Alpha Spark Detector
Author: Jay Howson
Date: September-2018
The Concept of an Alpha Spark Detector is simple; High voltage is applied between a thin wire or mesh grid and and parallel ground plane a few mm below it.
![](http://www.nuclearphysicslab.com/npl/wp-content/uploads/20191015_180348-1.jpg)
The voltage is set such that a breakdown does not occur. However, if an alpha particle ionizes the air between the grid and ground plane.
(an alpha particle will leave a trail of ionized particles as it collides with air molecules and sheds energy until coming to rest)
A break down (spark) will occur where that ionization took place, and only where the ionization took place. Giving a quality visual indicator that an alpha particle was present.
![](http://www.nuclearphysicslab.com/npl/wp-content/uploads/20191015_180528.jpg)
I find the device to be a very useful tool for demonstrating how far alpha particles can travel in air, and how they are easily stopped by thin materials like kitchen plastic wrap. I regularly use it to perform demos for kids, etc.
![](http://www.nuclearphysicslab.com/npl/wp-content/uploads/20191015_180541.jpg)