[2P01-29] Poster session

[2P16] Measurement of the mean free path of dilute gases utilizing the principle of a Pirani vacuum gauge: a theme for undergraduate student laboratory experiments

*Yusuke Suetsugu^1,2 (1. High Energy Accelerator Research Organization (Japan), 2. Nihon University (Japan))

This presentation proposes a cost-effective, time-efficient undergraduate laboratory experiment to measure the mean free path of gas molecules using the principle of a Pirani vacuum gauge. While vacuum science is crucial for engineering students, traditional laboratory courses are limited by high equipment costs and time constraints. The proposed setup features a thin tungsten filament in a cylindrical pipe heated by an external power source. Using a Wheatstone bridge and a Raspberry Pi-based data acquisition system, we observe how the filament's temperature shifts with pressure. The total heat transfer rate plotted against the log of pressure forms an S-shaped curve, transitioning from the pressure-independent viscous flow regime to the linearly proportional molecular flow regime. The mean free path at this transition pressure is estimated from the curve's inflection point, where it approximately equals the filament's diameter. This setup helps students learn vacuum technology, the kinetic theory of gases, and computer-aided measurements.

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