V. Stepanov

CERN, Genève, Geneva, Switzerland

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Publications (14)13.74 Total impact

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    ABSTRACT: The system of superconducting toroids in the ATLAS experiment at CERN consists of three magnets. The Barrel Toroid was assembled and successfully tested in 2006. Next, two End-Cap Toroids have been tested on surface at 77 K and installed in the cavern, 100-m underground. The End Cap Toroids are based on Al stabilized Nb-Ti/Cu Rutherford cables, arranged in double pancake coils and conduction cooled at 4.6 K. The nominal current is 20.5 kA at 4.1 T peak field in the windings and the stored energy is 250 MJ per toroid. Prior to final testing of the entire ATLAS Toroidal system, each End Cap Toroid passed a commissioning test up to 21 kA to guarantee a reliable performance in the final assembly. In this paper the test results are described. It includes the stages of test preparation, isolation vacuum pumping and leak testing, cooling down, step-by-step charging to full current, training quenches and quench recovery. By fast discharges the quench detection and protection system was checked to demonstrate a safe energy distribution within the magnet after a quench or a triggered fast dump.
    No preview · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The ATLAS Barrel Toroid, the largest toroid ever built with 1.1 GJ stored energy, has been successfully tested after installation in the underground cavern in fall 2006. The eight coils of the Barrel Toroid were tested individually before and showed fully acceptable performances. We observed only one training quench during an individual coil test (at 30 A below the maximum test current) and no training during the test of the fully assembled toroid. At currents up to the nominal value of 20.5 kA, the toroid has been quenched inducing normal zones by means of heaters or by stopping the helium flow in the current leads. The quench safety system worked perfectly. Given the safe peak temperatures measured in the cold mass following various quenches, it is concluded that the Barrel Toroid can be operated safely. In this paper, the hot spot of the toroid is presented in detail: the measurement data are compared to various theoretical models.
    No preview · Article · Jul 2008 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The ATLAS Experiment at LHC, CERN will utilize a large, superconducting, air-cored toroidal magnet system with a long Barrel Toroid and two End Cap Toroids. Each End Cap Toroid contains eight racetrack coils mounted as a single cold mass in a cryostat vessel of approximately 10 m diameter and 5 m length. The operating current is 20.5 kA at 0.25 GJ stored energy and a peak field of 4.1 T in the windings. This paper presents the status of the End Cap Toroid Project. Final integration of the two cold masses, 120 tons each, into their respective vacuum cryostats is described. The specialized techniques, procedures and tooling infrastructure required for these operations are explained. Pre-installation cooldown to 85 K is reported. Installation of the toroids in the ATLAS cavern 100 m underground will be described. The final interfacing to the Barrel Toroid and services in the cavern will be reviewed along with preparations for final test and commissioning.
    No preview · Article · Jul 2008 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The Barrel Toroid (BT) provides the magnetic field for the muon detectors in the ATLAS experiment at CERN. The Toroid is built up from eight superconducting coils. Each coil consists of two 25 m times 5 m racetrack shape double pancakes impregnated and pre-stressed inside an aluminum coil casing. The 42-tons cold mass is cooled by forced-flow liquid helium circulating in aluminum pipes glued to its surface. The coils are tested on surface prior to their underground installation. The test program has started in September 2004 and finished in June 2005. This paper describes the test set up and various commissioning tests performed at the ATLAS Magnet Test Facility. It includes the aspects of test preparation, vacuum pumping, leak testing, cooling down, powering and warming up. The 8 coils have passed the tests successfully and have been assembled into the Toroid in the ATLAS cavern. The testing completes the production of the so far largest racetrack coils in the world
    Full-text · Article · Jul 2006 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: Each superconducting coil of the ATLAS Barrel Toroid has to pass the commissioning tests on surface before the installation in the underground cavern for the ATLAS Experiment at CERN. Particular acceptance criteria have been developed to characterize the individual coils during the on-surface testing. Based on these criteria and the limited time of the test, a compressed test program was proposed and realized. In only a few cases some additional tests were required to justify the coil performance and acceptance. In this paper the analysis of the test results is presented and discussed with respect to the acceptance criteria. Some differences in the parameters found between the identical coils are analyzed in relation to coil production features
    Full-text · Article · Jul 2006 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The Superconducting Barrel Toroid is providing (together with the two End-Cap Toroids not presented here) the magnetic field for the muon detectors in the ATLAS Experiment at the LHC at CERN. The toroid with outer dimensions of 25 m length and 20 m diameter, is built up from 8 identical racetrack coils. The coils with 120 turns each are wound with an aluminum stabilized NbTi conductor and operate at 20.5 kA at 3.9 T local field in the windings and is conduction cooled at 4.8 K by circulating forced flow helium in cooling tubes attached to the cold mass. The 8 coils of 25 m × 5 m are presently under construction and the first coils have already been fully integrated and tested. Meanwhile the assembly of the toroid 100 m underground in the ATLAS cavern at CERN has started. The 8 coils are individually tested on surface before installation. In this paper the test of the first coil, unique in size and manufacturing technology, is described in detail and the results are compared to the previous experience with the 9 m long B0 model coil.
    Full-text · Article · Jul 2005 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The ATLAS detector for the LHC at CERN requires a superconducting solenoid, which provides the magnetic field for the inner detector. The ATLAS central solenoid and its associated proximity cryogenics system has been designed by KEK in collaboration with CERN. Following construction and preliminary tests at Toshiba in Japan the equipment has been shipped to CERN. The system is being prepared for the integration in the common cryostat with the LAr calorimeter, whereafter a full on-surface test has to be completed before its final installation 100 m underground in the ATLAS cavern. For this purpose a provisional set-up for commissioning of the final proximity cryogenics, the connecting chimney and the solenoid has been established. A number of tests and simulations have been conducted in applying a new process control system to validate the cryogenics functionalities, the electrical powering scheme as well as the magnet control and safety systems. The present status of the solenoid project and the results of the various cryogenic and electrical tests are reported.
    Full-text · Article · Jul 2004 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: Three pairs of 20.5 kA current leads for the ATLAS Toroid Magnets have been designed, manufactured and tested at Kurchatov Institute. The current leads have a high mechanical reliability and the vacuum tightness under 30 bars of internal pressure. The insulation between the current carrying parts and the mounting flange, the hydraulic connections and the temperature gauges withstand the overvoltage of at least 2 kV. The current leads are fully equipped with diagnostics needed for safety and control. The current leads were tested up to 24 kA. According to CERN's specification they were also tested in the absence of any cooling at very slow current discharge rate (5 A/s) from 20.5 kA to zero without any excessive overheating. Nowadays the current leads are successfully used at the ATLAS Magnet Test Facility at CERN.
    Full-text · Article · Apr 2002 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: SST-1 tokamak, under fabrication at Institute for Plasma Research (IPR), India, deploys superconducting coils for both toroidal field (TF) and poloidal field (PF) magnets. A NbTi based 135 strands cable-in-conduit conductor (CICC) has been fabricated for this purpose by M/S Hitachi Cable Ltd. (Japan) under specification and supervision of IPR. In order to test the performance of this CICC under SST-1 operating scenarios, a Model Coil (MC) has been designed, fabricated and tested at Kurchatov Institute (KI), Russia using the SST-1 CICC under a collaborative program between IPR and KI. The MC was designed to have the same maximum field-to-current ratio (5 T at 10 kA) as of the SST-1 TF coils. Typical SST-1 disturbances were simulated with a toroidal array of four longitudinal disturbances simulating coils and with two transverse disturbances simulating coils.
    Full-text · Article · Apr 2002 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: Steady State Superconducting Tokamak (SST-1) presently being fabricated at Institute for Plasma Research (IPR), India, deploys superconducting coils for both toroidal field (TF) and poloidal field (PF) magnets. NbTi/Cu based cable-in-conduit conductor (CICC) has been industrially manufactured for this purpose by M/S Hitachi Cable Ltd. (Japan) with IPR specifications. The suitability of CICC in SST-1 operating scenario has been validated through a series of simulating tests carried on a Model Coil (MC) wound with the SST-1 CICC. The Model Coil was designed, fabricated and tested at Khurchatov Institute (KI), Russia under a collaborative program between IPR and KI. The MC was designed to have the same flux density (5 T at 10 kA) as of the SST-1 TF coils. Typical SST-1 disturbances were simulated with the help of a toroidal array of four longitudinal coils and two transverse coils simulating the disturbances. In the course of the tests, the mass flow rate per hydraulic path was up to g/s, transport current up to 12 kA and the ramp field up to 2 T/s. The results obtained from these MC tests validated the CICC design parameters as well as its appropriateness as the base conductor for the SST-1 superconducting magnet systems.
    Full-text · Conference Paper · Mar 2002
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    ABSTRACT: A small (several hundred watts) model of a three phase saturated core HTS fault current limiter (FCL) was developed and tested. Iron yokes of all three phases were saturated by a single DC HTS coil. The coil comprised a 60 turns single pancake (ID 135 mm), wound after heat treatment from Bi-2223 multifilamentary tape in Ag matrix. The critical current of the pancake in liquid nitrogen was 8 A. The tests have shown that the limiting value of the AC current (at 50 Hz) can be easily adjusted in the range from 8 A to 20 A depending on the value of the DC current in the HTS coil. The optimum value of the latter is 4 A, corresponding to the 8 times increase of the differential resistance in the current limiting mode. The response time is very short (less that 1 ms). Under tests the short-circuiting event was made in one, two and all three phases. The case of short-circuiting of one phase in the three-phase FCL is especially favorable from the standpoint of the voltages induced in HTS coil compared to the one-phase FCL
    No preview · Article · Apr 2000 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: A superconducting magnet intended for nonneutral electron plasma research has been developed and manufactured. The 260 mm room-temperature horizontal bore magnet consists of a main 3 T coil and of two orthogonal pairs of saddle-shaped steering coils, each capable of producing transverse fields of up to 0.03 T. The axial field is homogeneous in a 100 mm diameter and 600 mm long cylindrical volume within 0.25%, the azimuthal inhomogeneity within the same volume is less than 0.01%. All windings operate in a persistent current mode. The liquid helium evaporation rate is less than 6 l/day. The magnet has operated successfully at the University of California, Berkeley, since the first half of 1995. I. INTRODUCTION Over the last decade, non-neutral plasma studies have proven to be one of the most fruitful areas of research in basic plasma physics [1],[2]. Pure electron, ion, positron, and anti-proton plasmas have been created. Non-neutral plasma research is applicable to several other physi...
    Preview · Article · May 1998
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    Alexei V. Dudarev · Andrew V. Gavrilin · Yu.A. Ilyin · Vadim V. Stepanov
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    ABSTRACT: Results of an experimental investigation of current carrying capacity of two-strand cable with insulated strands, at linearly changing transport current, are presented. The experimental procedure permits to exclude completely a reduction of the cable current carrying capacity due to uneven distribution of the current throughout the strands. It enables to study separately an influence of the non-uniform magnetic field from one strand on the quench current value of another strand as the one of possible causes of the quench current degradation in multistrand cables as compared with the sum of quench currents of strands at the same rate of current change. It is shown that, due to the mutual effect of the strands, the reduction of quench current of each strand in the two-strand cable (and the reduction of the cable quench current, relatively) can reach 10 %. In the considered range of the transport current change rate (1 A/s÷10 kA/s), the cable quench current degradation is connected mainly with a decrease of critical parameters of strands situated in the magnetic field of each other. Considerable dependence of the cable quench current on the transport current change rate is not observed. Theoretical analysis of the results is given. It is demonstrated that the smoothness of I-V characteristic of strands can give a substantial reduction of the cable quench current degradation connected with some difference in resistances of the strands joints with current leads
    Full-text · Article · Aug 1996 · IEEE Transactions on Magnetics
  • A.V. Dudarev · I.O. Shugaev · V.V. Stepanov

    No preview · Article ·