Generation of 25 T with an all-superconducting magnet system: field profile and field quality measurements of a layer-wound 4 T REBCO insert coil for a 21 T LTS magnet

Nuclear Magnetic Resonance (NMR) spectroscopy is a wide-spread analytical technique which is used in a large range of different fields, such as quality control, food analysis, material science and structural biology. In the widest sense, NMR is an analytical technique to determine the structure of molecules. At the time of writing this manuscript, commercial NMR spectrometers with a proton resonance frequency ≥ 900 MHz are only available from Bruker. In 2019, Bruker installed the first 1.1 GHz (25.8 T) NMR spectrometer at the St. Jude Children Research Hospital in Memphis, Tennessee, followed by the installation of the first 1.2 GHz (28.2 T) NMR spectrometer at the University of Florence in Italy in 2020. These were the first commercial NMR spectrometers operating at magnetic fields in excess of what can be achieved with conventional low temperature superconductors, and which depend on high temperature superconductors to generate the required magnetic field. In this paper, the requirements on commercial NMR magnets are discussed and the history of high-field NMR magnets is reviewed. Bruker’s R&D program for 1.1 and 1.2 GHz NMR magnets and spectrometers will be described, and some of the key properties of these first commercial NMR magnets with high-temperature superconductors are reported.

Section: Bruker's 1x Ghz Hts/lts Hybrid Magnet Programmentioning

confidence: 99%

Commercial gigahertz-class NMR magnets

Wikus

Frantz

Kümmerle

et al. 2022

“…The SCIF is responsible for decreasing the magnitude of the center magnetic field, degrading the homogeneity of the field and inducing temporal drift [10]. Essentially, the screening currents affect both the quality and the stability of the magnetic field [11,12], which are key features for successful high field applications. But they can also lead to additional undesirable consequences by impacting the mechanical behavior of the tapes operated in very high magnetic field conditions [13].…”

Section: Introductionmentioning

confidence: 99%

Electromagneto-mechanical model of high temperature superconductor insert magnets in ultra high magnetic fields

Trillaud

Berrospe-Juarez

Zermeño³

et al. 2022

Second-Generation High Temperature Superconducting (2G HTS) tapes are considered to be the main candidates for the development of future ultra high DC magnetic ﬁeld magnets. In such application, the usability of the HTS magnets can be strongly impaired by large screening currents developed in the ﬂat strip of the tapes. These currents lead to the generation of a Screening Current Induced Field (SCIF) that can deteriorate the performance by aﬀecting the stability and the homogeneity of the magnetic ﬁeld. Besides the SCIF, there is also the likely mechanical degradation of the tapes under the action of large Lorentz forces. The mechanical degradation and the presence of large screening currents intertwine to aﬀect the reliable operation of 2G HTS magnets. To study those combined issues, an electromagneto-mechanical model based on tensile mechanical characterization of short samples was built to simulate the coupled electromagnetic and mechanical behaviour of insert magnets made of 2G HTS tapes under very high magnetic ﬁeld. The coupling is carried out by considering the dependence of the n index and the critical current density Jc on the local relative deformation in addition to the magnetic ﬂux density. The case study is the Little Big Coil (LBC, version 3) which broke the world record of the strongest continuous magnetic ﬁeld achieved to this date. An analysis of the electromagneto-mechanical behavior of the LBC is conducted on the basis of information extracted from literature to show that the proposed model can assess the current magnitude at which the insert magnet quenched. Additionally, it is shown that the model can also provide some insights on the impact of the mechanical degradation of the tape on the SCIF hysteresis loop. The studies are conducted on the original LBC and on versions that include additional modifications such as harnessing and co- winding with rigid metallic tapes. These modifications are employed to limit the mechanical degradation of the HTS insert magnet under ultra high magnetic field. They are expected to deliver extra safety margin to 2G HTS insert magnets.

“…In recent years, the applications of high-field REBa 2 CuO y (REBCO) coils have remarkably progressed towards NMR MRIs, accelerators, and other such devices [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. As such, studies have reported on the mechanical deteriorations or damages of the REBCO coils [8,14].…”

Section: Introductionmentioning

confidence: 99%

Numerical evaluation of the deformation of REBCO pancake coil, considering winding tension, thermal stress, and screening-current-induced stress

Ueda

Awazu

Tokunaga

et al. 2021

In recent years, the applications of high-field REBa2CuOy (REBCO) coils have remarkably progressed towards NMR MRIs, accelerators, and other such devices. In a REBCO coil, the magnetic field due to the screening current is generated in the direction opposite to the field by the transport current, thus reducing the magnetic field, deteriorating the field homogeneity, and affecting the time stability of the magnetic field. Recently, the additional force and stress due to the screening current (referred to as screening-current-induced stress) has become a topic of concern. The screening current results in non-uniform current distributions in the REBCO tape. Therefore, the distribution of electromagnetic force in REBCO coils differs from that during the designing of the coil, assuming that the current flow in the tape is uniform. Thus, there is the possibility that the existence of screening current is a serious problem in the mechanical design of REBCO coils. In this study, we evaluate the electromagnetic force and stress due to the screening current by using the developed numerical simulation code for the electromagnetics and stress. We discuss the winding tension, thermal and electromagnetic stresses, and mechanical strength structure of the REBCO coil.