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.”
The European Organization for Nuclear Research (French: Organisation européenne pour la recherche nucléaire, originally “Conseil Européen pour la Recherche Nucléaire“), known as CERN (/ˈsɜrn/; French pronunciation: [sɛʁn]; see History) is an international organization whose purpose is to operate the world’s largest particle physics laboratory.
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.