"All science is either physics or stamp collecting." - Ernest Rutherford
RadSense : Custom electronics to make radiation detection totally RAD!
Building a "semi-directional" radiation and/or cosmic-ray detector is not an easy feat. In vue of this I aimed to design, construct, and test a portable and versatile Silicon photo-diode Radiation Detector suitable for the 5keV-10MeV detection range to accurately quantify low energy gamma-rays emanating from radioactive sources. In this (long) Instructables, I'll first explain briefly some theoretical concepts underlying the operation of the detector and core properties. I'll then take you through the different tests undertaken and the relevant research investigated during the multiple design iterations.
So, how do we plan to detect the radiation? With semi-conductor radiation detectors! Or, more precisely, using photodiodes. We basically substitute Geiger Mueller tubes with PiN photodiodes to detect alpha and gamma radiation particles. Let's start with a little background science, before we go on to the construction :)
NOTE - pay attention if you don't want to become a radio-active zombie: With radiation sources precaution is key - it is not safe to be around sources of high radiation and this device should NOT, in any circumstances, be used as a reliable way of detecting harmful radiation in the environment.
Spark chambers, Geiger's, and Photo-multiplier tube detectors... etc all these types of detectors are either cumbersome, expensive, or use high-voltages to operate. There exist few maker friendly variations of the latter, including these: Sparkfun and Adafruit. There are other methods for detecting radiation, such as solid-state detectors, for example Germanium detectors. However these are also expensive to produce and require special equipment, such as liquid nitrogen cooling. On the contrary, solid-state detectors are very cost effective. They are widely used and play an important role in high-energy particle physics, medical physics and astro-physics.
My goal for this Instructables project was to design a portable solid-state radiation detector capable to accurately quantify low energy gamma-rays emanating from radioactive sources. The system consists of an array of reverse biased large surface area silicon PiN diodes, which output to a charge pre-amplifier, a differentiator amplifier, a discriminator, and a comparator. The output of all successive stages are converted to digital signals for analysis.
I start by describing the principles of silicon particle detectors, PiN diodes, reverse biasing and other important associated parameters. I then explain the different investigations that were conducted, and the choices made. At the end, introduce the final prototype and the tests I did.