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Astro-Particle Physics: Imaging Air Cherenkov Telescopes (Iacts)

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IceAct: Cosmic Ray Air Cherenkov telescopes as an upgrade to the IceCube Neutrino Observatory at the South Pole Larissa Paul, Anna AbadSantos, Antonio Banda, Aine Grady, Sean McLaughlin, Matthias Plum and Karen Andeen Department of Physics, Marquette University, Milwaukee WI, USA Student researchers Astro-particle physics: Imaging Air Cherenkov Telescopes (IACTs): Testing epoxy for the use at the South Pole: at work • Cosmic rays - Particles Source? IACTs detect Cherenkov light produced in the atmosphere by air showers: this The IceAct cameras consist of 61 PMMA Winston cones (WCs) glued onto the with the highest known allows us to study the purely electromagnetic component of the air shower with glass of 61 SiPMs with epoxy. The epoxy used in previous versions of the energy in the universe excellent energy and mass resolution prototype was not cold-rated, causing rapid degradation of the camera at Polar • Discovered in 1912, still a • technique is complementary to the particle detectors already in place at the temperatures. A reliable cold-rated epoxy is vital to ensure many years South Pole of successful data taking. the IceAct lot of unknowns: camera • What are cosmic rays? • will allow us to significantly improve several measurements that we are • What are the astrophysical sources of cosmic interested in through: We are testing two different cold-rated epoxies for rays? • cross-calibrations of the different detector components against each other long-term reliability and reproducibility: • How are they accelerated? • reconstruction of events with different detector configurations • Goal #1: release equal amounts of epoxy drops • Air showers onto each SiPM. Cascades of secondary particles generated by cosmic IceAct: • Problem: viscosity of epoxy changes with time exposed to air, causing the ray particles interacting with the earth's atmosphere. amount of epoxy released by a “measured” pipet to be reduced over time. Prototypes for an IACT array at the South Pole have been designed and devel- • Solution: test different timing and application methods to find repeatable • The cascade of particles can be divided into 3 oped. Each telescope has a 61-pixel camera with a total field of view of 12o. components: method to achieve consistent drop sizes on a microscope slide. • small (~50 cm) and low cost (~$10,000) • Goal #2: discover how much epoxy is needed. • Electromagnetic component: electrons, • capable of withstanding the harsh positrons, gammas • Problem: too little epoxy will not reliably attach WCs to SiPMs. environment of the Antarctic winter • Solution: affix small plexiglass rods to microscope slides (instead of the • Muonic component: high energetic muons with temperatures down to -100of and • Hadronic component: everything heavier than a expensive WCs and SiPMs) using different epoxy drop sizes. Measure the wind speeds exceeding 50 mph breaking weight limit using weights and a 3-D printed slide-holding muon, mostly pions and kaons decaying into the • single photon counting obtained other two components Cherenkov light apparatus. using silicon photomultipliers (SiPMs) • Goal #3: check the reliability of the strength test over many cold cycles. • Cherenkov light • nanosecond accuracy achieved using high precision timing devices Light produced by charged particle • Problem: the epoxy may not maintain its direction particle particles traveling faster than Successful Antarctic field work January 2020: strength in simulated Antarctic conditions the speed of light in the medium over time. • Matthias Plum, researcher of our group, was deployed at the South Pole • Solution: find the number of cold cycles the • Installed a new telescope in the field epoxy can handle by putting samples in freezer IceCube Neutrino Observatory: • Upgraded both telescopes with a heating structure developed at Marquette at -80o for 48 hours. Then remove the samples 3D print of the pipette holder from the freezer and repeat the strength tests, A multi-part observatory located at the geographic South checking for cracks in the epoxy or slide. Pole inside the glacial ice sheet Repeat the testing cycle until cracks in the IceCube In-Ice Array: epoxy or slide exist. • 5160 optical sensors Horizontal and vertical probe holder 3 plexiglass rod instrumenting 1 km Drilling holes • Detects light produced into the in ice by: Student researcher glass slide Plexiglass Monitoring the telescopes: rods • High energy muon at work bundles from air The IceAct prototypes take data autonomously, but basic telescope parameters 5 kg weight attached to a to probe Polishing the showers must be monitored to address any problems in a timely fashion. Therefore we plexiglass • Particles from are developing new monitoring software: example plots for monitoring the telescope rods neutrino interactions • design a mock detector to produce in the ice “data” which will be used in the Summary and Outlook: development of the monitoring software IceTop Surface Array: • Prototypes of a new IceAct array are already making complementary air • write software to monitor this "live" • 162 tanks containing shower measurements for the IceCube Neutrino Observatory at the South Pole. 3 incoming data, automatically send 3 m of ice equipped • Both telescope prototypes were upgraded in January 2020 and had a successful notifications to users when safe limits with 2 optical sensors data taking season in 2020. are violated, and produce figures for • Detects light produced • The epoxy tests are ongoing and are already providing promising results. human detector monitoring to ensure in ice by the electro- • Monitoring software upgrades will be ready for the next data-taking season the telescopes are collecting data properly magnetic and muonic air shower components beginning March 2021!.
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