3 - First attempts: an alpha spark detector

A project log for Open Radiation Detector

Quickly identify radioactive materials with a pocket-sized ion chamber. Built from standard parts for easy manufacture and low cost.

Carlos Garcia SauraCarlos Garcia Saura 10/04/2017 at 17:210 Comments

Today I want to share my first attempt at building a spark particle detector.

Spark detectors consist on a strip of wires parallel to a high voltage plane. A strong electric field is created, and every time a high energy particle ionizes the air between the electrodes, it causes an avalanche effect and a spark appears.

From my ignorance as a novice in the field, I initially thought that the most important part of spark detectors were the parallel cables. So I went ahead and designed a circuit board with a "finger electrode" with a flat arrangement. A prototype was quickly made using a Cyclone PCB Factory:

The next video shows the ""spark detector"" in action. The high voltage was generated using the flyback circuit from a document scanner, and was fed into the electrode through a protection resistance of several megohms.

First time on, the circuit was already creating very promising spikes!

Unfortunately, it was too good to be true. The sparks observed were NOT due to background radiation. This became evident after bringing a radiation source (from a smoke sensor) near the detector and seeing no change in activity at all.

Among the many reasons for failure were the small and non-homogeneous electric field and tiny ionization volume. The randomness of the sparks seems to arise from local changes in humidity: every time a spark occurs, it dries the air around it and reduces the chance of a spark happening in the same spot.

So this prototype was left behind as an anecdotal, tiny light show. In the next updates we will show the newer designs that actually work as a radiation detector. Be sure to follow the project to stay tuned.

And thanks for reading! Have you ever tinkered with spark particle detectors? Share your experience and comments below!