Atmospheric shower simulation studies with CORSIKA ARISTOTLE - PowerPoint PPT Presentation

Atmospheric shower simulation studies with CORSIKA ARISTOTLE UNIVERSITY OF THESSALONIKI Physics Department Atreidis George

High energy gamma ray astronomy at 100 GeV - 100 TeV High energy gamma rays photons.  Coming from a distant source  outside the Earth. Energies beyond those achievable  in man-made accelerators. When a VHE gamma-ray enters the Earth's atmosphere, it generates an  atmospheric shower.  secondary charged particles  Cherenkov light

Detection – Air showers interaction atmospheric shower air shower telescopes (AST) Cherenkov photons

Atmospheric shower simulation with Corsika Primary particle – gamma ray photon.  Three sets of showers. Every set consists of 10 showers.  The primary particle energy is.  First set  10 TeV Second set  40 TeV Third set  70 TeV Zenith angle  20 deg.  Azimuth angle  from -180 to 180 deg.  Observation level  110m above sea level.  The results are average values for each set of shower. 

Coordinate system in Corsika The coordinates in CORSIKA are defined with respect to a Cartesian  coordinate system.  The positive x -axis points to the magnetic North.  The positive y -axis points to the West.  The z axis points upwards.  The origin is located at sea level. Θ  Zenith angle. Φ  Azimuth angle.

Gamma particles distribution Gamma particles distribution 2,00E+04 1,60E+04 No of gamma particles 1,20E+04 8,00E+03 4,00E+03 0,00E+00 0 200 400 600 800 1000 Depth (g/cm**2) 10 TeV Starting point. Shower maximum The top of the atmosphere. Observation level. at a depth of 420 g/cm 2 . 110 m above sea level.

Gamma particles distribution Gamma particles distribution 1,20E+05 No of gamma particles 8,00E+04 4,00E+04 0,00E+00 0 200 400 600 800 1000 Depth (g/cm**2) 10 TeV 40 TeV 70 TeV  Big primary energy  more gamma particles.  Shower maximum  goes deeper.

Positrons distribution Positrons distribution 20000 16000 No of positrons 12000 8000 4000 0 0 200 400 600 800 1000 Depth (g/cm**2) 10 TeV 40 TeV 70 TeV  Big primary energy  more positrons.  Shower maximum  goes deeper.

Electrons distribution Electrons distribution 25000 20000 No of electrons 15000 10000 5000 0 0 200 400 600 800 1000 Depth (g/cm**2) 10 TeV 40 TeV 70 TeV  Big primary energy  more electrons.  Shower maximum  goes deeper.

Lateral electron density at observation level Lateral electron density for the three primary energies 8,00E-05 the density is Electron density 6,00E-05 reduced about 80% 4,00E-05 2,00E-05 0,00E+00 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Distance from core (cm) 10 TeV 40 TeV 70 TeV at a distance of 14 m from the core

Shower energy distribution Longitudinal energy distribution 1,25E+04 1,00E+04 Energy (GeV) 7,50E+03 5,00E+03 2,50E+03 0,00E+00 0 200 400 600 800 1000 Depth g/cm**2 10 TeV  Continuing reduction in the shower energy.  Energy loss  energy deposit into air.

Energy deposit into air Energy deposit (primary particle 70 TeV) 2000 ionization energy deposit 1600 cut energy for Energy (GeV) cut energy for gamma particles 1200 electrons – positrons (0.15GeV) (0.15 GeV) 800 400 0 0 200 400 600 800 1000 Depth (g/cm**2) gammas e+-ioniz e+-cut

Number of charged particles at observation level Observation level  110 m above sea level Number of electrons - positrons at observation level 300 N e >N p 250 200 150 100 50 0 1 2 3 Energy (TeV) No of electrons No of positrons More primary energy  more particles at observation level.

Locations of Cherenkov detectors in the simulation  Number of Cherenkov detectors in x direction  10  Number of Cherenkov detectors in y direction  8  Distance of detectors in x direction  1200 cm  Distance of detectors in y direction  1500 cm  Length of the detector in x direction  80 cm  Length of the detector in y direction  50 cm.

Production of Cherenkov photons per 20g/cm 2 Production of Cherenkov photons per 20 g/cm**2) 1,60E+08 More Cherenkov photons No of Cherenkov photons at the shower maximum. 1,20E+08 8,00E+07 4,00E+07 0,00E+00 0 200 400 600 800 1000 1200 Depth (g/cm**2) Primary particle 70 TeV Starting point. Observation level. The top of the atmosphere. 110 m above sea level.

Total production of Cherenkov photons Cherenkov photons distribution 3,00E+09 No of Cherenkov photons 2,00E+09 observation level 1,00E+09 0,00E+00 0 200 400 600 800 1000 1200 Depth (g/cm**2) 10 TeV 40 TeV 70 TeV  The Cherenkov photons generated at all depths reach the observation level.  At great depths the number of Cherenkov photons created are small, so the total number tends to become stable.

Increase Cherenkov photons with energy • Number of Cherenkov photons arriving at the observation level. Total Cherenkov photons - energy 3,00E+09 No of Cherenkov photons 2,00E+09 1,00E+09 0,00E+00 0 10 20 30 40 50 60 70 80 Primary particle energy Cherenkov  The increase in the Cherenkov photons in connection with the energy of the primary particle is almost linear.

Experiments in High Energy Gamma Ray Astronomy Telescope arrays for the detection of Cherenkov light H.E.S.S. experiment   Located in Namibia, near the Gamsberg mountain.  Energies from 100GeV to 100TeV. MAGIC experiment   Located in La Palma, one of the Canarian islands.  Energies >100GeV.  Mirror surface 236m 2 . VERITAS experiment   Located in southern Arizona of the USA.  Energies from 50GeV to 50TeV.  An array of four 12m optical reflectors.

New Experiment - CTA Location   Not yet determined. Three telescope types   Four 24 m telescopes with 5 o field-of-view.  23 telescopes of 12 m diameter with 8 o field-of-view.  32 telescopes of 7 m diameter with a 10 o field-of-view. Telescopes distribution   The telescopes are distributed over 3 km 2 on the ground.  The effective collection area of the array is considerably larger than this at energies beyond 10 TeV. Cost   Array layout has a nominal construction cost of 80 M € and meets the main design goals of CTA.

Conclusions The high-energy range above 10TeV For very high primary particle energy ~100TeV the maximum of the shower goes deeper and the Cherenkov light reaches its ultimate intensity at about 800 g/cm 2 or ~2 km in altitude. So The observation level The detectors should be should be lower. extended more widely. Two implementation options or a smaller number either a large number of larger telescopes of small telescopes

Thank you for your time