Conclusions from 12 Years Operational Experience of the Cryoplants for the Superconducting Magnets of the LEP Experiments

The Large Electron Positron Collider (LEP) has ended its last physics run in November 2000, and it is at present being dismantled to liberate the tunnel for the Large Hadron Collider (LHC) project to be completed by end of 2005. The cryogenic systems for the superconducting solenoid and focusing quadrupoles for the two LEP experiments, ALEPH and DELPHI, each supplying a cooling power of 800 W/4.5 K entropy equivalent, have accumulated more then 100'000 hours of running time. The paper summarises the 12 years cryogenic experience in the various operating modes: cool-down, steady state, recovery after energy fast dump, utilities failures and warm-up of the superconducting magnets. The detailed operation statistics is presented and compared to the other CERN cryogenic systems. Emphasis is given to the technical analysis of the fault conditions and of their consequences on the helium refrigeration production time in view of the future operation of the LHC cryogenics

The cryogenic system for the superconducting solenoid magnet of the CMS experiment

The design concept of the CMS experiment, foreseen for the Large Hadron Collider (LHC) project at CERN, is based on a superconducting solenoid magnet. The large coil will be made of a four layers winding generating the 4 T uniform magnetic induction required by the detector. The length of the solenoid is 13 m with an inner diameter of 5.9 m. The mass kept at liquid helium temperature totals 220 t and the electromagnetic stored energy is 2.7 GJ. The windings are indirectly cooled with a liquid helium flow driven by a thermosyphon effect. The external cryogenic system consists of a 1.5 kW at 4.5 K (entropy equivalent) cryoplant including an additional liquid nitrogen precooling unit and a 5000 litre liquid helium buffer. The whole magnet and cryogenic system will be tested at the surface by 2003 before final installation in the underground area of LHC

The CERN Cryogenic Test Facility for the Atlas Barrel Toroid Magnets

The superconducting magnet system of the ATLAS detector will consist of a central solenoid, two end-cap toroidal magnets (ECT) and the barrel toroid magnet (BT) made of eight coils symmetrically placed around the central axis of the detector. The magnets will be tested individually in a 5000 m2 experimental area prior to their final installation at an underground cavern of the LHC Collider. For the BT magnets, a dedicated cryogenic test facility has been designed which is currently under the construction and commissioning phase. A liquid nitrogen pre-cooling unit and a 1200 [email protected] refrigerator will allow flexible operating conditions via a rather complex distribution and transfer line system. Flow of two-phase helium for cooling the coils is provided by centrifugal pumps immersed in a saturated liquid helium bath. The integration of the pumps in an existing cryostat required the adoption of novel mechanical solutions. Tests conducted permitted the validation of the technical design of the cryostat and its instrumentation. The characteristics of one pump were measured and pressure rise of 300 mbar at nominal flow of 80 g/s confirmed the specifications

New cryogenic facilities for testing superconducting equipments for the CERN Large Hadron Collider

CERN's major project, the Large Hadron Collider (LHC), has moved to an implementation phase with machine construction to be completed by 2005. To achieve the design proton-proton centre of mass energy of 14 TeV in the given 27 km circumference LEP tunnel, the LHC will make an extensive use of high-field superconducting magnets using Nb-Ti filament operated at 1.9 K. In order to test, on the one han d, the superconducting cables of the magnets and, on the other hand, the expected performance of several of these magnets assembled in a string representing the lattice period of the machine (107 m lo ng), CERN has installed new cryogenic test facilities. The paper briefly describes these new facilities with all their associated equipments

Refrigeration System for the ATLAS Experiment

The proposed ATLAS detector for the 27 km circumference LHC collider is of unprecedented size and complexity. The magnet configuration is based on an inner superconducting solenoid and large superconducting air-core toroids (barrel and two end-caps) each made of eight coils symmetrically arranged outside the calorimetry. The total cold mass approaches 600 tons and the stored energy is 1.7 GJ. The cryogenic infrastructure will include a 6 kW @ 4.5 K refrigerator, a precooling unit and distribution systems and permits flexible operation during cool-down, normal running and quench recovery. A dedicated LN2 refrigeration system is proposed for the three liquid argon calorimeters (84 m3 of LAr). Magnets and calorimeters will be individually tested prior to their definitive installation in a large scale cryogenic test area on the surface. The experiment is scheduled to be operational in 2005

Cryogenics for CERN experiments: past, present and future

Use of cryogenics at CERN was originated (in the 1960s) by bubble chambers and the associated s.c. solenoids. Complex cryoplants were installed to provide cooling at LH2 and LHe temperatures. Continuity (in the 1970s) in He cryogenics for experiments was provided by spectrometer magnets for fixed target physics of the SPS accelerator. More recently (in the 1980s), large "particle-transparent" s.c. solenoids for collider experiments (LEP) have been built demanding new cryoplants. The LHC experiments (in the 2000s) will continue the tradition with s.c. dipoles (ALICE and LHCb), solenoids (CMS, ATLAS) and toroids (ATLAS) of unusual size. Cryogenics for experiments using noble liquids follows the same trend since the development (in the 1970s) of the first shower LAr detectors. A LKr calorimeter (about 10 m3) will be operated in 1996 and the ATLAS experiment foresees a set of three huge LAr calorimeters (almost 90 m3 total volume of liquid) to be installed underground

The ATLAS magnet test facility at CERN

The magnet system for the ATLAS detector at CERN consists of a Barrel Toroid (BT), two End-Cap Toroids (ECT) and a Central Solenoid (CS). The overall dimensions of the system are 20 m in diameter by 26 m in length. Before underground installation all coils will be tested on surface in a magnet test facility which is under construction. Moreover two model coils are tested as well as subsystems. In this paper the design and construction of the test facility is presented. (3 refs)

Selected reactive oxygen species and antioxidant enzymes in common bean after Pseudomonas syringae pv. phaseolicola and Botrytis cinerea infection

Phaseolus vulgaris cv. Korona plants were inoculated with the bacteria Pseudomonas syringae pv. phaseolicola (Psp), necrotrophic fungus Botrytis cinerea (Bc) or with both pathogens sequentially. The aim of the experiment was to determine how plants cope with multiple infection with pathogens having different attack strategy. Possible suppression of the non-specific infection with the necrotrophic fungus Bc by earlier Psp inoculation was examined. Concentration of reactive oxygen species (ROS), such as superoxide anion (O2 -) and H2O2 and activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were determined 6, 12, 24 and 48 h after inoculation. The measurements were done for ROS cytosolic fraction and enzymatic cytosolic or apoplastic fraction. Infection with Psp caused significant increase in ROS levels since the beginning of experiment. Activity of the apoplastic enzymes also increased remarkably at the beginning of experiment in contrast to the cytosolic ones. Cytosolic SOD and guaiacol peroxidase (GPOD) activities achieved the maximum values 48 h after treatment. Additional forms of the examined enzymes after specific Psp infection were identified; however, they were not present after single Bc inoculation. Subsequent Bc infection resulted only in changes of H2O2 and SOD that occurred to be especially important during plant–pathogen interaction. Cultivar Korona of common bean is considered to be resistant to Psp and mobilises its system upon infection with these bacteria. We put forward a hypothesis that the extent of defence reaction was so great that subsequent infection did not trigger significant additional response

Search for anomalies in the neutrino sector with muon spectrometers and large LArTPC imaging detectors at CERN

A new experiment with an intense ~2 GeV neutrino beam at CERN SPS is proposed in order to definitely clarify the possible existence of additional neutrino states, as pointed out by neutrino calibration source experiments, reactor and accelerator experiments and measure the corresponding oscillation parameters. The experiment is based on two identical LAr-TPCs complemented by magnetized spectrometers detecting electron and muon neutrino events at Far and Near positions, 1600 m and 300 m from the proton target, respectively. The ICARUS T600 detector, the largest LAr-TPC ever built with a size of about 600 ton of imaging mass, now running in the LNGS underground laboratory, will be moved at the CERN Far position. An additional 1/4 of the T600 detector (T150) will be constructed and located in the Near position. Two large area spectrometers will be placed downstream of the two LAr-TPC detectors to perform charge identification and muon momentum measurements from sub-GeV to several GeV energy range, greatly complementing the physics capabilities. This experiment will offer remarkable discovery potentialities, collecting a very large number of unbiased events both in the neutrino and antineutrino channels, largely adequate to definitely settle the origin of the observed neutrino-related anomalies.Comment: Contribution to the European Strategy for Particle Physics - Open Symposium Preparatory Group, Kracow 10-12 September 201

Redox activities and ROS, NO and phenylpropanoids production by axenically cultured intact olive seedling roots after interaction with a mycorrhizal or a pathogenic fungus

Las raíces de las plántulas de olivo, en cultivo axénico, fueron colocadas alternativamente en contacto con Rhizophagus irregulares (micorrícicos) o con hongos Verticillim dahliae (patógenos). También se incluyeron tratamientos MeJA. Las raíces intactas (generación de anión superóxido, superóxido dismutasa y actividades de peroxidasa) se midieron en las actividades in vivo del apoplasto. Todos nuestros resultados mostraron que las actividades redox apoplásticas de raíces de las plántulas intactas en contacto con el hongo micorriza compatible fueron claramente atenuados en comparación con el hongo patógeno o tratado con MeJA, incluso en las primeras etapas usadas en el tratamiento. Los fenoles totales, flavonoides y glucósidos fenilpropanoides, también fueron cuantificados. Las raíces en contacto con el hongo micorriza no mejoraron la biosíntesis de compuestos fenólicos con respecto a los controles, mientras que los de contacto con el patógeno mejoraron de forma significativa la biosíntesis de todas las fracciones fenólicas medidas. Las especies reactivas del oxígeno y la acumulación de óxido nítrico en las raíces fueron examinadas por microscopía de fluorescencia. Todos ellas presentaron una acumulación mucho mayor en las raíces en contacto con el patógeno que con el hongo micorriza. En total, estos resultados indican que las raíces de las plántulas intactas de olivo, claramente diferenciadas entre micorrizas y hongos patógenos, atenuan las reacciones de defensa contra la primera para facilitar su creación, mientras que induce una reacción de defensa fuerte y sostenida contra el segundo. Ambas especies reactivas de oxígeno y nitrógeno parecían estar involucrados en estas respuestas desde los primeros momentos de contacto. Sin embargo, se necesitan más investigaciones para aclarar la diafonía propuesta entre ellos y sus respectivas funciones en estas respuestas ya que las imágenes de fluorescencia de las raíces revelaron que las especies reactivas del oxígeno se acumulan principalmente en el apoplasto (congruente con las actividades redox medidas en este compartimento), mientras el óxido nítrico se almacena principalmente en el citosol.Roots of intact olive seedlings, axenically cultured, were alternatively placed in contact with Rhizophagus irregularis (mycorrhizal) or Verticillim dahliae (pathogenic) fungi. MeJA treatments were also included. In vivo redox activities in the apoplast of the intact roots (anion superoxide generation, superoxide dismutase and peroxidase activities) were measured. All our results showed that apoplastic redox activities of intact seedling roots in contact with the compatible mycorrhizal fungus were clearly attenuated in comparison with the pathogenic fungus or treated with MeJA, even at the early stages of treatment used. Total phenolics, flavonoids and phenylpropanoid glycosides were also quantified. Roots in contact with the mycorrhizal fungus did not enhance the biosynthesis of phenolic compounds with respect to controls, while those in contact with the pathogenic one significantly enhanced the biosynthesis of all phenolic fractions measured. Reactive oxygen species and nitric oxid accumulation in roots were examined by fluorescence microscopy. All of them presented much higher accumulation in roots in contact with the pathogenic than with the mycorrhizal fungus. Altogether these results indicate that intact olive seedling roots clearly differentiated between mycorrhizal and pathogenic fungi, attenuating defense reactions against the first to facilitate its establishment, while inducing a strong and sustained defense reaction against the second. Both reactive oxygen and nitrogen species seemed to be involved in these responses from the first moments of contact. However, further investigations are required to clarify the proposed crosstalk between them and their respective roles in these responses since fluorescence images of roots revealed that reactive oxygen species were mainly accumulated in the apoplast (congruently with the measured redox activities in this compartment) while nitric oxid was mainly stored in the cytosol.-- Ministerio de Ciencia e Innovación. Proyecto CGL2009-12406 -- Junta de Extremadura. Proyecto PRI09A023peerReviewe