Enrico Borriello
Cherenkov Effect
and
High Energy Cosmic Rays revelation
High Energy Astrophysics
October 16, 2008
Summary
1. Cherenkov effect
2. Cherenkov Radiation additonal features
3. Aerodinamic analogy: Sonic Boom
4. Rigorous treatment: fine structure
6. Cosmic Rays
7. Imaging Air Cherenkov Telescopes (MAGIC)
8. Pierre Auger Observatory
9. Ice Cube Neutrino Observatory
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cherenkov Eff
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cherenkov Eff
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cherenkov Eff
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cherenkov Eff
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cherenkov Eff
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cherenkov Eff
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cherenkov Eff
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cherenkov Eff
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cherenkov Eff
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Threshold velocity:
Cherenkov Radiation additonal
Limit angle:
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Aerodinamic analogy: Sonic
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Aerodinamic analogy: Sonic
58
q  32
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Aerodinamic analogy: Sonic
58
cos q 
q  32
S
A
 A 
S
 1.18 S
cos q
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Aerodinamic analogy: Sonic
S  330 m/s
A  389 m/s
58
cos q 
q  32
S
A
 A 
S
 1.18 S
cos q
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Rigorous treatment: fine st
Ultrarelativistic
particle:
β1
1cm of water:
L = 1 cm, n = 1.33
Violet light:
λ = 4000 Å = 0.4 μm
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Rigorous treatment: fine st
q qC q
ENRICO BORRIELLO, Astrofisica delle alte energie, O
Cosmic rays are charged particles (usually a proton or a heavy nucleus) that constantly rain down on us from
space. When a cosmic ray particle reaches Earth, it collides with a nucleus high in the atmosphere, producing
many secondary particles, which share the original primary particle's energy. The secondary particles
subsequently collide with other nuclei in the atmosphere, creating a new generation of energetic particles that
continue the process, multiplying the total number of particles. The resulting particle cascade, called an
extensive air shower, arrives at ground level with billions of energetic particles extending over an area as
large as 10 square miles.
AIRES simulation of what
happens when a proton with
1Tev of energy hits the
atmosphere about 20km above
the ground. The shower is in a
20km x 5km x 5km box
superimposed on a scale map of
Chicago's lakefront.
Cosmic rays are charged particles (usually a proton or a heavy nucleus) that constantly rain down on us from
space. When a cosmic ray particle reaches Earth, it collides with a nucleus high in the atmosphere, producing
many secondary particles, which share the original primary particle's energy. The secondary particles
subsequently collide with other nuclei in the atmosphere, creating a new generation of energetic particles that
continue the process, multiplying the total number of particles. The resulting particle cascade, called an
extensive air shower, arrives at ground level with billions of energetic particles extending over an area as
large as 10 square miles.
AIRES simulation of what
happens when a proton with
1Tev of energy hits the
atmosphere about 20km above
the ground. The shower is in a
20km x 5km x 5km box
superimposed on a scale map of
Chicago's lakefront.
Imaging Air Cherenkov Telescopes (IACTs)
IACTs are ground bases telescopes optimazied for the detection of
photons.
The detectors used have a light collection mirror and a camera, so they
resemble optical telescopes at least superficially.
These telescopes detect light produced by the Cherenkov effect, by
relativistic particles slowing down is in the atmosphere.
IACT-s record many Cherenkov photons for a single original gamma; they
are seen by the camera as an image whose characteristics allow to
identify the recorded particle as a gamma, and to specify its direction and
energy.
MAGIC
(Major Atmospheric Gamma-ray Imaging
Cherenkov Telescope)
is a γ-ray telescope situated at the Roque
de los Muchachos Observatory on La
Palma, one of the Canary Islands, at about
2200 m above sea level. It detects particle
showers released by cosmic gamma-rays,
using the Cherenkov radiation. With a
diameter of 17 meters for the reflecting
surface, it is the largest in the world.
MAGIC is sensitive to cosmic γ-rays with
energies between 50 GeV and 30 TeV
Technical specifications
■ Collecting area of 236 m² consisting of 50 cm x 50
cm Aluminium individual reflectors
■ A lightweight carbon fibre frame
■ A detector consisting of 396 separate hexagonal
photomultiplier detectors in the center
(diameter: 2.54 cm) surrounded by 180 larger
photomultiplier detectors (diameter: 3.81 cm).
■ Data are transferred in analogue form by fibre
optic cables
■ Signal digitization is done via an ADC (analogdigital converter) of frequency 2 GHz
■ The weight of the whole telescope is 40,000 kg
■ The reaction time to move to any section of the
sky is up to 40 seconds
On the vast plain known
as the Pampa Amarilla (yellow
prairie) in western Argentina, the
Pierre Auger Cosmic Ray Observatory
is studying the universe's highest energy
particles, which shower down on Earth in the form
of cosmic rays. While cosmic rays with low to moderate
energies are well understood, those with extremely high energies
remain mysterious. By detecting and studying these rare particles, the
AugerOservatory is tackling the enigmas of their origin and existence.
On the vast plain known
as the Pampa Amarilla (yellow
prairie) in western Argentina, the
The Auger Observatory is a "hybrid detector,"
employing two independent methods to detect
and study high-energy cosmic rays.
One technique detects high energy
particles through their interaction
with water placed in surface
detector tanks. The other
technique tracks the
development of air
showers by observing
ultraviolet light emitted
high in the Earth's
atmosphere.
Pierre Auger Cosmic Ray Observatory
is studying the universe's highest energy
particles, which shower down on Earth in the form
of cosmic rays. While cosmic rays with low to moderate
energies are well understood, those with extremely high energies
remain mysterious. By detecting and studying these rare particles, the
AugerOservatory is tackling the enigmas of their origin and existence.
~E-2.7
knee
1 part m-2 yr-1
ankle
1 part km-2
yr-1
LHC
~E-3
~E-2.7
Auger is sensitive to
cosmic rays with energies
greater than
1015 eV
1,600 water tanks cover an enormous section of the Pampa and serve as particle detectors. Each 12,000 liter
tank, separated from each of its neighbors by 1.5 kilometers, is completely dark inside - except when particles
from a cosmic ray air shower pass through it. These energetic particles are traveling faster than the speed of
light in water when they reach the detectors; therefore, they produce Cherenkov light that can be measured
by photomultiplier tubes mounted on the tanks. Extensive air showers contain billions of secondary particles
and can cause nearly simultaneous bursts of light in more than five tanks. Scientists can determine the energy
of the primary cosmic ray particle based on the amount of light they detect from a sample of secondary
particles. Slight differences in the detection times at different tank positions help scientists determine the
trajectory of the incoming cosmic ray.
Neutrino telescopes
Geographic
South Pole
Skiway
South Pole Station
AMANDA
IceCube
Deployments
2005: 1
2006: 8
2007: 13
2008: 14
2009: 14
2010: 14
2011: 11+
AMANDA 01/ 2000
78
74
73
72
67
66
65
59
58
57
56
47
50
49
48
IceCube string and
IceTop station 01/05
46
40
39
38
30
29
21
IceCube string and
IceTop station 01/06
IceTop station
only 2006
IceCube string and
IceTop station 02/07
22 strings
1320 digital modules
52 surface detectors
Thank you
ENRICO BORRIELLO, Astrofisica delle alte energie, O