Dynamic magnetic measurements of superconducting magnets for the LHC

Buckley, J.; Richter, David H.; Walckiers, L.; Wolf, R.; Verweij, Arjan

doi:10.1109/77.402725

Cited by 15 publications

(13 citation statements)

References 8 publications

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“…constant temperature of 1.8 K 2. temperature increase during injection from 1.8 to 4.3 K 3. temperature decrease during injection from 2 to 1.6 K Both current distribution (amplitude) and average B3 change during injection, as reported earlier [10]. At the restart of the ramp, however, the current distribution does not show any sudden changes, while the usual average snap-back pic- ture is obtained.…”

Section: Current Distribution and Operating Temperaturesupporting

confidence: 53%

“…In addition, each strand sees a changing external field which rotates along the cable with period equal to the cable twist pitch Lp, similar to what is measured in the aperture [8][9][10]. The direction of the field change is therefore not necessarily parallel to the initial magnetic moment M of the filament.…”

Section: The Decay Mechanismmentioning

confidence: 70%

“…We believe that the decay of the field error is caused by the change of the initial filament magnetization M due to the current redistribution among the strands of the cable [10]. The current redistribution changes the internal field in the cable and, as is shown below, reduces M. The idea that current redistribution reduces M is not new [11], although the mechanism proposed earlier seems unlikely.…”

Section: The Decay Mechanismmentioning

confidence: 77%

“…As already known [8][9][10] the local field exhibits variations on the length scale of a cable twist pitch. These local variations are most probably due to the current distribution in the strands of each cable.…”

Section: Current Distribution and Operating Temperaturementioning

confidence: 86%

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Field errors decay and "snap-back" in LHC model dipoles

Bottura

Walckiers

Wolf

1997

IEEE Trans. Appl. Supercond.

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The magnetic field in accelerator magnets decays when the current is kept constant during the particles injection phase, and returns quickly (snaps back) to the original values as soon as ramping is restarted. Here we show results of measurements of the decay of the field errors in 10 m long LHC model dipole magnets. In accordance with previous findings, precycles and stops at intermediate current levels influence the decay. We discuss a possible mechanism causing the decay and snap-back, based on the internal field change in the cable.

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Section: Current Distribution and Operating Temperaturesupporting

confidence: 53%

Section: The Decay Mechanismmentioning

confidence: 70%

Section: The Decay Mechanismmentioning

confidence: 77%

Section: Current Distribution and Operating Temperaturementioning

confidence: 86%

See 2 more Smart Citations

Field errors decay and "snap-back" in LHC model dipoles

Bottura

Walckiers

Wolf

1997

IEEE Trans. Appl. Supercond.

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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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Magnetic Field Mapping

Henrichsen

2002

Encyclopedia of Imaging Science and Technology

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Magnetic field mapping is the production of maps or images of magnetic fields in space. Magnetic field maps are needed for designing and optimizing of magnets used in particle accelerators, spectrometers (mass, nuclear magnetic resonance, and electron paramagnetic resonance), and magnetic resonance imaging systems. Magnetic field maps are also used in geologic exploration where the variations in the magnitude and direction of the earth's magnetic field are indicative of subsurface features and objects. Field mapping relies on various methods of measuring the magnetic field, generally one point at a time. These measurement methods are the main focus of this article. It is curious to note that most measurement methods have remained virtually unchanged for a very long period, but the equipment has been subject to continual development. In this article, only the more commonly used methods are discussed. These methods are complementary and a wide variety of the equipment is readily available from industry. For the many other existing measurement methods, a more complete discussion can be found in two classical bibliographical reviews. Much of the material was presented at the CERN Accelerator School on Measurement and Alignment of Accelerator and Detector Magnets.

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Dynamic magnetic measurements of superconducting magnets for the LHC

Cited by 15 publications

References 8 publications

Field errors decay and "snap-back" in LHC model dipoles

Field errors decay and "snap-back" in LHC model dipoles

Loss and dynamic magnetic field measurements in LHC dipoles

Magnetic Field Mapping

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