Showing papers by "Giorgio Ambrosio published in 2016"
TL;DR: The High Luminosity (HiLumi) Large Hadron Collider (LHC) project has, as the main objective, to increase the LHC peak luminosity by a factor five and the integrated luminosity, which will be achieved mainly with a new interaction region layout which will allow a stronger focusing of the colliding beams as discussed by the authors.
Abstract: The High Luminosity (HiLumi) Large Hadron Collider (LHC) project has, as the main objective, to increase the LHC peak luminosity by a factor five and the integrated luminosity by a factor ten. This goal will be achieved mainly with a new interaction region layout, which will allow a stronger focusing of the colliding beams. The target will be to reduce the beam size in the interaction points by a factor of two, which requires doubling the aperture of the low-β (or inner triplet) quadrupole magnets. The use of Nb3Sn superconducting material and, as a result, the possibility of operating at magnetic field levels in the windings higher than 11 T will limit the increase in length of these quadrupoles, called MQXF, to acceptable levels. After the initial design phase, where the key parameters were chosen and the magnet's conceptual design finalized, the MQXF project, a joint effort between the U.S. LHC Accelerator Research Program and the Conseil Europeen pour la Recherche Nucleaire (CERN), has now entered the construction and test phase of the short models. Concurrently, the preparation for the development of the full-length prototypes has been initiated. This paper will provide an overview of the project status, describing and reporting on the performance of the superconducting material, the lessons learnt during the fabrication of superconducting coils and support structure, and the fine tuning of the magnet design in view of the start of the prototyping phase.
121 citations
TL;DR: In this article, a detailed visual inspection of the first generation coils was carried out to investigate cable dimensional changes during heat treatment and the position of the windings in the coil straight section and in the end region.
Abstract: As part of the Large Hadron Collider Luminosity upgrade (HiLumi-LHC) program, the US LARP collaboration and CERN are working together to design and build a 150 mm aperture Nb3Sn quadrupole for the LHC interaction regions. A first series of 1.5 m long coils were fabricated and assembled in a first short model. A detailed visual inspection of the coils was carried out to investigate cable dimensional changes during heat treatment and the position of the windings in the coil straight section and in the end region. The analyses allow identifying a set of design changes which, combined with a fine tune of the cable geometry and a field quality optimization, were implemented in a new, second-generation, coil design. In this paper we review the main characteristics of the first generation coils, describe the modification in coil lay-out, and discuss their impact on parts design and magnet analysis.
28 citations
TL;DR: In this paper, the first short model MQXFS-AT has been assembled at LBNL with coils fabricated by LARP and CERN and showed how it relies strongly on experience acquired during the LARP 120mm-aperture HQ magnet series.
Abstract: In preparation for the high-luminosity upgrade of the Large Hadron Collider (LHC), the LHC Accelerator Research Program (LARP) in collaboration with CERN is pursuing the development of MQXF: a 150-mm-aperture high-field Nb3Sn quadrupole magnet. The development phase starts with the fabrication and test of several short models (1.2-m magnetic length) and will continue with the development of several long prototypes. All of them are mechanically supported using a shell-based support structure, which has been extensively demonstrated on several R&D models within LARP. The first short model MQXFS-AT has been assembled at LBNL with coils fabricated by LARP and CERN. In this paper, we summarize the assembly process and show how it relies strongly on experience acquired during the LARP 120-mm-aperture HQ magnet series. We present comparison between strain gauges data and finite-element model analysis. Finally, we present the implication of the MQXFS-AT experience on the design of the long prototype support structure.
27 citations
TL;DR: The Fermilab Mu2e experiment has been developed to search for evidence of charged lepton flavor violation through the direct conversion of muons into electrons as mentioned in this paper, where the transport solenoid is an s-shaped magnet that guides the muons from the source to the stopping target.
Abstract: The Fermilab Mu2e experiment has been developed to search for evidence of charged lepton flavor violation through the direct conversion of muons into electrons. The transport solenoid is an s-shaped magnet that guides the muons from the source to the stopping target. It consists of 52 superconducting coils arranged in 27 coil modules. A full-size prototype coil module, with all the features of a typical module of the full assembly, was successfully manufactured by a collaboration between INFN-Genoa and Fermilab. The prototype contains two coils that can be powered independently. To validate the design, the magnet went through an extensive test campaign. Warm tests included magnetic measurements with a vibrating stretched wire and electrical and dimensional checks. The cold performance was evaluated by a series of power tests and temperature dependence and minimum quench energy studies.
23 citations
TL;DR: Rochepault et al. as mentioned in this paper analyzed the behavior of cable dimensions during heat treatment and provided estimates of the space to be accommodated in the tooling for coil expansion and contraction.
Abstract: Author(s): Rochepault, E; Ferracin, P; Ambrosio, G; Anerella, M; Ballarino, A; Bonasia, A; Bordini, B; Cheng, D; Dietderich, DR; Felice, H; Garcia Fajardo, L; Ghosh, A; Holik, EF; Izquierdo Bermudez, S; Perez, JC; Pong, I; Schmalzle, J; Yu, M | Abstract: In high field magnet applications, Nb3Sn coils undergo a heat treatment step after winding. During this stage, coils radially expand and longitudinally contract due to the Nb3Sn phase change. In order to prevent residual strain from altering superconducting performances, the tooling must provide the adequate space for these dimensional changes. The aim of this paper is to understand the behavior of cable dimensions during heat treatment and to provide estimates of the space to be accommodated in the tooling for coil expansion and contraction. This paper summarizes measurements of dimensional changes on strands, single Rutherford cables, cable stacks, and coils performed between 2013 and 2015. These samples and coils have been performed within a collaboration between CERN and the U.S. LHC Accelerator Research Program to develop Nb3Sn quadrupole magnets for the HiLumi LHC. The results are also compared with other high field magnet projects.
21 citations
TL;DR: The U.S. LHC Accelerator Research Program (LARP) has been developing Nb3Sn quadrupoles of increasing performance for the high-luminosity upgrade of the large hadron collider as discussed by the authors.
Abstract: The U.S. LHC Accelerator Research Program (LARP) has been developing Nb3Sn quadrupoles of increasing performance for the high-luminosity upgrade of the large hadron collider. The 120-mm aperture high-field quadrupole (HQ) models are the last step in the R&D phase supporting the development of the new IR Quadrupoles (MQXF). Three series of HQ coils were fabricated and assembled in a shell-based support structure, progressively optimizing the design and fabrication process. The final set of coils consistently applied the optimized design solutions and was assembled in the HQ03a model. This paper reports a summary of the HQ03a test results, including training, mechanical performance, field quality, and quench studies.
16 citations
TL;DR: In this article, the magnet support structure of the first short model was designed, and two units were fabricated and tested at CERN and at LBNL, and the results of the assembly and the cooldown tests with dummy coils, which were performed at both the Cern and at the U.S. LARP were reported.
Abstract: Within the scope of the High-Luminosity LHC project, the collaboration between CERN and U.S. LARP is developing new low- $\beta$ quadrupoles using the Nb3Sn superconducting technology for the upgrade of the LHC interaction regions. The magnet support structure of the first short model was designed, and two units were fabricated and tested at CERN and at LBNL. The structure provides the preload to the collar–coil subassembly by an arrangement of outer aluminum shells pretensioned with water-pressurized bladders. For the mechanical qualification of the structure and the assembly procedure, superconducting coils were replaced with solid aluminum “dummy coils,” and the structure was preloaded at room temperature and then cooled-down to 77 K. The mechanical behavior of the magnet structure was monitored with the use of strain gauges installed on the aluminum shells, the dummy coils, and the axial preload system. This paper reports on the outcome of the assembly and the cooldown tests with dummy coils, which were performed at CERN and at LBNL, and presents the strain gauge measurements compared with the 3-D finite-element model predictions.
14 citations
TL;DR: The U.S. LHC Accelerator Research Program (LARP) and CERN are combining efforts for the HiLumi-LHC upgrade to design and fabricate 150mm-aperture interaction region quadrupoles with a nominal gradient of 130 T/m using Nb3Sn.
Abstract: The U.S. LHC Accelerator Research Program (LARP) and CERN are combining efforts for the HiLumi-LHC upgrade to design and fabricate 150-mm-aperture, interaction region quadrupoles with a nominal gradient of 130 T/m using Nb3Sn. To successfully produce the necessary long MQXF triplets, the HiLumi-LHC collaboration is systematically reducing risk and design modification by heavily relying upon the experience gained from the successful 120-mm-aperture LARP HQ program. First generation MQXF short (MQXFS) coils were predominately a scaling up of the HQ quadrupole design allowing comparable cable expansion during Nb3Sn formation heat treatment and increased insulation fraction for electrical robustness. A total of 13 first generation MQXFS coils were fabricated between LARP and CERN. Systematic differences in coil size, coil alignment symmetry, and coil length contraction during heat treatment are observed and likely due to slight variances in tooling and insulation/cable systems. Analysis of coil cross sections indicate that field-shaping wedges and adjacent coil turns are systematically displaced from the nominal location and the cable is expanding less than nominally designed. Lastly, a second generation MQXF coil design seeks to correct the expansion and displacement discrepancies by increasing insulation and adding adjustable shims at the coil pole and midplanes to correct allowed magneticmore » field harmonics.« less
12 citations
TL;DR: In this article, the authors developed a dedicated six-channel acoustic emission detection system and accompanying software aimed at localizing mechanical events during the coil cold testing at Fermilab.
Abstract: Acoustic emission (AE) detection is a noninvasive technique allowing the localization of the mechanical events and quenches in superconducting magnets. Application of the AE technique is especially advantageous in situations where magnet integrity can be jeopardized by the use of voltage taps or inductive pickup coils. As the prototype module of the transport solenoid (TS) for the Mu2e experiment at Fermilab represents such a special case, we have developed a dedicated six-channel AE detection system and accompanying software aimed at localizing mechanical events during the coil cold testing. The AE sensors based on transversely polarized piezoceramic washers combined with cryogenic preamplifiers were mounted at the outer surface of the solenoid aluminum shell, with a 60° angular step around the circumference. Acoustic signals were simultaneously acquired at a rate of 500 kS/s, prefiltered and sorted based on their arrival time. Next, based on the arrival timing, angular and axial coordinates of the AE sources within the magnet structure were calculated. We present AE measurement results obtained during cooldown, spot heater firing, and spontaneous quenching of the Mu2e TS module prototype and discuss their relevance for mechanical stability assessment and quench localization.
9 citations
14 Apr 2016
TL;DR: The reference design of MQXFS1, the first 1.5 m prototype of the low-beta quadrupoles (MQXF) for the LHC High Luminosity Upgrade, was presented in this article.
Abstract: This report presents the reference design of MQXFS1, the first 1.5 m prototype of the low-beta quadrupoles (MQXF) for the LHC High Luminosity Upgrade. The MQXF quadrupoles have 150 mm aperture, coil peak field of about 12 T, and use $Nb_{3}Sn$ conductor. The design is based on the LARP HQ quadrupoles, which had 120 mm aperture. MQXFS1 has 1st generation cable cross-section and magnetic design.
9 citations
TL;DR: In this paper, a protection study of the updated Nb3Sn low-β quadrupoles (MQXF) is presented, benefiting from the experience gained by studying the previous design.
Abstract: In 2023, the LHC luminosity will be increased, aiming at reaching 3000 fb-1 integrated over ten years. To obtain this target, new Nb3Sn low-β quadrupoles (MQXF) have been designed for the interaction regions. These magnets present a very large aperture (150 mm, to be compared with the 70 mm of the present NbTi quadrupoles) and a very large stored energy density (120 MJ/m3). For these reasons, quench protection is one of the most challenging aspects of the design of these magnets. In fact, protection studies of a previous design showed that the simulated hot spot temperature was very close to the maximum allowed limit of 350 K; this challenge motivated improvements in the current discharge modeling, taking into account the so-called dynamic effects on the apparent magnet inductance. Moreover, quench heaters design has been studied to be going into more details. In this study, a protection study of the updated MQXF is presented, benefiting from the experience gained by studying the previous design. As a result, a study of the voltages between turns in the magnet is also presented during both normal operation and most important failure scenarios.
TL;DR: The Mu2e Transport Solenoid as discussed by the authors consists of fifty-two coils arranged in twenty-seven coil modules that form the S-shaped cold mass, each coil is wound from Al-stabilized NbTi superconductor.
Abstract: The Mu2e Transport Solenoid consists of fifty-two coils arranged in twenty-seven coil modules that form the S- shaped cold mass. Each coil is wound from Al-stabilized NbTi superconductor. The coils are supported by an external structural aluminum shell machined from a forged billet. Most of the coil modules house two coils with the axis of each coil oriented at an angle of approximately five degrees with respect to each other. The coils are indirectly cooled with LHe circulating in tubes welded on the shell. In order to enhance the cooling capacity, pure aluminum sheets connect the inner bore of the coils to the cooling tubes. The coils are placed inside the shell by the means of a shrink fit procedure. A full-size prototype, with all the features of the full assembly, was successfully manufactured in a collaboration between INFN-Genoa and Fermilab. In order to ensure an optimal mechanical pre-stress at the coil-shell interface, the coils are inserted into the shell through a shrink fitting process. We present the details of the prototype with the design choices as validated by the structural analysis. The fabrication steps are described as well. Index Terms—Superconducting Magnets, Solenoids, Accelerator Magnets
TL;DR: In this article, an analytical model using interfilament coupling current influence for the inductance lowering has been implemented in the quench calculation code QLASA, and the comparison with experimental data is given.
Abstract: This paper presents the analysis of some quench tests addressed to study the dynamic effects in the 1-m-long 120-mm-aperture Nb3Sn quadrupole magnet, i.e., HQ02b, designed, fabricated, and tested by the LHC Accelerator Research Program. The magnet has a short sample gradient of 205 T/m at 1.9 K and a peak field of 14.2 T. The test campaign has been performed at CERN in April 2014. In the specific tests, which were dedicated to the measurements of the dynamic inductance of the magnet during the rapid current discharge for a quench, the protection heaters were activated only in some windings, in order to obtain the measure of the resistive and inductive voltages separately. The analysis of the results confirms a very low value of the dynamic inductance at the beginning of the discharge, which later approaches the nominal value. Indications of dynamic inductance variation were already found from the analysis of current decay during quenches in the previous magnets HQ02a and HQ02a2; however, with this dedicated test of HQ02b, a quantitative measurement and assessment has been possible. An analytical model using interfilament coupling current influence for the inductance lowering has been implemented in the quench calculation code QLASA, and the comparison with experimental data is given. The agreement of the model with the experimental results is very good and allows predicting more accurately the critical parameters in quench analysis (MIITs, hot spot temperature) for the MQXF Nb3Sn quadrupoles, which will be installed in the High Luminosity LHC.
TL;DR: In this paper, the authors compare the heat flow characteristics and thermal diffusion timescales of different heater designs and imaged the resulting thermal distributions using a high-sensitivity thermal video camera.
Abstract: Protection heaters are essential elements of a quench protection scheme for high-field accelerator magnets. Various heater designs fabricated by LARP and CERN have been already tested in the LARP high-field quadrupole HQ and presently being built into the coils of the high-field quadrupole MQXF. In order to compare the heat flow characteristics and thermal diffusion timescales of different heater designs, we powered heaters of two different geometries in ambient conditions and imaged the resulting thermal distributions using a high-sensitivity thermal video camera. We observed a peculiar spatial periodicity in the temperature distribution maps potentially linked to the structure of the underlying cable. Two-dimensional numerical simulation of heat diffusion and spatial heat distribution have been conducted, and the results of simulation and experiment have been compared. Imaging revealed hot spots due to a current concentration around high curvature points of heater strip of varying cross sections and visualized thermal effects of various interlayer structural defects. Thermal imaging can become a future quality control tool for the MQXF coil heaters.