Performance testing and evaluation method for permalloy material for construction of magnetically-shielded room

Patent metadata

Field	Value
Publication number	US-12584884-B2
Application number	US-202519021574-A
Country	US
Kind code	B2
Filing date	Jan 15, 2025
Priority date	Apr 18, 2024
Publication date	Mar 24, 2026
Grant date	Mar 24, 2026

Abstract

There is provided a performance testing and evaluation method for a permalloy material for construction of a magnetically-shielded room and relates to testing and evaluation on alloy shielding performance. The present disclosure aims to solve the problem of failure to satisfy the requirements of different application scenarios for the magnetic field shielding due to lack of in-depth research on the shielding effect of the current permalloy in the magnetically-shielded rooms. The method includes: at step 1 , selecting a permalloy sample, and conducting quality inspection on the sample to ensure the sample is compliance with an experiment requirement; at step 2 , setting up an experimental apparatus; where the permalloy sample is vertically placed, and a magnetic field generation coil and a magnetic field measuring sensor are respectively placed at left and right sides of the permalloy sample; at step 3 , carrying out shielding performance testing and evaluation on the permalloy sample.

First claim

What is claimed is:

1 . A performance testing and evaluation method for a permalloy material for construction of a magnetically-shielded room, comprising the following steps:
at step 1 , selecting a sample of the permalloy material, and conducting quality inspection on the sample to ensure the sample is compliance with an experiment requirement; appearance inspection: inspecting whether the appearance of the sample is flat, and whether there is a damage or oxidation on surface of the sample; size inspection: measuring the size of the sample, including length, width and thickness, to ensure compliance with the experimental requirement; weight inspection: weighing the sample to ensure the weight of the sample is within a limit, and removing cavity phenomenon in the sample; at step 2 , setting up an experimental apparatus; wherein the sample is placed in a vertical direction, and the sample is located between a magnetic field generation coil and a magnetic field measuring sensor, and the magnetic field generation coil has a circular plane and the circular plane is parallel to the vertical direction; a distance of the magnetic field generation coil and the magnetic field measuring sensor from the sample is: at ⅓ to ½ of the longest side of the sample, wherein the sample is a permalloy plate; at step 3 , carrying out shielding performance testing and evaluation on the sample; at step 31 , by adjusting a current of the magnetic field generation coil, generating magnetic fields with different strengths and frequencies along a horizontal direction perpendicular to the vertical direction and the circular plane, and by using the magnetic field sensor, performing real-time monitoring on a size of the magnetic field shielded by the permalloy plates and recording corresponding data; at step 32 , performing Fast Fourier analysis on data collected by the magnetic field sensor to obtain a valid value of the magnetic field corresponding to the applied frequency, namely, the B 0 and Bs in the following formula; evaluating the shielding effect of the permalloy plate under different frequencies and strengths, with the shielding effect calculation formula shown in the Formula (5):

SF
B

=

❘
"\[LeftBracketingBar]"

B
0

(
r
)

❘
"\[RightBracketingBar]"

❘
"\[LeftBracketingBar]"

B
s

(
r
)

❘
"\[RightBracketingBar]"

(
5
)

wherein B 0 represents a magnetic field value at the position of the magnetic field sensor with the shielding of the permalloy plates under a same current;
Bs represents a magnetic field value at the position of the magnetic field sensor without the shielding of the permalloy plate under a same current;
at step 33 , performing evaluation on the shielding effect quantitatively and determining key performance parameters: permeability, hysteresis, conductivity, and size, shape and thickness of the plates;
at step 34 , by comparative experiments and simulation, verifying the accuracy and reliability of an evaluation result, and applying the experiment result to the designing and construction of the magnetically-shielded room; and
at step 4 , based on the evaluation result, selecting the permalloy material with an optimized evaluation result and utilizing the optimized evaluation result to optimize the structure and parameters of the magnetically-shielded room, so as to complete the testing and evaluation for performance of the permalloy material;
before testing and evaluation is performed on the shielding performance of the permalloy sample in the step 3 , a magnetized state of a zero-magnetic apparatus material under the magnetic field conditions with different amplitudes is accurately constructed;
wherein the process of constructing the magnetized state of the zero-magnetic apparatus material under the magnetic field conditions with different amplitudes is shown below:
by Jiles-Atherton model, based on an energy balance equation in material magnetization process, a relationship of a magnetization intensity M, a reversible magnetization intensity M rev , an irreversible magnetization intensity M irr , and an ideal magnetization intensity M an is obtained, as shown in the formulas (1) to (4):

M
=

M
rev

+

M
irr

(
1
)

M
rev

=

c
⁡
(

M
an

-

M
irr

)

(
2
)

M
an

=

M
s

[

coth
⁡
(

Assignees

• Harbin Inst Technology

Inventors

• Sun Zhiyin
• Li Yunzhao
• Li Liyi
• Li Pengxuan
• Li Ziqi
• Zhang Xiaoyuan

Classifications

• G01R31/00

  Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere ({measuring superconductive properties G01R33/1238;} testing line transmission systems H04B3/46; testing or measuring semiconductors or solid state devices during manufacture {H10P74/00}) · CPC title

• G01R31/001 Primary

  Measuring interference from external sources to, or emission from, the device under test, e.g. EMC, EMI, EMP or ESD testing (measuring electromagnetic fields G01R29/08; circuits for generating HV pulses in dielectric strength testing G01R31/14) · CPC title

• G01N27/72 Primary

  by investigating magnetic variables · CPC title