Proceedings of the Korean Society of Medical Physics Conference (한국의학물리학회:학술대회논문집)
- 2002.09a
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- Pages.275-278
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- 2002
Growth and Decay of Alpha Tracks in a Large Scale Cloud Chamber after Injection of Radon
- Wada, Shinichi (Dept. of Radiological Technology, Faculty of Medicine, Niigata University) ;
- Kobayashi, Tsuneo (Dept. of Physics, School of Medicine, Fukushima Medical University) ;
- Katayama, Yoshiro (ProTec Inc., Saitama) ;
- Iwami, Toshiaki (Niigata Kounan High School) ;
- Kato, Tsuguhisa (Tokyo Metropolitan University of Health Sciences) ;
- Cameron, John R. (Dept. of Medical Physics, University of Wisconsin-Madison)
- Published : 2002.09.01
Abstract
The recognition of the natural background radiation is important not only for radiological education but also for the promotion of people's scientific view about radiation. We made a "room" on the web showing natural background radiation as part of a VRM (Virtual Radiation Museum). The "room" shows the video images of the tracks of charged particles from natural background radiation, alpha and beta ray track from known sources using a Large Scale Diffusion Cloud Chamber. The purpose of this study is to make clear the origin of a kind of track (named A-track) which is thick and easy to recognize with the length less than several cm in the cloud chamber, and to make numerical explanation of its counting rate. The study was carried out using a Large Scale Diffusion Cloud Chamber (Phywe, Germany) installed in the Niigata Science Museum. The Model RNC (Pylon Electronics, Canada) was used as Rn-222 source. Ra-226 activity in RNC was 111.6 Bq calibrated with NIST protocol. Rn-222 gas was injected into the cloud chamber. Continuous video recording with use of Digital Handycam (SONY, Japan) was carried out for 360 min. after injection of Rn-222 gas. The number of alpha-ray track (alpha track) in the video images was analyzed. The growth and decay curve of the total activity of Rn-222 and its alpha emitting progeny were calculated and compared with the count of the alpha tracks. As a result the alpha tracks formed by Rn-222 injection resemble A-Tracks. The relationship between A-track in the cloud chamber and atmospheric Rn is discussed.