Stable Superconducting Coils

Stekly, Z. J. J.; Zar, Jacob L.

doi:10.1109/tns.1965.4323653

Cited by 184 publications

(36 citation statements)

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“…Following recent design reviews, a number of modifications have been introduced [2], leading to the conductor designs detailed in Table I, for the envelope of operating conditions in the PF Coils reported in Table II. The main change with respect to the original design is a reduction in the Cu:nonCu ratio of the low field conductors (PF2 to PF5), implying that the Stekly condition of cryogenic stability [3] is no longer respected. Experiments on subsize conductors [4] have suggested that in the planned regime of operation, and for the expected perturbation spectrum, full cryostability (i.e.…”

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confidence: 99%

Test Results From the PF Conductor Insert Coil and Implications for the ITER PF System

Bessette

Bottura

Devred

et al. 2009

IEEE Trans. Appl. Supercond.

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Abstract-In this paper we report the main test results obtained on the Poloidal Field Conductor Insert coil (PFI) for the International Thermonuclear Experimental Reactor (ITER), built jointly by the EU and RF ITER parties, recently installed and tested in the CS Model Coil facility, at JAEA-Naka. During the test we (a) verified the DC and AC operating margin of the NbTi Cable-in-Conduit Conductor in conditions representative of the operation of the ITER PF coils, (b) measured the intermediate conductor joint resistance, margin and loss, and (c) measured the AC loss of the conductor and its changes once subjected to a significant number of Lorentz force cycles. We compare the results obtained to expectations from strand and cable characterization, which were studied extensively earlier. We finally discuss the implications for the ITER PF system. Index Terms-Cable-in-conduit conductors, fusion reactors, Nb-Ti superconducting material, superconducting magnets. I. BACKGROUND ON ITER PF CONDUCTORST HE ITER Poloidal Field (PF) conductors have undergone a significant evolution in the past years. In the original ITER design (2001) the Cable-in-Conduit Conductors (CICCs) were optimized to match the current/field levels in each of the six PF coils [1]. Following recent design reviews, a number of modifications have been introduced [2], leading to the conductor designs detailed in Table I, for the envelope of operating conditions in the PF Coils reported in Table II. The main change with respect to the original design is a reduction in the Cu:nonCu ratio of the low field conductors (PF2 to PF5), implying that the Stekly condition of cryogenic stability [3] is no longer respected. Experiments on subsize conductors [4] have suggested that in the planned regime of operation, and for the expected perturbation spectrum, full cryostability (i.e. a copper fraction corresponding to the Stekly limit) is excessive. In fact, for the conditions considered, it is more convenient to design the conductor for larger temperature margin, increasing the fraction of Nb-Ti, while maintaining the copper fraction to the strict minimum demanded for protection. To achieve the operating requirements of Table II, two main conditions must be met. Firstly, the cable performance must be close to the sum of the projected performance of the individual strands, without the occurrence of the premature quenches often seen in large size Nb-Ti conductors and attributed to current non-uniformity [4], [5] (see also later discussion). In practice, we quantify this first condition using the temperature margin above the operating temperature. The design value of the temperature margin is 1.5 K, with a maximum uncertainty of 0.5 K, which results in a minimum acceptable margin of 1 K.Secondly, all AC loss sources in the cable must be controlled, so to limit the temperature increase due to the heating due to the pulsed operation. In particular, the product of the cable demagnetization factor and coupling time constant, , proportional to coupling loss, must be smalle...

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mentioning

confidence: 99%

Test Results From the PF Conductor Insert Coil and Implications for the ITER PF System

Bessette

Bottura

Devred

et al. 2009

IEEE Trans. Appl. Supercond.

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“…They joined the superconducting wire to a copper conductor along its entire length and arranged for the copper to be well cooled by heat transfer to the liquid helium bath [24]. In normal operating conditions, all the current flows in the superconductor, but if any disturbance hits the superconductor and raises its temperature above critical, the current switches to the copper and generates Ohmic heat which is transferred to the helium.…”

Section: Making Magnets That Workmentioning

confidence: 99%

A century of superconducting technology

Wilson¹

2012

AIP Conference Proceedings

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“…The other criterion is that the temperature of the conductor must be less than the critical temperature T c , in order for the normal region to shrink. The concept of cryogenic stability was dates from 1965 [19]. The topic of cryogenic stability is well covered by Wilson [20] and for some types of magnets by Green [21].…”

Section: The Transverse Heat Transfer Coefficient Needed For Cryogenimentioning

confidence: 99%

What Caused the Lead burn-out in Spectrometer Magnet 2B

Green¹

2010

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The spectrometer solenoids are supposed to be the first magnets installed in the MICE Cooling Channel [1] to [7]. The results of the test of Spectrometer Magnet 2B are reported in a previous MICE Note [8], [9]. Magnet 2B was tested with all five coils connected in series. The magnet failed because a lead to coil M2 failed before it could be trained to its full design current of 275 A. First, this report describes the condition of the magnet when the lead failure occurred. The lead that failed was between the cold mass feed-through and the heavy lead that connected to coil M2 and the quench protection diodes. It is believed that the lead failed because the minimum propagation zone (MPZ) length was too short. The quench was probably triggered by lead motion in the field external to the magnet center coil. The effect of heat transfer on quench propagation and MPZ length is discussed. The MPZ length is compared for a number of cases that apply to the spectrometer solenoid 2B as built and as it has been repaired. The required heat transfer coefficient for cryogenic stability and the quench propagation velocity along the leads are compared for various parts of the Magnet leads inside the cold mass cryostat. The effect of the insulation on leads on heat transfer is and stability is discussed.

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Stable Superconducting Coils

Cited by 184 publications

References 1 publication

Test Results From the PF Conductor Insert Coil and Implications for the ITER PF System

Test Results From the PF Conductor Insert Coil and Implications for the ITER PF System

A century of superconducting technology

What Caused the Lead burn-out in Spectrometer Magnet 2B

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