Magnetic characterization of Mumetal® for passive shielding of stray fields down to the nano-Tesla level

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment · 2021 · Benefit · Moderate evidence

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BenefitModerate evidencePaper 2733

Annealing Mumetal® significantly increases its magnetic permeability by more than an order of magnitude. A 1-mm thin layer of annealed Mumetal® can effectively shield stray magnetic fields down to the nano-Tesla level around the CLIC beamline.

Study snapshot

PublicationNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment · 2021

Study typeengineering

Reported directionBenefit

Evidence ratingModerate

Abstract

The luminosity of a particle collider is an extremely crucial performance parameter describing its capability of producing interactions in the collision point. However, imperfections in a collider can lead to luminosity loss. Among different imperfections, an important one is stray magnetic fields. For the Compact Linear Collider (CLIC), a collider being considered as one of the main options in Europe after the Large Hadron Collider, simulations showed an unprecedented sensitivity of the machine to fields on the order of 0.1 nT. Hence, such tight constraints require special design considerations to prevent performance loss. Different shielding techniques are available in the literature, typically relying on an active shielding strategy and capable of reducing the magnetic field amplitudes down to the nano-Tesla level. However, measuring fields with such amplitudes is challenging by using state-of-the-art commercially available sensors and therefore, a passive shielding strategy, consisting in enveloping sections of the beamline with a magnetic shield, is a more attractive option. For CLIC, Mumetal®, a Ni–Fe alloy with advertised relative permeability above 100,000, was chosen. In this paper, the DC and AC magnetic characterization of two samples of Mumetal®, one annealed in its final form and the other one non-annealed is presented, showcasing how the annealing results in a boost of the magnetic permeability of more than order of magnitude. As a case study, the shielding performance of a 1-mm thin layer of Mumetal® enveloping CLIC’s beamline is estimated. Effect: Positive

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeengineering

Effect directionbenefit

PopulationNot supplied

Sample size2

ExposureNot supplied

Evidence strengthModerateConfidence: 70% · Peer reviewed: yes

Main findings

Outcomes measured

magnetic permeability
shielding performance

Limitations

Study focused on material characterization and simulation estimates, not in situ collider performance data.
Only two samples tested, limiting generalizability.
Shielding performance estimated rather than empirically measured in operational conditions.

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": null,
    "source": "stray magnetic fields",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": 2,
  "outcomes": [
    "magnetic permeability",
    "shielding performance"
  ],
  "main_findings": "Annealing Mumetal® significantly increases its magnetic permeability by more than an order of magnitude. A 1-mm thin layer of annealed Mumetal® can effectively shield stray magnetic fields down to the nano-Tesla level around the CLIC beamline.",
  "effect_direction": "benefit",
  "limitations": [
    "Study focused on material characterization and simulation estimates, not in situ collider performance data.",
    "Only two samples tested, limiting generalizability.",
    "Shielding performance estimated rather than empirically measured in operational conditions."
  ],
  "evidence_strength": "moderate",
  "confidence": 0.7,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "Mumetal",
    "magnetic shielding",
    "stray magnetic fields",
    "nano-Tesla",
    "Compact Linear Collider",
    "magnetic permeability",
    "passive shielding"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.3,
      "reason": "Related to magnetic field exposure and shielding in particle accelerator environments."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1016/j.nima.2020.164904
PubMed: Not supplied

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