Antonella Chiuchiolo | CERN - Academia.edu (original) (raw)

Papers by Antonella Chiuchiolo

In the framework of the Luminosity upgrade of the Large Hadron Collider (HL - LHC), a remarkable ... more In the framework of the Luminosity upgrade of the Large Hadron Collider (HL - LHC), a remarkable R&D effort is now ongoing at the European Organization for Nuclear Research (CERN) in order to develop a new generation of accelerator magnets and superconducting power transmission lines. The magnet technology will be based on Nb$_{3}$Sn enabling to operate in the 11 - 13 T range. In parallel, in order to preserve the power converters from the increasing radiation level, high power transmission lines are foreseen to feed the magnets from free - radiation zones. These will be based on high temperature superconductors cooled down with helium gas in the range 5 - 30 K. The new technologies will require advanced design and fabrication approaches as well as adapted instrumentation for monitoring both the R&D phase and operation. Resistive sensors have been used so far for voltage, temperature and strain monitoring but their integration still suffers from the number of electrical wires and th...

In the framework of the Luminosity upgrade of the Large Hadron Collider (HL-LHC), a remarkable R&... more In the framework of the Luminosity upgrade of the Large Hadron Collider (HL-LHC), a remarkable R&D effort is now ongoing at the European Organization for Nuclear Research (CERN) in order to develop a new generation of accelerator magnets and superconducting power transmission lines. The magnet technology will be based on Nb3Sn enabling to operate in the 11-13 T range. In parallel, in order to preserve the power converters from the increasing radiation level, high power transmission lines are foreseen to feed the magnets from free-radiation zones. These will be based on high temperature superconductors cooled down with helium gas in the range 5-30 K. The new technologies will require advanced design and fabrication approaches as well as adapted instrumentation for monitoring both the R&D phase and operation. Resistive sensors have been used so far for voltage, temperature and strain monitoring but their integration still suffers from the number of electrical wires and the complex compensation of magnetic and thermal effects. These issues might be overcome by developing a new technology based on fiber optic sensors for their well-known advantages like the small size, the intrinsic electrical insulation, immunity to electromagnetic interferences and multiplexing capability although the environmental complexity makes the technology not well assessed yet in the field of superconductivity. This thesis presents the progress done in the material selection and temperature characterization (in the range 300-4.2 K) of coated FBG sensors. Results of their implementation in the 20-m-long power transmission line for the helium gas temperature monitoring are also reported. FBG sensors in bonded and embedded configuration have been also integrated in sub-scale Nb3Sn dipole magnets for monitoring the main stages of the magnet service life. Experimental results are presented during magnet assembly and thermal cycle down to 1.9 K, when applied compressive forces reach up to 200 MPa, during energization up to 20 kA and quench monitoring under high magnetic fields (up to 13 T).

IEEE Transactions on Applied Superconductivity, 2020

The first of series (FoS) multiplet built for the Super-FRS at GSI/FAIR was delivered to a dedica... more The first of series (FoS) multiplet built for the Super-FRS at GSI/FAIR was delivered to a dedicated magnet test facility at CERN. After a series of tests at room temperature, it was cooled down to 4.5 K and is now under cold powering test. The commissioning of the CERN test facility is performed in parallel with the magnet testing. The quadrupole and the sextupole magnet enclosed in the cryostat module are superferric magnets with a large aperture diameter of 380 mm. The yoke length of the quadrupole magnet and the sextupole magnet is 1200 mm and 500 mm, respectively. The features of the magnets are vacuum impregnated racetrack coils made of Nb-Ti conductor and a maximum integrated gradient of 11.4 T/m × m for the quadrupole magnet and 20 T/m2 × m for the sextupole magnet, respectively. This paper presents the design issues of the magnets, especially of the quadrupole magnet, an overview of a qualification process of the multiplets, and preliminary test results.

Le Centre pour la Communication Scientifique Directe - HAL - memSIC, Jun 12, 2022

Sensors

Thanks to their characteristics, optical fiber sensors are an ideal solution for sensing applicat... more Thanks to their characteristics, optical fiber sensors are an ideal solution for sensing applications at cryogenic temperatures, such as the monitoring of superconducting devices. Their applicability at such temperatures, however, is not immediate as optical fibers exhibit a non-linear thermal response which becomes rapidly negligible below 50 K. A thorough analysis of such a response down to cryogenic temperatures then becomes necessary to correctly translate the optical interrogation readings into the actual fiber temperature. Moreover, to increase the fiber sensitivity down to a few kelvin, special coatings can be used. In this manuscript we described the thermal responses experimental characterization of four commercially available optical fiber samples with different polymeric coatings in the temperature range from 5 K to 300 K: two with acrylate coatings of different thickness, one with a polyimide coating and one with a polyether–ether–ketone (PEEK) coating. Multiple thermal ...

Optical Fiber Sensors Conference 2020 Special Edition, 2021

Optical Fiber Sensors Conference 2020 Special Edition, 2021

IEEE Transactions on Applied Superconductivity, 2018

Within the 11T dipole magnet conductor development for the high-luminosity LHC upgrade, two types... more Within the 11T dipole magnet conductor development for the high-luminosity LHC upgrade, two types of Nb 3 Sn cable based on the powder-in-tube (PIT) and the Rod and Restack processes (RRP) are tested in racetrack configuration in the short model coil (SMC) magnets. In 2016 and 2017, the performances of three different coils wound with 40-strand cables, one made of OST RRP 132/169 and two of PIT 120 strands have been measured using the SMC structure. This paper reports on the main design parameters of the SMC-11T-3 (RRP), and the SMC-11T-4 and SMC-11T-5 (PIT) magnets including details on the instrumentation, applied preload, maximum expected performances, residual resistivity ratio, splice resistances, and inductances. For SMC-11T-3, eight consecutive runs have been performed varying the azimuthal prestress from 150 to 200 MPa with the aim to study the impact of the transverse pressure on the magnet stability and degradation. Only two runs were done for SMC-11T-4 and SMC-11T-5. For the three magnets, the training behavior at both 4.2 and 1.9 K is analyzed in terms of training rate, quench location, maximum quench current and its dependence to the helium bath temperature, the level of transverse prestress, and current ramp rate. The main outcome of the tests on the coil performance is given as conclusion. Index Terms-High luminosity LHC, high field Nb 3 Sn magnets, superconducting coils racetrack.

IEEE Transactions on Applied Superconductivity, 2018

Since 2010 to present, several subsize magnet assemblies, designed as test beds for the validatio... more Since 2010 to present, several subsize magnet assemblies, designed as test beds for the validation of impregnated Nb 3 Sn-based coil technology, have been tested at the Superconducting Magnet Test Facility (SM18) at CERN. These short model coils and racetrack model coils have been used to study two types of Rutherford cables foreseen for the coils of the Nb 3 Sn magnets in the framework of the HL-LHC upgrade and High Field Magnet program of CERN. During several test campaigns, the Rod Restack Process and the Powder-In-Tube conductors have been characterized in terms of performance and quench propagation velocity (QPV). Moreover, hot spot temperature (HST) increase during quenches has been estimated from the analysis of the registered voltage and current signals. In this paper, the multiphysics problem of quench propagation in Nb 3 Sn cables is addressed under adiabatic conditions by means of a set of analytical formulae and several finite element models with different level of complexity in ANSYS APDL, COMSOL Multiphysics, and MATLAB. These models are aimed at describing the conductor behavior in terms of HST and QPV observed during the training of racetrack coils at SM18.

IEEE Transactions on Applied Superconductivity, 2018

The EuCARD2 collaboration aims at the development of a 10 kA-class superconducting, high current ... more The EuCARD2 collaboration aims at the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, to be tested in small coils and magnets capable to deliver 3-5 T when energized in stand-alone mode, and 15-18 T when inserted in a 12-13 T background magnet. REBCO tape, assembled in a Roebel cable, was selected as conductor. The developed REBCO tape has reached a record engineering critical current density, at 4.2 K and 18 T of 956 A/mm 2. Roebel cable carried up to 13 kA at 20 K when tested in a small coil (Feath-erM0.4). Then a first dipole magnet, wound with two low-grade Roebel cables of 25 m each, was assembled and tested. The dipole reached the short sample critical current of 6 kA generating more than 3 T central field at about 5.7 K, with indications of good current transfer among cable strands and of relatively soft transition. The construction of a costheta dipole is also discussed. Eucard2 is

IEEE Transactions on Applied Superconductivity, 2018

The replacement of the LHC Nb-Ti inner triplet magnets with more powerful quadrupole magnets base... more The replacement of the LHC Nb-Ti inner triplet magnets with more powerful quadrupole magnets based on Nb 3 Sn superconductor, as foreseen by the HiLumi LHC Project, has pushed the technology advancement not only in the manufacturing process and tooling but also in the instrumentation. For the short model quadrupole magnet MQXFS-5, fabricated and tested at CERN, fiber optic sensors, based on fiber Bragg grating (FBG) technology, have been proposed for monitoring the magnet mechanical behavior from its assembly to its operation in cryogenic conditions. After the experience gained with the FBG integration in short model racetrack coils, the paper deals with the first integration of 16 FBG sensors arranged into eight fibers and glued on the coils and on the support structure of the Nb 3 Sn quadrupole. The advantages offered by the FBGs' multiplexing capability has allowed the integration improvement of the FBG-based measuring system in the magnet structure as well as in the test facility. Examples of strain measurements during magnet assembly, cool-down and powering are presented in the paper and compared with strain gauges data.

IEEE Transactions on Applied Superconductivity, 2019

For the High Luminosity Upgrade of the CERN Large Hadron Collider, lower β* quadrupole magnets ba... more For the High Luminosity Upgrade of the CERN Large Hadron Collider, lower β* quadrupole magnets based on advanced Nb 3 Sn conductors will be installed on each side of the ATLAS and CMS experiment insertion zones. As part of the technological developments needed to achieve the required field gradient of 132.6 T/m within a 150-mm aperture, short length model magnets, named MQXFS, are tested both at the CERN SM18 and FERMI Lab test facilities. The model magnets rely on two types of Nb 3 Sn conductors (RRP and PIT) and on an innovative bladders and keys design to provide mechanical support against the Lorentz forces. In 2016 and 2017, the powering tests of the first two models MQXFS3 (RRP) and MQXFS5 (PIT) proved that nominal performance (16.5 kA) could be reached with excellent memory of the quench current after thermal cycle. However both magnets showed a slow training behavior with clear observations of voltage disturbances before the quench. Besides MQXFS5 only could reach ultimate current (17.9 kA) whereas erratic behavior was observed on MQXFS3 due to conductor local degradation at the head of one of the coil. In 2018, this limiting coil was changed and the applied azimuthal pre-stress increased. If ultimate current could then be reached, no stable current could be maintained due to identified defect on the outer layer of the new coil. Finally the outcome of the test of the new model MQXFS4, featuring the final RRP conductors that will be used for the series production and variation on the inner layer quench heater designs are here reported in details.

The Super FRS is a two-stage in flight separator to be built next to the site of GSI, Darmstadt, ... more The Super FRS is a two-stage in flight separator to be built next to the site of GSI, Darmstadt, Germany as part of FAIR (Facility for Anti-proton and Ion Research). Its three branches allow to carry out a wide variety of experiments. Due to the large acceptance needed, the magnets of the Super-FRS require a large aperture and therefore only a superconducting solution is feasible. A superferric design was chosen in which the magnetic field is shaped by an iron yoke. For the dipole magnets only the superconducting coils are in a cryostat. These magnets are manufactured by Elytt Energy (Spain). The multiplets, assemblies of quadrupoles and higher order multipole magnets, are completely immersed in a liquid Helium bath. They are being built at ASG (Italy). The first of two first of series multiplets, a short assembly containing 2 magnets, was tested at a dedicated test facility at CERN (Switzerland). The 2nd FoS multiplet, containing 9 magnets, and the FoS dipole will be tested soon. S...

Optics Letters, 2015

This contribution presents distributed and multipoint fiber-optic monitoring of cryogenic tempera... more This contribution presents distributed and multipoint fiber-optic monitoring of cryogenic temperatures along a superconducting power transmission line down to 30 K and over 20 m distance. Multipoint measurements were conducted using fiber Bragg gratings sensors coated with two different functional overlays (epoxy and poly methyl methacrylate (PMMA)) demonstrating cryogenic operation in the range 300-4.2 K. Distributed measurements exploited optical frequency-domain reflectometry to analyze the Rayleigh scattering along two concatenated fibers with different coatings (acrylate and polyimide). The integrated system has been placed along the 20 m long cryostat of a superconducting power transmission line, which is currently being tested at the European Organization for Nuclear Research (CERN). Cool-down events from 300-30 K have been successfully measured in space and time, confirming the viability of these approaches to the monitoring of cryogenic temperatures along a superconducting transmission line.

ABSTRACT The use of Fiber Bragg Grating sensors is becoming particularly challenging for monitori... more ABSTRACT The use of Fiber Bragg Grating sensors is becoming particularly challenging for monitoring different parameters in extreme operative conditions such as ultra-low temperatures, high electromagnetic fields and strong mechanical stresses. This work reports the use of the FBG for a new generation of accelerator magnets with the goal to develop an adequate sensing technology able to provide complementary or alternative information to the conventional strain gauges through the whole service life of the magnet. The study is focused on the mechanical performances of the magnet structure, which has to preserve the sensitive coils from any damage during the entire magnet fabrication process preventing even microscopic movements of the winding that can eventually initiate a transition from superconducting to normal conducting state of the material used (called in the specific literature as Òquenchî). The FBGs have been glued on the aluminium structure of two magnets prototypes by using an adhesive suitable for cryogenic temperature. The feasibility of the bonding procedure for bare sensors at 4.2 K leads to the validation of the final integration of the FBGs for the structural monitoring of the magnet during the assembly and cool down at 77 K.

Second International Conference on Applications of Optics and Photonics, 2014

ABSTRACT The design, fabrication and tests of a new generation of superconducting magnets for the... more ABSTRACT The design, fabrication and tests of a new generation of superconducting magnets for the upgrade of the LHC require the support of an adequate, robust and reliable sensing technology. The use of Fiber Optic Sensors is becoming particularly challenging for applications in extreme harsh environments such as ultra-low temperatures, high electromagnetic fields and strong mechanical stresses offering perspectives for the development of technological innovations in several applied disciplines.

23rd International Conference on Optical Fibre Sensors, 2014

ABSTRACT New generation of superconducting magnets for high energy applications designed, manufac... more ABSTRACT New generation of superconducting magnets for high energy applications designed, manufactured and tested at the European Organization for Nuclear Research (CERN) require the implementation of reliable sensors able to monitor the mechanical stresses affecting the winding from fabrication to operation in magnetic field of 13 T. This work deals with the embedding of Fiber Bragg Grating sensors in a short model Nb3Sn dipole magnet in order to monitor the strain developed in the coil during the cool down to 1.9 K, the powering up to 15.8 kA and the warm up, offering perspectives for the replacement of standard strain gauges.

2014 Third Mediterranean Photonics Conference, 2014

In the framework of the Luminosity upgrade of the Large Hadron Collider (HL - LHC), a remarkable ... more In the framework of the Luminosity upgrade of the Large Hadron Collider (HL - LHC), a remarkable R&D effort is now ongoing at the European Organization for Nuclear Research (CERN) in order to develop a new generation of accelerator magnets and superconducting power transmission lines. The magnet technology will be based on Nb$_{3}$Sn enabling to operate in the 11 - 13 T range. In parallel, in order to preserve the power converters from the increasing radiation level, high power transmission lines are foreseen to feed the magnets from free - radiation zones. These will be based on high temperature superconductors cooled down with helium gas in the range 5 - 30 K. The new technologies will require advanced design and fabrication approaches as well as adapted instrumentation for monitoring both the R&D phase and operation. Resistive sensors have been used so far for voltage, temperature and strain monitoring but their integration still suffers from the number of electrical wires and th...

In the framework of the Luminosity upgrade of the Large Hadron Collider (HL-LHC), a remarkable R&... more In the framework of the Luminosity upgrade of the Large Hadron Collider (HL-LHC), a remarkable R&D effort is now ongoing at the European Organization for Nuclear Research (CERN) in order to develop a new generation of accelerator magnets and superconducting power transmission lines. The magnet technology will be based on Nb3Sn enabling to operate in the 11-13 T range. In parallel, in order to preserve the power converters from the increasing radiation level, high power transmission lines are foreseen to feed the magnets from free-radiation zones. These will be based on high temperature superconductors cooled down with helium gas in the range 5-30 K. The new technologies will require advanced design and fabrication approaches as well as adapted instrumentation for monitoring both the R&D phase and operation. Resistive sensors have been used so far for voltage, temperature and strain monitoring but their integration still suffers from the number of electrical wires and the complex compensation of magnetic and thermal effects. These issues might be overcome by developing a new technology based on fiber optic sensors for their well-known advantages like the small size, the intrinsic electrical insulation, immunity to electromagnetic interferences and multiplexing capability although the environmental complexity makes the technology not well assessed yet in the field of superconductivity. This thesis presents the progress done in the material selection and temperature characterization (in the range 300-4.2 K) of coated FBG sensors. Results of their implementation in the 20-m-long power transmission line for the helium gas temperature monitoring are also reported. FBG sensors in bonded and embedded configuration have been also integrated in sub-scale Nb3Sn dipole magnets for monitoring the main stages of the magnet service life. Experimental results are presented during magnet assembly and thermal cycle down to 1.9 K, when applied compressive forces reach up to 200 MPa, during energization up to 20 kA and quench monitoring under high magnetic fields (up to 13 T).

IEEE Transactions on Applied Superconductivity, 2020

The first of series (FoS) multiplet built for the Super-FRS at GSI/FAIR was delivered to a dedica... more The first of series (FoS) multiplet built for the Super-FRS at GSI/FAIR was delivered to a dedicated magnet test facility at CERN. After a series of tests at room temperature, it was cooled down to 4.5 K and is now under cold powering test. The commissioning of the CERN test facility is performed in parallel with the magnet testing. The quadrupole and the sextupole magnet enclosed in the cryostat module are superferric magnets with a large aperture diameter of 380 mm. The yoke length of the quadrupole magnet and the sextupole magnet is 1200 mm and 500 mm, respectively. The features of the magnets are vacuum impregnated racetrack coils made of Nb-Ti conductor and a maximum integrated gradient of 11.4 T/m × m for the quadrupole magnet and 20 T/m2 × m for the sextupole magnet, respectively. This paper presents the design issues of the magnets, especially of the quadrupole magnet, an overview of a qualification process of the multiplets, and preliminary test results.

Le Centre pour la Communication Scientifique Directe - HAL - memSIC, Jun 12, 2022

Sensors

Thanks to their characteristics, optical fiber sensors are an ideal solution for sensing applicat... more Thanks to their characteristics, optical fiber sensors are an ideal solution for sensing applications at cryogenic temperatures, such as the monitoring of superconducting devices. Their applicability at such temperatures, however, is not immediate as optical fibers exhibit a non-linear thermal response which becomes rapidly negligible below 50 K. A thorough analysis of such a response down to cryogenic temperatures then becomes necessary to correctly translate the optical interrogation readings into the actual fiber temperature. Moreover, to increase the fiber sensitivity down to a few kelvin, special coatings can be used. In this manuscript we described the thermal responses experimental characterization of four commercially available optical fiber samples with different polymeric coatings in the temperature range from 5 K to 300 K: two with acrylate coatings of different thickness, one with a polyimide coating and one with a polyether–ether–ketone (PEEK) coating. Multiple thermal ...

Optical Fiber Sensors Conference 2020 Special Edition, 2021

Optical Fiber Sensors Conference 2020 Special Edition, 2021

IEEE Transactions on Applied Superconductivity, 2018

Within the 11T dipole magnet conductor development for the high-luminosity LHC upgrade, two types... more Within the 11T dipole magnet conductor development for the high-luminosity LHC upgrade, two types of Nb 3 Sn cable based on the powder-in-tube (PIT) and the Rod and Restack processes (RRP) are tested in racetrack configuration in the short model coil (SMC) magnets. In 2016 and 2017, the performances of three different coils wound with 40-strand cables, one made of OST RRP 132/169 and two of PIT 120 strands have been measured using the SMC structure. This paper reports on the main design parameters of the SMC-11T-3 (RRP), and the SMC-11T-4 and SMC-11T-5 (PIT) magnets including details on the instrumentation, applied preload, maximum expected performances, residual resistivity ratio, splice resistances, and inductances. For SMC-11T-3, eight consecutive runs have been performed varying the azimuthal prestress from 150 to 200 MPa with the aim to study the impact of the transverse pressure on the magnet stability and degradation. Only two runs were done for SMC-11T-4 and SMC-11T-5. For the three magnets, the training behavior at both 4.2 and 1.9 K is analyzed in terms of training rate, quench location, maximum quench current and its dependence to the helium bath temperature, the level of transverse prestress, and current ramp rate. The main outcome of the tests on the coil performance is given as conclusion. Index Terms-High luminosity LHC, high field Nb 3 Sn magnets, superconducting coils racetrack.

IEEE Transactions on Applied Superconductivity, 2018

Since 2010 to present, several subsize magnet assemblies, designed as test beds for the validatio... more Since 2010 to present, several subsize magnet assemblies, designed as test beds for the validation of impregnated Nb 3 Sn-based coil technology, have been tested at the Superconducting Magnet Test Facility (SM18) at CERN. These short model coils and racetrack model coils have been used to study two types of Rutherford cables foreseen for the coils of the Nb 3 Sn magnets in the framework of the HL-LHC upgrade and High Field Magnet program of CERN. During several test campaigns, the Rod Restack Process and the Powder-In-Tube conductors have been characterized in terms of performance and quench propagation velocity (QPV). Moreover, hot spot temperature (HST) increase during quenches has been estimated from the analysis of the registered voltage and current signals. In this paper, the multiphysics problem of quench propagation in Nb 3 Sn cables is addressed under adiabatic conditions by means of a set of analytical formulae and several finite element models with different level of complexity in ANSYS APDL, COMSOL Multiphysics, and MATLAB. These models are aimed at describing the conductor behavior in terms of HST and QPV observed during the training of racetrack coils at SM18.

IEEE Transactions on Applied Superconductivity, 2018

The EuCARD2 collaboration aims at the development of a 10 kA-class superconducting, high current ... more The EuCARD2 collaboration aims at the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, to be tested in small coils and magnets capable to deliver 3-5 T when energized in stand-alone mode, and 15-18 T when inserted in a 12-13 T background magnet. REBCO tape, assembled in a Roebel cable, was selected as conductor. The developed REBCO tape has reached a record engineering critical current density, at 4.2 K and 18 T of 956 A/mm 2. Roebel cable carried up to 13 kA at 20 K when tested in a small coil (Feath-erM0.4). Then a first dipole magnet, wound with two low-grade Roebel cables of 25 m each, was assembled and tested. The dipole reached the short sample critical current of 6 kA generating more than 3 T central field at about 5.7 K, with indications of good current transfer among cable strands and of relatively soft transition. The construction of a costheta dipole is also discussed. Eucard2 is

IEEE Transactions on Applied Superconductivity, 2018

The replacement of the LHC Nb-Ti inner triplet magnets with more powerful quadrupole magnets base... more The replacement of the LHC Nb-Ti inner triplet magnets with more powerful quadrupole magnets based on Nb 3 Sn superconductor, as foreseen by the HiLumi LHC Project, has pushed the technology advancement not only in the manufacturing process and tooling but also in the instrumentation. For the short model quadrupole magnet MQXFS-5, fabricated and tested at CERN, fiber optic sensors, based on fiber Bragg grating (FBG) technology, have been proposed for monitoring the magnet mechanical behavior from its assembly to its operation in cryogenic conditions. After the experience gained with the FBG integration in short model racetrack coils, the paper deals with the first integration of 16 FBG sensors arranged into eight fibers and glued on the coils and on the support structure of the Nb 3 Sn quadrupole. The advantages offered by the FBGs' multiplexing capability has allowed the integration improvement of the FBG-based measuring system in the magnet structure as well as in the test facility. Examples of strain measurements during magnet assembly, cool-down and powering are presented in the paper and compared with strain gauges data.

IEEE Transactions on Applied Superconductivity, 2019

For the High Luminosity Upgrade of the CERN Large Hadron Collider, lower β* quadrupole magnets ba... more For the High Luminosity Upgrade of the CERN Large Hadron Collider, lower β* quadrupole magnets based on advanced Nb 3 Sn conductors will be installed on each side of the ATLAS and CMS experiment insertion zones. As part of the technological developments needed to achieve the required field gradient of 132.6 T/m within a 150-mm aperture, short length model magnets, named MQXFS, are tested both at the CERN SM18 and FERMI Lab test facilities. The model magnets rely on two types of Nb 3 Sn conductors (RRP and PIT) and on an innovative bladders and keys design to provide mechanical support against the Lorentz forces. In 2016 and 2017, the powering tests of the first two models MQXFS3 (RRP) and MQXFS5 (PIT) proved that nominal performance (16.5 kA) could be reached with excellent memory of the quench current after thermal cycle. However both magnets showed a slow training behavior with clear observations of voltage disturbances before the quench. Besides MQXFS5 only could reach ultimate current (17.9 kA) whereas erratic behavior was observed on MQXFS3 due to conductor local degradation at the head of one of the coil. In 2018, this limiting coil was changed and the applied azimuthal pre-stress increased. If ultimate current could then be reached, no stable current could be maintained due to identified defect on the outer layer of the new coil. Finally the outcome of the test of the new model MQXFS4, featuring the final RRP conductors that will be used for the series production and variation on the inner layer quench heater designs are here reported in details.

The Super FRS is a two-stage in flight separator to be built next to the site of GSI, Darmstadt, ... more The Super FRS is a two-stage in flight separator to be built next to the site of GSI, Darmstadt, Germany as part of FAIR (Facility for Anti-proton and Ion Research). Its three branches allow to carry out a wide variety of experiments. Due to the large acceptance needed, the magnets of the Super-FRS require a large aperture and therefore only a superconducting solution is feasible. A superferric design was chosen in which the magnetic field is shaped by an iron yoke. For the dipole magnets only the superconducting coils are in a cryostat. These magnets are manufactured by Elytt Energy (Spain). The multiplets, assemblies of quadrupoles and higher order multipole magnets, are completely immersed in a liquid Helium bath. They are being built at ASG (Italy). The first of two first of series multiplets, a short assembly containing 2 magnets, was tested at a dedicated test facility at CERN (Switzerland). The 2nd FoS multiplet, containing 9 magnets, and the FoS dipole will be tested soon. S...

Optics Letters, 2015

This contribution presents distributed and multipoint fiber-optic monitoring of cryogenic tempera... more This contribution presents distributed and multipoint fiber-optic monitoring of cryogenic temperatures along a superconducting power transmission line down to 30 K and over 20 m distance. Multipoint measurements were conducted using fiber Bragg gratings sensors coated with two different functional overlays (epoxy and poly methyl methacrylate (PMMA)) demonstrating cryogenic operation in the range 300-4.2 K. Distributed measurements exploited optical frequency-domain reflectometry to analyze the Rayleigh scattering along two concatenated fibers with different coatings (acrylate and polyimide). The integrated system has been placed along the 20 m long cryostat of a superconducting power transmission line, which is currently being tested at the European Organization for Nuclear Research (CERN). Cool-down events from 300-30 K have been successfully measured in space and time, confirming the viability of these approaches to the monitoring of cryogenic temperatures along a superconducting transmission line.

ABSTRACT The use of Fiber Bragg Grating sensors is becoming particularly challenging for monitori... more ABSTRACT The use of Fiber Bragg Grating sensors is becoming particularly challenging for monitoring different parameters in extreme operative conditions such as ultra-low temperatures, high electromagnetic fields and strong mechanical stresses. This work reports the use of the FBG for a new generation of accelerator magnets with the goal to develop an adequate sensing technology able to provide complementary or alternative information to the conventional strain gauges through the whole service life of the magnet. The study is focused on the mechanical performances of the magnet structure, which has to preserve the sensitive coils from any damage during the entire magnet fabrication process preventing even microscopic movements of the winding that can eventually initiate a transition from superconducting to normal conducting state of the material used (called in the specific literature as Òquenchî). The FBGs have been glued on the aluminium structure of two magnets prototypes by using an adhesive suitable for cryogenic temperature. The feasibility of the bonding procedure for bare sensors at 4.2 K leads to the validation of the final integration of the FBGs for the structural monitoring of the magnet during the assembly and cool down at 77 K.

Second International Conference on Applications of Optics and Photonics, 2014

ABSTRACT The design, fabrication and tests of a new generation of superconducting magnets for the... more ABSTRACT The design, fabrication and tests of a new generation of superconducting magnets for the upgrade of the LHC require the support of an adequate, robust and reliable sensing technology. The use of Fiber Optic Sensors is becoming particularly challenging for applications in extreme harsh environments such as ultra-low temperatures, high electromagnetic fields and strong mechanical stresses offering perspectives for the development of technological innovations in several applied disciplines.

23rd International Conference on Optical Fibre Sensors, 2014

ABSTRACT New generation of superconducting magnets for high energy applications designed, manufac... more ABSTRACT New generation of superconducting magnets for high energy applications designed, manufactured and tested at the European Organization for Nuclear Research (CERN) require the implementation of reliable sensors able to monitor the mechanical stresses affecting the winding from fabrication to operation in magnetic field of 13 T. This work deals with the embedding of Fiber Bragg Grating sensors in a short model Nb3Sn dipole magnet in order to monitor the strain developed in the coil during the cool down to 1.9 K, the powering up to 15.8 kA and the warm up, offering perspectives for the replacement of standard strain gauges.

2014 Third Mediterranean Photonics Conference, 2014