How to build your own Alpha Particle Spark Detector : Introduction
Introduction:
I was introduced to alpha particle spark detectors when I watched a Youtube Video [1] by Carl Willis of his home made spark detector. I like the detector so much I wanted to build one for myself. So I researched the topic and read the seminal work from 1944 by W.Y. Chang and S. Rosenblum [2].
Overview:
The device is pretty simple. Take a thin tungsten wire, charge it to about 3000 volts with respect to ground. Position the wire approximately 1/16" (1.5 mm) above a smooth brass ground plate. The air acts like an insulator between the highly charged wire and ground plate.
When an alpha particle passes in between the wire and the electrode it ionizes the air between. The high voltage potential between the wires and the electrode, is triggered by the ionization of the alpha particle, which causes an electrical avalanche that we see as an electrical discharge (spark) between the wires and the electrode.
This detector is only sensitive to alpha (α) particles and will Not detect beta(β), x-ray or gamma(γ) radiation.
Our device operates on this same principle but there are a few changes. First I am using thinner copper wires (.003 diameter) that are held at ground potential. It is the metal plate that is charged to approximately 8000 volts. The wire is positioned approximately 0.1" (3mm) away from the metal plate.
Caution: This device uses a high voltage power supply and radioactive materials. Please follow the proper precautions.
The following is the parts list:
- (4) 3 KV capacitors Allied PN# 70016091
- (2) 6KV diodes Images PN# DI-6KV
- (1) 510 ohm 5W Allied PN# 70204781
- (1) Prototyping pcb Allied PN# 70219395
- (1) Adj HV power supply Images PN# HVT-07
- (1) Metal plate (see text)
- (1) .003 copper wire Images PN# CW.003
- Misc. 1/8" plastic, 22 ga. wire. copper foil tape.
Schematic and Board Cutout:
How to build your own Alpha Particle Spark Detector
Build Instructions:
Buy Images Alpha Particle Spark Detector, here
The following is a schematic of the alpha particle spark detector.
We begin by creating the holder for the .003 diameter copper wire. We start with a basic proto-typing board, shown below.
We mark the top side of the bard with a rectangle.
Cut out the rectangle.
Building The PC Board Detector:
How to build your own Alpha Particle Spark Detector
Build Instructions continued.
After board is cut,We can solder the .003 copper wire across the opening. I soldered five wires across the opening, approximately equally spaced.. One one side I soldered a 22 guage insulated wire that would connect the assembly to ground.
Next I obtained a 1/8" thick x 1" x 3/5" metal plate. To this I attached copper foil tape to make an electrical connection. Just about any metal can be used for this plate. You can also use copper clad PC board. The main criteria for the plate is that it doesn't flex or bend.
Testing The PC Board Detector:
How to build your own Alpha Particle Spark Detector
Build Instructions Conclusion.
You can purchase an off-the-shelf adjustable high voltage power supply suitable for this project. Using the power supply we wire up our components as detailed in the schematic, photo of set-up is shown below.
The metal plate has two 1/8" plastic squares next to it. The prototyping board rests on the plastic squares as shown. The wires are positioned approximately 0.1" above the metal plate.
Power is applied to the detector. There should not be any electrical discharge until an alpha particle shown is brought near the detector. If your detector immediately begins to arc, (have a discharge between the wires and plate) use the potentiometer on the adjustable power supply to reduce power. If that doesn't work, you need to increase the space between the wires and the plate. Also note, the .003 copper wires should be soldered taunt across the opening so that they do not droop down close to the plate.
PC Board Detector Bibliography & Supplier list:
How to build your own Alpha Particle Spark Detector
Tutorial Appendix
Parts Suppliers:
-
Allied Electronics
- alliedelec.com
- 866-433-5722
- (local distributor)
-
Images Scientific Instruments
- imagesco.com
- 718-966-3694
Bibliography:
- Carl Willis Youtube video
- "A simple Counting System for Alpha-Ray Spectra and the Energy Distribution of Po Alpha Particles"
W.Y. Chang and S.Rosenblum, Dec. 29, 1944 - "Charactistice of an alpha particle corona-streamer counter in air."
A.J. Tavendale, June 13, 1962 - "Counting Particles from Space."
Shawn Carlson Scientific American Feb, 2001 - "Spark Chamber Project: Step by Step procedure."
Andree Robichaud-Veronneau