Reliability analysis for the quench detection in the LHC machine

The Large Hadron Collider (LHC) will incorporate a large amount of superconducting elements that require protection in case of a quench. Key elements in the quench protection system are the electronic quench detectors. Their reliability will have an important impact on the down time as well as on the operational cost of the collider. The expected rates of both false and missed quenches have been computed for several redundant detection schemes. The developed model takes account of the maintainability of the system to optimise the frequency of foreseen checks, and evaluate their influence on the performance of different detection topologies. Seen the uncertainty of the failure rate of the components combined with the LHC tunnel environment, the study has been completed with a sensitivity analysis of the results. The chosen detection scheme and the maintainability strategy for each detector family are given

Quench Heater Experiments on the LHC Main Superconducting Magnets

In case of a quench in one of the main dipoles and quadrupoles of CERN's Large Hadron Collider (LHC), the magnet has to be protected against excessive temperatures and high voltages. In order to uniformly distribute the stored magnetic energy in the coils, heater strips installed in the magnet are fired after quench detection. Tests of different quench heater configurations were performed on various 1 m long model and 15 m long prototype dipole magnets, as well as on a 3 m long prototype quadrupole magnet. The experiments aimed at optimising the layout of the quench heater strips, minimising the complexity of the protection system and determining its redundancy. In this paper we discuss the results of the performed experiments and describe the optimised quench heater design for the LHC main magnets

Protection of the Superconducting Corrector Magnets for the LHC

n the LHC about 6500 superconducting corrector magnets will be powered either in stand-alone mode or in electrical circuits of up to 154 magnets. Single corrector magnets are designed to be self-protected in case of a quench. The protection scheme of magnets powered in series depends on the energy stored in the magnet and on the number of magnets in the circuit. A quench is detected by measuring the resistive voltage of the circuit. The power converter is switched off, and for most circuits part of the energy is extracted with a resistor. Some magnets may require a resistor or possibly a diode parallel to the magnet in order to avoid overheating of the superconducting wire or an unacceptable voltage level. Experiments have been performed to understand quenching of prototype corrector magnets. In order to determine the adequate protection schemes for the magnet circuits the results have been used as input for simulations to extrapolate to the LHC conditions

Thermohydraulics of Resistive Transitions of the LHC Prototype Magnet String: Theoretical Modeling and Experimental Results

In preparation for the Large Hadron Collider (LHC) project, a 40 m-long prototype superconducting magnet string, representing a half-cell of the machine lattice, has been built and operated. The superconducting magnets which comprise this string normally operate in a pressurized static bath of superfluid helium at a pressure of 1 bar and at a temperature of 1.9 K. At 13.1 kA they have about 15.3 MJ of stored magnetic energy. A series of tests was performed to assess the thermohydraulics of resistive transitions (quenches) of the string of magnets. These measurements provide the necessary foundation for describing of the observed pressure rise as the combination of two processes, each acting on a different time scale. The measurements are presented and an explanatory model description of the events is given

Influence of dietary Na-butyrate, initial BW, and beak trimming on BW uniformity and growth performance of brown-egg laying pullets from heatching to 42 d of age

The influence of initial BW of the pullets and beak trimming on growth performance and BW uniformity was studied in Lohmann Brown pullets fed diets supplemented or not with Na-butyrate (Butirex C4; Novation 2002 S. L.) from hatching to 42 d of ag

Recuperación de las interacciones entre el haya (Fagus sylvatica) y los hongos ectomicorrícicos 140 años después del fin de la actividad minera

Even the increasing use of restoration, it does not always imply a shortterm answer in ecosystems that guarantees the recovery of their structure, functions, and services. So far, most studies evaluating ecosystem recovery have used metrics that ignore the complexity needed to structure communities of organisms that form ecosystems. Here, we analyze the recovery of species interactions (metric with a certain level of complexity) in a large time scale ('100 years). In particular, we characterized, using molecular identification, the ectomicorrhyzal (EcM) fungal communities present in 18 beech trees inside and seven outside an ancient iron in Navarra (northern Spain), in use from the XIV century until 140 years ago, as well as seven beech trees from a nearby oldgrowth forest. Species richness of EcM fungi was similar for the three locations, while differences were found for species composition in the area damaged by mining and compare to outside the mine and the reference beech forest. Our results suggest the need to assess ecosystem recovery with more complex metrics (e.g. architecture of interaction networks) in order to accurately estimate the real time required for ecosystems to fully recover. © 2019 Los Autores.Este trabajo ha sido financiado por el Plan Nacional de Investigación RETOS (CGL2015-70452-R) y la acreditación de excelencia “María de Maeztu” 2018-2022 (MDM-2017-0714). ARU fue financiada por el programa de becas predoctorales (2016) de la Fundación Tatiana Guzman el Bueno

Design and construction of a 1 m model of the low current superconducting quadrupole for the LHC insertions

About one hundred individually powered low current superconducting quadrupoles will be installed in the LHC insertions. One of the design requirements was to keep the excitation current of the magnet below 6 kA in view of minimizing the costs of the powering circuits. The design of the quadrupole is based on a 8.2 mm NbTi cable, and is designed for a nominal gradient of 200 T/m at 1.9 K. In this paper we present the design of the quadrupole and discuss the construction details of the 1 m single aperture model which has been recently completed