The Beijing Spectrometer III (BESIII) superconducting solenoid magnet, which is running in the Beijing Electron Positron Collider II (BEPC-II), is an important part of BESIII and provides a 1 Tesla field in the main drift chamber. A 3-D mapping device with three 3-D probes was fabricated to measure the field components of , and . The mapping of the magnetic field of the BESIII superconducting solenoid magnet is presented, with the accelerator interaction region magnets located inside the BESIII solenoid excited to different current values. A set of polynomials, and a few trigonometric-Bessel terms are used to fit the data. The measurements and the functional model agree to 5 Gauss within the main drift chamber tracking volume at nominal field values.

Magnetic Field Mapping in the BESIII Solenoid

Mapping is a useful tool in the magnetic field analysis and design. In some specific research area, such as the nuclear magnetic resonance or the magnetic resonance imaging (MRI), it is important to map the magnetic field in the interesting space with high accuracy and low time consumption. In this paper, a numerical way for mapping the magnetic field in the center volume of an air-core solenoid is presented, based on the solution of the Laplace's equation for the field. Through the mathematical analysis on the mapping calculation, the error of the mapping can be estimated using the condition number of the matrix, which is related by the measurement points and the highest order of the solution of the Laplace's equation. Considering the simplicity and the accuracy, the helical cylindrical line (HCL) method is described to measure the magnetic flux density using one probe. As an example, a practical MRI magnet was mapped by the HCL method. The measurement values of the magnetic flux density are simulated according to the parameters of the MRI magnet. Based on these values, the magnetic flux density in the estimated volume can be obtained through the HCL method. Comparing the measurement value with the mapping result, the method is feasible and convenient to produce satisfactory results in the field mapping. This method will give some convenience and accuracy for mapping the magnetic field in the center volume of the air-core solenoid.

Study on Magnetic Field Mapping Method in the Center Volume of the Air-Core Solenoid

【Mapping is a useful tool in the magnetic field analysis and design. In some specific research area, such as the nuclear magnetic resonance (NMR) or the magnetic resonance imaging (MRI), it is important to map the magnetic field in the interesting space with high accuracy. In this paper, an indirect mapping method in the center volume of an air-core solenoid is presented, based on the solution of the Laplace's equation for the field. Through the mathematical analysis on the mapping calculation, we know that the condition number of the matrix, generated by the measurement points, can greatly affect the error of mapping result. Two different arrangement methods of the measurement points in field mapping are described in this paper: helical cylindrical line (HCL) method and parallel cylindrical line (PCL) method. According to the condition number, the HCL method is recommended to measure the field components using one probe. As a simple example, we mapped the magnetic fields in a MRI main magnet system. Comparing the results in the different methods, it is feasible and convenient to apply the condition number to reduce the error in the field mapping calculation. Finally, some guidelines were presented for the magnetic field mapping in the center volume of the air-core solenoid.】

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

The Mu2e experiment at Fermilab plans to search for charged-lepton flavor violations by looking for neutrino-less muon to electron conversions in the field of the nucleus. A complex solenoid system and precise knowledge of its magnetic field play a major role in the experimental approach Mu2e has chosen. It is essential to map the solenoid field up to 10−4 accuracy. This article describes the design of the Field Mapping System Mu2e will use to measure the magnetic field. Two different mechanical mapper systems, a survey-based position determination of the in-house calibrated three-dimensional Hall probes, a motion control system, and a data acquisition and readout system are presented.

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Mu2e Solenoid Field Mapping System Design

Nowadays the magnetic field mapping is widely used in the design and analysis of NMR/MRI magnet system, the the and accuracy of mapping result has become more and more important. here are several factors affectT ing 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. he magnetic field in T 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, must be some errors in the there 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.

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

The mapping of the magnetic field of the Belle detector's large superconducting solenoid is described. The mapping was done with the accelerator magnets located inside the Belle solenoid excited to their nominal field values. To cope with geometrical constraints, we developed a novel moving mechanism for the field probes that uses an ultrasonic motor located in the strong magnetic field.

O. Nitoh

Papers

Magnetic field mapping of the Belle solenoid