H.H.J. ten Kate

CERN, Genève, Geneva, Switzerland

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Publications (419)749.75 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The stability of high-current superconductors is challenging in the design of superconducting magnets. When the stability requirements are fulfilled, the protection against a quench must still be considered. A main factor in the design of quench protection systems is the resistance growth rate in the magnet following a quench. The usual method for determining the resistance growth in impregnated coils is to calculate the longitudinal velocity with which the normal zone propagates in the conductor along the coil windings. Here, we present a 2D numerical model for predicting the normal zone propagation velocity in Al stabilized Rutherford NbTi cables with large cross section. By solving two coupled differential equations under adiabatic conditions, the model takes into account the thermal diffusion and the current redistribution process following a quench. Both the temperature and magnetic field dependencies of the superconductor and the metal cladding materials properties are included. Unlike common normal zone propagation analyses, we study the influence of the thickness of the cladding on the propagation velocity for varying operating current and magnetic field. To assist in the comprehension of the numerical results, we also introduce an analytical formula for the longitudinal normal zone propagation. The analysis distinguishes between low-current and high-current regimes of normal zone propagation, depending on the ratio between the characteristic times of thermal and magnetic diffusion. We show that above a certain thickness, the cladding acts as a heat sink with a limited contribution to the acceleration of the propagation velocity with respect to the cladding geometry. Both numerical and analytical results show good agreement with experimental data.
    09/2014;
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    ABSTRACT: New-generation high-field superconducting magnets pose a challenge relating to the protection of the coil winding pack in the case of a quench. The high stored energy per unit volume calls for a very efficient quench detection and fast quench propagation in order to avoid damage due to overheating. A new protection system called Coupling-Loss Induced Quench (CLIQ) was recently developed and tested at CERN. This method provokes a fast change in the magnet transport current by means of a capacitive discharge. The resulting change in the local magnetic field induces inter-filament and inter-strand coupling losses which heat up the superconductor and eventually initiate a quench in a large fraction of the coil winding pack. The method is extensively tested on a Nb-Ti single-wire test solenoid magnet in the CERN Cryogenic Laboratory in order to assess its performance, optimize its operating parameters, and study new electrical configurations. Each parameter is thoroughly analyzed and its impact on the quench efficiency highlighted. Furthermore, an alternative method is also considered, based on a CLIQ discharge through a resistive coil magnetically coupled with the solenoid but external to it. Due to the strong coupling between the external coil and the magnet, the oscillating current in the external coil changes the magnetic field in the solenoid strands and thus generates coupling losses in the strands. Although for a given charging voltage this configuration usually yields poorer quench performance than a standard CLIQ discharge, it has the advantage of being electrically insulated from the solenoid coil, and thus it can work with much higher voltage.
    Cryogenics 09/2014; · 1.17 Impact Factor
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    ABSTRACT: Measurements of four-lepton (4ℓ, ℓ=e,μ) production cross sections at the Z resonance in pp collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant mass regions m_{ℓ^{+}ℓ^{-}}>5 GeV and 80<m_{4ℓ}<100 GeV, the measured cross sections are 76±18(stat)±4(syst)±1.4(lumi) fb and 107±9(stat)±4(syst)±3.0(lumi) fb at sqrt[s]=7 and 8 TeV, respectively. By subtracting the nonresonant 4ℓ production contributions and normalizing with Z→μ^{+}μ^{-} events, the branching fraction for the Z boson decay to 4ℓ is determined to be (3.20±0.25(stat)±0.13(syst))×10^{-6}, consistent with the standard model prediction.
    Physical Review Letters 06/2014; 112(23):231806. · 7.73 Impact Factor
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    ABSTRACT: A new and promising method for the protection of superconducting high-field magnets is developed and tested on the so-called MQXC quadrupole magnet at the CERN magnet test facility. The method relies on a capacitive discharge system inducing, during a few periods, an oscillation of the transport current in the superconducting cable of the coil. The corresponding fast change of the local magnetic field introduces a high coupling-current loss, which, in turn, causes a fast quench of a large fraction of the coil due to enhanced temperature. Results of measured discharges at various levels of transport current are presented and compared to discharges by quenching the coils using conventional quench heaters and an energy extraction system. The hot-spot temperature in the quenching coil is deduced from the coil voltage and current. The results are compared to simulations carried out using a lumped-element dynamic electro-thermal model of the so-called MQXC magnet developed with Cadence PSpice. The calculated voltages and currents are in good agreement with the measured data. Simulation and test results show that this new protection system, called coupling-loss induced quench, is a feasible method to reduce the hot-spot temperature in high-field superconducting magnets, even more when used in combination with conventional quench heaters.
    IEEE Transactions on Applied Superconductivity 06/2014; 24(3). · 1.20 Impact Factor
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    ABSTRACT: The new generation of high-field superconducting accelerator magnets poses a challenge concerning the protection of the magnet coil in the case of a quench. The very high stored energy per unit volume requires a fast and efficient quench heating system in order to avoid damage due to overheating. A new protection system for superconducting magnets is presented, comprising a combination of a novel coupling-loss induced quench (CLIQ) system and conventional quench heaters. CLIQ can provoke a very fast transition to the normal state in coil windings by introducing coupling loss and thus heat in the coil's conductor. The advantage of the hybrid protection system is a global transition, resulting in a much faster current decay, a significantly lower hot-spot temperature, and a more homogeneous temperature distribution in the magnet's coil.
    Superconductor Science and Technology 03/2014; 27(4):044023. · 2.76 Impact Factor
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    ABSTRACT: A search is presented for dark matter pair production in association with a W or Z boson in pp collisions representing 20.3 fb-1 of integrated luminosity at s=8 TeV using data recorded with the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet with the jet mass consistent with a W or Z boson, and with large missing transverse momentum are analyzed. The data are consistent with the standard model expectations. Limits are set on the mass scale in effective field theories that describe the interaction of dark matter and standard model particles, and on the cross section of Higgs production and decay to invisible particles. In addition, cross section limits on the anomalous production of W or Z bosons with large missing transverse momentum are set in two fiducial regions.
    Physical Review Letters 01/2014; 112(4):041802. · 7.73 Impact Factor
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    ABSTRACT: We use a recently developed quench protection heater modeling tool for an analysis of heater delays in superconducting high-field Nb3Sn accelerator magnets. The results suggest that the calculated delays are consistent with experimental data, and show how the heater delay depends on the main heater design parameters.
    01/2014;
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    ABSTRACT: The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO will look for axions or axion-like particles (ALPs) originating in the Sun via the Primakoff conversion of the solar plasma photons. In terms of signal-to-noise ratio, IAXO will be about 4-5 orders of magnitude more sensitive than CAST, currently the most powerful axion helioscope, reaching sensitivity to axion-photon couplings down to a few $\times 10^{-12}$ GeV$^{-1}$ and thus probing a large fraction of the currently unexplored axion and ALP parameter space. IAXO will also be sensitive to solar axions produced by mechanisms mediated by the axion-electron coupling $g_{ae}$ with sensitivity $-$for the first time$-$ to values of $g_{ae}$ not previously excluded by astrophysics. With several other possible physics cases, IAXO has the potential to serve as a multi-purpose facility for generic axion and ALP research in the next decade. In this paper we present the conceptual design of IAXO, which follows the layout of an enhanced axion helioscope, based on a purpose-built 20m-long 8-coils toroidal superconducting magnet. All the eight 60cm-diameter magnet bores are equipped with focusing x-ray optics, able to focus the signal photons into $\sim 0.2$ cm$^2$ spots that are imaged by ultra-low-background Micromegas x-ray detectors. The magnet is built into a structure with elevation and azimuth drives that will allow for solar tracking for $\sim$12 h each day.
    01/2014;
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    ABSTRACT: The US LARP collaboration has been pursuing the development of Nb3Sn technology for the interaction region low-beta quadrupole magnets for the future LHC luminosity upgrade. A key component for safe operation of these high-field magnets is the quench protection system. Due to the high stored energy density and the low stabilizer fraction in the conductor, quench propagation in the windings needs to be accelerated to limit the hot spot temperature and coil internal voltages during a quench. For this purpose, quench protection heaters are used to introduce multiple quenches across the windings. Heater delay, i.e. the time delay between heater activation and normal zone initiation under the heater, is a critical design parameter. We present an analysis of the heater delays characteristics for Nb3Sn coil windings based on our recently developed Code for Heater Delay Analysis (CoHDA), and compare with experimental results for various operational currents and temperatures in the LARP HQ and LQ magnets. We demonstrate applicability of our simulation model for heater design optimization of the LHC type low-beta quadrupole coils.
    IEEE Transactions on Applied Superconductivity 01/2014; 24(3). · 1.20 Impact Factor
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    ABSTRACT: Quench detection on superconducting bus bars and other devices with a low normal zone propagation velocity and low voltage build-up is quite difficult with conventional quench detection techniques. Currently, on ATLAS superconducting bus bar sections, superconducting quench detectors (SQD) are mounted to detect quench events. A first version of the SQD essentially consists of an insulated superconducting wire glued to a superconducting bus line or windings, which in the case of a quench rapidly builds up a relatively high resistance that can be easily and quietly detected. We now introduce a new generation of drastically improved SQDs. The new version makes the detection of quenches simpler, more reliable, and much faster. Instead of a superconducting wire, now a superconducting thin film is used. The layout of the sensor shows a meander like pattern that is etched out of a copper coated 25 μm thick film of Nb-Ti glued in between layers of Kapton. Since the sensor is now much smaller and thinner, it is easier to install and build up a high resistance with a much shorter response time. The design of the sensors is explained. The test results of the new sensors in a few variants in a calibration setup as well as when mounted on the windings surface of a magnet are reported.
    IEEE Transactions on Applied Superconductivity 01/2014; 24(3):1-4. · 1.20 Impact Factor
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    ABSTRACT: The recently developed Coupling-Loss-Induced Quench (CLIQ) protection system is a new method for initiating a fast and voluminous transition to the normal state for protecting high energy density superconducting magnets. Its simple and robust electrical design, its lower failure rate, and its more efficient energy deposition mechanism make CLIQ often preferable to other conventional quench protection methods. The system is now implemented for the protection of a two meter long superconducting quadrupole model magnet and as such fully characterized in the CERN magnet test facility. Test results convincingly show that CLIQ allows for a more global quench initiation and thus a faster discharge of the magnet energy than conventional quench heaters. Nevertheless, the CLIQ performance is strongly affected by the length of the magnet to protect, hence an optimization is required for effective application to full size magnets. A series of measures for the optimization of a quench protection system for a quadrupole magnet based on CLIQ is outlined here. The impact of various key parameters on CLIQ’s performance, the most efficient CLIQ configuration, and the advantage of installing multiple CLIQ units are assessed.
    Physics procedia 01/2014;
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    ABSTRACT: This paper presents a recently developed Code for Heater Delay Analysis (CoHDA), which is a tool for modeling protection heater induced quenches in superconducting Nb3Sn high-field accelerator magnets. CoHDA thermal model computes numerically the heat diffusion from the heater to the coil and estimates the time delay to quench initiation by comparing the coil temperature with its critical surface. The model takes into account heater geometry, power, various insulation layers and coil properties. Computational heater delays are compared to experimental data from the US LHC Accelerator Research Program (LARP) Nb3Sn High-gradient Quadrupole (HQ) magnet with good agreement. Based on the results, CoHDA provides a useful tool for quench protection design in impregnated magnets.
    IEEE Transactions on Applied Superconductivity 01/2014; 24(4). · 1.20 Impact Factor
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    ABSTRACT: The so-called CERN-LHC DS upgrade relies on the use of 11-T dipole magnets. For these magnets, 40 strands Nb3Sn type Rutherford cables based on 0.7-mm wires are being developed. Recently, four samples of the cables were characterized in the CERN FRESCA cable test station. The critical current and the premature quench current due to magneto-thermal instability were measured at 1.9 and 4.3 K in a background magnetic field between 0 and 9.6 T (the peak magnetic field on the conductor, including the self-field of the cable, ranges from ~ 2 T to ~ 12 T). Two cable samples were based on Powder-In-Tube (PIT) wire and two on Restacked-Rod-Process (RRP) wire. The PIT samples were identical and without a core in the cable while one of the RRP samples features a 25- μm-thick stainless steel core. All cables samples tested have a width and a thickness of about 14.7 and 1.25 mm, respectively. Cables and sample holders were manufactured at CERN. In this paper, we report and discuss the cable test results and compare them to the performance of witness strands, heat treated and measured on ITER-VAMAS type sample holders.
    IEEE Transactions on Applied Superconductivity 01/2014; 24(3):1-5. · 1.20 Impact Factor
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    ABSTRACT: A new protection system for superconducting magnets called CLIQ (Coupling Loss Induced Quench system) was recently developed at CERN. Recent tests on Nb Ti coils showed that CLIQ is a valid, efficient, and promising method for the protection of high magnetic field superconducting magnets. However, the protection of new generation Nb3Sn accelerator magnets is even more challenging due to the much higher stored energy per unit volume and to the significantly larger enthalpy needed to initiate and propagate a normal zone in such coils. Now the CLIQ system is tested for the first time on a Nb3Sn magnet in the CERN magnet test facility in order to investigate its performance in practice thereby validating the method for this type of superconducting magnets as well. Furthermore, we successfully reproduced the electro thermal transients during a CLIQ discharge. Finally, the implementation of various CLIQ based protection schemes for the full scale Nb3Sn quadrupole magnet for the LHC high luminosity upgrade is discussed. The impact of key system parameters on CLIQ performance and the advantages and drawbacks of using multiple CLIQ units on a single magnet are discussed.
    IEEE Transactions on Applied Superconductivity 01/2014; · 1.20 Impact Factor
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    ABSTRACT: This Letter presents measurements of the polarization of the top quark in top-antitop quark pair events, using 4.7 fb^{-1} of proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at sqrt[s]=7 TeV. Final states containing one or two isolated leptons (electrons or muons) and jets are considered. Two measurements of α_{ℓ}P, the product of the leptonic spin-analyzing power and the top quark polarization, are performed assuming that the polarization is introduced by either a CP conserving or a maximally CP violating production process. The measurements obtained, α_{ℓ}P_{CPC}=-0.035±0.014(stat)±0.037(syst) and α_{ℓ}P_{CPV}=0.020±0.016(stat)_{-0.017}^{+0.013}(syst), are in good agreement with the standard model prediction of negligible top quark polarization.
    Physical Review Letters 12/2013; 111(23):232002. · 7.73 Impact Factor
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    ABSTRACT: A search is made for massive long-lived highly ionising particles with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb-1 of pp collision data taken at sqrt(s)=7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e <= |q| <= 17e and masses 200 GeV <= m <= 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism.
    12/2013;
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    I. Shilon, A. Dudarev, H. Silva, U. Wagner, H. H. J. ten Kate
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    ABSTRACT: IAXO, the new International AXion Observatory, will feature the most ambitious detector for solar axions to date. Axions are hypothetical particles which were postulated to solve one of the puzzles arising in the standard model of particle physics, namely the strong CP (Charge conjugation and Parity) problem. This detector aims at achieving a sensitivity to the coupling between axions and photons of one order of magnitude beyond the limits of the current detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field distributed over a very large volume to convert solar axions to detectable X-ray photons. Inspired by the ATLAS barrel and end-cap toroids, a large superconducting toroid is being designed. The toroid comprises eight, one meter wide and twenty one meters long racetrack coils. The assembled toroid is sized 5.2 m in diameter and 25 m in length and its mass is about 250 tons. The useful field in the bores is 2.5 T while the peak magnetic field in the windings is 5.4 T. At the operational current of 12 kA the stored energy is 500 MJ. The racetrack type of coils are wound with a reinforced Aluminum stabilized NbTi/Cu cable and are conduction cooled. The coils optimization is shortly described as well as new concepts for cryostat, cold mass, supporting structure and the sun tracking system. Materials selection and sizing, conductor, thermal loads, the cryogenics system and the electrical system are described. Lastly, quench simulations are reported to demonstrate the system's safe quench protection scheme.
    IEEE Transactions on Applied Superconductivity 09/2013; 24(3):4500104. · 1.20 Impact Factor
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    I. Shilon, A. Dudarev, H. Silva, U. Wagner, H. H. J. ten Kate
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    ABSTRACT: Axions are hypothetical particles that were postulated to solve one of the puzzles arising in the standard model of particle physics, namely the strong CP (Charge conjugation and Parity) problem. The new International AXion Observatory (IAXO) will incorporate the most promising solar axions detector to date, which is designed to enhance the sensitivity to the axion-photon coupling by one order of magnitude beyond the limits of the current state-of-the-art detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field distributed over a very large volume to convert solar axions into X-ray photons. Inspired by the successful realization of the ATLAS barrel and end-cap toroids, a very large superconducting toroid is currently designed at CERN to provide the required magnetic field. This toroid will comprise eight, one meter wide and twenty one meter long, racetrack coils. The system is sized 5.2 m in diameter and 25 m in length. Its peak magnetic field is 5.4 T with a stored energy of 500 MJ. The magnetic field optimization process to arrive at maximum detector yield is described. In addition, materials selection and their structure and sizing has been determined by force and stress calculations. Thermal loads are estimated to size the necessary cryogenic power and the concept of a forced flow supercritical helium based cryogenic system is given. A quench simulation confirmed the quench protection scheme.
    08/2013; 1573(1).
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    Physics Letters B. 06/2013; 723(s 1–3):15–32.
  • Emmanuele Ravaioli, Arjan P. Verweij, Herman H. J. ten Kate
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    ABSTRACT: A Fast Power Abort in the LHC superconducting main dipole circuit consists in the switch-off of the power converter and the opening of the two energy-extraction switches. Each energy-extraction unit is composed of redundant electro-mechanical breakers, which are opened to force the current through an extraction resistor. When a switch is opened arcing occurs in the switch and a voltage of up to 1 kV builds up across the extraction resistor with a typical ramp rate of about 80 kV/s. The subsequent voltage transient propagates through the chain of 154 dipoles and superposes on the voltage waves caused by the switch-off of the power converter. The resulting effect caused intermittent triggering of the quench protection systems along with heater firings in the magnets when the transient occurred during a ramp of the current. A delay between power converter switch-off and opening of the energy-extraction switches was introduced to prevent this effect. Furthermore, the output filters of the power converters were modified in order to damp faster the voltage waves generated after the power-converter switch-off and to lower their amplitude. Finally, snubber capacitors were added in parallel to the extraction switches to help the commutation process by reducing the arcing effect and thus smoothing the voltage transient. A set of dedicated tests has been performed in order to understand the voltage transients and to assess the impact of the circuit modifications on the quench detection system. The results have been compared to the simulations of an electrical model of the LHC main dipole circuit developed with the Cadence suite (PSpice based).
    IEEE Transactions on Applied Superconductivity 06/2013; 23(3):4000104. · 1.20 Impact Factor

Publication Stats

3k Citations
749.75 Total Impact Points

Institutions

  • 1994–2014
    • CERN
      • • Information Technology Department (IT)
      • • Technology Department (TE)
      Genève, Geneva, Switzerland
  • 2010–2013
    • University of Freiburg
      • Faculty of Mathematics and Physics
      Freiburg, Lower Saxony, Germany
  • 1981–2013
    • Universiteit Twente
      • Faculty of Science and Technology (TNW)
      Enschede, Overijssel, Netherlands
  • 2002
    • Toshiba Corporation
      Edo, Tōkyō, Japan
  • 2001
    • Florida State University
      • National High Magnetic Field Laboratory
      Tallahassee, FL, United States
    • National High Magnetic Field Laboratory
      Tallahassee, Florida, United States
  • 1997
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States
  • 1993–1995
    • Lawrence Berkeley National Laboratory
      • • Nuclear Science Division
      • • Accelerator and Fusion Research Division
      Berkeley, California, United States