Electrical and magnetic performance of the LHC short straight sections

The Short Straight Section (SSS) for the Large Hadron Collider arcs, containing in a common cryostat the lattice quadrupoles and correction magnets, have now entered series production. The foremost features of the lattice quadrupole magnets are a two-in-one structure containing two 56 mm aperture, two-layers coils wound from 15.1 mm wide NbTi cables, enclosed by the stainless steel collars and ferromagnetic yoke, and inserted into the inertia tube. Systematic cryogenic tests are performed at CERN in order to qualify these magnets with respect to their cryogenic and electrical integrity, the quench performance and the field quality in all operating conditions. This paper reports the main results obtained during tests and measurements in superfluid helium. The electrical characteristics, the insulation measurements and the quench performance are compared to the specifications and expected performances for these magnets. The field in the main quadrupole is measured using three independent systems: 10-m long twin rotating coils, an automatic scanner, and single stretched wire. A particular emphasis is given to the integrated transfer function which has a spread of around 12 units rms in the production and is a critical issue. The do-decapole harmonic component, which required trimming through a change in coil shims, is also discussed. Finally, the magnetic axis measurements at room temperature and at 1.9 K, providing the nominal vertical shift for installation are reported.peer-reviewe

European Strategy for Accelerator-Based Neutrino Physics

Massive neutrinos reveal physics beyond the Standard Model, which could have deep consequences for our understanding of the Universe. Their study should therefore receive the highest level of priority in the European Strategy. The discovery and study of leptonic CP violation and precision studies of the transitions between neutrino flavours require high intensity, high precision, long baseline accelerator neutrino experiments. The community of European neutrino physicists involved in oscillation experiments is strong enough to support a major neutrino long baseline project in Europe, and has an ambitious, competitive and coherent vision to propose. Following the 2006 European Strategy for Particle Physics (ESPP) recommendations, two complementary design studies have been carried out: LAGUNA/LBNO, focused on deep underground detector sites, and EUROnu, focused on high intensity neutrino facilities. LAGUNA LBNO recommends, as first step, a conventional neutrino beam CN2PY from a CERN SPS North Area Neutrino Facility (NANF) aimed at the Pyhasalmi mine in Finland. A sterile neutrino search experiment which could also be situated in the CERN north area has been proposed (ICARUS-NESSIE) using a two detector set-up, allowing a definitive answer to the 20 year old question open by the LSND experiment. EUROnu concluded that a 10 GeV Neutrino Factory, aimed at a magnetized neutrino detector situated, also, at a baseline of around 2200 km (+-30%), would constitute the ultimate neutrino facility; it recommends that the next 5 years be devoted to the R&D, preparatory experiments and implementation study, in view of a proposal before the next ESPP update. The coherence and quality of this program calls for the continuation of neutrino beams at CERN after the CNGS, and for a high priority support from CERN and the member states to the experiments and R&D program.Comment: Prepared by the program committee of the Neutrino `town meeting', CERN, 14-16 May 2012 and submitted to the European Strategy For European Particle Physic

Performance of LHC Main Dipoles for Beam Operation

At present about 90% of the main dipoles for the LHC have been manufactured and one of the three cold mass assemblers has already completed the production. 85% of the 1232 dipoles needed for the tunnel have been tested and accepted. In this paper we mainly deal with the performance results: the quench behaviour, the magnetic field quality, the electrical integrity quality and the geometry features will be summarized

Accelerators for Physics Experiments : From Diagnostics and Control to Design

This thesis develops techniques of control-methods, optimization, and diagnostics of accelerator equipment and the produced particle beams with emphasis on the Large Hadron Collider (LHC) project at CERN. From a solid knowledge of the characteristics of the manufactured accelerator equipment gained from in-depth measurements and analysis of measured data, a link to an enhanced equipment design can be made. These techniques will be demonstrated in applications related to the LHC magnet production and to the LHC upgrade studies. The LHC is a 27 km long superconducting accelerator, which CERN, the European high-energy particle physics research organisation, is presently being commissioned in a tunnel 80 m under ground level in the Geneva region. This machine forms the last link in an interconnected chain of several particle accelerators at CERN. The overall system performance, i.e. the quality of particle beams being accelerated in this accelerator chain is directly related to the control of the quality of the superconducting magnets used in the last link, in the LHC. Different upgrade scenarios to reach the ultimate design luminosity and beyond that, implying major machine changes are presently being studied. These scenarios all pose very challenging design requirements for magnets situated in the beam collision regions where extremely radioactive environments have to be dealt with. The LHC is expected to produce very highly energetic and intense particle beams for a number of physics experiments during the next decades, making the subjects of the thesis both timely and important. The work described has been performed at CERN, which has become the largest high-energy physics laboratory in the world. Here, a number of particle accelerators are connected in series to permit the acceleration of particles to unprecedented high energies to explore the nature of our universe. The accelerators at CERN are assembled of a large number of parts requiring a high level of technological know-how. Control systems and optimization procedures play a natural and necessary role to fulfil the requirements. Diagnostics and control system technology have been used to increase the efficiency of accelerator operation. An extensive analysis of the measured magnetic field have been used to optimize the delicate process of controlling the assembly of superconducting accelerator magnets for the LHC. This paper also describes the control procedures developed, to permit the adjustment of the geometric shape of the 15 m long dipole to optimize the field quality and beam aperture. From a detailed statistical analysis of the collected geometry data from the 1232 LHC main dipole magnets unresolved issues concerning the measurements were explained and corrected, providing more accurate information for the alignment of the main dipoles and quadrupoles. The LHC will start operation in 2008, after a most careful installation of all magnets and a huge volume of other equipment in the accelerator tunnel. In particular, the very specialized welding techniques and the brazing of tubes, bellows and conductors, have posed great challenges. Tenths of thousands of welds that have to withstand temperature changes of 300 K and operation with super-fluid helium at 1.9 K have been made. The magnet systems that create the conditions for particle collisions in the two main experiments, the insertion triplets, will have to be exchanged when upgrading the performance of the machine. The upgrade of the machine’s luminosity is expected after 4 years of LHC operation at nominal luminosity. Unless the new magnets are very carefully designed and well shielded the particle debris from the increased collision rates will perturb their operation. Using a new superconductor technology, limiting the probability of magnet quenches, combined with a new layout of the insertion region can minimize the effect of the impinging debris. The necessary shielding layout to protect the magnet coils will be discussed. The future of accelerators for particle physics is important: the development of accelerator technology to produce neutrino beams from beta decaying ions is one possibility for new physics. This subject will be treated from the aspect of energy deposition from decay products in superconducting magnet coils.QC 2010092

Accelerators for Physics Experiments : From Diagnostics and Control to Design

This thesis develops techniques of control-methods, optimization, and diagnostics of accelerator equipment and the produced particle beams with emphasis on the Large Hadron Collider (LHC) project at CERN. From a solid knowledge of the characteristics of the manufactured accelerator equipment gained from in-depth measurements and analysis of measured data, a link to an enhanced equipment design can be made. These techniques will be demonstrated in applications related to the LHC magnet production and to the LHC upgrade studies. The LHC is a 27 km long superconducting accelerator, which CERN, the European high-energy particle physics research organisation, is presently being commissioned in a tunnel 80 m under ground level in the Geneva region. This machine forms the last link in an interconnected chain of several particle accelerators at CERN. The overall system performance, i.e. the quality of particle beams being accelerated in this accelerator chain is directly related to the control of the quality of the superconducting magnets used in the last link, in the LHC. Different upgrade scenarios to reach the ultimate design luminosity and beyond that, implying major machine changes are presently being studied. These scenarios all pose very challenging design requirements for magnets situated in the beam collision regions where extremely radioactive environments have to be dealt with. The LHC is expected to produce very highly energetic and intense particle beams for a number of physics experiments during the next decades, making the subjects of the thesis both timely and important. The work described has been performed at CERN, which has become the largest high-energy physics laboratory in the world. Here, a number of particle accelerators are connected in series to permit the acceleration of particles to unprecedented high energies to explore the nature of our universe. The accelerators at CERN are assembled of a large number of parts requiring a high level of technological know-how. Control systems and optimization procedures play a natural and necessary role to fulfil the requirements. Diagnostics and control system technology have been used to increase the efficiency of accelerator operation. An extensive analysis of the measured magnetic field have been used to optimize the delicate process of controlling the assembly of superconducting accelerator magnets for the LHC. This paper also describes the control procedures developed, to permit the adjustment of the geometric shape of the 15 m long dipole to optimize the field quality and beam aperture. From a detailed statistical analysis of the collected geometry data from the 1232 LHC main dipole magnets unresolved issues concerning the measurements were explained and corrected, providing more accurate information for the alignment of the main dipoles and quadrupoles. The LHC will start operation in 2008, after a most careful installation of all magnets and a huge volume of other equipment in the accelerator tunnel. In particular, the very specialized welding techniques and the brazing of tubes, bellows and conductors, have posed great challenges. Tenths of thousands of welds that have to withstand temperature changes of 300 K and operation with super-fluid helium at 1.9 K have been made. The magnet systems that create the conditions for particle collisions in the two main experiments, the insertion triplets, will have to be exchanged when upgrading the performance of the machine. The upgrade of the machine’s luminosity is expected after 4 years of LHC operation at nominal luminosity. Unless the new magnets are very carefully designed and well shielded the particle debris from the increased collision rates will perturb their operation. Using a new superconductor technology, limiting the probability of magnet quenches, combined with a new layout of the insertion region can minimize the effect of the impinging debris. The necessary shielding layout to protect the magnet coils will be discussed. The future of accelerators for particle physics is important: the development of accelerator technology to produce neutrino beams from beta decaying ions is one possibility for new physics. This subject will be treated from the aspect of energy deposition from decay products in superconducting magnet coils.QC 2010092

Neutrino factories

Neutrinos are produced by many processes in our universe. These elusive particles reach the earth having a certain energy permitting them to react with nuclei in detectors that are specifically designed to probe their properties. However, to get higher intensities and higher energy neutrinos for better statistics and better physics reach, the use of accelerators is necessary to advance in the field of neutrino research. To produce neutrinos with an accelerator, one needs to send a high power beam onto a target to get particles or isotopes that produce neutrinos with the required properties, by decay. The parent particles have to be collected and prepared for injection into an accelerating structure. Accelerator-based experiments can tune the energy of the produced neutrinos by boosting and controlling the energy of the parent particle. The produced neutrinos will travel the distance between the source and the detector, generally through earth; the distance the neutrino travels through earth, the energy of the neutrino as well as the flavor of the neutrino give important information on their interaction with matter. The position of the physics detector is coupled to the energy of the neutrino, since the neutrino oscillation length varies inversely with the energy. The position of the detector is chosen depending on what kind of physics is being explored. “Short Baseline” experiments (a few km between the target and the detector) need beam powers up to a few hundred kW and longer baseline experiments, having detectors at from a few hundred up to thousands of km, need beam power on target reaching the MW range. “Next Generation” facilities will go up to many MW. Longer baseline experiments address physics related to oscillations of active neutrinos, while short baseline facilities do research related to the search for neutrinos not yet observed, so called sterile neutrinos. Getting the sensitivities needed for physics today translates to beampower on target reaching up to 5 MW for some of the proposed facilities. The potential of the neutrino beam can be enhanced by accelerating and storing the parent particles in a decay ring. In the case where muons are used for neutrino production, the pions produced in the target are collected and focused into a decay pipe behind the target, where they decay into muons. Challenging cooling and phase space manipulations of the muons make injection of the muon beam into the accelerator chain possible. Then follows acceleration up to the energy of a storage ring, and the neutrino useful for physics is produced in long straight sections directed to the physics detector. Alternatively, beta active isotopes produced in a target can be collected in an ion source, accelerated and stored in a race track decay ring where beta decay gives neutrinos aimed at the experiment