Experiments with MoNa “ Dude…Cool Beams”

1. Experiments with MoNa“Dude…Cool Beams” What is MoNA, and how does it work? All of our experiments involve MoNA (Modular Neutron Array). It is a plastic detector, called a scintillator, that is mostly used to detect neutrons. As neutrons are not electrically charged, it is difficult to “see” them (they have no electrical interaction with other atoms). However, when a neutron hits a nucleus of the matter in the detector, the positively charged nucleus moves and becomes excited. To lose the energy it gained, the nucleus releases photons, which can be detected by photomultipliers (PMT) at both extremities of MoNA’s plastic bars. Team Francica- (L to R) Katie Borowicz Juliette Buet, Hunter Nisonoff, Lawton Tellin MoNA Experiment #1 Purpose: To determine the position of a radioactive source using MoNA. How? As light has to travel through the detector to reach the photomultipliers on either end, you can use the differences in time and energy between the two signals coming from each end to determine where the neutrons hit the bar. The two signals are shown on the oscilloscope screen. However, to determine the position of an unknown source, we first have to make a calibration. The radioactive source is placed in the middle of the bar, so it should take the same time for the light to go to both left and right photomultipliers. We then put the radioactive source at different places along MoNA and take a few values for each position (about 5) so that our data will be more accurate. Neutron detection in a MoNA bar Oscilloscope Experiment #2 Purpose: Same as experiment #1, but using a computer program called SpecTcl which is much more accurate than an oscilloscope. The most difficult step was to become comfortable with the very technical software. This time, all the calculations were done by the computer (time difference and the center of the energy peak) and we calculated the estimate error of our data. This calculation, however, was only partly done by the computer, using the integrated area under the peak. Experiment #3 Purpose: using MoNA, we tried to measure the angle at which cosmic ray particles, called muons, arrived at the detector and their velocity inside MoNA.  How? The rays have a lot of energy and cross all of the MoNA bars. To measure the angle, we only use the position at which the muon hits the top and bottom bars and find out the angle thanks to trigonometry. Measuring the velocity was done simply by using the formula distance over time. Screenshot of data of experiment 2