Jie's Introduction

Temperature is a factor in every part of our lives; everything that we do is affected by it. All the effects of temperature that we experience are due to the cumulative effects of the energies of trillions of particles. The temperatures that we experience everyday are due to the consequence of the average thermal energies of millions and billions of particles working together. The thermal energy of a single particle is very different from average energies. Statistical physics predicts the probability variation of temperature to be an exponential curve; with many particles with small energies and very few particles with large amounts of energy. This information can be used to measure single particles. It is easier to measure the particles with the more energy. This experiment uses a Silicon Photomultiplier (SiPM) to detect the thermal energy of the particles with the most energy. An SiPM uses the technology previously employed in the Avalanche Photodiode. A diode is reverse-biased until just before breakdown voltage and it stays at that state until a source of energy (such as thermal energy) pushes it past breakdown. It then releases all of its charge and then slowly resets. An SiPM is different in that it uses an array of many Avalanche Photodiodes are made into a silicon wafer. The photodiodes are so small that they can be counted as individual pixels. Therefore, an SiPM can determine how many particles have enough energy to set it off. Every time a photodiode fires, a current runs though the SiPM. By measuring the energy released by the SiPM, the number of individual particles which have enough energy to set off the SiPM can be determined. (Calibration should be in the Methods and Materials?) An SiPM was calibrated using electromagnetic energy instead of thermal energy because electromagnetic energy is easier to control. A dark box was set up with a LED at one end and the SiPM in another. Since each photon that hit the SiPM reliably produced an effective pulse, it was possible to calculate the number of pixels fired. This made it possible to calculate the amount of energy released if a single pixel was fired.

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