Conductor development for a wide bore 10 T Nb3Sn model dipole magnet

An 87.8 mm bore single aperture 10 T Nb3Sn model dipole magnet is under development as a next step in the realization of high-field Nb3Sn dipole magnets. The magnet is a 2 layer cos(&thetas;)-dipole model as an alternative for the proposed NbTi D1 beam separator magnets for the LHC. After completion of the general magnetic and mechanical design, all attention is focused on the manufacturing and cabling of a novel powder-in-tube Nb3Sn conductor. This Nb3Sn conductor is characterized by a high non-Cu Jc of 2680 A/mm2 at 10 T with an effective filament size of about 20 ¿m. Cabling should result in a Rutherford type of cable exhibiting a moderate Jc degradation due to the cabling process itself, a low transverse stress sensitivity and a controllable minimum value of Rc. The conductor development program is presented and the results are evaluated. Progress on the actual realization of the coils is briefly describe

Numerical Analysis of the Screening Current-Induced Magnetic Field in the HTS Insert Dipole Magnet Feather-M2.1-2

Screening currents are field-induced dynamic phenomena which occur in superconducting materials, leading to persistent magnetization. Such currents are of importance in ReBCO tapes, where the large size of the superconducting filaments gives rise to strong magnetization phenomena. In consequence, superconducting accelerator magnets based on ReBCO tapes might experience a relevant degradation of the magnetic field quality in the magnet aperture, eventually leading to particle beam instabilities. Thus, persistent magnetization phenomena need to be accurately evaluated. In this paper, the 2D finite element model of the Feather-M2.1-2 magnet is presented. The model is used to analyze the influence of the screening current-induced magnetic field on the field quality in the magnet aperture. The model relies on a coupled field formulation for eddy current problems in time-domain. The formulation is introduced and verified against theoretical references. Then, the numerical model of the Feather-M2.1-2 magnet is detailed, highlighting the key assumptions and simplifications. The numerical results are discussed and validated with available magnetic measurements. A satisfactory agreement is found, showing the capability of the numerical tool in providing accurate analysis of the dynamic behavior of the Feather-M2.1-2 magnet.Comment: 14 pages, 18 figure

High-temperature superconducting screens for magnetic field-error cancellation in accelerator magnets

Accelerators magnets must have minimal magnetic field imperfections to reduce particle-beam instabilities. In the case of coils made of high-temperature superconducting (HTS) tapes, the magnetization due to persistent currents adds an undesired field contribution, potentially degrading the magnetic field quality. In this paper we study the use of superconducting screens based on HTS tapes for reducing the magnetic field imperfections in accelerator magnets. The screens exploit the magnetization by persistent currents to cancel out the magnetic field error. The screens are aligned with the main field component, such that only the undesired field components are compensated. The screens are self-regulating, and do not require any externally applied source of energy. Measurements in liquid nitrogen at 77 K show for dipole-field configurations a significant reduction of the magnetic field error up to a factor of four. The residual error is explained via numerical simulations accounting for the geometric defects in the HTS screens, achieving satisfactory agreement with experimental results. Simulations show that if screens are increased in width and thickness, and operated at 4.5 K, field errors may be eliminated almost entirely for the typical excitation cycles of accelerator magnets

Assessing the Quality of Decision Support Technologies Using the International Patient Decision Aid Standards instrument (IPDASi)

Objectives To describe the development, validation and inter-rater reliability of an instrument to measure the quality of patient decision support technologies (decision aids). Design Scale development study, involving construct, item and scale development, validation and reliability testing. Setting There has been increasing use of decision support technologies – adjuncts to the discussions clinicians have with patients about difficult decisions. A global interest in developing these interventions exists among both for-profit and not-for-profit organisations. It is therefore essential to have internationally accepted standards to assess the quality of their development, process, content, potential bias and method of field testing and evaluation. Methods Scale development study, involving construct, item and scale development, validation and reliability testing. Participants Twenty-five researcher-members of the International Patient Decision Aid Standards Collaboration worked together to develop the instrument (IPDASi). In the fourth Stage (reliability study), eight raters assessed thirty randomly selected decision support technologies. Results IPDASi measures quality in 10 dimensions, using 47 items, and provides an overall quality score (scaled from 0 to 100) for each intervention. Overall IPDASi scores ranged from 33 to 82 across the decision support technologies sampled (n = 30), enabling discrimination. The inter-rater intraclass correlation for the overall quality score was 0.80. Correlations of dimension scores with the overall score were all positive (0.31 to 0.68). Cronbach's alpha values for the 8 raters ranged from 0.72 to 0.93. Cronbach's alphas based on the dimension means ranged from 0.50 to 0.81, indicating that the dimensions, although well correlated, measure different aspects of decision support technology quality. A short version (19 items) was also developed that had very similar mean scores to IPDASi and high correlation between short score and overall score 0.87 (CI 0.79 to 0.92). Conclusions This work demonstrates that IPDASi has the ability to assess the quality of decision support technologies. The existing IPDASi provides an assessment of the quality of a DST's components and will be used as a tool to provide formative advice to DSTs developers and summative assessments for those who want to compare their tools against an existing benchmark

Pregnancy and neonatal outcomes of COVID-19: The PAN-COVID study

Objective To assess perinatal outcomes for pregnancies affected by suspected or confirmed SARS-CoV-2 infection. Methods Prospective, web-based registry. Pregnant women were invited to participate if they had suspected or confirmed SARS-CoV-2 infection between 1st January 2020 and 31st March 2021 to assess the impact of infection on maternal and perinatal outcomes including miscarriage, stillbirth, fetal growth restriction, pre-term birth and transmission to the infant. Results Between April 2020 and March 2021, the study recruited 8239 participants who had suspected or confirmed SARs-CoV-2 infection episodes in pregnancy between January 2020 and March 2021. Maternal death affected 14/8197 (0.2%) participants, 176/8187 (2.2%) of participants required ventilatory support. Pre-eclampsia affected 389/8189 (4.8%) participants, eclampsia was reported in 40/ 8024 (0.5%) of all participants. Stillbirth affected 35/8187 (0.4 %) participants. In participants delivering within 2 weeks of delivery 21/2686 (0.8 %) were affected by stillbirth compared with 8/4596 (0.2 %) delivering ≥ 2 weeks after infection (95 % CI 0.3–1.0). SGA affected 744/7696 (9.3 %) of livebirths, FGR affected 360/8175 (4.4 %) of all pregnancies. Pre-term birth occurred in 922/8066 (11.5%), the majority of these were indicated pre-term births, 220/7987 (2.8%) participants experienced spontaneous pre-term births. Early neonatal deaths affected 11/8050 livebirths. Of all neonates, 80/7993 (1.0%) tested positive for SARS-CoV-2. Conclusions Infection was associated with indicated pre-term birth, most commonly for fetal compromise. The overall proportions of women affected by SGA and FGR were not higher than expected, however there was the proportion affected by stillbirth in participants delivering within 2 weeks of infection was significantly higher than those delivering ≥ 2 weeks after infection. We suggest that clinicians’ threshold for delivery should be low if there are concerns with fetal movements or fetal heart rate monitoring in the time around infection

Next generation materials for future magnet development at CERN

Looking into the future of CERN's higher energy Accelerators, as in the Future Circular Collider (FCC) and beyond, 16T magnetic fields and above are needed. High Temperature Superconductors (HTS) are now delivering ultra-high fields, with 30 Tesla and higher being achieved by many groups around the world. CERN has the first results of using a high current (10 kA) HTS, with REBCO cables, in an Accelerator type magnet development. This paper presents the multiple technologies and new concepts that were used in the design, build, and testing of a set of high current dipole models. We present the technology advancements in the areas of: advanced modelling, materials used in the magnet construction, quench detection and protection, and field quality. Finally, we take a glimpse at CERN's exciting 20+ Tesla accelerator conceptual magnet designs

Parametric FEM modeling of multilayer castellated canted cosine theta (CCT) magnets

Canted cosine theta (CCT) magnets have received increased attention in the recent years due to their inherent characteristics of high field quality and low conductor stresses, as each turn is supported by the metallic former. CCT geometry is suitable for complex magnets—such as nested dipoles, which allow full 360° control of the magnetic field direction. Modeling and design of such magnets is the subject of this work. A parametric 3D modeling framework for multilayer CCT magnets has been developed and optimized allowing efficient model generation without a need for both: CAD software and time consuming meshing. The model has been created using the APDL scripting language and solved using the Ansys software. By direct generation of nodes and elements the time to generate a model with one million elements was of the order of 10 min. A framework for script generation was developed, as well as the relations between the mesh parameters and the total number of nodes and elements. Detailed mesh dependence study was carried-out with in-depth analysis of solver performance (solution time, amount of written data, RAM requirements). Global and local convergence criteria were introduced to find the optimal mesh size. The case of a four layer 2.5 Tm nested dipole was analyzed in details including the worst-case scenario with full debonding between the CCT layers. Thanks to the castellations the nested-dipole is safe to support 144 000 Nm of torque due to Lorentz forces even with full de-bonding between the layers

Magnetic Measurements at Warm of the First FCC-ee Final Focus Quadrupole Prototype

The first FCC-ee final focus quadrupole prototype has been designed, manufactured, assembled and tested at warm. The prototype is a single aperture quadrupole magnet of the CCT type. One edge of the magnet was designed with local multipole cancellation, whereas the other was left with the conventional design. An optimized rotating induction-coil sensor was used. A technique was developed to take into account field distortions due to the environment of the test and distinguish them from magnet effects, demonstrating an excellent field quality for the prototype.The first FCC-ee final focus quadrupole prototype has been designed, manufactured, assembled and tested at warm. The prototype is a single aperture quadrupole magnet of the CCT type. One edge of the magnet was designed with local multipole cancellation, whereas the other was left with the conventional design. An optimized rotating induction-coil sensor was used. A technique was developed to take into account field distortions due to the environment of the test and distinguish them from magnet effects, demonstrating an excellent field quality for the prototype

Low-beta Quadrupole Designs for the LHC Luminosity Upgrade

Several scenarios are considered for the upgrade of the LHC insertions in view of increasing the luminosity beyond 1034 cm-2s-1. In the case of “quadrupole first” option, superconducting low-b quadrupoles with apertures in the range of 90-110 mm are required in view of increased heat loads and beam crossing angles. We present possible low-b quadrupole designs based on existing Nb$_{3}$Sn and LHC NbTi superconductors, present scaling laws for the magnet parameters and discuss relative advantages of the underlying triplet layouts

Mechanical design of a nested 4-layer Canted Cosine Theta (CCT) dipole

Nested CCT dipoles could be used in particle accelerators and proton therapy machines to bend a beam of charged particles in any direction. In the present study, a mechanical design of a 4 layer nested CCT dipole is evaluated with Finite Element Method (FEM). A full parametric 3D model of a 2.5 Tm 4-layer CCT dipole has been developed using the APDL scripting in the ANSYS software. The, so called, bottom up approach with direct generation of nodes and elements has been utilized, optimizing for the speed of the model generation as the time consuming meshing was bypassed. The properties of the Nb-Ti strands with the surrounding CTD-101K epoxy were obtained with a dedicated homogenization model. Resulting orthotropic properties were fully accounted for in the simulation. The shear stresses in the bonding composite layer: Kapton+S2-glass+CTD-101K were computed. With the results above the limit of 10 MPa, the necessity to provide additional rigidity against the torque was confirmed – castellated design. The shear stresses were mostly caused by thermal effects, and only ~25 % was caused by the Lorentz forces. The influence of the boundary conditions was analysed, leading to their optimal choice limiting the deformation due to Lorentz forces to 91 μm