo-multipliers also measure when the light arrives very precisely, so the position of the light emission along the bar can be determined within a few centimeters by measuring the time difference of the signals at the left and the right end. This time difference has to be known to within 250 picoseconds.
With the precise timing information, we also can calculate the velocity of the neutrons. We place a start detector before the reaction target—where the neutron is still part of the rare isotope—and use MoNA-LISA as a time-of-flight detector. The neutrons travel a distance of about 10 m in less than 100 nanoseconds. The sweeper magnet that is placed between the target and MoNA-LISA deflects all charged particles; otherwise they would interfere with the measurement of the neutrons.
The Modular Neutron Array and Large Multi-Institutional Scintillator Array (MoNA-LISA) is an efficient detector for high-energy neutrons. It is operated by a collaboration between Augustana College, Central Michigan University, Davidson College, Gettysburg College, Hampton University, Hope College, Indiana University at South Bend, Indiana Wesleyan University, Michigan State University, Ohio Wesleyan University, St. John’s College, and Wabash College.
Funding acknowledgement: The Modular Neutron Array and the Large Multi-Institutional Scintillator Array were each funded by NSF through separate MRI grants to the participating institutions. For MoNA, this includes: NSF-PHY 0132434, 0132405, 0132532, 0132507, 0132567, 0132367, 0132438, 0132725, and 0132641. For LISA, this includes: NSF-PHY 0922794, 0922409, 0922462, 0922559, 0922622, 0922473, 0922446, 0922537, and 0922335.
