Modifying Cloud Chamber Technologies for Secondary Educative Purposes

TEIGHIN NORDHOLT

he/him | age 18 | Grand Bay-Westfield, NB

Senior Bronze Excellence Award at the 2022 Canada-Wide Science Fair

Edited by Miranda Doris

Radiation is a widely misunderstood concept among students and few tools exist to help instruct the topic. A cloud chamber is a visual radiation detection apparatus whose design has not yet been investigated through the explicit lens of education. This study aims to address this gap through the engineering design process. Modifications to both central components, the cooling plate, and the chamber, were completed, tested, and compared in terms of performance and price. It was found that a modified heatsink is the best option for a cooling plate, and that polycarbonate functions best as the construction material due to its high transparency and resistance to chemicals. These findings can be applied to help instruct New Brunswick’s new “Nuclear Energy” units of grade nine and ten science to help build a population with a stronger understanding of radiation.

INTRODUCTION

There is a lack of accessible educational instruments for radiation detection. After its advent in 1911, the diffusion cloud chamber was quickly abandoned by the scientific community in favor of rapidly developing and more capable technologies. In the eyes of the enthusiast, however, the cloud chamber remains a powerful tool to visually depict the phenomena of radiation. Through the supersaturation of an alcohol and a large temperature gradient, cloud chambers show a trail of condensed vapor created by passing particles of ionizing radiation. During the past century and into this decade, improvements have been made to individual components and to the overall design of the cloud chamber (Cheney, 2020; Toda et al., 2019; Zeze et al., 2012). Despite these works, there remain many multidisciplinary applications of a cloud chamber that have not yet been explored.

The visual nature of a cloud chamber could have applications in the educational sector to address growing misconceptions of students about radiation. Radiation is a widely misunderstood phenomenon that is often feared because of recent nuclear disasters such as Chernobyl and Fukushima (Cuttler, 2014). Fukushima, in particular, has resulted in many papers analyzing how Japanese students understand radiation (Neumann & Hopf, 2012, 2013; Tsubokura et al., 2018). Such understanding was determined to be subpar internationally and across demographics, and current global secondary school curricula were found to not sufficiently explore the technicalities of radiation and its dangers (Cardoso et al., 2020; Neumann & Hopf, 2012; Neumann & Hopf, Siersma et al., 2021; Plotz, 2016; Rego & Peralta, 2006; Siersma et al., 2021; Tsubokura et al., 2018). In addition to this, teachers do not seem to know how to address this gap in knowledge, which has generally been attributed to a scarcity of teaching materials (Cardoso et al., 2020; Neumann & Hopf, 2012; Plotz, 2016; Rego & Peralta, 2006; Siersma et al., 2021; Tsubokura et al., 2018). A more comprehensive and affordable cloud chamber can make this technology more accessible for use in classrooms.

High school students’ lack of understanding of radiation has negatively impacted the capacity to implement nuclear energy technologies across the globe. In New Brunswick, the provincial government has invested substantially in small modular reactors, but the implementation of these technologies has been opposed by the general public (Poitras, 2022). Low-scale nuclear power could help transition the economies of regions with low population density, like New Brunswick to a greener model that is not reliant on fossil fuels. However, the population's understanding and fear of radiation could stand to be a large barrier to this. With a recent reform to provincial grade nine and ten science class curricula that includes nuclear power, New Brunswick is making progress by investing in generational comprehension (GNB, 2020). In the early stages of this reform, and with a lack of centralized teaching directives, the effectiveness of this change is yet to be concluded. Cloud chambers may be the perfect tool for instructors to help them teach their students about radiation and nuclear energy.

The potential applications of cloud chamber technologies have been greatly forwarded by the works of non-professionals. Several recent projects detail improvements made to the hardware of cloud chambers (Cheney, 2020; Kamata, 2012; Toda et al., 2019; Zeze et al., 2012). Hobbyists like Zeze and Cheney, among others, have published papers that describe their influence on the development of this technology. This research has contributed to an exciting way to cool the chamber, breaking the convention of using dry ice. Cheney and Toda showed separately that thermoelectric Peltier units can be used to create a large temperature differential both efficiently and conveniently (Cheney, 2020; Zeze et al., 2012). Despite this, Peltier units are hard to install, thus the cooling plate design suggested by Kamata is appealing from the perspective of accessibility (Kamata, 2012). This, on top of developments regarding efficiency, sensitivity, size, and power consumption, depict the large impact of non-professionals on these technologies.

Many individuals have looked at cloud chambers for different contexts, but none have been designed for applications in education. This paper will thus focus on applying the investigations of hobbyists on cloud chambers, with the goal of creating an accessible, interactive, and visual radiation detection tool to help address students’ misunderstanding of radiation.

METHOD

A range of changes to the design of a cloud chamber were implemented through the engineering design process with the goal of improving cloud chamber accessibility and performance. By targeting the cooling system, alcohol type and volume, as well as the construction materials and design, this study aimed to address a gap in what is currently available for instructors by creating an accessible cloud chamber for use in high schools.

This approach was consistent with that of other research regarding cloud chamber design. Cheney, for example, conducted his Ph.D. at the Massachusetts Institute of Technology on the development of a “miniature, low-power, solid state, continuously sensitive, diffusion cloud chamber” for use in educational settings (Cheney, 2020). He was led to his final chamber through quantitative testing of a variety of cooling and power delivery systems.

Variables & Data Collection
First, when testing variations to the design of the cooling plate, temperature was measured with an Arduino Uno microcomputer, an Adafruit BMP280 temperature sensor, and Excel Data Streamer. The Arduino code used for data collection is included in the Supplementary Information. Several related investigations also chose to assess temperature in this way (Esteban, 2016; Toda et al., 2019; Zeze et al., 2012).

Next, when assessing the effectiveness of the constructed cloud chambers, particle detection rates were compared to independent variables such as the cost of construction and the materials and evaporative substance used. These rates were collected with a button wired to an Arduino, which recorded the time and total particle count when pressed. This code is also found in the Supplementary Information.

Procedure
Cooling plates were constructed by modifying an aluminum heatsink. For testing purposes, the cooling plates were cooled in a freezer for twenty-four hours, then removed and placed on a lab bench at room temperature. As previously mentioned, this was monitored with a temperature sensor and an Arduino. The sensor was covered with plastic wrap to protect it from water damage, and was held with multiple elastic bands to the cooling plate as they ensure high pressure and consistency. A photograph of the modified heatsink inside of the insulative box with the temperature monitoring apparatus attached during data collection can be found in the Supplemental Information. Data collection stopped, and the trial was deemed finished after temperatures reached an asymptotic value, which occurred no sooner than after 30 minutes. The details of all cooling plate tests are summarized in the table below.

**Table 1.** Description of heatsink testing.

In order to compare the viability of constructed cloud chambers with current market options, the Arbor Scientific (ArbSci) cloud chamber was purchased for a total of $550 CAD. It was the only all-inclusive cloud chamber available for purchase online in Canada. The modified heatsink with the insulative box and the cooling plate of ArbSci’s cloud chamber were tested on the coldest setting of the freezer. This freezer temperature more accurately modeled future use but was not used during the temperature trials due to time constraints.

The modified heatsink and insulative box were used to construct the remainder of the cloud chamber. Four pieces of acrylic were cut from COVID-19 desk barriers to follow the perimeter of the heatsink with a height of 10cm and were glued with acrylic cement. An aluminum cooking tray was attached with aluminum tape to the top to hold water, and three pieces of felt were suspended from this. As there were gaps between the acrylic and the heatsink, Vaseline was used around the edge to sustain the internal atmosphere. To run the trial, the felt was saturated with methanol, the radiation source from ArbSci was placed into the apparatus and boiling water was poured into the cooking tray. This was done in a dark room, and a flashlight was used to illuminate the chamber. After a few minutes, white and linear tracks began forming above the surface of the heatsink, and data collection was completed.

Numerous issues were present with this apparatus. First, the aluminum heatsink did not provide contrast with the tracks of radiation, and was thus spray-painted black. In addition, the employment of Vaseline created a huge mess and was not overly effective. Hot glue was poured onto a sheet of aluminum foil in the shape of the perimeter of the apparatus, and the acrylic was placed down into it. This created a level surface that maintained the internal environment. The improved apparatus was then rerun, and performance greatly increased.

Next, variations in the amount of methanol were tested. Before, it was non-quantitatively poured to saturate the felt. In this trial, 20mL of methanol was tested, which was derived from the ratio of methanol to chamber volume employed by ArbSci. 35mL of methanol was then tested which yielded better results than the previous trial.

After a number of trials, the acrylic began peeling and large cracks appeared (Figure 1a). According to a provider of plastic material fabrication services, acrylic has no chemical resistance to alcohols, especially in the high-temperature environments created in the cloud chamber (Zazo, 2014).

Therefore, a glass container of similar dimensions to that of the acrylic box was obtained, and the cooking tray was fastened with aluminum tape. It was run according to the previously outlined procedure with 35mL of methanol, and data collection was completed.

Finally, polycarbonate sheeting and isopropyl alcohol were used as substitutes to acrylic and methanol due to polycarbonate’s resistance to isopropyl alcohol (Polycarbonate Chemical Compatibility Chart, 2018). The design of the acrylic cloud chamber was replicated with these materials. After a trial, it was suspected that the water quickly dissipated heat through the aluminum tray, so it was replaced with a polycarbonate box of similar size (Figure 1b). Data collection was then completed.

**Figure 1.** (a) The effect of methanol on the acrylic of the constructed cloud chamber and (b) The final version of the cloud chamber, fully constructed with polycarbonate.

Cooling plate
Below, Figure 2 visualizes the temperature change data for each of the temperature trials, as previously described in Table 1.

**Figure 2**: Temperature of modified heatsinks over time

Note the large differences in temperature before and after trial 3.

The goal of these modifications was to maximize the temperature from room temperature while minimizing cost. A larger “r” value, as defined in Figure 3, is thus desirable. The price and temperature values for each trial is summarized below in Table 2.

**Figure 3.** Comparison test formula. Note that Trial 6 resulted in the largest “r” value.

**Figure 4**: Compared temperatures of the modified heatsink and ArbSci’s cooling plate.

It is important to note that while the modified heatsink reached lower temperatures, it was not able to sustain the performance of ArbSci, as shown in Figure 4 above.

Cloud chamber
The results of the cloud chamber trials are shown below in Figure 5.

**Figure 5.** Results of cloud chamber particle detection tests.

Acrylic trials #1 and #2 are the particles detected by the acrylic cloud chambers whose felt was non-quantitatively soaked. Note that they did not attain the same number of particles as the ArbSci cloud chamber, and detected particles for a shorter period of time. Acrylic trial #3 is that of the trial using 20mL of methanol, and only detected eight particles. Finally, acrylic trial #4 represents the final acrylic test using 35mL of methanol where intense cracking greatly impaired vision and decreased confidence in the results.

It should be noted as well that the glass cloud chamber detected significantly fewer particles than ArbSci, while the polycarbonate setups eventually surpassed it. For more details on the exact particle detection amounts and particle detection durations of each trial, see the Supplementary Information.

The Supplementary Information also includes two t-tests. The first of which compares the particle detection rates of the final polycarbonate apparatus with the average of the ArbSci trials, and indicates a significant difference between the two, t(1852) = 10.7, p = 3.72E-26. The second t-test compares the first polycarbonate trial and the average of the first two acrylic trials, t(515) = -0.5, p = 0.303. The main difference between these trials was the type of alcohol used. As the p value is larger than 0.05, it can be concluded that alcohol did not have a significant effect on particle detection rates, increasing confidence in the success of the second polycarbonate trial.

DISCUSSION

Table 2 shows that heatsink modifications suggested by Kamata (2012), and further insulation of the setup was successful, as each successive trial corresponding to these changes had lower final temperatures than the previous. The developed formula in Figure 3 also shows these changes to be cost-effective. These findings are important as they provide data to support the cooling plate design of Kamata (2012). It can now be shown that they are effective in terms of price and performance, which is important for recommendations surrounding the employment of this design for use in educative contexts.

The first acrylic cloud chamber was constructed from acrylic which was obtained for free from old COVID-19 plexiglass barriers used in schools, which helped lower the price. While it did not reach the performance of ArbSci, as seen in both the particle count and duration, it still provided clear tracks while active. Despite this, the issue of acrylic’s chemical resistance greatly hindered this apparatus. As seen in Figure 1a, intense cracking due to alcohol exposure reduced visibility.

Next, a small glass container was used to make a cloud chamber, but was severely limited in effectiveness due to what was likely poor transfer of heat through the cooking pan and glass to the felt that housed the alcohol. While the cost and ease of construction of this apparatus was similar to the acrylic, it did not match it in terms of particle detection amounts, and less distinct particle tracks were observed. Glass may be applicable, especially as it is not known to have interactions with alcohols, but further exploration is required to improve heat transfer.

Finally, the final polycarbonate cloud chamber outperformed ArbSci in terms of detection time, amount, and cost. This design serves to potentially be a great resource for teachers, especially those in New Brunswick, looking to provide a visual demonstration on radiation to strengthen their students’ understanding of the phenomenon. Specific features were improved, yielding high numbers of detected particles, longer detection durations, better visibility, a larger field of view, and lower cost. These will help improve the apparatus’ accessibility and its functionality in classrooms. It is hoped that the widespread adoption of cloud chambers in education will lead to a population with strong foundations in the science of radiation, easing the implementation of nuclear technologies as we work to transition into a greener economy.

The results of this research are limited due to low numbers of trials per setup and the overall design method. In addition, some combinations of variables were not tested, such the ArbSci cloud chamber with isopropyl alcohol. This decreases confidence that any one modification contributed directly to a change in result, however this is an expected drawback of the engineering design method. A cloud chamber was ultimately designed for the explicit purpose of education and the iterative process helped yield this design.

With these limitations, it is first recommended that further research is conducted on the designs presented above. Solidifying a design would be greatly beneficial for the conversation of this apparatus in the context of education. It is also recommended that a study be conducted on the effect of cloud chambers on students’ conceptions of radiation. Other studies have identified this issue, which has become especially prominent in New Brunswick with the reform of grade nine and ten science curricula.

CONCLUSION

Little research has been conducted on the design of cloud chambers through the explicit lens of accessibility for education. Modifications to a heatsink were completed and tested with a temperature sensor, then a variety of cloud chamber apparatuses were constructed in accordance with previous results and the suggestions of other researchers. It is recommended that the procedure outlined above is followed to create a polycarbonate cloud chamber. The use of the constructed cooling plate along with isopropyl alcohol, boiled water, a source of radiation, and a flashlight makes a cost-effective cloud chamber with great viewing angles and clear tracks.

This presented design is both less costly and more effective than market options in Canada. While research has improved the design of the cloud chamber, none has answered the calls of researchers for a cheap and effective tool to visualize radiation for use in education. These findings fill this gap by providing details on optimizing the design of a cloud chamber for several criteria critical to education such as cost, accessibility, and effectiveness.

SUPPLEMENTAL FIGURES

**Figure S1.** Modified heatsink inside of the insulative box with temperature monitoring apparatus attached during data collection

**Table S1:** Additional material dimensions

**Table S2.** Cost of cloud chambers and their components

**Table S3.** Particle detection amount and duration for constructed cloud chambers

**Table S4.** Two-sample t-test between particle detection rates of the second polycarbonate trial and the ArbSci average

**Table S5.** Two-sample t-test between particle detection rates of the first polycarbonate trial and the acrylic average

**Arduino code for temperature monitoring:** The above code was employed with an Arduino Uno and an Adafruit BMP 280 temperature. The results were plotted in Excel Data Streamer.

**Arduino code for particle counting:** When a button wired into serial port 7 of an Arduino Uno is pressed, the above code records the time and how many times it has been pressed.

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