Is our cloud chamber showing correct tracks from U-238 decay chain?

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In summary, the tracks seen in the cloud chamber project are likely beta and alpha tracks from the decays of Pb-210, Bi-210, and Po-210. These decays occur continuously and in equal amounts, but may vary in energy and range. The decay process is probabilistic and will continue until all atoms have decayed to stable nuclei. If the sample is not pure Pb-210, other isotopes may also contribute to the visible decays.
  • #1
Jr_Particle_Hunters
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Hi. We are using a Pb-210 needle source for our cloud chamber science project. Are we correct that the tracks we are seeing inside the chamber radiating off the needle are:

1) Beta tracks from Pb-210 decaying into Bi-210 (in the .063 MeV range)
2) Beta tracks from Bi-210 decaying into Po-210 (in the 1.1 MeV range)
3) Alpha tracks from Po-210 decaying into stable Pb-206 (in the 5.4 MeV range)

If that is correct, are the tracks being produced continuously and in equal amounts?

Also, does that mean the radioactive decay chain of U-238 starts happening from the very first moment of the U-238's existence and continues to happen without ever stopping until all the atoms become stable lead?

Thanks! We really appreciate your help.
 
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  • #2
Jr_Particle_Hunters said:
If that is correct, are the tracks being produced continuously and in equal amounts?
If you start with a pure Pb-210 source, initially you only have Pb-210 decays, with Bi-210 decays (half-life 5 days) quickly growing (within days to weeks) as the first atoms decayed to Bi-210. Po-210 has a half-life of 138 days, that needs longer until it reaches the same activity.

If you start with pure U-238, the same arguments apply, initially you don't get all decays in equal amounts, but after a while this is a very good approximation.

Nothing stops until everything decayed to stable nuclei.
 
  • #3
mfb said:
If you start with a pure Pb-210 source, initially you only have Pb-210 decays, with Bi-210 decays (half-life 5 days) quickly growing (within days to weeks) as the first atoms decayed to Bi-210. Po-210 has a half-life of 138 days, that needs longer until it reaches the same activity.

If you start with pure U-238, the same arguments apply, initially you don't get all decays in equal amounts, but after a while this is a very good approximation.

Nothing stops until everything decayed to stable nuclei.
Thank you for replying so quickly!

Based on what you wrote, so if we bought our needle from a company that used pure Pb-210 to coat the needle head, and we began our experiments about two weeks after receiving it, then we are likely seeing beta tracks from both the Pb-210 decay and Bi-210 decay in almost equal amounts?
(During our experiments, we noticed shorter, faint beta tracks that traveled off the needle, and we also noticed brighter betas that traveled as far as 8 inches off the needle. Is that possibly the two different beta decays, one having a higher MeV?)

Also, why do we see alpha tracks coming off the needle if Po-210 needs longer to decay?
 
  • #4
Jr_Particle_Hunters said:
Based on what you wrote, so if we bought our needle from a company that used pure Pb-210 to coat the needle head, and we began our experiments about two weeks after receiving it, then we are likely seeing beta tracks from both the Pb-210 decay and Bi-210 decay in almost equal amounts?
Within 15%, yes.
Jr_Particle_Hunters said:
(During our experiments, we noticed shorter, faint beta tracks that traveled off the needle, and we also noticed brighter betas that traveled as far as 8 inches off the needle. Is that possibly the two different beta decays, one having a higher MeV?)
The decay energy in a beta decay is distributed over the neutrino and the electron. The energies you listed are just the maximal electron energy, it can also be lower. In addition, the range of electrons can vary even for the same energy.
Jr_Particle_Hunters said:
Also, why do we see alpha tracks coming off the needle if Po-210 needs longer to decay?
The decay is a probabilistic process. You will see activity all the time, but it will be higher a year after you bought the sample.
Your sample won't be pure Pb-210, other isotopes can contribute to the visible decays.
 
  • #5
mfb said:
Within 15%, yes.The decay energy in a beta decay is distributed over the neutrino and the electron. The energies you listed are just the maximal electron energy, it can also be lower. In addition, the range of electrons can vary even for the same energy.
The decay is a probabilistic process. You will see activity all the time, but it will be higher a year after you bought the sample.
Your sample won't be pure Pb-210, other isotopes can contribute to the visible decays.

You rock! Thanks!
 

1. What is the U-238 decay chain?

The U-238 decay chain is a series of radioactive decays that occur in the element uranium-238, resulting in the formation of a stable isotope of lead. This decay chain is also known as the uranium series.

2. How does the U-238 decay chain work?

The U-238 decay chain starts with the decay of U-238 into thorium-234, followed by a series of alpha and beta decays until it reaches lead-206, which is a stable isotope. Each decay in the chain results in the formation of a new element with a smaller atomic number.

3. What are the products of the U-238 decay chain?

The products of the U-238 decay chain are a series of radioactive elements, including thorium, radium, radon, and polonium, before reaching the stable lead-206. These elements have varying half-lives, with some decaying quickly and others decaying over thousands of years.

4. How long does the U-238 decay chain take?

The U-238 decay chain has a half-life of about 4.47 billion years, which is the time it takes for half of the original amount of U-238 to decay into other elements. This means it can take billions of years for all the U-238 to decay completely.

5. What are the uses of the U-238 decay chain?

The U-238 decay chain has several practical applications, including nuclear power generation, radiometric dating, and medical treatments. It is also used in scientific research to study the behavior of radioactive materials and their effects on the environment.

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