observing the sky continuously at extreme photon energies with … · 2019. 11. 4. · observing...
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Observing the sky continuously at extreme photon energies with ALTO/CoMET
Mohanraj SenniappanPhD Student, Linnaeus University.
Yvonne Becherini, Michael Punch, Jean-Pierre Ernenwein, Satyendra Thoudam,Tomas Bylund
Partikledagarna - 3rd Oct 2019 - Linköping
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The Energetic Universe
Image Credit: NASA, ESA
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Image Credit: APOD
● Very high energy photons: 100 GeV to 100 TeV.
● Unlike Cosmic rays, γ-rays travel rectilinearly in the Universe.
● Helps to understand particle acceleration in extreme environments like AGN jets, accretion disks, supernova remnant etc.,
● Also to test Lorentz-Invariance Violation and effects of axion-like particles.
Image Credit: EGRET
Crab Nebula Cen A 3C 279Courtesy: C. Spiering
Image Credit: NASA, ESA Image Credit: APOD Image Credit: EGRET
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The ALTO Observatory
ALTO is a future ground-based very high energy gamma-ray observatory based on water Cherenkov technique. The key features include,
● In the Southern hemisphere● Continuous Monitoring● At high altitude (> 4 km)● Wide field of view● Hybrid detectors● Excellent timing accuracy● Modular design● Simple to construct● Long duration experiment● Open Observatory
→ Daily observations of Southern sources → Observations may be done 24h per day → Low threshold E ≥ 200 GeV → ~2 steradian → Improved S/B discrimination → Improved ang. resolution(~ 0.1° at few TeV) → Phased construction and easy maintenance → Minimize human intervention at high-altitude → Should operate for 30 years → Distribute data to the community
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Planned ALTO Detector Design
A unit of water Cherenkov detector with Scintillator base
A cluster of 6 units
An array of 1242 units
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Summary of Monte Carlo Simulation & Analysis
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Corsika – Shower Generation GEANT4
Detector geometry & response
Point-like gamma-ray source
Diffuse cosmic-ray proton
Shower reconstruction
Iterative procedure between the NKG lateral-distribution fit and the particle-front timing fit. … follows S/B background
discrimination.
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Signal over Background Discriminationgamma-rays protons
Defining variables Eg., ratio of no. of water tanks hit to no. of scintillator hits.
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BDT Classifier output
The best variables are analyzed using Multi Variate Analysis (MVA) – Boosted Decision Trees (BDT) in four different energy bins.
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ALTO performance plots
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5.4 σ in 30 min
PKS 2155-304 at z = 0.116 in flaring state
A BL Lac at z = 0.6 in flaring state viewed through galactic plane
3 σ in 2 months
(integrated time)> 10 TeV
G. Galanti et al. 2019 ALP Model
[GeV][GeV]
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ALTO Prototype at Linnaeus University
Al scintillator tanks filled with Linear Alkylbenzene + POPOP + PPO
On site electronics
In run since Feb’19
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Monitoring
mm
In WaterIn Water
In ScintillatorIn Scintillator
Thr
Thr
Thr
Thr
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Future Steps of ALTO
● Completion of the current simulations.● Continuous monitoring of the prototype and installation of two
new Buwa tanks – a cheaper industrial solution in steel.
● A cluster installation on site in Peru/Argentina.● We will be happy to welcome new interested collaborators
from Sweden .
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Image Credit: hortidaily
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Future Steps of ALTO - CoMET
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Idea: enhance the sensitivity of ALTO during darkness with HiSCORE.
● First observations with ALTO and mini-HiSCORE stations at Linnaeus University this autumn during darkness, beginning from the end of October.
● Weather Station installed on top of a tank for monitoring the sky quality
● First simulations of CoMET on the ALTO full array to start this autumn.
Weather station
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Live Event Display in YouTube
Live Stream Link
Thank you for your attention
Follow our blog in, alto-gamma-ray-observatory.org for future updates.
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BACKUP SLIDES
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Backup slide: VHE Gamma-ray Astronomy
Image Credit: NASA, ESA Image Credit: APOD Image Credit: EGRET
VHE γ-rays in Atmosphere
● Pair production and Bremsstrahlung radiation generates cascade of e+, e- and γ-rays leads to air shower.
Ground based observation
● Air Cherenkov Telescopes – H.E.S.S., MAGIC, VERITAS
● Particle Detectors – ALTO, LHAASO, HAWC
Courtesy: C. Spiering
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Back up slide: Charge in data
Distributions obtained when triggers originate
from other channels
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Backup slide: ALTO/CoMET
Image Credit: NASA, ESA Image Credit: APOD Image Credit: EGRET
Courtesy: C. Spiering
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Among all the advantages of particle detection in gamma-ray astronomy, there are also some limits:– The position of the shower maximum is difficult to reconstruct,– Limited angular resolution in the low energy range.
Our new investigation channel:– During darkness, couple the detection of the particles in the shower with the detection of Cherenkov light in the atmosphere.