This was our first attempt at making a cloud chamber. In one class period, we combined pieces of black foam and a square plastic container using hot glue. 

The container lid was hot glued to the edges of the foam container we cut out, allowing the container to be mounted upside down and removed easily whenever we needed to perform maintenance to the felt or introduce radioactive objects.

The dry ice was placed into the cavity underneath the container lid and "sealed" using a separate piece of foam cut to fit the remaining opening of the foam container.

What worked:

• The hot glue did a good job holding the container lid to the foam and the alcohol-storing foam block to the top of the container

• The alcohol foam did an okay job holding the alcohol

What did not work:

• The dry ice did not cool the container lid nearly enough to get close to the required -30°C needed.

  • This was likely due to:

    • No ventilation for the dry ice to out gas through

    • The plastic container lid acting as a thermal insulator

    • The dry ice not being in direct contact with the container lid / floor of the cloud chamber

• The upside-down container and container lid method was harder than expected to separate when we needed to open the chamber

• The alcohol-storing foam block was too porous and bulky, making it difficult to store large amounts of alcohol and to achieve a consistent evaporation of the alcohol.

We quickly realized the temperature issues of design iteration #1. So, we created a new version on the fly, using a thin, tall, and oval-shaped plastic container placed on top of a circular sheet metal plate, made by cutting out the center of a sheet metal pie pan.

We were still utilizing the spongey foam block for alcohol storage.

We also tried placing the dry ice into the chamber on its own.

What worked:

• The sheet metal plate was cooled quicker than the plastic lid of the first design

What did not work:

• The sheet metal plate still was not producing any visible fog or vapor within the container and was not reaching the necessary cold temperature.

• The plastic container couldn't maintain an airtight seal due to it only being held in place on top of the metal plate with only our hands.

• Placing dry ice into the chamber does not work.

Once we saw that having a metal base worked better, we attempted to better contain the system, using two uncut pie pans to seal off the dry ice and act as the base of the cloud chamber. Then, a circular cup from Panera was used to make the cloud chamber. The thought here was to reduce the volume of the chamber and improve the temperature gradient (the cup could be placed in the center of the pie pan, which is where the temperature was lowest).

We were still utilizing the spongey foam block for alcohol storage.

What worked:

• We saw our first signs of alcohol vapor with this design (see right) 

  • This was observed when we used our infrared thermometer to measure the metal pan's temperature through the container. The thermometer's red laser interacted with the falling alcohol vapor / particles, illuminating them.

What did not work:

• No vapor "fog" was visible still, resulting in no streaks of ionizing radiation being observed. We believed this was still due to a lack of temperature gradient, specifically not cold enough temperatures at the base 

  • We were only reaching around -6°C

After design iteration #3, Mr. Taylor had the idea to use a circular container he had that was large enough to fit the metal pie pans inside. 

This way, our chamber could use the container lid to seal itself off like design iteration #1, while still benefitting from the colder temperatures of the metal pie pan containing dry ice.

We were still utilizing the spongey foam block for alcohol storage.

What worked:

• The signs of alcohol vapor were must stronger than before (see right)

  • This was encouraging as it meant we had put a sufficient amount of alcohol into the foam and temperature was our only issue. It also showed we could replicate the event.

What did not work:

• The pie pan still was not reaching the necessary -30°C

• We noticed that we had reached the storage capacity of the foam and it was leaking liquid alcohol quickly

  • Resulted in the metal pie pan and the Fiesta ware plate being covered in isopropyl alcohol

    • This likely would have blocked any ionizing radiation from reaching any cooled vapor anyway

  • We wanted a more reliable way for the alcohol to be released at the quantities we used.

Taking what we learned from our previous design iterations, we did further research over the May 17th weekend and returned with a plan for improvement. 

In our second iteration, we improved the bottom plate temperature by using an upside-down flexible aluminum metal pie pan that was in direct contact with the dry ice.

Additionally, we replaced the plastic container with a cylindrical glass container that fit well around the pie pan, creating a decent seal on its own.

To aid in the visibility of any streaks of ionizing radiation, we partly wrapped the glass container in Christmas lights, added sticky black felt to the top of the pie pan, and used a felt ring to hold the alcohol to the top of the container rather than a full circle of felt or foam. 

Felt was chosen over the blocky foam used in our first design iteration because we found it to be better at soaking up the alcohol and it took up less space within the chamber.

In order to keep the felt ring attached to the top of the chamber, we initially tried using hot glue as we had with previous designs, but the hot glue adhered much less to glass than it did to plastic. So, we had to use both hot glue and a flexible tube cut slightly too large for the container, that way it pressed against the walls and held in place below the felt ring.

Lastly, we used a syringe to better control and track how much alcohol we were using in the chamber.

What worked:

• The dry ice in direct contact with a metal pie pan achieved our ideal temperature range for the bottom plate (-30°C to -36°C) (measured using infrared thermometer)

  • It also dropped in temperature quicker than the previous design

  • We found using a larger piece(s) of dry ice helped lengthen the cloud chamber's operation

• Felt ring allowed for much better visibility of the chamber.

• Christmas lights illuminated the interior of the chamber.

• Glass container and pie pan seal performed well.

  • Additionally, glass is marginally better radiation protection than the previous plastic container.

What did not work:

• We used too little alcohol for our cloud chamber's size (15mL was too little)

  • Prevented us from viewing any streaks on our first attempt

• The sticky black felt, and base overall, was so cold and the chamber air so moist, that lots of frost covered the base.