Measurement of AC loss and magnetic field during ramps in the LHC model dipoles

Ang, Z.; Bejar, Isaac I.; Bottura, L.; Richter, David H.; Sheahan, Megan; Walckiers, L.; Wolf, R.

doi:10.1109/77.783401

Cited by 41 publications

(33 citation statements)

References 4 publications

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“…Magnetic measurements were performed in vertical cryostats at temperatures ranging from 1.7 K to 1.9 K. Details on the magnetic measurement system are given in [2]. In short models the end effects were found to influence strongly the field harmonics integrals.…”

Section: Methodsmentioning

confidence: 99%

Field quality of the short superconducting dipole models for the LHC

Delsolaro

Ang²,

Bottura³

et al. 2002

IEEE Trans. Appl. Supercond.

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Abstract-A full characterization of the magnetic field in warm and cold conditions was performed as a part of the standard test on the LHC 1-m long superconducting dipole models. Furthermore, dedicated measurement campaigns addressed the effect of current cycles and quenches on field quality. Powering and quenches were found to generate characteristic instabilities in the geometric harmonics. Detailed results are presented on this phenomenon, as well as correlations between warm and cold measurements and field reconstructions.

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Section: Methodsmentioning

confidence: 99%

Field quality of the short superconducting dipole models for the LHC

Delsolaro

Ang²,

Bottura³

et al. 2002

IEEE Trans. Appl. Supercond.

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“…But when ICR is small the full frequency dependence of Q coup (f) comes into play. In such cases at sufficiently high frequencies Q coup (f) departs from linearity and eventually passes through a maximum at a critical frequency (2) and hence a total loss of the form: (4) in which, according to Verweij [6], R eff = 2π(DE)f c where E is a function of (w/t) and the number of cables in the stack and D is a function of the individual-cable properties, N and L p . To summarize, values of R eff are obtainable by way of: (i) the slope of the linear Q t (f) versus f line, (ii) the "raw" initial slope of a nonlinear Q t (f), (iii) the initial slope of a nonlinear Q t (f) after fitting the data to equation (3), (iv) f c itself, either directly observed or obtained by data fitting to equation (3).…”

Section: Coupling Loss/magnetizationmentioning

confidence: 99%

“…Thus to constrain M coup both R c and N 3 R a /20 should be as large as possible (but not too high in the interest of cable stability). For the NbTi LHC cable recommended values of R c were 15 ± 5 µΩ [4] and 20 ± 10 µΩ [5]; accordingly for the adjacent-strand resistance the prefactor N 3 /20 (≈ 1,000 for the LHC-inner) allows R a to be as small as 0.2 µΩ (cf. [6]) which ensures current-sharing while not degrading R c .…”

Section: Coupling Magnetizationmentioning

confidence: 99%

Magnetic measurement of interstrand contact resistance and persistent-current magnetization of Nb3Sn Rutherford cables with cores of MgO tape and woven S-glass ribbon

Collings¹,

Sumption²,

Susner³

et al. 2012

AIP Conference Proceedings

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Rutherford cables exhibit two classes of parasitic magnetization both of which can distort the bore-field of an accelerator magnet: (1) a static magnetization ("hysteretic") resulting from intrastrand persistent currents, and (2) a dynamic magnetization produced by interstrand coupling currents passing through interstrand contact resistances (ICR) during field ramping. Interstrand coupling can be controlled by a core placed between the layers of the cable. Stainless steel ribbon (with its associated native oxide coating) is a frequently used core. Recently, however, MgO-paper tapes and woven s-glass ribbons have been suggested as alternative core materials in the interests of improved flexibility and compatibility with the cabling process. Interstrand contact resistances can be extracted from the results of AC loss measurement. Accordingly pickup-coil magnetization measurements of AC loss have been carried out on a group of cables with paper and ribbon cores. This paper reports on the resulting ICR results which it compares to those from uncored and stainless-steel-cored cables; it concludes by comparing the LHC-ramp-rate induced coupling magnetization of a typical cored Nb 3 Sn Rutherford cable with its transport-current-moderated persistent-current magnetizations at low and high fields.

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“…As the result we obtained the values (2) where . Measurements of were done by the stationary coils [3], [4] and the Hall probe setup described in [5]. Rotating coils [6] were used for the evaluation of the higher order harmonics at the reference radius 17 mm.…”

Section: Measurements Techniquesmentioning

confidence: 99%

Loss and dynamic magnetic field measurements in LHC dipoles

Akhmetov

Amet

Balaazi

et al. 2002

IEEE Trans. Appl. Supercond.

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Abstract-Knowledge of AC loss and dynamic magnetic field distortion in the main LHC dipoles is both important for the assessment of the accelerator performance and providing insight into the properties of assembled magnets. We measured the loss due to the current cycling in a few 1-meter long model dipoles, 15-meter long dipole prototypes and pre-series magnets. As expected the loss depends linearly on the rate of the current change. From the slope of this dependence, the contact resistance between the strands of the opposite layers of the cable, , was evaluated for the inner winding of the dipole. We discuss the method to estimate the value in the outer winding. The value has been also derived independently from measurements of the magnetic field. For this, the ramp rate dependent component of the main field as well as of the harmonics has been measured. The main magnetic field measurements were performed using both stationary coils and Hall probes. Rotating coils were used to perform the harmonic measurements.

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Measurement of AC loss and magnetic field during ramps in the LHC model dipoles

Cited by 41 publications

References 4 publications

Field quality of the short superconducting dipole models for the LHC

Field quality of the short superconducting dipole models for the LHC

Magnetic measurement of interstrand contact resistance and persistent-current magnetization of Nb3Sn Rutherford cables with cores of MgO tape and woven S-glass ribbon

Loss and dynamic magnetic field measurements in LHC dipoles

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