1. M. R. Evanger a M. Rajabali a, R. E. Turner a, B. Luther a, T. Baumann c, Y. Lu b, M. Thoennessen b,c, E. Tryggestad c a Concordia College, Moorhead, MN b Michigan State University, East Lansing, MI c National Superconducting Cyclotron Laboratory, East Lansing, MI Neutron Testing of the Micro-Modular Neutron Array M. R. Evanger a, M. Rajabali a, R. E. Turner a, B. Luther a, T. Baumann c, Y. Lu b, M. Thoennessen b,c, E. Tryggestad c a Concordia College, Moorhead, MN b Michigan State University, East Lansing, MI c National Superconducting Cyclotron Laboratory, East Lansing, MI ABSTRACT Eight of the 144 detector modules composing the Modular Neutron Array (MoNA), a large- area neutron detector, were placed in a beam of intermediate energy neutrons produced from a 155 MeV/u 36 Ar beam striking a 1 cm Al target at the National Superconducting Cyclotron Laboratory. Micro-MoNA (  MoNA), the eight-module set-up, was arranged in two vertically stacked horizontal planes of four modules placed 5 m from the Al target. Each module consisted of a 200 x 10 x 10 cm 3 bar of BC-408 plastic scintillator with photomultiplier tubes mounted on each end. Two 1 cm plastic scintillator veto bars were placed in front of each horizontal plane. Tests were conducted with and without a shadow bar. MoNA is designed to measure the energy and position of neutrons. The energy is deduced from neutron's time-of-flight relative to a start detector. The position is calculated from the time difference between the two photomultiplier tubes (PMTs) at each end. This first neutron energy spectrum measured with  MoNA as well as the position resolution of the detectors are presented here. This work supported in part by grants from the National Science Foundation. Centimeters/channel: 1.87 Calculated Shadow: 11.8 channels = 21.69 cm SETUP ELECTRONICS 45 cm206.6 cm 475 cm 35.5 cm 14.5 cm START DETECTOR ALUMINUM TARGET BRASS SHADOW BAR BRASS SHADOW BAR DIMENSIONS 7.65 cm 27.40 cm 5.10 cm EIGHT MoNA BARS BEAM DIRECTION VETO BARS  MoNA SETUP Horizontal Position of Bar 7, No Shadow Bar (no veto) Horizontal Position of Bar 7, With Shadow Bar (no veto) CHARACTERISTIC PMT ENERGY DEPOSITION SPECTRA [No veto is applied. Spectra are shown for corresponding PMTs on a MoNA bar. PMT 11 and PMT 15 are on bar 7 (front bar), PMT 10 and PMT 14 are on bar 6 (directly behind bar 7).] PMT 11 PMT 15 NEUTRON TIME-OF-FLIGHT SPECTRA The neutron energy is deduced from the measured time-of-flight relative to the start detector. HORIZONTAL POSITION RESOLUTION TIME-OF-FLIGHT FOR BAR 7 (without veto) RENDERING OF COMPLETE MoNA MoNA The 155 MeV/u 36 Ar beam impinges the Aluminum target and produces neutrons and charged particles. When the brass bar is placed in the production cone a shadow is formed on the MoNA bars, where no particles are detected. Using the shadow bar’s measurements, the shadow dimensions can be calculated and compared with actual data, and the position resolution of the MoNA bars can be determined. © T. Baumann 2001 SUMMARY PMT 10 PMT 14 MoNA will be a large-area neutron detector located at the NSCL. MoNA will have a frontal area of 160 x 200 cm 2.  MoNA tests were conducted to determine if the MoNA bars detected neutrons properly and to find horizontal position resolution, energy deposition, and neutron energy. A more detailed description of MoNA can be found on poster 5P1.071, P.J. Van Wylen et. al., in this session. The eight MoNA bars used for the  MoNA setup were placed behind two 112 x 10 x 1 cm 3 veto bars, that did not cover the entire length of the 200 cm bars. 4 5 6 7 0 1 2 3 TIME-OF-FLIGHT FOR BAR 7 (with veto)  MoNA showed that MoNA bars successfully detect neutrons. The horizontal position resolution of the MoNA bars was found to be no greater than 7.5 cm FWHM.  MoNA showed that energy deposition and neutron energy can be effectively measured with the MoNA bars. Thirty-two MoNA bars were assembled and tested at the NSCL. 4 channel difference = 7.5 cm FWHM