C.T.R.威尔逊制作的膨胀型云雾室是世界上最早的带电粒子径迹探测器之一，但其具有灵敏时间短、不能连续工作的缺陷. 而扩散型云雾室可以连续工作，它通过热端将酒精加热转化为蒸气，酒精蒸气扩散到冷端后冷却形成过饱和蒸气，从而使得通过过饱和蒸气的带电粒子径迹可以在强光照射下被观察到. 本工作根据其工作原理设计并制作了扩散型云雾室，在云室内部无放射源的情况下观察到了质子、β 射线和宇宙射线的径迹; 在放置一般烟雾报警器的241Am α 放射源的情况下，观察到了α 粒子径迹. 根据拍摄到的视频以及测量的几何数据，估计了该241Am 放射源的放射性活度.

The expansion cloud chamber，invented by C. T. R. Wilson，is the earliest charged particle detectorin the world. It is effective，and yet the conditions for operation are not continuously maintained. Hence the diffusion cloud chamber is developed. The diffusion cloud chamber is continuously sensitized to radiation. A diffusion cloud chamber is designed and made according to its principle. With an Am-241 α radiation source ( from a smoke detector) put inside the cloud chamber，the tracks of α-particles are observed. In addition，the tracks of protons，β particles and cosmic rays are observed as well. The radioactive activity of the source is estimated based on the video footage and the geometry data acquired.