IEEE Transactions on Applied Superconductivity, 2009
After final installation in the LHC tunnel, the MQM and MQY quadrupole magnets of the LHC inserti... more After final installation in the LHC tunnel, the MQM and MQY quadrupole magnets of the LHC insertions are now being commissioned to their nominal currents. These two types of magnets operate at 1.9 K and 4.5 K and with nominal currents ranging from 3600 A to 5390 A. From the very first acceptance tests of the bare magnets coming from the manufacturers, they have been powered using different cycles, in different configurations, at different temperatures and in different tests facilities. In this paper we present the global results of these powering tests. We aim at separating common from individual features of these groups of magnets. Temperature dependence of the training, temperature margin, and ultimate current can be extracted from these tests. As these magnets are used to match the optics and the dispersion in the machine, the projected ultimate current at which they can be operated is critical in view of operation of LHC.
The use of a recently decommissioned 15-meters long twin aperture LHC supercon-ducting magnet pro... more The use of a recently decommissioned 15-meters long twin aperture LHC supercon-ducting magnet prototype having a transverse magnetic fieldB ≈ 9.5 T provides the unique opportunity for the construction of a new powerful experiment to measure the Vacuum Magnetic Birefringence (VMB). The values or the limit values of the mass and of the coupling constant to two photons of possible dark matter candidates such as axions are aimed to be deduced from such an experiment. In this article, the technical feasibility study of a new setup to measure the VMB will be presented. It is based on a linear optical resonant cavity house in the LHC superconducting dipole prototype. The mechanical integrations of the optical components inside the magnet aperture as well as the optical detection principles will be presented. A comparison of the expected performances with respect to the present reference results for this type of experiment will also be given.
A new method to amplify the photon-axion conversions in magnetic field is proposed using a buffer... more A new method to amplify the photon-axion conversions in magnetic field is proposed using a buffer gas at a specific pressure. As a first result, new bounds for mass and coupling constant for purely laboratory experiments aiming to detect any hypothetical scalars and pseudo-scalars which can couple to photons were obtained at 95% confidence level, excluding the PVLAS result newly disclaimed.
IEEE Transactions on Applied Superconductivity, 2012
The Alpha Magnetic Spectrometer (AMS) is a particle detector designed to search for anti-matter, ... more The Alpha Magnetic Spectrometer (AMS) is a particle detector designed to search for anti-matter, dark matter and the origin of cosmic rays in space. A superconducting magnet has been developed to generate 0.78 T field at the center. The magnet system consists of a pair of large “dipole” coils together with two series of six racetrack coils, arranged circumferentially in order to minimize the stray field. The coils, series connected, are wound with an aluminum-stabilized mono-strand NbTi conductor and are cooled by a superfluid helium circuit. The superconducting magnet was successfully tested up to the operating current of 410 A, however the decision was taken to equip the spectrometer with a NdFeB permanent magnet in order to maximize the experiment life. The paper describes the results of the superconducting magnet tests and in particular analyses an anomalous increasing of the coil temperature during magnet charging.
A dependence of the electrical resistance on uniaxial tensile stress applied to the CoFeSiB metal... more A dependence of the electrical resistance on uniaxial tensile stress applied to the CoFeSiB metallic glass sample is measured. The anomaly observed in this characteristic is identified as the so-called “negative” magnetoresistance which is due to the influence of domain walls on the dc current running normal to them. The effect observed is recognized as an additional evidence for the stress-induced sign change of the saturation magnetostriction expected in the sample used in the experiment. This conclusion is drawn considering the correlation between the results of resistometric measurements and an observation of the domain structure of the sample under stress. It is shown additionally that the resistometric method allows to estimate the value of the Young modulus of the metallic glass sample investigated.Es wird eine Abhängigkeit des elektrischen Widerstands von der uniaxialen Dehnungsspannung an metallischen CoFeSiB-Glasproben gemessen. Die in diesen Charakteristiken beobachtete Anomalie wird als sogenannte „negative” Magnetowiderstandsänderung identifiziert, die durch den Einfluß von Domänenwänden auf den Gleichstrom hervorgerufen wird, der senkrecht dazu fließt. Der beobachtete Effekt wird als zusätzlicher Hinweis für spannungsinduzierte Vorzeichenänderung der Sättigungsmagnetostriktion betrachtet, die für die im Experiment benutzte Probe erwartet wird. Dies wird unter Berücksichtigung der Korrelation zwischen den Ergebnissen der Widerstandsmessungen und der Beobachtung einer Domänenstruktur der Probe unter Spannung angenommen. Zusätzlich wird gezeigt, daß die Widerstandsmethode erlaubt, den Wert des Elastizitätsmoduls der untersuchten metallischen Gläser zu bestimmen.
The stress dependence of the saturation magnetostriction λs is investigated. Under load the magne... more The stress dependence of the saturation magnetostriction λs is investigated. Under load the magnetostriction λs changes its sign from an initially positive to a negative value which could be directly observed with help of the magnetooptical Kerr effect by a rotation of the domains from a parallel to a perpendicular direction with respect to the band direction.Es wird über die Spannungsabhängigkeit der Sättigungsmagnetostriktion λs berichtet. Die Magnetostriktion λs ändert ihr Vorzeichen unter einer Zugspannung vom positiven Ausgangswert ins Negative. Diese Änderung konnte unmittelbar unter Anwendung des magnetooptischen Kerreffektes durch eine Änderung der Richtung der magnetischen Bereichsstruktur von parallel nach senkrecht zur Bandrichtung beobachtet werden.
The stress dependence of the saturation magnetostriction, λs, of amorphous Co73Fe5Si9B13 alloy is... more The stress dependence of the saturation magnetostriction, λs, of amorphous Co73Fe5Si9B13 alloy is investigated. Under load the magnetostriction, λs, changes its sign from an initially positive to a negative value. This change is directly observed by means of the magnetooptical Kerr effect. The orientation of the domains relative to the ribbon direction is found to depend on the sign of λs. Under an applied stress therefore a rotation of the orientation of the domains is observed.Die Sättigungsmagnetostriktionskonstante λs einer amorphen Co73Fe5Si9B13-Legierung wird in Abhängigkeit von einer angelegten elastischen Spannung untersucht. Unter Belastung wechselt die Magnetostriktionskonstante λs ihr Vorzeichen von positiven zu negativen Werten. Diese Änderung wird direkt mit Hilfe des magnetooptischen Kerr-Effektes beobachtet. Die Ausrichtung der Domänen bezüglich der Bandachse erweist sich als vom Vorzeichen von λs abhängig. Bei angelegter Spannung wird deshalb eine Rotation der Ausrichtung der Domänen beobachtet.
IEEE Transactions on Applied Superconductivity, 2009
After final installation in the LHC tunnel, the MQM and MQY quadrupole magnets of the LHC inserti... more After final installation in the LHC tunnel, the MQM and MQY quadrupole magnets of the LHC insertions are now being commissioned to their nominal currents. These two types of magnets operate at 1.9 K and 4.5 K and with nominal currents ranging from 3600 A to 5390 A. From the very first acceptance tests of the bare magnets coming from the manufacturers, they have been powered using different cycles, in different configurations, at different temperatures and in different tests facilities. In this paper we present the global results of these powering tests. We aim at separating common from individual features of these groups of magnets. Temperature dependence of the training, temperature margin, and ultimate current can be extracted from these tests. As these magnets are used to match the optics and the dispersion in the machine, the projected ultimate current at which they can be operated is critical in view of operation of LHC.
The use of a recently decommissioned 15-meters long twin aperture LHC supercon-ducting magnet pro... more The use of a recently decommissioned 15-meters long twin aperture LHC supercon-ducting magnet prototype having a transverse magnetic fieldB ≈ 9.5 T provides the unique opportunity for the construction of a new powerful experiment to measure the Vacuum Magnetic Birefringence (VMB). The values or the limit values of the mass and of the coupling constant to two photons of possible dark matter candidates such as axions are aimed to be deduced from such an experiment. In this article, the technical feasibility study of a new setup to measure the VMB will be presented. It is based on a linear optical resonant cavity house in the LHC superconducting dipole prototype. The mechanical integrations of the optical components inside the magnet aperture as well as the optical detection principles will be presented. A comparison of the expected performances with respect to the present reference results for this type of experiment will also be given.
A new method to amplify the photon-axion conversions in magnetic field is proposed using a buffer... more A new method to amplify the photon-axion conversions in magnetic field is proposed using a buffer gas at a specific pressure. As a first result, new bounds for mass and coupling constant for purely laboratory experiments aiming to detect any hypothetical scalars and pseudo-scalars which can couple to photons were obtained at 95% confidence level, excluding the PVLAS result newly disclaimed.
IEEE Transactions on Applied Superconductivity, 2012
The Alpha Magnetic Spectrometer (AMS) is a particle detector designed to search for anti-matter, ... more The Alpha Magnetic Spectrometer (AMS) is a particle detector designed to search for anti-matter, dark matter and the origin of cosmic rays in space. A superconducting magnet has been developed to generate 0.78 T field at the center. The magnet system consists of a pair of large “dipole” coils together with two series of six racetrack coils, arranged circumferentially in order to minimize the stray field. The coils, series connected, are wound with an aluminum-stabilized mono-strand NbTi conductor and are cooled by a superfluid helium circuit. The superconducting magnet was successfully tested up to the operating current of 410 A, however the decision was taken to equip the spectrometer with a NdFeB permanent magnet in order to maximize the experiment life. The paper describes the results of the superconducting magnet tests and in particular analyses an anomalous increasing of the coil temperature during magnet charging.
A dependence of the electrical resistance on uniaxial tensile stress applied to the CoFeSiB metal... more A dependence of the electrical resistance on uniaxial tensile stress applied to the CoFeSiB metallic glass sample is measured. The anomaly observed in this characteristic is identified as the so-called “negative” magnetoresistance which is due to the influence of domain walls on the dc current running normal to them. The effect observed is recognized as an additional evidence for the stress-induced sign change of the saturation magnetostriction expected in the sample used in the experiment. This conclusion is drawn considering the correlation between the results of resistometric measurements and an observation of the domain structure of the sample under stress. It is shown additionally that the resistometric method allows to estimate the value of the Young modulus of the metallic glass sample investigated.Es wird eine Abhängigkeit des elektrischen Widerstands von der uniaxialen Dehnungsspannung an metallischen CoFeSiB-Glasproben gemessen. Die in diesen Charakteristiken beobachtete Anomalie wird als sogenannte „negative” Magnetowiderstandsänderung identifiziert, die durch den Einfluß von Domänenwänden auf den Gleichstrom hervorgerufen wird, der senkrecht dazu fließt. Der beobachtete Effekt wird als zusätzlicher Hinweis für spannungsinduzierte Vorzeichenänderung der Sättigungsmagnetostriktion betrachtet, die für die im Experiment benutzte Probe erwartet wird. Dies wird unter Berücksichtigung der Korrelation zwischen den Ergebnissen der Widerstandsmessungen und der Beobachtung einer Domänenstruktur der Probe unter Spannung angenommen. Zusätzlich wird gezeigt, daß die Widerstandsmethode erlaubt, den Wert des Elastizitätsmoduls der untersuchten metallischen Gläser zu bestimmen.
The stress dependence of the saturation magnetostriction λs is investigated. Under load the magne... more The stress dependence of the saturation magnetostriction λs is investigated. Under load the magnetostriction λs changes its sign from an initially positive to a negative value which could be directly observed with help of the magnetooptical Kerr effect by a rotation of the domains from a parallel to a perpendicular direction with respect to the band direction.Es wird über die Spannungsabhängigkeit der Sättigungsmagnetostriktion λs berichtet. Die Magnetostriktion λs ändert ihr Vorzeichen unter einer Zugspannung vom positiven Ausgangswert ins Negative. Diese Änderung konnte unmittelbar unter Anwendung des magnetooptischen Kerreffektes durch eine Änderung der Richtung der magnetischen Bereichsstruktur von parallel nach senkrecht zur Bandrichtung beobachtet werden.
The stress dependence of the saturation magnetostriction, λs, of amorphous Co73Fe5Si9B13 alloy is... more The stress dependence of the saturation magnetostriction, λs, of amorphous Co73Fe5Si9B13 alloy is investigated. Under load the magnetostriction, λs, changes its sign from an initially positive to a negative value. This change is directly observed by means of the magnetooptical Kerr effect. The orientation of the domains relative to the ribbon direction is found to depend on the sign of λs. Under an applied stress therefore a rotation of the orientation of the domains is observed.Die Sättigungsmagnetostriktionskonstante λs einer amorphen Co73Fe5Si9B13-Legierung wird in Abhängigkeit von einer angelegten elastischen Spannung untersucht. Unter Belastung wechselt die Magnetostriktionskonstante λs ihr Vorzeichen von positiven zu negativen Werten. Diese Änderung wird direkt mit Hilfe des magnetooptischen Kerr-Effektes beobachtet. Die Ausrichtung der Domänen bezüglich der Bandachse erweist sich als vom Vorzeichen von λs abhängig. Bei angelegter Spannung wird deshalb eine Rotation der Ausrichtung der Domänen beobachtet.
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