CLIC Detector Main Solenoid Design & Status Report

The magnet system for the CLIC Detector concepts is composed of the central solenoid in combination with the two forward anti-solenoids and the ancillary systems necessary for their operation, including the so-called push-pull scenario, allowing the quick exchange of the two detectors on the beam line. An overview of the design parameters of the detector main solenoids is presented hereafter.Comment: LCWS2011, Granada, Spai

: Rapport de fouille programmée 2008-2010

La fouille du comptoir littoral protohistorique de Pech Maho, reprise en 2004, a fait l'objet de entre 2008 et 2010 d'un second programme triannuel. Les travaux entrepris durant cette période ont principalement porté sur les phases récentes du site, plus précisément sur les phases III (v. 325-225/200 av. n. ère) et IV (v. 200 av. n. ère), cette dernière ayant été définie à l'occasion du programme en cours. En effet, il est apparu que la destruction brutale du site intervenant dans le dernier quart du IIIe s. av. n. ère ne signifiait pas l'abandon du gisement, mais que lui succédait immédiatement une phase caractérisée par une série de manifestations à caractère rituel, qui culminent avec l'érection d'un bûcher funéraire (fouillé anciennement) ayant reçu simultanément les corps d'une quinzaine d'individus. Le triannuel 2008-2010 a été l'occasion de préciser les observations préliminaires réalisées entre 2005 et 2007, en confirmant définitivement le séquençage venant d'être évoqué. Ce dernier autorise une très large relecture des données de fouille anciennes, où bon nombre de documents naguère dépeints comme étant caractéristiques d'une " couche de guerre " (restes d'équidés, pièces d'armement...) doivent en réalité être replacés dans ce contexte rituel où se conjuguent sacrifices d'équidés, dépôt d'armes, de pièces de harnachement ou d'autres objets porteurs de sens, sans compter d'autres manifestations jusque là peu documentées. La présence de restes humains, dont certains semblent avoir reçu un traitement particulier, participe également de cette phase ; ici encore, une relecture des données de fouille anciennes est dorénavant possible, révélant le caractère tout à fait exceptionnel de cette phase. La fouille 2008-2010 a ainsi porté sur trois zones distinctes. La première (zone 77) a porté sur une portion de l'îlot I, accolé au rempart méridional, portion qui n'avait été que partiellement concernée par les recherches menées par J. Campardou puis Y. Solier dans les années 1960 et 1970. La fouille a révélé l'existence d'un vaste " dépotoir " à ciel ouvert d'au moins une centaine de mètres carrés au sol, mis en place postérieurement à la destruction du site. Aménagé au milieu des ruines ou des bâtiments désaffectés et délimité par endroits par des murs nouvellement construits, cet ensemble se matérialise par une imposante couche de cendres de plusieurs dizaines de centimètres d'épaisseur, renfermant un abondant mobilier (céramiques brisées, restes de faune, coquillages...), interprété comme étant les restes de repas collectifs. La présence d'un chenet en terre cuite ou encore d'une broche à rôtir est à mettre en rapport avec la préparation de ces repas (banquet ?), la quantité importante de cendres témoignant quant à elle de feux particulièrement nourris, peut-être étalés dans le temps. Ce qui prend la forme d'un véritable " autel de cendres " fait suite à des dépôts de restes d'équidés réalisés sur la portion de rue située en façade, et précède la mise en place du bûcher collectif évoqué en préambule. L'ensemble paraît s'inscrire dans une démarche cohérente, dont la signification précise nous échappe, mais qu'il serait vain de vouloir déconnecter de l'épisode violent qui intervient à Pech Maho durant les dernières années du IIIe s. av. n. ère. Une nouvelle zone de fouille (zone 78) a été ouverte en 2008 dans la partie nord-occidentale du plateau de Pech Maho. De ce côté, un nouvel îlot a été fouillé pour ainsi dire intégralement, révélant tout d'abord que l'état visible (IIIe s.) constituait non seulement la reprise d'un bâtiment antérieur de plan manifestement méditerranéen (type " maison à pastas "), mais se superposait également à un édifice monumental dont la chronologie remonte au moins au milieu du Ve s. av. n. ère, édifice indiqué par une série de quatre bases monolithiques ayant reçu des piliers en bois, implantées en bordure occidentale de la rue 7. Dans son état de la fin du IIIe s., ce bâtiment dont l'originalité réside en partie dans l'emploi quasi exclusif de la terre massive, comprend en réalité deux parties. La première semble moins correspondre à une simple maison qu'à une entité à vocation économique (en l'occurrence commerciale), associant un entrepôt (incendié au moment de la destruction des années 225-200), une pièce de vie et un espace plus difficile à caractériser (cour ?), accessible par un couloir ouvert au sud sur la rue 6. Accolé à l'ouest, décalé sur le plan topographique, deux pièces en enfilade accessibles au sud via un escalier " monumental " se caractérisent par la présence de foyers, dallages et bases maçonnées interprétées avec vraisemblance comme des supports de stèles. La présence de crânes humains exposés est en outre attestée, de même que le démantèlement systématique des éléments porteurs de sens, vraisemblablement intervenu au moment du pillage concomitant de l'acte violent marquant la fin de l'habitat stricto sensu. La phase post destruction est ici particulièrement bien attestée, notamment par la présence d'un important dépôt d'ossements d'équidés au niveau du couloir précédemment cité. Preuve supplémentaire qu'une partie du bâti était alors en élévation, ce dépôt tout à fait singulier qui comporte plusieurs séquences a également livré une amphore vinaire, de l'armement ainsi que des mors de chevaux ; enfin, il témoigne indirectement du caractère particulier que revêtait auparavant cet îlot, la concordance topographique entre ce type de vestige et des édifices particuliers (bâtiments ou espaces publics, fortification...) étant dorénavant confirmée à l'échelle du site. La dernière zone (zone 71) correspond à la fortification, et plus précisément aux abords de la porte principale. Après avoir procédé à une relecture fine des différents états du rempart, de la porte en elle-même et de la tour en quart de cercle qui la flanque côté Ouest, la fouille s'est concentrée sur les abords extérieurs de cette porte, au niveau des " défenses avancées " en partie dégagées par Y. Solier dans les années 1970. Il apparaît désormais que ces aménagements participent d'une réorganisation globale du système d'accès, intervenant à la charnière des IVe-IIIe s. av. n. ère, soit les débuts de la phase III. De puissants terrassements sont destinés à aménager une rampe d'accès E-O menant à la porte charretière, tandis qu'une passerelle correspond au sud à un accès piéton enjambant le nouveau fossé creusé à ce moment. L'ensemble participe d'une réorganisation complexe du système de défenses, et notamment des abords de la porte principale où sont manifestement mis en œuvre des principes poliorcétiques empruntés au registre hellénistique. La fouille a également permis de retrouver l'extrémité occidentale du système de fossé archaïque, jusque-là fort mal documenté. Or, bien qu'amputé par les réaménagements du IIIe s., ce système s'avère plus complexe que prévu. En effet, l'idée d'un fossé unique daté de la phase Ib (v. 540-510) doit dorénavant être abandonnée : deux ouvrages fossoyés se succèdent, en se recoupant partiellement, le premier étant contemporain du tout premier état de la fortification (phase Ia, v. 560-540). Un des apports les plus novateurs de la zone 71 est la mise en évidence, au niveau du fossé correspondant à l'état IIIe s. de la fortification, de dépôt

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Towards Ultra-Thin Detector Magnet Designs by Insulating Coil Windings With V2_203_3-Epoxy Composite

We have measured temperature dependent resistivity of two types of vanadium oxide (V$_{2}$O$_{3}$) epoxy composites from 77 K to room temperature. Such a composite could be used as an insulating layer between the windings of a superconducting magnet. During a magnet quench, the composite is expected to change from insulating to metallic at approximately 150 K, re-distributing the current through the heated windings. Our measurement results show significantly different phase transition characteristics of the samples. A sample mixed using 99.7% pure V$_{2}$O$_{3}$powder with sharp edges in particles and an average equivalent circle diameter (ECD) of 4.5 $\mu$m has a factor of 23 resistivity change and a sample mixed using 95% pure V$_{2}$O$_{3}$powder with round edges in particles and an average ECD of 70 $\mu$m has a change of three orders of magnitude, respectively. Using V$_{2}$O$_{3}$-epoxy composite as an insulating layer between the coil windings might allow thinner detector magnet designs since the current and heat would spread more uniformly across the magnet during a quench.We have measured temperature dependent resistivity of two types of vanadium oxide (V 2 O 3 ) epoxy composites from 77 K to room temperature. Such a composite could be used as an insulating layer between the windings of a superconducting magnet. During a magnet quench, the composite is expected to change from insulating to metallic at approximately 150 K, re-distributing the current through the heated windings. Our measurement results show significantly different phase transition characteristics of the samples. A sample mixed using 99.7% pure V 2 O 3 powder with sharp edges in particles and an average equivalent circle diameter (ECD) of 4.5 μ m has a factor of 23 resistivity change and a sample mixed using 95% pure V 2 O 3 powder with round edges in particles and an average ECD of 70 μ m has a change of three orders of magnitude, respectively. Using V 2 O 3 -epoxy composite as an insulating layer between the coil windings might allow thinner detector magnet designs since the current and heat would spread more uniformly across the magnet during a quench

Aluminium-Stabilized High-Temperature Superconducting Cable for Particle Detector Magnets

Within the context of EP R&D;, CERN is developing a high-temperature superconducting (HTS) conductor for future superconducting detector magnet projects. The conductor features a Rare-Earth Barium Copper Oxide (REBCO) tapes soldered to a copper-coated high-purity aluminium stabilizer. Critical currents of the 200 mm long straight cable samples measured with various numbers of REBCO tapes at 77 K are consistent with empirical scaling formulas for critical current within 10%. A few percent deviations are expected to arise from the critical current variation along the length of the HTS tape. No degradation was observed after multiple soldering and de-soldering cycles at 165 $^\mathrm{\circ}$C with Bi–Sn based solder and after thermal cycling between 77 K and room temperature. However, extreme bending (of 100 mm radius) of the already soldered HTS cable leads to failure of the cable. We repeated the critical current measurements with a 650 mm long cable loop sample with 85 mm bending radius, where the HTS tapes were soldered after the aluminium profile was bent. The critical current of the HTS cable loop was 7% lower than the prediction. Based on the first critical current measurements, the HTS cable preparation method presented in this work results in repeatable quality aluminium-stabilized HTS cable

MOSFET-based HTS flux pump

We have developed a high-temperature superconducting (HTS) flux pump using high-power metal-oxide-semiconductor field-effect transistors (MOSFETs) for switching. For its primary coil, two commercial transformers are utilized, each consisting of two copper coils wound on a single iron core, which enables changing the load current over primary current ratio (101 or 194) between the primary and secondary coils. Full-wave rectification is achieved with two half-wave secondary circuits, each of them having six HTS one-turn coils to lower the resistance. Each secondary coil is composed out of nickel-reinforced BSCCO tapes, where 12 MOSFETs have been soldered in parallel straight to the tapes and controlled with analog electronics. Secondary coils are clamped to custom-made copper-stabilized HTS current leads. A support structure for keeping the HTS coils in place was 3D-printed using cryogenic-compatible composite material PETG-CF20. Resistances of the two secondary circuits were measured to be 4 and 7 at 77 K with a total critical current of 980 A. We successfully ramped up a 50 µH Conductor on Round Core solenoid at 77 K using our HTS flux pump with 50 Hz AC voltage source. We achieved a maximal load current of 900 A and exceeded the 715 A critical current of the solenoid. During the thermal runaway of the magnet, the increased load voltage limits the maximum load current supplied by the flux pump

HTS Detector Magnet Demonstrator Based on a 3D-Printed Partially-Insulated Support Cylinder

In this work, we extend the experimental demonstration of partially-insulated, ultra-radiation transparent detector magnet technology based on a 3D-printed aluminium alloy support structure containing 10% of silicon. This demonstrator magnet has a bore diameter of 390 mm, effective wall thickness of 3.7 mm, and it has 15 turns corresponding to 19 meters of HTS conductor. The HTS conductor of the magnet consists of a stack of four ReBCO tapes with a width of 4 mm. We measured the magnet to be fully superconducting at 4.2 K with an operating current of 4.5 kA. A time constant of the magnetic field delay to a current step measured was 83 s. This detector magnet technology may be used in future particle detector magnets, such as the AMS-100 solenoid, where one of the key design requirement is a passive self-protection by partial-insulation which ensures continuous operation and stable magnetic field even with a locally damaged conductor

Self-protected high-temperature superconducting demonstrator magnet for particle detectors

A high temperature superconducting (HTS) demonstration coil has been developed in the frame of the Experimental Physics department Research and Development program at CERN The magnet extends the recent experimental demonstration of aluminium-stabilised HTS conductors and supports the development of future large scale detector magnets. The HTS magnet has five turns and an open bore diameter of 230 mm. Up to 30 K, the coil was measured to be fully superconducting across four central turns at 4.4 kA, the maximum available current of existing power supply. The central magnetic field is 0.113 T, the peak field on the conductor is 1.2 T and the coil has a stored magnetic energy of 0.1 kJ. A 3D-printed aluminium alloy (Al10SiMg) cylinder acts both as a stabiliser and a mechanical support for the superconductor. The resistivity of Al10SiMg was measured at cryogenic temperatures, and has a residual resistivity ratio of approximately 2.5. The ability to solder ReBCO tapes (a stack of four REBCO tapes, 4 mm wide, Fujikura) to Al10SiMg stabiliser, electroplated with copper and tin, forming a coil, is demonstrated using tin-lead solder at 188 $^{∘}$C. The HTS magnet was proven to be stable when superconductivity was broken locally using a thin-film heater. Despite voids in the solder joint between HTS and stabiliser, no degradation of the magnet’s performance was observed after 12 thermal cycles and locally quenching the magnet. A numerical model of the transient behaviour of solenoid with partially shorted turns is developed and validated against measurements. Our work experimentally and numerically validates that using an aluminium alloy as a stabiliser for HTS tapes can result in a stable, lightweight and transparent magnet

Characteristics of Aluminium-Stabilized HTS Detector Magnet Cable at 4 K and 5 T

A high-temperature superconducting (HTS) cable for future particle detector magnets has been developed using a 99.3% pure aluminium alloy as a stabilizer for the HTS. This HTS conductor features a stack of four ReBCO tapes (4 mm wide, SuperOx) soldered to a tin-coated copper-clad aluminium alloy cable profile using tin–lead solder at 188 °C. Here, we experimentally demonstrate that the cable withstands both thermal cycling between 4 K and room temperature and Lorentz forces induced by external magnetic field of 5 T when the HTS cable is driven by 4.5 kA. The HTS cable has no visual damage and no change in the critical current after being exposed multiple times to these extreme conditions. We show that since the phase transition of ReBCO is gradual, an aluminium alloy with low residual resistivity ratio (RRR) can be used as a stabilizer, which brings many advantages, such as a better availability compared to pure aluminium and a mechanically stronger cable

Using the Standard Linear Ramps of the CMS Superconducting Magnet for Measuring the Magnetic Flux Density in the Steel Flux Return Yoke

The principal difficulty in large magnetic systems having an extensive flux return yoke is to characterize the magnetic flux distribution in the yoke steel blocks. Continuous measurements of the magnetic flux density in the return yoke are not possible and the usual practice uses software modelling of the magnetic system with special three-dimensional (3-D) computer programs. The 10,000-tonne flux return yoke of the Compact Muon Solenoid (CMS) magnet encloses a 3.8 T superconducting solenoid with a 6-m-diameter by 12.5-m-length free bore and consists of five dodecagonal three-layered barrel wheels around the coil and four endcap disks at each end. The yoke steel blocks, up to 620 mm thick, serve as the absorber plates of the muon detection system. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field outside of the solenoid volume, which was measured with a field-mapping machine. To verify the magnetic flux distribution calculated in the yoke steel blocks, direct measurements of the magnetic flux density with 22 flux loops installed in selected regions of the yoke were performed during the CMS magnet test in 2006 when four ``fast'' discharges of the CMS coil (190 s time-constant) were triggered manually to test the magnet protection system. No fast discharge of the CMS magnet from its operational current of 18.2~kA, which corresponds to a central magnetic flux density of 3.8 T, has been performed that time. For the first time, in this paper we present measurements of the magnetic flux density in the steel blocks of the return yoke based on the several standard linear discharges of the CMS magnet from the operational magnet current of 18.2~kA. To provide these measurements, the voltages induced in the flux loops (with amplitudes of 20-250~mV) have been measured with six 16-bit DAQ modules and integrated offline over time. The results of the measurements during magnet linear ramps performed with a current rate as low as 1-1.5~A/s are presented and discussed