LOPES (telescope)
Encyclopedia
The LOPES project is a cosmic ray
detector array, located in Karlsruhe
, Germany, and is operated in coincidence with an existing, well calibrated air shower experiment called KASCADE
.
There are different ways to observe cosmic ray
s, or, more accurately, the air showers
that cosmic rays produce when they enter our atmosphere
. Traditionally, one directly measures the shower products that make it all the way to the surface. These may be detected by using for example particle counters. In the case of KASCADE, the muons in the shower produce a short flash of Cherenkov light
when they traverse a slab of scintillator material. These flashes can be registered using photomultiplier
s.
The LOPES project aims to demonstrate the feasibility of a different technique, in which not the shower products themselves are observed, but secondary radio radiation that is generated by the shower. Charged particles in the shower, mostly electron
s and positron
s, are deflected slightly in Earth's magnetic field
. As these particles change direction, they emit synchrotron radiation
. This radiation is visible as a bright flash on the sky for several nanoseconds at frequencies up to a few hundred MHz. It is hoped that the LOPES project will pave the way for more cosmic ray experiments with digital radio telescopes, such as LOFAR
.
In the first phase until 2003, LOPES consisted of ten dipole antenna
s. This has been expanded to a total number of 30 antennas as of summer 2005. These antennas are read out digitally and are connected to a central computer. Here, the data from the antennas is correlated by software, so that the antennas together essentially form a phased array
. The software can point the array by forming a virtual beam and is also able to adaptively suppress interference from other sources, such as radio and tv stations.
The test array was first set up at the MPIfR in Bonn to check the hardware and develop the software. Afterwards it has been installed at the KASCADE experiment in Karlsruhe. This is a running and well calibrated air shower experiment, which provides LOPES with a suitable trigger
and reconstructed shower parameters. These parameters will act as a starting point for LOPES and will be used to calibrate its results.
LOPES is a collaboration of ASTRON
(Netherlands Foundation for Research in Astronomy, Dwingeloo
, The Netherlands), the Max-Planck-Institut für Radioastronomie (Bonn, Germany), Radboud University
(Nijmegen, The Netherlands), the Institute of Data Processing and Electronics (IPE) and the Institut für Kernphysik (IK), both at Forschungszentrum Karlsruhe (Karlsruhe, Germany), and the KASCADE-Grande collaboration. The KASCADE-Grande collaboration consists of groups from Germany, Poland, Romania, and Italy.
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
detector array, located in Karlsruhe
Karlsruhe
The City of Karlsruhe is a city in the southwest of Germany, in the state of Baden-Württemberg, located near the French-German border.Karlsruhe was founded in 1715 as Karlsruhe Palace, when Germany was a series of principalities and city states...
, Germany, and is operated in coincidence with an existing, well calibrated air shower experiment called KASCADE
KASCADE
KASCADE is a European physics experiment started in 1996 at Forschungszentrum Karlsruhe, Germany, an extensive air shower experiment array to study the cosmic ray primary composition and the hadronic interactions in the energy range of 1016–1018 eV, measuring simultaneously the electronic, muonic...
.
There are different ways to observe cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
s, or, more accurately, the air showers
Air shower (physics)
An air shower is an extensive cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a primary cosmic ray enters the atmosphere...
that cosmic rays produce when they enter our atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
. Traditionally, one directly measures the shower products that make it all the way to the surface. These may be detected by using for example particle counters. In the case of KASCADE, the muons in the shower produce a short flash of Cherenkov light
Cherenkov radiation
Cherenkov radiation is electromagnetic radiation emitted when a charged particle passes through a dielectric medium at a speed greater than the phase velocity of light in that medium...
when they traverse a slab of scintillator material. These flashes can be registered using photomultiplier
Photomultiplier
Photomultiplier tubes , members of the class of vacuum tubes, and more specifically phototubes, are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum...
s.
The LOPES project aims to demonstrate the feasibility of a different technique, in which not the shower products themselves are observed, but secondary radio radiation that is generated by the shower. Charged particles in the shower, mostly electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s and positron
Positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...
s, are deflected slightly in Earth's magnetic field
Earth's magnetic field
Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
. As these particles change direction, they emit synchrotron radiation
Synchrotron radiation
The electromagnetic radiation emitted when charged particles are accelerated radially is called synchrotron radiation. It is produced in synchrotrons using bending magnets, undulators and/or wigglers...
. This radiation is visible as a bright flash on the sky for several nanoseconds at frequencies up to a few hundred MHz. It is hoped that the LOPES project will pave the way for more cosmic ray experiments with digital radio telescopes, such as LOFAR
LOFAR
LOFAR is the Low Frequency Array for radio astronomy, built by the Netherlands astronomical foundation ASTRON and operated by ASTRON's radio observatory....
.
In the first phase until 2003, LOPES consisted of ten dipole antenna
Dipole antenna
A dipole antenna is a radio antenna that can be made of a simple wire, with a center-fed driven element. It consists of two metal conductors of rod or wire, oriented parallel and collinear with each other , with a small space between them. The radio frequency voltage is applied to the antenna at...
s. This has been expanded to a total number of 30 antennas as of summer 2005. These antennas are read out digitally and are connected to a central computer. Here, the data from the antennas is correlated by software, so that the antennas together essentially form a phased array
Phased array
In wave theory, a phased array is an array of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.An antenna array...
. The software can point the array by forming a virtual beam and is also able to adaptively suppress interference from other sources, such as radio and tv stations.
The test array was first set up at the MPIfR in Bonn to check the hardware and develop the software. Afterwards it has been installed at the KASCADE experiment in Karlsruhe. This is a running and well calibrated air shower experiment, which provides LOPES with a suitable trigger
Trigger (particle physics)
In particle physics, a trigger is a system that uses simple criteria to rapidly decide which events in a particle detector to keep when only a small fraction of the total can be recorded. Trigger systems are necessary due to real-world limitations in data storage capacity and rates...
and reconstructed shower parameters. These parameters will act as a starting point for LOPES and will be used to calibrate its results.
LOPES is a collaboration of ASTRON
ASTRON
ASTRON is the Netherlands Foundation for Research in Astronomy. ASTRON is an abbreviation of the Dutch Stichting ASTRonomisch Onderzoek in Nederland. This translates to NFRA in English, which is sometimes used to refer to ASTRON in English texts. Its main offices are in Dwingeloo at the site of the...
(Netherlands Foundation for Research in Astronomy, Dwingeloo
Dwingeloo
Dwingeloo is a town halfway between Meppel and Assen in the Dutch province of Drenthe. It is a part of the municipality of Westerveld.The town is known internationally because of the radio telescope of the Dwingeloo Radio Observatory , located on the edge of the Dwingeloo Heath, 3 km south of...
, The Netherlands), the Max-Planck-Institut für Radioastronomie (Bonn, Germany), Radboud University
Radboud University Nijmegen
Radboud University Nijmegen is a public university with a strong focus on research in Nijmegen, the Netherlands...
(Nijmegen, The Netherlands), the Institute of Data Processing and Electronics (IPE) and the Institut für Kernphysik (IK), both at Forschungszentrum Karlsruhe (Karlsruhe, Germany), and the KASCADE-Grande collaboration. The KASCADE-Grande collaboration consists of groups from Germany, Poland, Romania, and Italy.