Can this diagram make any sense? [counts of alpha decay]

In summary, you are trying to determine the effective distance for a chamber containing a radioactive isotope, based on pressure readings. You are having trouble converting pressure readings into an effective distance.
  • #1
MortalWombat
4
0
Hello all you physics folks,

this is my first post, so if I screw this up, go easy on me :)

Here's the problem I'm working on and that I simply can't get my head wrapped around:

I have a table of 10 values of counts per second (cps) of alpha decay of Americium-241, depending on the pressure ##p## inside a chamber, where at a distance of ##x_0 = 6## cm a detector is mounted.

I have to plot the cps...but not against the pressure, but a distance corresponding to that pressure at normal pressure levels (##p = 1 bar##). I am to use Boyle-Marriots law
$$
p \cdot V = p \cdot A \cdot x = const.
$$

Since the cross-section of the chamber ##A## can be considered constant, we have
$$
p \cdot x = const.
$$

But this means that for decreasing pressure the distances get longer (that makes sense), but when I plot ##p_i## vs ##x_i##, I get an increasing cps count for longer distances, which is pretty much the opposite of what we'd want...any idea where I made a mistake here? Do I have to modify the cps counts in any way?

EDIT: my bad, I wanted to post a screenshot of my current graph
http://imgur.com/vegvPSu
 
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  • #2
So what is the meaning of that x in the equation?
How do you change the pressure in the chamber? You have a piston that you move in the chamber?
 
  • #3
MortalWombat said:
But this means that for decreasing pressure the distances get longer (that makes sense), but when I plot ##p_i## vs ##x_i##, I get an increasing cps count for longer distances

You mean you plot pressure "p" vs effective distance "x"... where do the counts per second appear in such a plot? Isn't this just a plot of y=A/x, for some constant A?
 
  • #4
let's see.
You have a chamber with a radioactive isotope, and a detector at a set distance.
With increasing pressure in the chamber , you count the number of detections.

I imagine that the number of detections should vary inversely with the pressure. Is that what happens?

Then you want to plot the number of detections, versus an effective distance, with regards to pressure.

Your problem is how to convert the pressure into an effective distance?

Since, by increasing the pressure, the density of the gas also increases, and thereby the number of gas particles the radiation has a chance of encountering also increase.
Would not the effective distance would then just be Px/Po times Xo, where Po and Xo are the base values at 1 bar, and Px is the values of the prescribed pressure readings.
Or have I interpreted the experiment incorrectly.
 
  • #5
256bits said:
let's see.
You have a chamber with a radioactive isotope, and a detector at a set distance.
With increasing pressure in the chamber , you count the number of detections.

I imagine that the number of detections should vary inversely with the pressure. Is that what happens?

Then you want to plot the number of detections, versus an effective distance, with regards to pressure.

Your problem is how to convert the pressure into an effective distance?

Since, by increasing the pressure, the density of the gas also increases, and thereby the number of gas particles the radiation has a chance of encountering also increase.
Would not the effective distance would then just be Px/Po times Xo, where Po and Xo are the base values at 1 bar, and Px is the values of the prescribed pressure readings.
Or have I interpreted the experiment incorrectly.

Yep, that's pretty much it. I figured it out yesterday night, the plot now looks like this
0faisWG.png


So after a short distance nearly all alpha particles are absorbed or stopped by air molecules, and then the counts are pretty much 0 for higher distances.
 
  • #6
Excellent.
 

FAQ: Can this diagram make any sense? [counts of alpha decay]

What is alpha decay?

Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle, which consists of two protons and two neutrons. This process results in a decrease in the atomic number by two and the atomic mass by four.

How can a diagram represent alpha decay?

A diagram can represent alpha decay by showing the initial atomic nucleus, the emitted alpha particle, and the resulting daughter nucleus. The arrows in the diagram indicate the movement of particles and the change in atomic number and mass.

What does the count of alpha decay mean?

The count of alpha decay refers to the number of alpha particles that are emitted from a radioactive material over a certain period of time. This count can be used to determine the rate of decay and the half-life of the material.

Can the diagram predict the exact timing of alpha decay?

No, the diagram cannot predict the exact timing of alpha decay. The process of alpha decay is random and cannot be accurately predicted. However, the diagram can show the probability of alpha decay occurring over a certain period of time.

How does the diagram help in understanding alpha decay?

The diagram helps in understanding alpha decay by visually representing the process and its effects on the atomic nucleus. It also allows for the comparison of different radioactive materials and their rates of alpha decay. Additionally, the diagram can be used to explain the concept of half-life and the stability of nuclear isotopes.

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