Established in 1954, the organization is based in the northwest suburbs of Geneva on the Franco–Swiss border, (46°14′3″N 6°3′19″E) and has twenty European member states.
The term CERN is also used to refer to the laboratory, which employs just under 2,400 full-time employees and 1,500 part-time employees, and hosts some 10,000 visiting scientists and engineers, representing 608 universities and research facilities and 113 nationalities.
CERN’s main function is to provide the particle accelerators and other infrastructure needed for high-energy physics research – as a result, numerous experiments have been constructed at CERN following international collaborations. It is also the birthplace of the World Wide Web.
The main site at Meyrin has a large computer centre containing powerful data-processing facilities, primarily for experimental-data analysis; because of the need to make these facilities available to researchers elsewhere, it has historically been a major wide area networking hub.
CERN research articles from Innovation Toronto
In a paper published today in the journal Nature, the ALPHA collaboration reports the first ever measurement on the optical spectrum of an antimatter atom. This achievement features technological developments that open up a completely new era in high-precision antimatter research. It is the result of over 20 years of work by the CERN1 antimatter community.
“Using a laser to observe a transition in antihydrogen and comparing it to hydrogen to see if they obey the same laws of physics has always been a key goal of antimatter research,” said Jeffrey Hangst, Spokesperson of the ALPHA collaboration.
Atoms consist of electrons orbiting a nucleus. When the electrons move from one orbit to another they absorb or emit light at specific wavelengths, forming the atom’s spectrum. Each element has a unique spectrum. As a result, spectroscopy is a commonly used tool in many areas of physics, astronomy and chemistry. It helps to characterise atoms and molecules and their internal states. For example, in astrophysics, analysing the light spectrum of remote stars allows scientists to determine their composition.
With its single proton and single electron, hydrogen is the most abundant, simple and well-understood atom in the Universe. Its spectrum has been measured to very high precision. Antihydrogen atoms, on the other hand are poorly understood. Because the Universe appears to consist entirely of matter, the constituents of antihydrogen atoms – antiprotons and positrons – have to be produced and assembled into atoms before the antihydrogen spectrum can be measured. It’s a painstaking process, but well worth the effort since any measurable difference between the spectra of hydrogen and antihydrogen would break basic principles of physics and possibly help understand the puzzle of the matter-antimatter imbalance in the Universe.
Today’s ALPHA result is the first observation of a spectral line in an antihydrogen atom, allowing the light spectrum of matter and antimatter to be compared for the first time. Within experimental limits, the result shows no difference compared to the equivalent spectral line in hydrogen. This is consistent with the Standard Model of particle physics, the theory that best describes particles and the forces at work between them, which predicts that hydrogen and antihydrogen should have identical spectroscopic characteristics.
The ALPHA collaboration expects to improve the precision of its measurements in the future. Measuring the antihydrogen spectrum with high-precision offers an extraordinary new tool to test whether matter behaves differently from antimatter and thus to further test the robustness of the Standard Model.
ALPHA is a unique experiment at CERN’s Antiproton Decelerator facility, able to produce antihydrogen atoms and hold them in a specially-designed magnetic trap, manipulating antiatoms a few at a time. Trapping antihydrogen atoms allows them to be studied using lasers or other radiation sources.
“Moving and trapping antiprotons or positrons is easy because they are charged particles,” said Hangst. “But when you combine the two you get neutral antihydrogen, which is far more difficult to trap, so we have designed a very special magnetic trap that relies on the fact that antihydrogen is a little bit magnetic.”
Antihydrogen is made by mixing plasmas of about 90 000 antiprotons from the Antiproton Decelerator with positrons, resulting in the production of about 25 000 antihydrogen atoms per attempt. Antihydrogen atoms can be trapped if they are moving slowly enough when they are created. Using a new technique in which the collaboration stacks anti-atoms resulting from two successive mixing cycles, it is possible to trap on average 14 anti-atoms per trial, compared to just 1.2 with earlier methods. By illuminating the trapped atoms with a laser beam at a precisely tuned frequency, scientists can observe the interaction of the beam with the internal states of antihydrogen. The measurement was done by observing the so-called 1S-2S transition. The 2S state in atomic hydrogen is long-lived, leading to a narrow natural line width, so it is particularly suitable for precision measurement.
The current result, along with recent limits on the ratio of the antiproton-electron mass established by the ASACUSA collaboration, and antiproton charge-to-mass ratio determined by the BASE collaboration, demonstrate that tests of fundamental symmetries with antimatter at CERN are maturing rapidly.
A precise measurement of absolute beam intensity is essential for many areas of science. It is a key parameter to monitor any losses in a beam and to calibrate the absolute number of particles delivered to the experiments.
However, this type of measurement is very challenging with traditional beam current diagnostics when it comes to low energy, low intensity beams due to the very low signal levels. Particle accelerator experts from the University of Liverpool have now experimentally demonstrated a new type of monitor in a collaboration with CERN, the GSI Helmholtz Centre for Heavy Ion Research and Friedrich Schiller University and Helmholtz Institute Jena.
A paper just published in the IOP “Superconducting Science and Thechnology” journal, the challenges of implementation and first beam measurements are reported. These are the first-ever measurements of this type performed in a synchrotron using both coasting and short bunched beams.
The Antiproton Decelerator (AD) is a synchrotron that provides low-energy antiprotons for studies of antimatter. These studies rely on creating antimatter atoms (such as anti-hydrogen) and using them as probes for the most fundamental symmetries in nature such as the invariance of CPT, or of the gravitational acceleration on matter and antimatter.
A precise measurement of the beam intensity in the AD is essential to monitor any losses during the deceleration and cooling phases of the AD cycle, and to calibrate the absolute number of particles delivered to the experiments. However, this is very challenging with traditional beam current diagnostics due to the low intensity of the antiproton beam which is of the order of only 10 Million particles, corresponding to beam currents as low as a few hundred nano-Amperes. To cope with this, a Cryogenic Current Comparator (CCC) based on a Superconducting QUantum Interference Device (SQUID) was developed and installed in the AD, in a collaboration between accelerator experts from the University of Liverpool and CERN, the GSI Helmholtz Centre for Heavy Ion Research, Friedrich Schiller University and the Helmholtz Institute Jena.
Previous incarnations of CCC’s for accelerators suffered from issues concerning sensitivity to mechanical vibrations and electromagnetic perturbations. Furthermore, these setups were used for measuring slow beams, usually from transfer lines of accelerators, and were unable to measure short bunched beams presenting fast current variations. In order to measure the beam current and intensity throughout the cycle of a synchrotron machine such as the AD, the CCC needed to be adapted to cope with the fast signals of bunched beams.
In an open access paper just published in the IOP “Superconducting Science and Thechnology” journal, Miguel Fernandes and co-authors describe the challenges of implementation and first beam measurements. These are the first-ever CCC beam current measurements performed in a synchrotron using both coasting and short bunched beams. The paper demonstrates the exciting prospects of this new type of beam diagnostics device.
In a study led by the University of Leeds, scientists have solved one of the most long-standing challenges in atmospheric science: to understand how particles are formed in the atmosphere.
The lead scientist on the study, Professor Ken Carslaw, from the School of Earth and Environment at the University of Leeds, said: “This is a major milestone in our understanding of the atmosphere. The CERN experiment is unique, and it has produced data that seemed completely out of reach just five years ago.”
Clouds in the atmosphere consist of tiny droplets, which form when water condenses around small particles in the atmosphere called ‘aerosols’.
Understanding how aerosols are formed is therefore vital for understanding cloud formation — a process that has, until now, been an uncertain quantity in climate models, introducing problems for climate change projections.
For over 30 years, scientists have been able to build computer simulations of atmospheric gases based on measurements of chemical reaction rates made in a laboratory. This capability has been essential to our current understanding of the atmosphere, including the destruction of the ozone layer.
Until now, the same level of understanding has not been possible for aerosol particles in the atmosphere because of the enormous challenges involved in reliably measuring particle formation in a laboratory.
The CLOUD experiment can measure the ‘nucleation’ of new atmospheric particles – that is, when certain molecules in the atmosphere cluster together and grow to form new particles – in a specially designed chamber under extremely well controlled environmental conditions. Nucleation is important because, by current estimates, about half of all cloud droplets are formed on aerosol particles that were created in this way.
Professor Carslaw concludes: “These new results will give us much more confidence in how particles and clouds are handled in global climate models.”