APRIM 2011-- Chiang Mai July 28, 2011 Heliospheric Physics with IceTop Paul Evenson University of...
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![Page 1: APRIM 2011-- Chiang Mai July 28, 2011 Heliospheric Physics with IceTop Paul Evenson University of Delaware Department of Physics and Astronomy.](https://reader035.fdocuments.in/reader035/viewer/2022062315/5697bfc31a28abf838ca53e0/html5/thumbnails/1.jpg)
APRIM 2011-- Chiang Mai July 28, 2011
Heliospheric Physics with
IceTop
Paul EvensonUniversity of
DelawareDepartment of
Physics and Astronomy
![Page 2: APRIM 2011-- Chiang Mai July 28, 2011 Heliospheric Physics with IceTop Paul Evenson University of Delaware Department of Physics and Astronomy.](https://reader035.fdocuments.in/reader035/viewer/2022062315/5697bfc31a28abf838ca53e0/html5/thumbnails/2.jpg)
Chiang Mai, July 28, 20112
IceCube: A New View of the Universe from the South Pole
![Page 3: APRIM 2011-- Chiang Mai July 28, 2011 Heliospheric Physics with IceTop Paul Evenson University of Delaware Department of Physics and Astronomy.](https://reader035.fdocuments.in/reader035/viewer/2022062315/5697bfc31a28abf838ca53e0/html5/thumbnails/3.jpg)
Chiang Mai, July 28, 20113
IceCube Collaboration
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Chiang Mai, July 28, 20114
Cosmic Neutrinos
• IceCube is a particle “telescope” that peers through the earth to open a new window onto the universe. It will observe violent astrophysical sources such as supernovae, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars.
• IceCube will also search for dark matter, and could reveal new physical processes associated with the origin of the highest energy particles in nature.
• This “new window” on the universe will open via neutrinos, not light.
• It is likely that the processes that produce these particles are scaled up versions of processes that occur in the solar system
![Page 5: APRIM 2011-- Chiang Mai July 28, 2011 Heliospheric Physics with IceTop Paul Evenson University of Delaware Department of Physics and Astronomy.](https://reader035.fdocuments.in/reader035/viewer/2022062315/5697bfc31a28abf838ca53e0/html5/thumbnails/5.jpg)
Chiang Mai, July 28, 20115
Ice Cube Concept
• Trillions of neutrinos stream through your body every second, but none may leave a trace in your lifetime.
• IceCube uses a large volume (one cubic kilometer) of ice at the South Pole to detect rare neutrino interactions.
• Most often these interactions generate an energetic muon.
• In the ultra-transparent ice, the muon radiates blue light that is detected by the optical sensors that comprise IceCube
• Muons follow the arrival direction of the original neutrino
• By measuring the arrival time and amount of light at each sensor the arrival direction of the neutrino is determined
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Chiang Mai, July 28, 20116
Ice Cube Operation
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Chiang Mai, July 28, 20117
Hot Water Drilling
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Chiang Mai, July 28, 20118
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Chiang Mai, July 28, 20119
IceTop Detectors
• Blocks of clear ice produced in tanks at the Pole
• Cherenkov radiation measured by standard IceCube photon detectors
• Two tanks separated by 10 meters form a station
2 m
0.9 m
Diffusely reflecting liner
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Chiang Mai, July 28, 201110
Installing the Detector “Tanks”
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Chiang Mai, July 28, 201111
Fill Tanks with Water then Just Let Them Freeze
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Chiang Mai, July 28, 201112
Removing Dissolved Air Produces Perfectly Clear Ice
• Dual degassing units are seen under 75 cm of ice
• DOMs are frozen into the ice
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Chiang Mai, July 28, 201113
PY03:4
PY04:12PY05:16
PY06:18
PY07:18
PY08:12
IIceCube Layout
100 m
Grid north
South Pole
Large showers with E ~ 100-1000 PeV will clarify transition from galactic to
extra-galactic cosmic rays.
Showers triggering 4 stations give ~300 TeV threshold for EAS array
Small showers (2-10 TeV) associated with the dominant muon background in the deep detector are detected as 2-tank coincidences at a station.
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Chiang Mai, July 28, 201114
“Showers” from Low Energy (1 - 10 GeV) Primary Particles
• Particles with energy as low as 1 GeV produce secondaries that survive to the surface
• Rarely does a single detector see more than one secondary from a primary
• Large detectors can have high enough counting rates to make statistically significant measurements of the primary flux
• Conventional detectors count muons or neutrons
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Chiang Mai, July 28, 201115
The First Extraterrestrial Event Detected by IceCube
Dec 14, 2006 photograph of auroras near Madison, WI
Dec 13, 2006 X3-Class Solar Flare (SOHO)
IceTop and Spaceship Earth Observations of the Solar Flare
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Chiang Mai, July 28, 201116
Why IceTop Works as a GeV Particle Spectrometer
• Neutron monitors are comparatively insensitive to the particle spectrum
• IceTop detectors are thick (90 g/cm2) so the Cherenkov light output is a function of both the species and energy of incoming particles
• Individual waveform recording, and extensive onboard processing, allow the return of pulse height spectra with ten second time resolution even at the kilohertz counting rate inherent to the detector
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Chiang Mai, July 28, 201117
Secondary Particle Spectra
• At the South Pole, spectra of secondary particles “remember” a lot of information about the primary spectrum.
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Chiang Mai, July 28, 201118
Response Functions
• Analog information from IceTop yields multiple response functions simultaneously
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Chiang Mai, July 28, 201119
Solar Particle Spectrum Published in Ap J Letters
• Excess count rate as a function of pre-event counting rate.
• Each point represents one discriminator in one DOM.
• By using the response function for each DOM we fit a power law (in momentum) to the data assuming that the composition is the same as galactic cosmic rays
• The lines show one sigma (systematic) errors
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Chiang Mai, July 28, 201120
IceTop and PAMELA
Credit: M. Casolino
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Chiang Mai, July 28, 201121
Neutron Monitors and IceTop
• Good agreement (with understanding of viewing direction)
• IceTop determines a precise spectrum
• Anisotropy comes entirely from the monitor network
• Here we see the failure of the “separability” assumption in one particular analysis of neutron monitor data alone
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Chiang Mai, July 28, 201122
Neutron Monitors and IceTop
• Cherenkov and neutron monitor response functions are similar but have significant differences
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Chiang Mai, July 28, 201123
• South Pole station has a 3-NM64 and detectors with no lead shielding.
• These “Polar Bares” responds to lower particle energy on average.
ENERGY SPECTRUM: POLAR BARE METHOD
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Chiang Mai, July 28, 201124
• “Polar Bares” responds to lower energy particles.
• Bare to NM64 ratio provides information on the particle spectrum.
• This event shows a dispersive onset as the faster particles arrive first.
• Spectrum softens to ~P – 5 (where P is rigidity), which is fairly typical for GLE.
• Dip around 06:55 UT may be related to the change in propagation conditions indicated by our transport model
• Element composition is a source of systematic error in the spectral index
ENERGY SPECTRUM: POLAR BARE METHOD
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Chiang Mai, July 28, 201125
Element Composition and Spectrum from IceTop and the Neutron Monitor
• Simulated loci of count rate ratios, varying spectral index (horizontal) and helium fraction (vertical).
• Statistical errors (+/- one sigma) are shown by line thickness.– 20 January 2005
spectrum – “Galactic” composition
• IceTop (black, blue) lines converge in the “interesting” region
• Bare/NM64 (red) line crosses at the proper (i.e. simulation input) values
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Chiang Mai, July 28, 201126
Conclusions
• IceTop is a powerful new tool in the study of energetic solar particles
• Now we just hope that the sun has not quit on us