E. Wildner

A very intense neutrino super beam experiment for leptonic CP violation discovery based on the European spallation source linac

Very intense neutrino beams and large neutrino detectors will be needed in order to enable the discovery of CP violation in the leptonic sector. We propose to use the proton linac of the European Spoliation Source currently under construction in Lund, Sweden, to deliver, in parallel with the spoliation neutron production, a very intense, cost effective and high performance neutrino beam. The baseline program for the European Spoliation Source linac is that it will be fully operational at 5 MW average power by 2022, producing 2 GeV 2.86 ms long proton pulses at a rate of 14 Hz. Our proposal is to upgrade the linac to 10 MW average power and 28 Hz, producing 14 pulses/s for neutron production and 14 pulses/s for neutrino production. Furthermore, because of the high current required in the pulsed neutrino horn, the length of the pulses used for neutrino production needs to be compressed to a few mu s with the aid of an accumulator ring. A long baseline experiment using this Super Beam and a megaton underground Water Cherenkov detector located in existing mines 300-600 km from Lund will make it possible to discover leptonic CP violation at 5 sigma significance level in up to 50% of the leptonic Dirac CP-violating phase range. This experiment could also determine the neutrino mass hierarchy at a significance level of more than 3 sigma if this issue will not already have been settled by other experiments by then. The mass hierarchy performance could be increased by combining the neutrino beam results with those obtained from atmospheric neutrinos detected by the same large volume detector. This detector will also be used to measure the proton lifetime, detect cosmological neutrinos and neutrinos from supernova explosions. Results on the sensitivity to leptonic CP violation and the neutrino mass hierarchy are presented

Steering field quality in the main dipole magnets of the Large Hadron Collider

More than 10% of the collared coils of the main LHC dipoles have been produced. In this paper, we compare the measured field quality to beam dynamics targets using correlations to measurements at 1.9 K. The present status of field quality is given and corrective actions carried out to center field quality on optimal values are presented. Differences among the three manufacturers are analyzed, and the main results that concern correlation between cold and warm measurements are outlined. Present trends in the production and open points are discussed.

Production follow-up of the LHC main dipoles through magnetic measurements at room temperature

In this paper, we review the tools used for controlling the production of the LHC main dipoles through warm magnetic measurements. For the collared coil measurements, control limits are based on the statistics relative to the pre-series production. For the cold mass, the difference between collared coil and cold mass is considered, allowing a very stringent test. In both cases, measurements are split in straight part average, variations and coil ends contributions. Two different alarm levels exist in case the measured field is out of limits. The analysis can be carried out at the manufacturer and allows detection of anomalies in the measured magnetic field. These can be either due to wrong measurements or caused by assembly defects. Techniques used to work out information on the magnet assembly from the field harmonics are outlined. We summarize the experience gathered on about 180 collared coils and 120 cold masses, pointing out the bad cases and investigating the reliability of the measurements.

A large aperture superconducting dipole for beta beams to minimize heat deposition in the coil

The aim of beta beams in a decay ring is to produce highly energetic pure electron neutrino and anti-neutrino beams coming from b-decay of 18Ne10+ and 6He2+ ion beams. The decay products, having different magnetic rigidities than the main ion beam, are deviated inside the dipole. The aperture and the length of the magnet have to be optimized to avoid that the decay products hit the coil. The decay products are intercepted by absorber blocks inside the beam pipe between the dipoles to protect the following dipole. A first design of a 6T arc dipole using a cosine theta layout of the coil with an aperture of 80 mm fulfils the optics requirements. Heat deposition in the coil has been calculated using different absorber materials to find a solution to efficiently protect the coil. Aspects of impedance minimization for the case of having the absorbers inside the beam pipe have also been addressed.

Control of the Dipole Cold Mass Geometry at CERN to Optimize LHC Performance

The detailed shape of the 15 m long superconducting LHC dipole cold mass is of high importance as it determines three key parameters: the beam aperture, nominally of the order of 10 beam standard deviations; the connectivity of the beam- and technical lines between magnets; the transverse position of nonlinear correctors mounted on the dipole ends. An offset of the latter produces unwanted beam dynamics perturbations. The tolerances are in the order of mm over the length of the magnet. The natural flexibility of the dipole and its mechanical structure allow deformations during handling and transportation which exceed the tolerances. This paper presents the observed deformations of the geometry during handling and various operations at CERN, deformations which are interpreted thanks to a simple mechanical model. These observations have led to a strategy of dipole geometry control at CERN, based on adjustment of the position of its central support (the dipole is supported at three positions, horizontally and vertically) to recover individually or statistically their original shape as manufactured. The implementation of this strategy is discussed, with the goal of finding a compromise between conflicting requirements: quality of the dipole geometry, available resources for corrective actions and magnet installation strategy whereby the geometry tolerances depend on the final magnet position in the machine

Automatic beam steering in the CERN PS Complex

The recombination, transfer and injection of the four beams from the PS Booster to the PS Main Ring, have a high level of intricacy and are a subject of permanent concern for the operation of the PS Injector Complex. These tasks were thus selected as a test bench for the implementation of a prototype of an automatic beam steering system. The core of the system is based on a generic trajectory optimizer, robust enough to cope with imperfect observations. The algorithmic engine is connected to pick-up monitors and corrector magnets and its decision can be validated by the operator through a graphics user interface. Automatic beam steering can only be efficient if the beam optics is fully confirmed by experimental observations, a condition which forces the systematic elimination of errors both in hardware and software.

The Opportunity Offered by the ESSnuSB Project to Exploit the Larger Leptonic CP Violation Signal at the Second Oscillation Maximum and the Requirements of This Project on the ESS Accelerator Complex

The European Spallation Source (ESS), currently under construction in Lund, Sweden, is a research center that will provide, by 2023, the worlds most powerful neutron source. The average power of t ...

Magnet acceptance and allocation at the LHC magnet evaluation board

The normal and superconducting magnets for the LHC ring have been carefully examined to insure that each of about 1900 assemblies is suitable for the operation in the accelerator. Hardware experts and accelerator physicists have contributed to this work that consisted in magnet acceptance, and sorting according to geometry, field quality and quench level. This paper gives a description of the magnet approval mechanism that has been running since four years, reporting in a concise summary the main results achieved.

Long Term Stability of the LHC Superconducting Cryodipoles After Outdoor Storage

The main superconducting dipoles for the LHC are being stored outdoors for periods from a few weeks to several years after conditioning with dry nitrogen gas. Such a storage before installation in the 27 km circumference tunnel may affect not only the mechanical and cryogenic functionality of the cryodipoles but also their quench and field performance. A dedicated task force was established to study all aspects of long term behavior of the stored cryodipoles, with particular emphasis on electrical and vacuum integrity, quench training behavior, magnetic field quality, performance of the thermal insulation, mechanical stability of magnet shape and of the interface between cold mass and cryostat, degradation of materials and welds. In particular, one specifically selected cryodipole stored outdoors for more than one year, was re-tested at cold. In addition, various tests have been carried out on the cryodipole assembly and on the most critical subcomponents to study aspects such as the hygrothermal behavior of the supporting system and the possible oxidation of the Multi Layer Insulation reflective films. This paper summarizes the main investigations carried out and their results

Parametric study of heat deposition from collision debris into the insertion superconducting magnets for the LHC luminosity upgrade

With a new geometry in a higher luminosity environment, the power deposition in the superconducting magnets becomes a critical aspect to analyze and to integrate in the insertion design. In this paper, we quantify the power deposited in magnets insertion at variable positions from the interaction point (IP). A fine characterization of the debris due to the proton-proton collisions at 7 TeV, shows that the energetic particles in the very forward direction give rise to non intuitive dependences of the impacting energy on the magnet front face and inner surface. The power deposition does not vary significantly with the distance to the interaction point, because of counterbalancing effects of different contributions to power deposition. We have found out that peak power density in the magnet insertion does not vary significantly with or without the target absorber secondaries (TAS) protection.