Can beta radiation be detected in an expansion cloud chamber?

In summary, the beta source does not produce any visible ionization, whereas the alpha source produces many visible tracks.
  • #1
CloudChamber
29
1
Hello all,
I just built an expansion cloud chamber and noted that while my alpha source (americium 241) produced a plethora of tracks, the beta source (strontium 90) produced no tracks at all-just mist. Does anyone know if beta radiation can be seen in an expansion type cloud chamber? Why or why not? Details would be great!
Thanks
 
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  • #2
I'm no expert but alpha particles consist two protons and two neutrons while a beta particle is simply a single electron (or positron). That is, an alpha particle is much heavier than a beta particle and so carries more energy at low speeds.
 
  • #3
so you're saying that a beta particle wouldn't have enough energy to ionize the air molecules in a cloud chamber traveling at such a slow speed, whereas an alpha particle would?
 
  • #4
The alpha particles are very heavily ionizing particles, all of which have the same initial energy. So all of the tracks are about the same length. The ionization density of the track in the cloud chamber is high because the alpha particles are slow, and the charge is high (2 protons). (Track ionization density is proportional to Z2)

The beta decay process involves the emission of both an electron and a (anti)neutrino. which share the energy of the decay of strontium 90 (and yttrium 90). So the energy of the betas ranges from 0 energy up to the maximum energy (about 2.28 MeV). Furthermore, because the betas are relativistic, the track ionization density is low. The energy of many of the betas is so high that they do not stop in the cloud chamber.
 
  • #5
Let's step back a bit. What is the activity of each source?
 
  • #6
Strontium 90 is around 140 Ci/g; americium 241 is 3.5 Ci/g.
 
  • #7
I would think that 10 visible tracks per sec might be about right, so maybe 1000 dps into 4 π. 1000 dps = 0.03 μCi. If you are interested in researching this more, look at http://pdg.lbl.gov/2011/reviews/rpp2011-rev-passage-particles-matter.pdf, especially the plot of stopping power on page 4. The beta particles are near the minimum (about 2 MeV per gram per cm2), while the alpha particles are near the peak on the left (x4 because Z=2).
 
  • #8
Yes, and how many grams of each do you have?
 
  • #9
I'm not quite so sure... I took the americium 241 out of a smoke detector, so I'd assume there would be 2.0 times 10^-4 mg, the standard amount in scientific notation. As for the strontium, I have no idea. The website, however, says the activity level of the strontium 90 source is .1uCi.
 
  • #10
Wow, looks like a great source, Bob S. I haven't really started looking through it yet, but I took a quick glance and it seems that restricted energy loss rates actually result in less visible ionization. Any quick explanations for why this is?
 
  • #11
Typical smoke detectors are 1 or 2 uCi. That's 10-20x the activity of your beta source.
 
  • #12
Ah, I see. Without that variable controlled its hard to make generalizations.
 

Related to Can beta radiation be detected in an expansion cloud chamber?

What is the difference between alpha and beta radiation?

Alpha and beta radiation are both forms of ionizing radiation, meaning they have enough energy to remove electrons from atoms. The main difference between them is their composition and ability to penetrate materials. Alpha radiation consists of two protons and two neutrons, and is relatively large and heavy, therefore it can only travel a short distance through air and can be easily stopped by a sheet of paper. Beta radiation, on the other hand, consists of high-speed electrons and can travel further through air and can be stopped by a sheet of aluminum.

Which type of radiation is more dangerous to humans?

Alpha radiation is generally considered more dangerous to humans because it is more likely to cause damage to living tissue. This is because alpha particles have a higher mass and charge than beta particles, making them more likely to interact with and damage cells in the body. However, the level of danger depends on the amount and duration of exposure to the radiation.

How do alpha and beta radiation affect the environment?

Both alpha and beta radiation can affect the environment by causing damage to plants, animals, and ecosystems. They can also contaminate soil and water sources, leading to harmful effects on the environment and potential health risks for humans and other living organisms. However, the extent of the impact depends on the amount and type of radiation released and the distance from the source.

What are some common sources of alpha and beta radiation?

Alpha and beta radiation can come from both natural and man-made sources. Some common sources of alpha radiation include radon gas, uranium, and radium. Beta radiation can come from sources such as strontium-90, cesium-137, and tritium. These radioactive elements can be found in various materials, including rocks, soil, and nuclear waste.

How can we protect ourselves from alpha and beta radiation?

The best way to protect ourselves from alpha and beta radiation is to minimize exposure and follow safety measures. This can include avoiding close contact with radioactive materials, using protective gear when handling them, and staying away from areas with high levels of radiation. In addition, following proper disposal procedures for radioactive waste can help prevent exposure to these types of radiation.

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