Transient helium heat transfer phase I—Static coolant

Steward, W. G.

doi:10.1016/0017-9310(78)90178-3

Cited by 104 publications

(26 citation statements)

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“…Combining 5.10 and 5.11, the onset time of the film boiling regime can be described by for open bath situation by [102] and [103] agree well in the steady state limit, see figure 5.11. For small V He /A He ratio and high q, Q f,I is nearly independent of q.…”

Section: Helium As a Coolant 125mentioning

confidence: 74%

“…Heat transfer into a volume of liquid helium is characterized by multiple regimes with many influencing parameters. A measurement by Steward gives a good insight of the heat transfer regimes [102]. Onset of film boiling The heat flow to liquid helium from a surface is limited by the diffusion of heat into a small and relatively hot surface layer.…”

Section: Helium As a Coolant 125mentioning

confidence: 99%

“…For other cases, the transition to film boiling depends on q, t f,I and V He /A He and it is therefore complex to describe. [102].…”

Section: Helium As a Coolant 125mentioning

confidence: 99%

“…Measurements on heat flow to supercritical helium on a short timescale with fast temperature measurement are presented in [102]. To account for the steady state heat conduction, a term a sc,ss is added to (5.16) and we can write h = a sc,c 1 2…”

Section: Supercritical Heliummentioning

confidence: 99%

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Stability of superconducting Rutherford cables for accelerator magnets

Willering

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f c e e r g s o r a c l r a t o m a n e t Gerard Willering S t a b i l i t y o f S u p e r c o n d u c t i n g r C b l e R u t h e f o r d a s PrefaceThe work described in this thesis results from an extensive collaboration between the special chair for Industrial Application of Superconductors in the Low Temperature Division at the University of Twente and the Magnets, Superconductors and Cryostats group at CERN. The research has been carried out at CERN as well as at the University of Twente and it is funded by both institutes. Part of the cable samples were prepared by GSI in the frame of research collaboration on cable stability.I am very grateful to the members of these groups for giving me the opportunity to perform the research, for their interest and useful discussions.i ContentsPreface i Chapter 1 IntroductionAfter the discovery of superconductivity in the beginning of the 20 th century the understanding of the phenomenon has grown. Practical conductors are produced for various magnet applications. Although the number of superconducting materials is high, only a few can be used in high-field and high-current density applications. This thesis deals with cable stability, with the focus on application in accelerator magnets.In this chapter a brief overview of the existing and near future accelerators and their superconducting magnets is presented. The most recent superconducting accelerator, the lhc and the near future superconducting accelerator sis 300 are described.The phenomenon of superconductivity is shortly discussed and practical superconductors are introduced with an emphasis on strands and cables. Different types of cables are presented and the relevance of this thesis for in particular the Rutherford type of cable is discussed.The terms quench and recovery are introduced. The importance of research on stability is illustrated by the large number of training quenches in the lhc main dipole magnets. Superconducting accelerator magnetsIn High Energy Physics the interaction of elementary particles is being studied. Many particle accelerators have been constructed to accelerate particles and collide them at high energy. Synchrotron accelerators provide a circular track with RFcavities to accelerate bunches of particles each cycle.Synchrotron accelerators require dipole magnets to bend the particle beam and keep it in its circular track. Quadrupole magnets are used to focus and defocus the beam and higher-order magnets correct field distortions and chromaticity. The collision energy depends on the magnetic field in the aperture of the dipole B a (T) and the bending radius of the dipole magnets r d (km) following E ≈ 0.3B a r d (TeV). The limitation in the track circumference is strongly dictated by the amount of material and the costs involved. In normal conducting magnets iron is applied to enhance the electromagnetic field produced with copper windings. The magnetic field in iron saturates at about 2 T, therefore the needed amount of copper windings and the costs involved increase strongly for hig...

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Section: Helium As a Coolant 125mentioning

confidence: 74%

Section: Helium As a Coolant 125mentioning

confidence: 99%

“…For other cases, the transition to film boiling depends on q, t f,I and V He /A He and it is therefore complex to describe. [102].…”

Section: Helium As a Coolant 125mentioning

confidence: 99%

Section: Supercritical Heliummentioning

confidence: 99%

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Stability of superconducting Rutherford cables for accelerator magnets

Willering

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“…Experimental and theoretical activities have been carried out to describe the different phases of heat exchange between a solid surface and LHe [10,11], which involve several physical phenomena, such as the Kapitza temperature discontinuity, the transition from nucleate to film boiling, and the characteristic thermal 'hysteresis' occurring in the inverse transition from film to nucleate boiling [11]. The model presented here takes into account these phenomena, emphasizing the role of a detailed description of heat exchange with liquid helium for the correct interpretation of the experimental results.…”

Section: Introductionmentioning

confidence: 99%

Comparing the thermal stability of NbTi and Nb₃Sn wires

Breschi

Trevisani

Bottura

et al. 2009

Supercond. Sci. Technol.

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The investigation of quenching in low temperature superconducting wires is of great relevance for a proper design of superconductive cables and magnets. This paper reports the experimental results of a vast measurement campaign of quench induced by laser pulses on NbTi and Nb 3 Sn wires in pool boiling Helium I. A comparison of the quench behavior of two typical NbTi and Nb 3 Sn wires is shown from different standpoints. Different qualitative behaviors of the voltage traces recorded during quenches and recoveries on NbTi and Nb 3 Sn wires are reported and analyzed. It is shown that the Nb 3 Sn wire exhibits a quench or no-quench behavior, whereas quenches and recoveries are exhibited by the NbTi wire. The two wires are also compared considering the behaviors of the two main parameters describing quench, i.e. quench energies and quench velocities, with respect to operation current and pulse duration and magnetic field. It is shown that the Nb 3 Sn wire exhibits a 'kink' of the quench energy vs current curve that makes the quench energy of Nb 3 Sn lower than that of NbTi at some intermediate current levels. Both the qualitative differences of the voltage traces and the different behaviors of quench energies and velocities are interpreted through a coupled electromagnetic-thermal model, with special emphasis on the detailed description of heat exchange with liquid helium. AbstractThe investigation of quenching in low temperature superconducting wires is of

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