Speaker
Description
Ultrahigh magnetic fields of 100 to 1000 T (multi-megagauss fields) can be produced destructively [1-4]. In this almost unexplored field range, more interesting magnetic field-induced phenomena are expected to be discovered, in addition to as previously reported the discovery of the novel high magnetic field phase of solid oxygen [5] and the dissociation of molecular orbitals in vanadium dioxide by a magnetic field [6,7].
When one considers the application of the megagauss fields to material science, one of the most important issues in the ultrahigh field generation is the reproducibility of the magnetic fields. It is naturally anticipated that the time variation of the magnetic field (field waveform) would be different at each field production because of the destruction of the coil every time, although the experimental parameters such as the electric energy and the coil dimensions are the same.
In our institute, two destructive magnetic field generation manners have been developed for longer than half century [1, 2]. One is the electromagnetic flux compression (EMFC) and the other one is the single-turn coil (STC). The EMFC can generate 1000 T – class magnetic fields [2] which are the highest magnetic fields one can utilize for material science. The alternate manner is explosive flux compression (ExFC) using chemical explosives [3]. The advantage of the EMFC to ExFC is that the magnitude of destruction along with the field generation is much smaller, and thus the field production system can be handled more easily. The parameters of the coil and those of the energy power source can control the field waveform. Even though, obtaining high reproducibility better than a 2-3 % difference is challenging for the EMFC at present because the probe part for measuring the magnetic field and several physical quantities of the sample material is also broken due to the implosion during the field generation process.
The STC is a more compact field generator than the EMFC and provides multi-megagauss fields up to 300 T [4]. The coil explosion takes place outer direction and thus the set-ups for the experiments including measurement probes survive if the field is typically lower than 200 T. The reproducibility of the generated field waveform is as good as a 2-3 % difference [8]. This is a big advantage for application of the megagauss fields to the material science. Several measurement techniques using STC have recently been developed [8 – 10].
The EMFC field generator was renewed recently [2] and several minor technical improvements on the STC were employed. In the presentation at the MT29 conference, waveforms of multi-megagauss fields taken recently with the EMFC and STC in The Institute for Solid State Physic, The University of Tokyo with several coils- and power source-parameters will be introduced, and the magnetic field properties including the field reproducibility will be discussed.
References
[1] N. Miura et al., J. Low Temp. Phys. 133, 139 (2003).
[2] D. Nakamura, et al., Rev. Sci. Instrum. 89, 095106 (2018)
[3] O. Portugall et al., Phys. D: Appl. Phys. 32, 2354 (1999).
[4] A. S. Dzurak, et al., Physica B 246-247, 40 (1998).
[5] T. Nomura et al., Phys. Rev. Lett. 112, 247201 (2014).
[6] Y. H. Matsuda, et al., Nat. Commun. 11, 3591 (2020).
[7] Y. H. Matsuda et al., J. Phys. Soc. Jpn. 91, 101008 (2022).
[8] S. Takeyama et al., J. Phys. Soc. Jpn. 81, 014702 (2012).
[9] A. Ikeda et al., Rev. Sci. Instrum. 88, 083906 (2017).
[10] T. Nomura et al., Rev. Sci. Instrum. 92, 063902 (2021).
