Annex A - Group Science Proposal

Topic was changed later; this is the research proposal for the first project that our group did(An investigation of the particles in a cloud chamber).
Names: Bryan Chang Ding Lun, Walter Koh Li Zhi, Kopparthi Sandeep, Sean Michael Koh
Class: S2-07
Group Reference: F

1.    Indicate the type of research that you are adopting:

[ ] Test a hypothesis: Hypothesis-driven research

[ ] Measure a value: Experimental research (I)

[ ] Measure a function or relationship: Experimental research (II)

[ ] Construct a model: Theoretical sciences and applied mathematics

[ X  ] Observational and exploratory research

[ ] Improve a product or process: Industrial and applied research

Title :                                                                                                                                                                 
An investigation of the particles in a cloud chamber

A.    Question being addressed

We, Group F of S207, wish to have a greater understanding of the concept of particle decay and radiation. Hence we have decided to use a cloud chamber/Wilson chamber to investigate this phenomenon.
The Wilson chamber is a sealed environment that contains a supersaturated vapour(usually water or alcohol). This supersaturated vapour is a vapour that lacks the condensation nuclei that it needs to condense. These condensation nuclei are provided when the radioactive material(Americium-241) undergoes particle decay.
Decay mode
Product of Decay
432.7 a
2.14·106 a
27.0 d
1.592·105 a
7340 a
14.9 d
10.0 d
4.8 min
32 ms
β 97.80%
α 2.20%
46.5 min
3.72 μs
2.2 min
3.25 h
1.9·1019 a
Table 1.

Firstly, radioactive particles are particles that are unstable. This instability is caused by the excess energy the particle has due to the ratio between it’s protons and it’s neutrons. Since all particles want to be more stable or be in their lowest energy state. Hence, these particles will decay into more stable forms by losing protons, neutrons, electrons or just

This loss of particles is known as Radiation. There are 3 types of radiation. Alpha, Beta and Gamma radiation. Alpha radiation is an ionizing radiation that consists of Alpha particles which are 2 Protons and 2 Neutrons, a form of helium. While Beta radiation is another type of radiation which consists of Beta particles, they are either electrons and positrons. Gamma radiation, which is not going to be thoroughly explored in this experiment is just energy. Our radiation source, Americium-241, will undergo Alpha,
Beta  and Gamma decay as seen in Table 1.

                                                                                       Figure 2.
An alpha particle as mentioned earlier, has a charge of +2, and a mass of 4. They are relatively slow and heavy and they have a low penetrating power as shown in Figure 4.  Since alpha particles have a large charge,  they ionise other atoms strongly.
A beta particle has a charge of -1 and it’s mass is about 1/2000th of a proton. Thus, beta particles are the same as an electron. Compared to alpha particles, beta particles are faster and lighter.  They have a medium penetrating power, as shown in Figure 4 and they ionise atoms as they move along. However, their process of ionisation is not as strong as that of the alpha particles.
A gamma ray , as the name suggests is a ray, which can be thought of as a burst of energy. They are waves, unlike the above mentioned forms of radiation, which are particles. They have a high penetration power, as seen in Figure 4. It needs a thick material, such as lead to reduce them significantly.  They do not ionise other atoms directly. However, they do cause other atoms to emit other particles, which will result in ionisation.  Gamma rays are emitted along with alpha and beta particles.
Figure 4

Of course, the question naturally arises: If atomic particles are so small we can’t use our senses to detect them, how do we know they are there? By inference. Humankind learned long ago that the input of the senses can be flawed. Optical, olfactory and tactile illusions abound. So to discover these miniscule particles. Humans have learned to look at the secondary effects and infer their causes. The concept was well captured by the venerated scientist Ernest Rutherford in the advice he gave to   James Chadwick when Chadwick was looking for evidence for the neutron. Rutherford advised,                                                              
                                                                                                                                                  Fig 5.           
“How could you find the Invisible Man in Piccadilly Circus? ...By the reactions of those he pushed aside.”(Lennard Bickel, 1979)

In the decay chain(term used to describe the chain of decay of a particle until it becomes stable) of Americium-241, it undergoes both Alpha and Beta decay. In order to connect this information to the Wilson chamber, one understand the effects of the Alpha and Beta particles on the alcohol. In the sealed environment of the Wilson Chamber, the supersaturated gas(Alcohol) becomes ionized upon coming in contact with the Alpha or Beta particles. These ionized particles serve as condensation nuclei. Hence, there will be condensed alcohol on the path where the Alpha/Beta particles were. This allows us to track the path of the Alpha/Beta particles.

It is important to take note is that the cloud chamber can detect cosmic radiation which is created when subatomic particles that originate from different galaxies and the Sun interact with the Earth’s atmosphere.

There are a variety of cosmic rays such as:

-  Galactic Cosmic Rays
- Come from outside the Solar System
-  Anomalous Cosmic Rays
- Come from the interstellar space at the edge of the heliospace

- Solar Energetic particles
- Associated with solar flares and other energetic solar flares

Figure 5. Path of Cosmic Radiation taken by other studies

It is easy to see that the cosmic radiation goes in a circular motion which can and should be used to tell the cosmic radiation and Alpha/Beta paths apart.

There are several radioactive materials in the world. However, for this experiment, we are specifically using Americium-241 for several reasons :
  • Americium has a long half life (432.7 years)
  • Easily accessible - Can be found in a variety of industrial equipment including smoke detectors which we are using for our experiment
  • The degree of harm from the radiation exposure, alpha particles of the smoke detectors is only considered to be very minimal
The cloud chamber that we are using for the experiment.

B.    Variables


  • Presence of a magnet
- Having the Neodymium magnets above the cloud chamber vs having it above a wooden table
  • The type of particles in the cloud chamber
- Alpha particles vs Beta particles
  • The radioactive source’s decay chain
- Table 1 states that there should be more Alpha than Beta particles
  • Location of the radioactive material (Americium-241)
- On top of the cloud chamber vs 50cm away from the cloud chamber


  • Curve of the tracks
  • Thickness of each track
  • Movement of the particles
  • Curve of the tracks
  • Thickness of each kind of track
  • Movement of the particles
  • Amount of Alpha and Beta tracks
  • Curve of the tracks
  • Thickness of the tracks
  • Movement of the particles
  • Amount of radiation detected by the GM counter

  • The size of the plastic container
  • Radiation source used
  • Amount of alcohol in the cloud chamber
  • Type of alcohol used
  • Type of felt used
  • Location of the experiment

B.    Hypotheses

1. A magnetic field will affect the path of the Alpha and Beta particles because Alpha carry a positive charge and Beta particles carry a negative charge. Hence, we hypothesize the Beta particles will move towards the positive pole and the Alpha particles will curve towards the Negative pole.
2. Alpha particles are hypothesized to have a thicker path than Beta particles. Since Alpha particles steal 2 electrons, ionizing the surrounding particles while Beta particles create a thin line through bouncing off the particles in a cloud chamber, this is hypothesized.
3. We hypothesized that there would be more Alpha than Beta particles in a period of 10s in a specific area.  This is due to the fact that there is more Alpha than Beta decay in the decay chain shown above

Decay mode
Product of Decay
432.7 a
2.14·106 a
27.0 d

4. We hypothesize that there would be more Alpha and Beta particles in the cloud chamber when the cloud chamber is directly next to the radiation source rather than 20cm away from it

C.    Description in detail of method or procedures


1 Metric Tape Measure
1 Room that can be dimmed
1 Pair of Scissors
1 Box of Disposable Glove
1 Hammer
1 Nipper
1 Ionizing smoke detector (Must contain Americium)
1 Tweezer
500g of Dry Ice
40ml of Rubbing Alcohol
1 Eye dropper
4 pairs of Safety Goggles
Gloves to handle Americium
High Speed Camera
1 Neodymium Magnet
GM Counter

Lab Coats



Cloud Chamber

This is the cloud chamber when it is taken apart. As you can see, the cloud chamber consists of three parts : The plastic container with felt inside, a wire strip that has LEDs attached on it and a wooden container with a black metal piece at the bottom.
Inside the wooden box is a black cardboard where dry ice is put inside to allow the alcohol to evaporate. One safety precaution of the black metal piece is that there is a string on the left hand side of the metal piece which can be pulled up so that the black piece does not need to be lifted by hand, thus reducing the risk of getting in contact with the dry ice, which can cause frostbite.
The wire strip shown here is to be put on the outside of the plastic container. On the yellow portion of the wire, there is a circuit board which houses a few LEDs in it to enable the observation of the movement of the particles during the experiment. At the end there is a red and black wire which has a crocodile clip at the end to be attached to either a power source or battery.
The last part of the cloud chamber is a plastic container with blue felt inside. The blue felt is there is absorb the propanol, or in our experiment we used alcohol. The radiation source, in this case the smoke detector, is to be placed under the plastic container. A problem is that the plastic container had a few holes on the different sides of the container which would lead to some of the alcohol escaping from the container while evaporating. However, this will not affect the experiment on a major scale so it is alright to leave it so.

Preparation of the Cloud Chamber

1. Prepare the black background of the cloud chamber. A black background will allow easier observation.
a) Cut a circle out of the black construction paper that will fit neatly inside the bottom of the plastic container.
b) Place the black circle in the petri dish.
2. Create the piece of felt that will cover the inside perimeter of the plastic container. The felt will be made to cover the perimeter in two layers to make sure it can hold enough alcohol to keep the chamber permeated with alcohol vapor for some time.
a)Measure the perimeter of the plastic container.
b) Cut out a rectangular strip of felt measuring the perimeter of the plastic container long by the height of the plastic container wide.
c)Put the felt inside the plastic container so that it covers the inner side, going around the inside perimeter. String the felt in order to hold it up.
3. Place the lid on the petri dish and the cloud chamber is ready for the experiment.
4.Enter an environment that can be made dark and away from any heat source. Bringing in all the other items required. It is important to have everything ready, as the steps need to be performed within a limited time frame.
5. Put the insulating gloves and glasses or goggles on to handle the dry ice.
6. Place the dry ice on the baking dish and crush the ice to small pieces with a hammer.
        a) The goal is to form a nice bed of tiny pieces of dry ice for the petri dish. Put the dry ice under the black surface.
7. Take the insulating gloves off and put on the original disposable gloves.
8. Using the eyedropper, soak the felt with the isopropyl alcohol.
9. Quickly place the radiation source inside the cloud chamber and put the lid on top (Step 9 has to be performed quickly after step 8 to trap the alcohol vapors in the chamber.)
10. Hold the cloud chamber between two hands to warm it up for a minute or two. The warmth from the hands will cause the isopropyl alcohol to evaporate and create a vapor that permeates the chamber. The vapor cannot  be see — it will only be apparent when it condenses into microscopic droplets, forming a mist.
10. Turn off the lights and/or darken the workroom and light up the cloud chamber with the LED lights.

11. Wait a few minutes. As the cloud chamber cools, it creates the conditions for a supersaturated vapor. By now, a very thin fog of alcohol vapor might be visible in the cloud chamber. Soon, tracks of condensation formed on ions left by radioactive decay particles passing through the chamber should be visible.

12. Reposition to a different spot. Observe at the 9 or 3 o'clock position.

13. If everything is in order as stated above, then the individual testing can begin.

Test 1:
1. Wait for there to be visible streaks in the cloud chamber and then hold a Neodymium magnet directly above the chamber and observe the results
2. Remove the magnet.
3. Record and observe the cloud chamber.

Test 2:
1. Observe the movement of the particles and record the movement and the shape of size and shape of the lines to detect the number of each type of lines

Test 3:
1. Measure out an area for the observation of the particles
2. When the experiment starts, record the number of alpha and beta particles within the cloud chamber by noting their differences (Alpha particles have thicker lines compared to beta particles)

Test 4:
1. Place the radioactive source 6cm away from one breadth.
2. When the streaks start to from, wait for 10 seconds and record down the number of alpha and beta particles in a 5cm radius.
3. When the time is over, immediately move the radioactive source to the other side.
4. Repeat step 2.

If the the tracks are too faint or there is not enough alcohol
17. When tracks become faint, re-warm the chamber in between hands. Every time the dish is re-warm, it will take a couple of minutes to create the conditions in the chamber for tracks to be visible. After a couple of re-warmings, there will not be enough alcohol left in the cloud chamber to form vapor.
18. Repeat steps 3 through 14 of the section titled “Preparing the cloud chamber” but skip step 9.

20. When finished with both parts of this experiment, dispose of the gloves in a normal garbage can.
21. Safely store the radioactive source or dispose of it in normal garbage

D:    Risk Assessment
The risk level of the different dangers is measured on a scale of 1 to 25. It is found by multiplying the possibility of the danger occurring (1 to 5) and the effect of the danger (1 to 5).

Prospective risks
Who is Affected by this risk?
On hand control measures
Risk rating
Defensive measures
Getting hands in contact with the rubbing alcohol/ethanol
People who forget to wear
Medication, etc
Constant reminders
Rubbing hands, mouth when handling alcohol
People who rub their hands and mouth
Washing of body parts touched
Constant reminders
Possible radiation from the americium
People who come into contact with radioactive material.
Thick gloves
Handling dry ice without gloves, causing frostbite
Users who handle dry ice
Use tongs to handle them
Keeping some tongs ready
Those in charge of the dry ice
Smelling alcohol during experiment
Users of alcohol
Do experiment in film cupboard in chemistry lab.
Exercise self control, proper ventilation
Getting electrocuted by the power source
Handlers of the electrical items
Keep a minimum distance from the power source
Wear gloves when handling the power source
Get hand clipped between the crocodile clips, causing bleeding and possible infection
Handler of the power source
Do not play a fool and make sure there is no one around you when handling the clips
Wear gloves that are thick
Handler of crocodile clips

Data analysis:
Using our camera, we can observe the streaks in the cloud chamber thoroughly and conclude how Neodymium magnets affect the path of the particles as shown in previous research done.
With Neodymium magnets
With wooden table

Since we know that Alpha and Beta particles curve with the presence of Neodymium magnets, we can use that knowledge to figure out which streaks are Alpha particles and Beta particles. Hence we can conclude how difference the thickness of the streaks are affected whether it was due to an Alpha or Beta particles.
Alpha particles average thickness
Beta particles average thickness

Due the research done before, we know that there should technically be more Alpha particles than Beta particles due to the fact that there is more Alpha particles early on in the decay chain. So we will count the amount of Alpha/Beta streaks on the screen in 10s periods.
Average amount of Alpha particles detected on the screen for 10s
Average amount of Beta particles detected on the screen for 10s

Prior experiments conducted by others concluded that there would be more radiation detected if the source is nearer to the cloud chamber. Hence we use a GM counter to find out how much radiation there is when the source is a specific distance away.
Amount of radiation recorded when the Radiation source is near the left breadth
Amount of radiation recorded when the Radiation source is near the right breadth

Video sources
Cloud Chamber | MIT Video. (2014, July 24). MIT Video. Retrieved , from

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Cobb, C., & Fetterolf, M. L. (2005). The joy of chemistry: the amazing science of familiar things. Amherst, N.Y.: Prometheus Books.

Emilio Segre, W.A., Nuclei and Particles, Second Edition, W. A. Benjamin Inc., 1977,
pages 109-110.

Hodgson, P.E., Gadioli, E., and Gadioli Erba, E., Introductory Nuclear Physics,
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Kastner, Jacob, Nature's Invisible Rays, U. S. Energy Research and Development
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Lennard Bickel, The Deadly Element: The Story of Uranium (New York:
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