CERN: Poljuljani osnovni zakoni fizike :: Nauka ~ Tehnika ~ Military

ISOLDE – Isotope Separator On-Line
An alchemical factory for nuclear physics

ISOLDE (On-Line Isotope Mass Separator) is a unique source of low-energy beams of radioactive isotopes - atomic nuclei that have too many or too few neutrons to be stable. The facility, located at the Proton-Synchrotron Booster (PSB), is like a small alchemical factory, changing one element to another, rather as the alchemists once imagined. It produces a total of more than 1000 different isotopes for a wide range of research. Up to now more than 600 isotopes of more than 60 elements - from helium to radium - have been produced, with half-lives down to milliseconds. Most of the experiments study the structure of the nucleus in different ways, but there are also experiments relevant to atomic physics, nuclear astrophysics, fundamental physics, solid-state physics and life sciences.

ISOLDE directs a beam of protons from the PSB onto special targets, yielding a wide variety of atomic fragments. Different components then extract the nuclei and separate them according to mass. The Radioactive beam EXperiment (REX) at ISOLDE accelerates the radioactive beams created in this way, increasing the range of possible experiments. Many of these use Miniball, a gamma-ray detector based on very pure germanium.

http://isolde.web.cern.ch/isolde/
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n_TOF – The neutron facility
Astrophysics, environment and medical applications

The neutron time-of-flight facility, n_TOF, is a neutron source that has been operating at CERN since 2001. It is a unique facility in which neutrons are produced in a wide range of energies and in very intense beams. This allows precise measurements of neutron related processes that are relevant for several fields.

One example is nuclear astrophysics where data produced by n_TOF are used to study the ordinary stellar evolution as well as supernovae. Intense neutron beams are also critical in the studies of processes of incineration of radioactive nuclear waste and for a better understanding of the effects of radiation in the treatment of tumors with beams of hadrons (hadrontherapy).

https://ntof-exp.web.cern.ch/ntof-exp/

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ACE – Antiproton Cell Experiment
Antiprotons versus cancer cells

ACE is a pioneering experiment that started in 2003. It aims to assess fully the effectiveness and suitability of antiprotons for cancer therapy. The experiment brings together a multidisciplinary team of experts in physics, biology and medicine from 10 institutes around the world who are the first to study the biological effects of antiprotons.

To date, particle-beam therapy has used mainly protons to destroy cancer cells. The particles are sent into a patient’s body with a pre-determined amount of energy, just enough that they stop when they reach the specific depth of the cancer. When such a beam of heavy, charged particles enters a human body, it initially inflicts very little damage. Only in the last few millimetres of the journey, as the beam ends its gradual slow-down and comes to an abrupt stop does significant damage occur. Unfortunately, although the beam destroys the cancer it also affects healthy cells along its path, so the damage to healthy tissues increases with repeat treatments.

The ACE experiment is testing the idea of using antiprotons as an alternative treatment, by directly comparing the effectiveness of cell irradiation using protons and antiprotons. When matter (in this case, the tumour cells) and antimatter (the antiprotons) meet, they annihilate (destroy each other), transforming their mass into energy. The aim is to make use of this effect, as an antiproton should annihilate with part of the nucleus of an atom in a cancer cell. The energy released by the annihilation should blow the nucleus apart and project the fragments into adjacent cancer cells, which should in turn be destroyed.

In the experimental set up, tubes were filled with live hamster cells suspended in gelatine to simulate a cross-section of tissue inside a body. Researchers sent a beam of protons or antiprotons with a range of 2 cm in water into one end of the tube, and evaluated how the fraction of surviving cells varies with the depth in the target. Initial results showed that four times fewer antiprotons than protons were needed to inflict the same level of cell damage. In treatment, this would mean significantly reduced damage to the healthy tissues. This shows that an antiproton beam could be highly valuable in treating cases of recurring cancer, where it is vital to avoid repeated damage to healthy cells.

ACE is an excellent example of how research in particle physics can bring innovative solutions with potential medical benefits. However, the validation process for any new medical treatment is lengthy. Even if all goes well, the first clinical application would still take a decade.

http://enlight.web.cern.ch/enlight/cms/?file=home

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ATRAP – Antihydrogen TRAP
Peer inside atoms of antihydrogen

ATRAP is an experiment to compare hydrogen atoms with their antimatter equivalents – antihydrogen atoms. In 2002, ATRAP provided the first glimpse inside these antiatoms after researchers successfully created and measured a large number of them.

An atom of antihydrogen consists of an antiproton and a positron (an antielectron). One of the difficulties in making antimatter is the energy the antiprotons possess when they are first made, shooting out at close to the speed of light. The researchers needed to slow them down as much as possible and this meant cooling them. ATRAP was the first to use cold positrons to cool antiprotons. The two ingredients were confined in the same trap and when they had both reached a similar temperature, some combined to form atoms of antihydrogen (a positron orbiting an antiproton). This technique was developed from another experiment at CERN called TRAP, the predecessor of ATRAP.

The current experiment was set up in the late 1990s at the same time as the experiment called ATHENA. Both had the same goals and similar methods for producing the antihydrogen atoms, but they used different detection methods.

While the ATHENA experiment came to an end in 2004, ATRAP is still in operation. It continues with its goal creating antihydrogen cold enough and trapped for long enough for precise measurements to compare with ordinary hydrogen.

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CAST – CERN Solar Axion Telescope
Gaze at the Sun for clues to antimatter mystery

CAST is an experiment to search for hypothetical particles called ‘axions’. These have been proposed by some theoretical physicists to explain why a subtle difference between matter and antimatter is found in processes involving the weak force, but not the strong force. If axions exist, they could be found in the centre of the Sun and they could also make up the invisible dark matter.

CAST is searching for these particles using a specialised telescope for looking at the Sun. It makes use of an unexpected hybrid of equipment from particle physics and astronomy. The telescope is made from a prototype of a dipole magnet for the Large Hadron Collider, with its hollow beam pipes acting as viewing tubes. To allow the magnet to operate in a superconducting state, it is supplied with cryogenic infrastructure previously used by the Large Electron Positron collider's DELPHI experiment. A focusing mirror system for X-rays (recovered from the German space programme), an X-ray detector at each end, and a moving platform add the final touches to turn the magnet into a telescope.

The idea is that the magnetic field acts as a catalyst to transform axions into X-rays, making them relatively easy to detect. The efficiency with which this takes place is greatly boosted both by the strength of the superconducting dipole magnet and its long length. CAST brings together techniques from particle physics and astronomy, while benefiting from CERN’s expertise in accelerators, X-ray detection, magnets and cryogenics.

http://cast.web.cern.ch/CAST/

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AEgIS – Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy
Measuring g with a beam of antihydrogen

The primary scientific goal of the AEgIS experiment - a collaboration of physicists from all over Europe - is the direct measurement of the Earth's gravitational acceleration, g on antihydrogen.

In the first phase of the experiment, the AEgIS team will pass an antihydrogen beam through a classical Moire deflectometer coupled to a position- sensitive detector to measure the strength of the gravitational interaction between matter and antimatter to a precision of 1%.

A system of gratings in the deflectometer splits the antihydrogen beam into parallel rays, forming a periodic pattern. From this pattern, physicists can measure how much the antihydrogen beam drops during its horizontal flight. Combining this shift with the time each atom flew and fell, the AEgIS team can then determine the strength of the gravitational force between the Earth and the antihydrogen atoms.

The AEgIS experiment will represent the first direct measurement of a gravitational effect on an antimatter system.

http://aegis.web.cern.ch/aegis/home.html

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OSQAR
Optical Search for QED vacuum magnetic birefringence, Axions and photon Regeneration

http://greybook.cern.ch/programmes/experiments/OSQAR.html

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ALPHA – Antihydrogen Laser PHysics Apparatus
Neutral trap to capture and analyse antihydrogen

The ALPHA experiment is a successor of an earlier antimatter experiment, ATHENA. Set up in late 2005 with similar overall research goals as its predecessor, ALPHA will make, capture and study atoms of antihydrogen and compare these with hydrogen atoms. This time, the physicists are using equipment of a different design which has evolved from the previous experiment.

Creating antihydrogen depends on bringing together the two component antiparticles, antiprotons and positrons, in a device for trapping particles with an electric charge. However, since antihydrogen atoms have no electric charge, they are not confined: once made the antiatoms drifted naturally to the walls of the trap. Because these walls were made of ordinary matter, the contact caused the antiatoms to annihilate a few microseconds after they were created.

ALPHA is picking up from where ATHENA left off. As well as the standard trap, ALPHA also makes use of a different trapping method to hold the antihydrogen atoms, and will keep them for a longer period before they annihilate with ordinary atoms. This should give the phy

http://alpha-new.web.cern.ch/

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COMPASS – COmmon Muon and Proton Apparatus for Structure and Spectroscopy
Particles built from quarks and gluons

COMPASS is a multi-purpose experiment taking place at CERN’s Super Proton Synchrotron accelerator.

It is looking into the complex ways in which the elementary quarks and gluons work together to give particles we observe, from the humble proton to the huge variety of more complex particles.

A major aim is to discover more about how the property called spin arises in protons and neutrons, in particular how much is contributed by the gluons that bind the quarks together via the strong force. To do this the experiment fires ‘heavy electrons’ (particles called muons) at a ‘polarized’ target.

Another important aim is to investigate the hierarchy or ‘spectrum’ of particles that quarks and gluons can form. To do this the experiment uses a beam of particles called pions. In these studies, the researchers will also look for particles called glueballs, which are made only of gluons.

About 240 physicists from 11 countries and 28 institutions work on the COMPASS experiment. The results will help physicists to gain a better understanding of the complex world inside protons and neutrons.

http://wwwcompass.cern.ch/

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CLOUD – Cosmics Leaving OUtdoor Droplets
Cosmic rays and cloud formation

CLOUD is an experiment that uses a cloud chamber to study the possible link between galactic cosmic rays and cloud formation. Based at the Proton Synchrotron at CERN, this is the first time a high-energy physics accelerator has been used to study atmospheric and climate science; the results could greatly modify our understanding of clouds and climate.

Cosmic rays are charged particles that bombard the Earth's atmosphere from outer space. Studies suggest they may have an influence on the amount of cloud cover through the formation of new aerosols (tiny particles suspended in the air that seed cloud droplets). This is supported by satellite measurements, which show a possible correlation between cosmic-ray intensity and the amount of low cloud cover. Clouds exert a strong influence on the Earth’s energy balance; changes of only a few per cent have an important effect on the climate. Understanding the underlying microphysics in controlled laboratory conditions is a key to unravelling the connection between cosmic rays and clouds.

The CLOUD experiment involves an interdisciplinary team of scientists from 18 institutes in 9 countries, comprised of atmospheric physicists, solar physicists, and cosmic-ray and particle physicists. The PS provides an artificial source of ‘cosmic rays’ that simulates natural conditions as closely as possible. A beam of particles is sent into a reaction chamber and its effects on aerosol production are recorded and analysed.

The initial stage of the experiment uses a prototype detector, but the full CLOUD experiment will include an advanced cloud chamber and a reactor chamber, equipped with a wide range of external instrumentation to monitor and analyse their contents. The temperature and pressure conditions anywhere in the atmosphere can be re-created within the chambers, and all experimental conditions can be controlled and measured, including the ‘cosmic ray’ intensity and the contents of the chambers.

http://cloud.web.cern.ch/cloud/

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DIRAC – DImeson Relativistic Atomic Complex
Pions and the strong force

DIRAC is an experiment to help physicists gain a deeper insight into the fundamental force called the strong force. This plays a crucial role in particle physics, as it binds together particles called quarks, which in turn make up many other particles, including the protons and neutrons that form the nuclei of ordinary atoms.

Relatively little work has been done at low energy to test the quantum theory of the strong force, or, equivalently, how the force behaves at longer distances.

DIRAC, a collaboration of 87 scientists from 7 countries, aims to address this gap by studying the decay of unstable ‘pionium atoms’. These are transient atoms in which positive and negative pions (unstable fundamental particles made of quarks) are bound together. They are produced using a beam from CERN’s Proton Synchrotron accelerator. Their ‘lifetime’, from creation to the end of the decay process, is being measured to a level of accuracy never achieved before.

http://dirac.web.cern.ch/DIRAC/

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NA62: Measuring rare kaon decays

The main aim of the NA62 experiment is to study rare kaon decays. Understanding these decays will help physicists to check some of the predictions that the Standard Model makes about short-distance interactions.

Specifically, NA62 will measure precisely the rate at which the charged kaon decays into a charged pion and a neutrino-antineutrino pair. To make beams rich in kaons, the NA62 team uses high-energy protons from the Super Proton Synchrotron (SPS) sent into a stationary beryllium target. The collision creates a beam which transmits almost one billion particles per second, about 6% of which are kaons.

Before entering into a large vacuum tank, each particle is measured by a silicon-pixel detector. A detector called CEDAR determines the types of particle in the beam from their Cherenkov radiation. Further detectors look for decay particles: a magnetic spectrometer in the tank measures charged tracks from kaon decays and a ring imaging Cherenkov detector (RICH) tells the team the nature of each decay particle. A large system of photon and muon detectors reject unwanted decays.

In 2 years of data taking the experiment is expected to detect about 80 decay candidates if the Standard Model prediction is correct.

This data will enable the NA62 team to determine the value of a quantity called |Vtd|, which defines the likelihood that top quarks decay to down quarks.

Understanding with precision the relations between quarks is one effective way to check the consistency of the Standard Model.

http://na62.web.cern.ch/na62/

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ASACUSA
Atomic Spectroscopy And Collisions Using Slow Antiprotons

An ANTIMATTER experiment at CERN's antiproton decelerator studying:

Laser and microwave precision spectroscopy of antiprotonic helium atoms (i.e., antiproton+electron+helium nucleus) for testing the CPT (matter-antimatter) symmetry, and cotributing to the fumdamental physical constants.

Antihydrogen ground-state hyperfine splitting measurement, for testing the CPT symmetry.

Atomic and nuclear collision cross sections at extremely low energies.

http://asacusa.web.cern.ch/ASACUSA/index-e.html

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