How to work the Geiger counter?

[Halo]

Tomorrow I am going to measure how well different material is stopping beta and gamma radiation. I have not done this before, so what I need to know is, how do you use a Geiger counter? Do you simply plug it in or do you have to adjust something on it first?

 

I would appreciate any help.

 

Thanks in advance!

[Schrödinger's hat]

Tomorrow I am going to measure how well different material is stopping beta and gamma radiation. I have not done this before, so what I need to know is, how do you use a Geiger counter? Do you simply plug it in or do you have to adjust something on it first?

 

I would appreciate any help.

 

Thanks in advance!

 

Typically you have one or more buttons or knobs to adjust the sensitivity (related to the voltage across the tube).

It's important not to set this too high for a variety of reasons.

The first is you can damage the device by setting it too high and exposing it to radiation.

The second is that it will become less accurate. Just after the counter discharges, there is a short time where it cannot discharge again.

You can compensate for this somewhat by reducing the number of events detected (reduce the voltage/sensitivity). To get a really good result, you should use statistics to estimate the number of events that you missed in this dead time.

Another source of error that you will have to consider is background radiation.

 

If you know some basic calculus it will also be useful to think about this equation [math] \frac{dy}{dx} = -\alpha y[/math], how it leads to [math]y=e^{-\alpha x}[/math] and how it could come from a constant proportion of the remaining y being removed with any change in x (ie. something being absorbed as it moves through a material).

Edited March 1, 2012 by Schrödinger's hat