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Pulse magnet of 10 T for power laser experiments with x-ray free-electron laser diagnostics
Authors:
Akihiko Ikeda,
Kosuke Noda,
Yutaro Yamanaka,
Yuma Urabe,
Keiichiro Kawai,
Yasuhiro H. Matsuda,
Hirotaka Nakamura,
Ryusuke Yamamoto,
Yoshiki Naito,
Yasuhiro Kuramitsu,
Kai Taketoshi,
Naoki Yamagata,
Norimasa Ozaki,
Tatiana Pikuz,
Yoichi Sakawa,
Takayoshi Sano,
Ryosuke Kodama,
Taichi Morita,
Tomoya Ogawa,
Kohei Miyanishi,
Toshinori Yabuuchi,
Rigon Gabriel,
Bakandreas Stavros,
Koenig Michel,
Bruno Albertazzi
Abstract:
The importance of investigating magnetized plasmas/solids in extreme conditions has grown over the last decades, particularly in the field of high energy density physics (HEDP), such as laboratory astrophysics and inertial confinement fusion. However, up to now, the unique capabilities of an X-ray free-electron laser (XFEL), such as high brilliance and low divergence have never been exploited for…
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The importance of investigating magnetized plasmas/solids in extreme conditions has grown over the last decades, particularly in the field of high energy density physics (HEDP), such as laboratory astrophysics and inertial confinement fusion. However, up to now, the unique capabilities of an X-ray free-electron laser (XFEL), such as high brilliance and low divergence have never been exploited for this type of research. In this paper, we present the first platform developed at SACLA, Japan, that combines a high-power optical laser for generating matter under extreme conditions of pressure and temperature, an XFEL probe, and an external magnetic field. The high current is produced using a 2 kV, 4.8 kJ pulsed power system giving a maximum current of 10 kA which is synchronized with the optical laser and XFEL in a vacuum environment. It flows through a split-pair coil to generate a high magnetic field (10 T at 6 kA) which has 1 cm access every 45$^{\circ}$ in the equatorial plane and 90$^{\circ}$ in the poloidal one. This platform offers new opportunities to study high-energy-density matter in strong magnetic fields, including shock propagation, instability growth, and turbulent plasma dynamics.
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Submitted 25 May, 2026;
originally announced May 2026.
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Non-linear diffusion and inhomogeneity of the magnetic field in single-turn coils: Insights from 3D multiphysics modeling
Authors:
Hideaki Kobayashi,
Yugaku Goyo,
Yuto Ishii,
Yasuhiro H. Matsuda,
Kunio Takekoshi,
Akihiko Ikeda
Abstract:
The single-turn coil method is a destructive pulsed magnet for generating over 100 T with a few $μ$-second pulse duration, and it inevitably causes the coil to explode. The temporal and spatial distributions of the electric current and magnetic field are highly inhomogeneous, arising from the skin effect, rapid temperature rise, and coil deformation. To grasp the dynamic phenomena in the single-tu…
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The single-turn coil method is a destructive pulsed magnet for generating over 100 T with a few $μ$-second pulse duration, and it inevitably causes the coil to explode. The temporal and spatial distributions of the electric current and magnetic field are highly inhomogeneous, arising from the skin effect, rapid temperature rise, and coil deformation. To grasp the dynamic phenomena in the single-turn coil, we conducted a finite element analysis using multiphysics simulation. We employed finite element method calculations using a fully 3D model of the single-turn coil with broken cylindrical symmetry. The calculated result revealed highly nonlinear diffusion of electric current, temperature, and magnetic fields, which are the sources of the inhomogeneous magnetic fields inside the single-turn coil in time and space.
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Submitted 15 May, 2026;
originally announced May 2026.
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Efficiency in a repetitive pulse magnet
Authors:
Akihiko Ikeda,
Yuto Ishii,
Yasuhiro H. Matsuda,
Go Yumoto,
Ayumi Abe,
Ryusuke Matsunaga
Abstract:
A repetitive-pulse magnet is a promising tool when combined with repetitive excitations, such as pulsed lasers. Technically, the repetition and the magnetic field values in a repetitive-pulse magnet are limited by the Joule heating in the coil. Here, we analytically examine the relationship between the coil's dimensions and its efficiency, assuming negligible heating of the coil, to design an opti…
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A repetitive-pulse magnet is a promising tool when combined with repetitive excitations, such as pulsed lasers. Technically, the repetition and the magnetic field values in a repetitive-pulse magnet are limited by the Joule heating in the coil. Here, we analytically examine the relationship between the coil's dimensions and its efficiency, assuming negligible heating of the coil, to design an optimized high-repetition, high-magnetic-field coil. We calculated the dependence of the maximum magnetic field, energy loss, pulse duration, form factor, impedance, and maximum current on the coil's geometry. We found that the smaller the coil, the more pulses and the more intense the magnetic fields we can obtain under a given condition. We argue that the obtained trend arises from a complex interplay among various parameters.
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Submitted 2 May, 2026;
originally announced May 2026.
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Magneto-optical imaging of macroscopic altermagnetic domains in MnTe
Authors:
Gakuto Watanabe,
Soichiro Yamane,
Ryotaro Maki,
Atsutoshi Ikeda,
Akimitsu Kirikoshi,
Junya Otsuki,
Takuya Aoyama,
Kenya Ohgushi,
Shingo Yonezawa
Abstract:
Altermagnets are a new class of magnets accompanying global time-reversal symmetry breaking (TRSB) without net magnetization. The TRSB results in formation of novel altermagnetic domains. Features of altermagnetic domains, in particular their responses to external stimuli, are essentially important but yet unexplored. Here, we report visualization of bulk altermagnetic domains in MnTe based on sca…
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Altermagnets are a new class of magnets accompanying global time-reversal symmetry breaking (TRSB) without net magnetization. The TRSB results in formation of novel altermagnetic domains. Features of altermagnetic domains, in particular their responses to external stimuli, are essentially important but yet unexplored. Here, we report visualization of bulk altermagnetic domains in MnTe based on scanning magneto-optical Kerr-effect microscopy using telecom infrared wavelength. We found two distinct TRSB domains with large Kerr rotations that do not scale with its tiny bulk magnetization. We also revealed controllability and stability of domains against magnetic or thermal perturbations. Our first observation of altermagnetic domains using a laboratory-scale simple optical technique showing their movable nature provide firm bases for future fundamental and application studies of altermagnets.
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Submitted 16 April, 2026;
originally announced April 2026.
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Non-Equilibrium Fluidization of Dense Active Suspension
Authors:
Yujiro Sugino,
Hiroyuki Ebata,
Yoshiyuki Sowa,
Atsushi Ikeda,
Daisuke Mizuno
Abstract:
We investigate dense suspensions of swimming bacteria prepared in a nutrient-exchange chamber. Near the pellet concentration, nonthermal fluctuations showed notable agreement between self and collective behaviors, a phenomenon not previously observed at equilibrium. The viscosity of active suspensions dramatically decreased compared to their inactive counterparts, where glassy features, such as no…
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We investigate dense suspensions of swimming bacteria prepared in a nutrient-exchange chamber. Near the pellet concentration, nonthermal fluctuations showed notable agreement between self and collective behaviors, a phenomenon not previously observed at equilibrium. The viscosity of active suspensions dramatically decreased compared to their inactive counterparts, where glassy features, such as non-Newtonian viscosity and dynamic heterogeneity, disappeared. Instead, the complex shear modulus showed a power-law rheology,$G^*(ω)\propto\left(-iω\right)^\frac{1}{2}$, indicating the role of bacterial activity in driving the system towards a critical jamming state.
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Submitted 1 February, 2024; v1 submitted 28 January, 2024;
originally announced January 2024.
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Superconductivity in the antiperovskite Dirac-metal oxide Sr$_3$SnO
Authors:
Mohamed Oudah,
Atsutoshi Ikeda,
Jan Niklas Hausmann,
Shingo Yonezawa,
Toshiyuki Fukumoto,
Shingo Kobayashi,
Masatoshi Sato,
Yoshiteru Maeno
Abstract:
Oxides with perovskite-based structures have been known as essential materials for fascinating phenomena such as high-temperature and unconventional superconductivity. Discoveries of these oxide superconductors have driven the science community to vastly extend the concepts of strongly correlated electron systems. The base of these materials, the cubic perovskite oxides, $AB$O$_3$, also exhibit su…
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Oxides with perovskite-based structures have been known as essential materials for fascinating phenomena such as high-temperature and unconventional superconductivity. Discoveries of these oxide superconductors have driven the science community to vastly extend the concepts of strongly correlated electron systems. The base of these materials, the cubic perovskite oxides, $AB$O$_3$, also exhibit superconductivity with $T_{\mathrm{c}}$ of up to 30 K, as reported for Ba$_{0.6}$K$_{0.4}$BiO$_3$. Perovskite oxides have their counterparts, antiperovskite oxides $A_3B$O (or "$B$O$A_3$"), in which the position of metal and oxygen ions are reversed and therefore metallic $B$ ions take unusual negative valence states. However, no superconductivity has been reported among antiperovskite oxides. Here, we report the discovery of the first superconducting antiperovskite oxide Sr$_3$SnO with $T_{\mathrm{c}}$ of around 5 K. Sr$_3$SnO possesses Dirac points in its electronic structure, originating from the inversion of bands with different parities. Based on theoretical analysis, we propose possibility of topological odd-parity superconductivity analogous to the superfluid $^3$He-B, in moderately hole-doped Sr$_3$SnO, originating from unusual orbital texture on the Fermi surface. We envision that this discovery of a new class of oxide superconductor with the inverted valence configuration will stimulate the exploration of topological materials science based on a variety of antiperovskite oxides.
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Submitted 23 February, 2017; v1 submitted 21 April, 2016;
originally announced April 2016.
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Photon stimulated desorption of and nuclear resonant scattering by noble gas atoms at solid surfaces
Authors:
Akihiko Ikeda
Abstract:
When a noble gas atom approaches a solid surface, it is adsorbed via the Van der Waals force, which is called physisorption. In this thesis, several experimental results concerning physisorbed atoms at surfaces are presented. First, photon stimulated desorption of Xe atoms from a Au substrate using nano-second laser is presented. With the time-of-flight measurements, the translational temperature…
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When a noble gas atom approaches a solid surface, it is adsorbed via the Van der Waals force, which is called physisorption. In this thesis, several experimental results concerning physisorbed atoms at surfaces are presented. First, photon stimulated desorption of Xe atoms from a Au substrate using nano-second laser is presented. With the time-of-flight measurements, the translational temperature and the desorption yield of desorbing Xe as a function of laser fluence are obtained. It is discovered that there are non-thermal and thermal desorption pathways. It is discussed that the former path involves a transient formation of the negative ion of Xe. The desorption flux dependence of the thermal pathway is also investigated. We found that at a large desorption fluxes the desorption flow is thermalized due to the post-desorption collisions. The resultant velocity and the temperature of the flow is found to be in good agreement with the theoretical predictions based on the Knudsen layer formation. Lastly, nuclear resonant scattering of synchrotron radiation by the multi- and mono-layer of $^{83}$Kr at a surface of the titanium oxide is presented. The use of the noble gas atoms as the probes of the electric field gradient at the solid surfaces is discussed.
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Submitted 20 April, 2015; v1 submitted 18 January, 2015;
originally announced January 2015.
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Knudsen layer formation in laser induced thermal desorption
Authors:
Akihiko Ikeda,
Masuaki Matsumoto,
Shohei Ogura,
Tatsuo Okano,
Katsuyuki Fukutani
Abstract:
Laser induced thermal desorption of Xe atoms into vacuum from a metal surface following the nano-second pulsed laser heating was investigated by the time-of-flight (TOF) measurement. The desorption flow was studied at a wide range of desorption flux by varying the initially prepared Xe coverage Θ (1 ML = 4.5*10^18 atoms/m^2). At Θ = 0.3 ML, the TOF of Xe was well represented by a Maxwell-Boltzmann…
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Laser induced thermal desorption of Xe atoms into vacuum from a metal surface following the nano-second pulsed laser heating was investigated by the time-of-flight (TOF) measurement. The desorption flow was studied at a wide range of desorption flux by varying the initially prepared Xe coverage Θ (1 ML = 4.5*10^18 atoms/m^2). At Θ = 0.3 ML, the TOF of Xe was well represented by a Maxwell-Boltzmann velocity distribution, which is in good agreement with thermal desorption followed by collision-free flow. At Θ > 0.3 ML, the peak positions of the TOF spectra were shifted towards the smaller values and became constant at large Θ, which were well fitted with a shifted Maxwell-Boltzmann velocity distribution with a temperature T_D and a stream velocity u. With T_D fixed at 165 K, u was found to increase from 80 to 125 m/ s with increasing Θ from 1.2 to 4 ML. At Θ > 4 ML, the value of u become constant at 125 m/ s. The converging feature of u was found to be consistent with analytical predictions and simulated results based on the Knudsen layer formation theory. We found that the Knudsen layer formation in laser desorption is completed at Knudsen number Kn <0.39.
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Submitted 8 March, 2013;
originally announced March 2013.
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Photostimulated desorption of Xe from Au(001) surfaces via transient Xe- formation
Authors:
Akihiko Ikeda,
Masuaki Matsumoto,
Shohei Ogura,
Katsuyuki Fukutani,
Tatsuo Okano
Abstract:
Photo-stimulated desorption (PSD) of Xe atoms from the Au(001) surface in thermal and nonthermal regimes was investigated by the time-of-flight measurement at photon energies of 6.4 and 2.3 eV. Xe was desorbed in a thermal way at high laser fluence, which was in good agreement with theoretical simulations. At a low laser fluence, on the other hand, desorption was induced only at a photon energy of…
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Photo-stimulated desorption (PSD) of Xe atoms from the Au(001) surface in thermal and nonthermal regimes was investigated by the time-of-flight measurement at photon energies of 6.4 and 2.3 eV. Xe was desorbed in a thermal way at high laser fluence, which was in good agreement with theoretical simulations. At a low laser fluence, on the other hand, desorption was induced only at a photon energy of 6.4 eV by a non-thermal one-photon process. We argue that the nonthermal PSD occurs via transient formation of Xe- on Au(001). The lifetime of Xe- is estimated to be ~15 fs with a classical model calculation. Whereas the electron affinity of Xe is negative in the isolated state, it is stabilized by the metal proximity effect.
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Submitted 23 June, 2012;
originally announced June 2012.