Search

Development of a 14T MRI magnet with a 900 mm warm bore was initiated by the Hefei Institute of Physical Science, Chinese Academy of Sciences. The homogeneity of the MRI magnet is less than 0.5 ppm in the spherical space with 22 cm diameter. A type of conductor like 11.7 T MRI Magnet is developed, which is called Rutherford cable in Channel (RIC). RIC conductor is subjected to huge electromagnetic loads and mechanical load during the operational period. Excessive strain occurred in Nb3Sn cable will lead to degradation of cable performance. This paper is focusing on the conductor mechanical analysis of the 14 T MRI magnet systems. Firstly, a ‘unit cell’ finite element (FE) model of the channel and insulation is built based on the conductor we designed. Then the equivalent material properties used for 14 T MRI main magnet are calculated according to the generalized Hooke's law. Finally, a quarter FE model is created based on the structural design of magnet system with the preload structure to investigate the stress and strain of conductor under the different operating conditions.

The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) has announced a project to design and manufacture a high field MRI magnet with a 900 mm warm bore and comprised of Nb3Sn Rutherford cables in 2017. The maximum magnetic induction of magnet system is 14.3 T and magnetic field homogeneity in a spherical volume with 22 cm diameter is better than 0.5 ppm. The high performance Nb3Sn strand is the potential options to use for such high field magnet system. ASIPP cooperates with Western Superconducting Technologies Company (WST) to develop high performance Nb3Sn strand whose critical current density Jc is higher than 2000 A/mm2 at 4.2 K, 12 T. To obtain the actual performance of WST high performance Nb3Sn strand, three short samples are prepared with different non-copper ratio or different heat treatment, the critical current Ic or quench current of all sample is measured at different field by the voltage-current (V-I) method, the residual resistivity ratio (RRR) of all sample is also measured. To study the strand whether it will be affected by low field instability, a small coil is built with WST strand, and the experimental result is presented and discussed in this paper.

In 2017,The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) has announced a project to develop a 14 T MRI for the research of brain science and neurology. A type of conductor like 11.7 T MRI Magnet is developed for main coil of 14T MRI, which is called Rutherford cable in channel (RIC). Conductor of 14 T MRI magnet is subjected to huge electromagnetic loads and mechanical load during the operational period. During the design, the material properties of conductor must be obtained to predict the stress-strain behavior accurately to simplify the finite element (FE) model. This paper proposes a finite element method for predicting equivalent properties of 14 T MRI main coil. Then a global finite element model of a small model coil is built to verify the effectiveness and accuracy of this method.