Stratospheric Cosmic Ray Detection
We seek to detect the particles that originate from the decay of cosmic rays. As primary cosmic rays enter the atmosphere they collide with atmospheric atoms and decay into pions, secondary cosmic rays. After travelling through the upper atmosphere, at around 15 km above Earth’s surface, pions decay into muons, which will in turn decay later on.
We will detect these particles with a cloud chamber and a camera. The cloud chamber contains supersaturated vapourized isopropyl alcohol that ionizes when energized particles pass through it, exposing their trails to the naked eye.
Our apparatus will be sent to the stratosphere in a weather balloon to detect the flux of muons and pions at different heights.
We aim to demonstrate the relativistic effects on muons, find the height at which pions are generated and check if the height at which these decay into muons has changed due to pollution.
CLOUD CHAMBERS
A cloud chamber is a particle detector which consists of a supersaturated vapour. When energetic charged particles interact with the gaseous mixture by knocking electrons off gas molecules via electrostatic collisions, a trail of ionized gas which follows the particle's path can be seen.
A cloud chamber consists of the sealed environment, a source of heat at the top and a cold bottom plate. This temperature gradient is crucial for the state of super condensation to be reached. The chamber also requires a source of liquid alcohol at the warm side of the chamber where the liquid evaporates, forming a vapor that cools as it falls through the gas and condenses on the cold bottom plate. Some sort of ionizing radiation is needed to ionize the gas particles and make the particles' paths. visible to the naked eye
By analyzing the different paths that a taken by a particle, we can deduce what kind of particle went through the gas. In the image above, we can appreciate radon gas decay inside a cloud chamber, which produces alpha particles, recognizable because of being thick, short and straight straight paths. In the image below, we show a sample of the paths followed by common particles.
OUR EXPERIMENT
We will detect muons and pions that originate from the decay of cosmic rays with a cloud chamber and cameras. We will place our cloud chamber inside a Pelican Box in a weather balloon provided by the Centre National d’études Spatiales (CNES) in partnership with the Canadian Space Agency. Our cameras will be taking pictures of the chamber at constant time intervals and store them in an SD card. After the flight we will run the images through an algorithm designed by our team that will tell us how many particles are seen of each type at different heights. With these results we will be able to estimate at what height pions are created and whether the height at which they decay has changed due to pollution. Additionally, we want to show that pions experience relativistic effects during their trip through the atmosphere and see what other particles we can detect up there. Even though cloud chambers are a usual experiment done in classrooms, we have not found any records of cloud chambers being sent to space other than CADMUS and their results have not been published yet
We will detect muons and pions that originate from the decay of cosmic rays with a cloud chamber and cameras. We will place our cloud chamber inside a Pelican Box in a weather balloon provided by the Centre National d’études Spatiales (CNES) in partnership with the Canadian Space Agency. Our cameras will be taking pictures of the chamber at constant time intervals and store them in an SD card. After the flight we will run the images through an algorithm designed by our team that will tell us how many particles are seen of each type at different heights. With these results we will be able to estimate at what height pions are created and whether the height at which they decay has changed due to pollution. Additionally, we want to show that pions experience relativistic effects during their trip through the atmosphere and see what other particles we can detect up there. Even though cloud chambers are a usual experiment done in classrooms, we have not found any records of cloud chambers being sent to space other than CADMUS and their results have not been published yet
OUR SETUP
The main three problems we faced when developing our idea were:
- Keeping a constant pressure of 1 atmosphere inside the dome as the outside drops to almost 0 atmospheres.
- Making sure that the isopropyl alcohol, which is more flammable than gasoline, did not pose a risk to the mission.
- Keeping the proper temperature gradient (22ºC at the top and -70ºC at the bottom) inside the dome while the temperature outside averages -35ºC.
DEALING WITH PRESSURE
In order to maintain the internal pressure constant, we used an O-ring sealing. O-rings are placed in a groove between two compressed surfaces to prevent airs and liquids to flow. In the images on the left, you can see our dome design and how an O-ring works.
DEALING WITH FIRE
In order for a substance to combust its concentration with respect to the concentration of air and inert gas, has to lie within certain limits, otherwise, combustion is impossible. In our case, we will substitute air by nitrogen inside the dome, making the isopropyl alcohol "fireproof".
DEALING WITH TEMPERATURE
As we ascend through the atmosphere temperature varies as shown in the graph to the left. In order to fight these effects and maintain the proper temperature gradient our temperature consists of: cryogel blankets, a by-product of aerogel, to maintain the temperature as constant as possible, heaters to keep the top of the dome at 25ºC and dry ice to cool down the bottom surface to -70ºC.
