Development of the Cherenkov Camera for the EUSO-SPB2 Mission and Analysis of Above-the-Limb Observations of Cosmic-Ray Particle Showers
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Gazda, Eliza Anna
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Abstract
Cosmic rays and neutrinos are particles that provide insights into high-energy events in the universe. These events take place beyond our Milky Way and have the power to accelerate charged particles to energies exceeding 1 ZeV. Detecting high-energy particles holds the key to understanding the distribution of gases and matter throughout the universe, the dynamics and laws governing the sources of these particles, and the particles themselves. These fundamental questions are subject to contemporary research, necessitating technological advancements for detecting and observing particles at increasingly higher energies. New methods and technologies improve detection sensitivity, and as detectors increase in size and efficiency, they collect more data. These data enable deeper insights into the phenomena driving cosmic-ray acceleration and propagation.
Recent advancements in detectors and telescopes, such as the Telescope Array or the Pierre Auger Observatory, have led to numerous breakthroughs in detecting Ultra-High-Energy (UHE) particles, including cosmic rays and Very-High-Energy (VHE) gamma rays. These discoveries have enhanced our understanding of the origins and acceleration mechanisms of cosmic rays and the nature of astrophysical accelerators like supernova remnants and active galactic nuclei. They have also provided valuable insights into the environments where these processes take place. The detection of VHE gamma rays has enabled the investigation of extreme astrophysical phenomena such as gamma-ray bursts and pulsar wind nebulae, shedding light on high-energy processes and their impact on cosmic environments.
These discoveries drive efforts for observatories like IceCube to detect UHE neutrinos. Neutrinos are neutral, weakly interacting particles capable of traveling vast distances through space without being absorbed or deflected by magnetic fields, offering direct information about their sources. The detection of UHE neutrinos could unveil the most energetic and distant astrophysical sources, including active galactic nuclei, gamma-ray bursts, and potentially undiscovered sources. This would provide a fresh perspective on the universe's most extreme environments and astrophysical processes, complementing the information obtained from cosmic rays and gamma rays.
One method for studying UHE cosmic rays and UHE neutrinos is with a Cherenkov detector from a balloon, satellite, or high-altitude ground observatory. A telescope positioned at high altitudes above the Earth and pointed at the Earth's horizon can utilize the Earth as part of the detector. Particles interact within the Earth, leading to the observation of air showers.
I designed, built, tested, and integrated a Cherenkov camera for the Extreme Universe Space Observatory (EUSO) on board the Super Pressure Balloon 2 (SPB2). My main contribution was to develop the camera front-end electronics and integrating the camera, thermal vacuum testing, and characterizing the performance of the camera in the field. Together with the rest of the team, we deployed the payload to fly as part of a NASA pathfinder mission. We operated the payload for two days before the balloon crash-landed in the Pacific. Despite the mission being cut short due to a balloon leak, we recorded air-shower data, validating the functionality of the design and the experiment. This data includes images of cosmic ray air showers within the energy range of 1PeV to 100PeV. This optical Cherenkov telescope was the first of its type to operate and successfully take data at such altitudes as a balloon payload.
From the observed flight data, my primary objective was to analyze 45 minutes of data collected while we tilted the telescope above the horizon. The goal was to search for detected UHE cosmic ray air showers since pointing the instrument above the limb allows the detection of cosmic rays of energies above 1PeV, to 100PeV. I have developed techniques for calibrating, cleaning, and identifying UHE cosmic ray candidates. Initially, we studied the data to characterize our telescope's behavior and response. I contributed to developing calibration methods to flatfield our detector response and identify different types of noise events. Subsequently, I devised image-cleaning algorithms to differentiate between air shower images and events caused by the light fluctuations in the night sky background. For the analysis of this 45-minute period, I also established and executed a simulation chain to determine the UHE cosmic ray flux. The number of detected cosmic air showers matches flux predictions and verifies the performance of the telescope.
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2024-07-30
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