Radio Detection of Cosmic Rays with LOPES and LOFAR

advertisement
Astroparticle Physics
with LOPES and LOFAR
Heino Falcke
ASTRON, Dwingeloo, The Netherlands
University of Nijmegen, The Netherlands
Tim Huege, Andreas Horneffer (MPIfR Bonn)
Andreas Nigl, Sven Lafèbre, Jan Kuijpers
(Univ. Nijmegen)
&
LOPES & KASCADE Grande Collaboration
Structure of Talk
• Intro: Cosmic Rays
• Radio Emission of CRs
– Properties
– Theory
• LOFAR & LOPES
• Neutrinos …
• Conclusions
Cosmic Ray Energy Spectrum
• The differential Cosmic
Ray spectrum is described
by a steep power law with
a E-2.75 decline.
• Low-energy cosmic rays
can be directly measured.
• High-energy cosmic rays
are measured through
their air showers.
UHECRs
Power law particle distribution in
astrophysical sources
M87 jet spectra of bright knots
Meisenheimer et al. (1997)
Optical and perhaps X-ray synchrotron require
TeV electrons and continuous re-acceleration in the jet!
3C273
Cosmic Ray Energy Spectrum
adopted from:
K. M annheim
(1998)
Multiplied by E2.75!
The GZK-Cutoff
AGASA
HiRes I
Randomization of charged particles
• Charged particles are randomized by
– the interstellar magnetic field in the
Milky Way (around the knee)
– the intergalactic magnetic field at
the highest energies
 Projected view of 20 trajectories of
proton primaries emanating from a
point source for several energies.
Trajectories are plotted until they
reach a physical distance from the
source of 40Mpc.
• At 1020 eV one can do cosmic ray
astronomy in the nearby universe.
1EeV = 1018 eV
Cronin (2004)
Clustering at the highest energies?
Neutrons and Galactic Astronomy
• Up to 1018 eV cosmic rays are
predominantly Galactic.
• At 1018 eV we have =109 for
neutrons (mn~1 GeV)
• Neutron lifetime =103sec×109=1012
sec =104.5yr
• This corresponds to a travel length
of 10 kpc!
• Proton Larmor radius at 1018 eV is
300 pc in Galactic B-field!
• Protons are isotropized – neutrons
travel on straight lines.
• At 1019 eV one could do Galactic
Neutron-Astronomy
AGASA arrival
directions of CRs
A (very) Brief History of Cosmic Rays
Victor Hess, 1912:
- discovered cosmic rays
in balloon flights,
through discharge of
Leyden jars
Pierre Auger, 1938:
- Research in Giant Air
Showers showed energies
of primary particles
above 1016 eV-- truly
unimaginable for the
time!
• 1960’s: Cosmic rays with energies of >1019 eV detected - how are they made??
• Greisen, Zatsepin, Kuzmin (GZK): there should be a limit at ~5 X 1019 eV
Shower Profiles
Longitudinal
- for different composition of primary -
Lateral
- for different secondary particles -
Cosmic Rays
Extensive Air Showers Detectors
AUGER: 3000 km2,1600 water tanks
& fluorescence
Advantages of Radio Air Showers
• Particle detectors on ground
only measure a small fraction
of electrons produced
• Height of cosmic ray
interaction depends on energy
• Energy calibration is greatly
improved by additional
information (e.g., Cerenkov)
• Radio could
– Observe 24hrs/day
– See shower maximum and
possibly evolution of shower
– Coherent emission reveals shape
Radio measurements are usually
triggered by particle detectors
Radio Emission from Cosmic Ray Air
Showers: History
• First discovery: Jelley et al.
(1965), Jodrell Bank at 44 MHz.
• Theory papers by Kahn & Lerche
(1968) and Colgate (1967)
• Firework of activities around the
world in the late 60ies & early
70ies.
• In the late 70ies radio astronomy
moved to higher frequencies and
also CR work ceased.
Jelley et al. (1965)
Theory: Coherent
Geosynchrotron Radiation

deflection of electron-positron pairs in the earth’s
magnetic field


coherent emission at low frequencies


emission on scales small compared to wavelength
dominance of geomagnetic mechanism visible in past
data


highly beamed pulses of synchrotron radiation
neglect Čerenkov radiation from charge excess, …
equivalent to past geomagnetic approaches (Kahn &
Lerche), but well-studied basis and conceptually
attractive
Falcke & Gorham (2003), Huege & Falcke (2003)
Numerical Calculations of
Geosynchrotron

Calculate the electromagnetic
radiation of a shower in the
geomagnetic field from
Maxwell’s equations:
a)
b)


semi-analytically (Mathematica)
Monte Carlo code
Calculate coherence effects,
spectrum, pulse form, for
realistic shower geometry
plus longitudinal evolution.
Next steps for Monte Carlo
code: E-field during severe
conditions (thunderstorms) and
Cherenkov process.
Huege & Falcke (2004)
Numerical Calculations of
Geosynchrotron




Most power is received at
low frequencies due to
coherence effects.
The spectrum falls off
around 50 MHz.
Overall trend fits with
historic account and rough
levels.
Absolute calibration of
historic data is uncertain
by a factor of 10!
spectrum
- R=0m
- R=100 m
- R=250 m
Data: scaled Spencer ‘69
& Prah 1971 (Haverah Park).
Huege & Falcke (2003)
(semi-analytic solution)
Numerical Calculations of
Geosynchrotron




Due to relativistic motion
the emission is highly
beamed in the forward
direction.
The emission falls off
radially and is broader for
smaller frequencies.
The foot print is several
hundred meters.
Higher energy cosmic rays
can be seen up to km.
radial dependence
Huege & Falcke (2003)
(semi-analytic solution)
Numerical Calculations of
Geosynchrotron



Surprisingly, the emission
is largely isotropic in
azimuth.
The footprint becomes
more elongated and bigger
for inclined showers.
New insight: Due to this
effect and the very low
attenuation of radio,
inclined showers should be
ideal for radio detections!
inclination dependence
Huege & Falcke (2005)
(Monte Carlo)
LOFAR
• interferometer for the
frequency range of 10 - 200
MHz
• array of 100 stations of 100
dipole antennas
• baselines of 10m to 400 km
• fully digital: received waves
are digitized and sent to a
central computer cluster
• Ideal for observing transient
events
LOFAR Cosmic Ray Performance
• The full LOFAR array will
measure CRs from 2·1014 eV
to 1020 eV with baselines
varying from 1 m to 300 km
 unique
• LOFAR will be an ideal multipurpose air shower detector
(almost) „for free“
– if we know how to use it
• Needs: Combination with
particle counters for
calibration somewhere.
 highly competitive giant air
shower array in the north!
LOFAR
Full Array
LOFAR
densely packed array
Galactic Pole
Falcke & Gorham (2003)
LOPES Partners
• MPIfR Bonn
– Project design and development
• Univ. Nijmegen
– data center, theory & software
• Uni/FZ Karlsruhe &
KASCADE Grande collab.
– air shower array & site, on-site
support
• ASTRON (Dwingeloo)
– antennas, basic electronic design
• BMBF (Ministry of Science)
– Funding within the new
”Verbundforschung
Astroteilchenphysik”
Cosmics @ Univ of Nijmegen
• L3 Cosmics
• NAHSA (CR detectors on schools)
• LOPES/LOFAR
–
–
–
–
–
FOM grant + ASTRON grant
2 PhD students, 1 Postdoc (tbd)
2 faculty
Data center for LOPES (multi-TB RAID server)
Will be lead institute for LOFAR cosmics
KASCADE
• The KASCADE experiment is
situated on the site of
Forschungszentrum Karlsruhe
in Germany.
• It measures simultaneously
the electromagnetic, muonic
and hadronic components of
extensive air showers.
• The goal of KASCADE is the
determination of the chemical
composition of primary
particles of cosmic rays
around and above the "knee„
(1015-1016 eV)
KASCADE
• The KASCADE experiment is
situated on the site of
Forschungszentrum Karlsruhe
in Germany.
• It measures simultaneously
the electromagnetic, muonic
and hadronic components of
extensive air showers.
• The goal of KASCADE is the
determination of the chemical
composition of primary
particles of cosmic rays
around and above the “knee”
(1015-1016 eV)
KASCADE-Grande
The red dots show the
location of new particle
detectors: expansion of
KASCADE to KASCADE
Grande
LOPES: Current Status

10 antenna prototype at KASCADE
(all 10 antennas running)

triggered by a large event trigger
(10 out of 16 array clusters)

offline correlation of KASCADE &
LOPES events
(not integrated yet into the KASCADE DAQ)

KASCADE can provide starting
points for LOPES air shower
reconstruction



core position of the air shower
direction of the air shower
size of the air shower
Hardware of LOPES10
LOPES-Antenna
Solar Burst Oct. 28
All-Sky Dirty Map (AzEl)
Solar Burst
Integration: 1 ms
Frequency: 45-75 MHz
Bandwidth: 30 MHz
Antennas: 8
Resolution: ~3°
Location: Karlsruhe
(research center)
Correlation, Imaging, and
Cleaning with aips++
dirty map
simulated
map
Solar Burst
Integration: 1 ms
Frequency: 45-75 MHz
Bandwidth: 30 MHz
Antennas: 8
cleaned
map
Resolution: ~3°
Location: Karlsruhe
(research center)
circular
beam
Digital Filtering

raw data from one antenna
Digital Filtering

power spectrum before and after filtering
Digital Filtering

time series after filtering
Digital Filtering

time series after filtering
Bright Event
Layout
Bright Event
E-Field
Bright Event
Power
Bright Event
Power after Beamforming
Bright Event
E-Field after Beamforming
Bright Event
Beamformed Power
Bright Event
Movie






All-sky map (AZ-EL)
Mapping with a timeresolution of 12.5 ns
Interpolation of sub-frames
Total duration is ~200 ns
No cleaning was
performed (would require
new software: clean in time
and space)
Location of burst agrees
with KASCADE location to
within 0.5°.
Neutrino-induced air showers
• At 1019 eV, horizontal neutrinos have 0.2% chance of producing a
shower along a ~250 km track, 0.5% at 1020 eV
• Could be distinguished from distant cosmic ray interactions by radio
wavefront curvature: neutrinos interact all along their track with equal
probability, thus are statistically closer & deeper in atmosphere
•
•
•
Example of tau neutrino
interactions: resulting tau lepton
decay produces large swath of
particles, out to 50km
Left: ground particle density
from electron decay channel.
Right: from pion decay channel
Results from studies for Auger air shower
array, Bertou et al. 2001, astroph/0104452
stolen from P. Gorham
Lunar Regolith Interactions & RF Cherenkov radiation
• At ~100 EeV energies, neutrino interaction length
in lunar material is ~60km
• Rmoon ~ 1740 km, so most detectable interactions
are grazing rays, but detection not limited to just
limb
• Refraction of Cherenkov cone at regolith surface
“fills in” the pattern, so acceptance solid angle is
~50 times larger than apparent solid angle of moon
• GLUE-type experiments have
huge effective volume  can set
useful limits in short time
• Large VHF array may have
lower energy threshold, also
higher duty cycle if phasing
allows multiple source tracking
Gorham et al. (2000)
Radio from Neutrinos in Ice
ANtarctic Impulsive Transient Antenna
M. Rosen, Univ. of Hawaii
Solar
Panels
ANITA
Gondola &
Payload
Antenna array
Cover (partially cut away)
600 km radius,
1.1 million km2
• NASA funding started 2003
• launch in 2006
• See also RICE project for ground-based experiments and talk by
Ad van den Berg (KVI).
Conclusions and Outlook










Cosmic rays are the pillars of astroparticle physics
With LOFAR, LOPES the Netherlands have the chance to make a
significant impact – there is a narrow window of opportunity
Growing competition: Auger (Karlsruhe & Leeds – Alan Watson),
Nancay radio experiment, HiRes?, various radio experiments for
neutrinos
Theory of Radio emission from air showers is now on solid physical
ground: geosynchrotron is sufficient to explain basic results of historic
data.
LOPES starts to work: hardware, software, data reduction algorithms,
integration with KASCADE (Grande).
LOPES has found the first unambiguous CR event: highest time
resolution ever (by a factor 10) and direct association with shower
within 0.5° by digital beam forming (we can’t say what that means yet!).
LOFAR can do lots of astroparticle physics!
New method opens an entirely new parameter range.
Interesting for Neutrino detection as well (needs more exploration).
Joint operation with neutrino telescopes, gravity wave experiments?
Download
Related flashcards

Optics

39 cards

Spectroscopy

27 cards

Photography

13 cards

Spectroscopy

36 cards

Create Flashcards