Design PPM Instrument for STEM Teaching Aid in Exploring Nuclear Physics Topic

Experiments on nuclear physics with precise measurements are exciting things to do. The experiment supports the STEM approach based on real experiments and especially if it is low-cost equipment. In this study, a preliminary study was conducted on the proton precession magnetometer (PPM) design, which will be used as a teaching aid for STEM learning to explore the atomic nucleus and as a magnetometer to determine the strength of the earth's magnetic field accurately. The PPM signal is susceptible to changes in the external magnetic field so that external magnetic disturbances such as electric currents and ferromagnetic materials in the building produce noise. So the measurements are carried out outside the building. The sensor uses two coils that are polarized opposite each other to eliminate the noise from the outside. In addition, analog filtering is also designed in a bandpass filter only to pass the desired frequency range. Since the PPM signal is tiny, the coil is coupled with a suitable capacitor to amplify the signal radiated by the protons through an inductor-capacitor resonance effect at the desired target frequency. Signal PPM measurement results in the time domain can be displayed, although visually, it is difficult to recognize because it is immersed in noise. However, when heard with the human ear, the distinctive sound of the PPM signal will be clear for about 3 seconds after applying polarizing current to the coil. Waves in the time domain can be converted into the frequency domain using audacity 3.0.2 software. The peak frequency obtained is 1914 Hz. Based on the values of these frequencies, based on the Larmor formula, the value of the earth's magnetic field obtained is 44.97 uT.