A study on the effect of the condition number in the magnetic field mapping of the Air-Core solenoid

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In this paper, a hybrid method is proposed to design an air-core superconducting solenoid system for 6 T axial uniform magnetic field using Niobium Titanium (NbTi) superconducting wire. In order to minimize the volume of conductor, the hybrid optimization method including a linear programming and a nonlinear programming was adopted. The feasible space of solenoid is divided by several grids and the magnetic field at target point is approximated by the sum of magnetic field generated by an ideal current loop at the center of each grid. Using the linear programming, a global optimal current distribution in the feasible space can be indicated by non-zero current grids. Furthermore the clusters of the non-zero current grids also give the information of probable solenoids in the feasible space, such as the number, the shape, and so on. Applying these probable solenoids as the initial model, the final practical configuration of solenoids with integer layers can be obtained by the nonlinear programming. The design result illustrates the efficiency and the flexibility of the hybrid method. And this method can also be used for the magnet design which is required the high homogeneity within several ppm (parts per million).

Section: Nonlinear Programmingmentioning

confidence: 99%

Hybrid design method for air-core solenoid with axial homogeneity

Huang¹,

Lee²,

Choi³

2016

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“…The measurement points are arranged using the helical cylindrical line (HCL) method because the condition number is less than the parallel cylindrical line (PCL) method [6]. In order to map the center volume of the magnet, the central axis of the cylindrical line should align with the magnet and the center of the cylindrical surface should align with the center of the mapped volume.…”

Section: Positioning Error In Mrimentioning

confidence: 99%

“…In the study, the errors was estimated by the difference between the mapping results and the rzBI() program results. In the mapping procedure, the error for has the minimum value when order = 7 and this is related with the condition number [6]. In order to reduce the mapping error, the parameters of the HCL method can also be obtained according to the condition number and listed in Table II.…”

Section: Positioning Error In Mrimentioning

confidence: 99%

Effect of sensor positioning error on the accuracy of magnetic field mapping result for NMR/MRI

Huang¹,

Lee²

2015

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Nowadays the magnetic field mapping is widely used in the design and analysis of the NMR/MRI magnet system, and the accuracy of mapping result has become more and more important. There are several factors affecting the accuracy of the mapping such as the mapping method, the precision of the sensor, the position of the measurement points, the calculation accuracy, and so on. In this paper the error due to the misalignment of the measurement points was discussed. The magnetic field in the central volume was mapped using an indirect method in an MRI magnet system and the magnetic field was fitted to a polynomial. Considering the misalignment between the original measurement points and the practical measurement points, there must be some errors in the mapping calculation and we called it positioning error. Several comparisons of the positioning error have been presented through the theoretical estimates and the exact magnetic field values. Finally, the allowable positioning errors were suggested to guarantee the accuracy of the magnetic field mapping within a certain degree for an example case.

“…Considering the range of field strength instrument using the Hall effect is from 0.1 mT to 3×10 4 mT, the mapping result is acceptable. Using the HCL arrangement method introduced in the reference [7][8], the absolute errors of each components in the mapped volume have been shown in Fig. 10.…”

mentioning

confidence: 99%

Study on magnetic field mapping within cylindrical center volume of general magnet

Huang¹,

Lee²

2016

Self Cite

For the magnetic field analysis or design, it is important to know the behavior of the magnetic field in an interesting space. Magnetic field mapping becomes a useful tool for the study of magnetic field. In this paper, a numerical way for mapping the magnetic field within the cylindrical center volume of magnet is presented, based on the solution of the Laplace's equation in the cylindrical coordinate system. The expression of the magnetic field can be obtained by the magnetic flux density, which measured in the mapped volume. According to the form of the expression, the measurement points are arranged with the parallel cylindrical line (PCL) method. As example, the magnetic flux density generated by an electron cyclotron resonance ion source (ECRIS) magnet and a quadrupole magnet were mapped using the PCL method, respectively. The mapping results show the PCL arrangement method is feasible and convenience to map the magnetic field within a cylindrical center volume generated by the general magnet.