Beam-ion losses induced by fast-ion-driven toroidal Alfven eigenmodes （TAE） were measured with a scintillator-based lost fast-ion probe （SLIP） in the large helical device （LHD）. The SLIP gave simultaneously the ...Beam-ion losses induced by fast-ion-driven toroidal Alfven eigenmodes （TAE） were measured with a scintillator-based lost fast-ion probe （SLIP） in the large helical device （LHD）. The SLIP gave simultaneously the energy E and the pitch angle X=arccos（v///v） distribution of the lost fast ions. The loss fluxes were investigated for three typical magnetic configurations of Rax-vac=3.60 m, 3.75 m. and 3.90 m, where Rax-vac is the magnetic axis position of the vacuum field. Dominant losses induced by TAEs in these three configurations were observed in the E/X regions of 50-190 keV/40°, 40-170 keV/25°, and 30-190 keV/30°, respectively. Lost-ion fluxes induced by TAEs depend clearly on the amplitude of TAE magnetic fluctuations, Rax-vac and the toroidal field strength Bt. The increment of the loss fluxes has the dependence of （bTAE/Bt）s. The power s increases from s = 1 to 3 with the increase of the magnetic axis position in finite beta plasmas.展开更多
Magnetic properties and magnetic structure of the Ba_(2)Mn(PO_(4))_(2) antiferromagnet featuring frustrated zigzag chains of S?52 Mn^(2+)ions are reported based on neutron diffraction,density-functional bandstructure ...Magnetic properties and magnetic structure of the Ba_(2)Mn(PO_(4))_(2) antiferromagnet featuring frustrated zigzag chains of S?52 Mn^(2+)ions are reported based on neutron diffraction,density-functional bandstructure calculations,as well as temperature-and field-dependent measurements of magnetization and specific heat.A magnetic transition at TN■5 K marks the onset of the antiferromagnetic order with the propagation vector k=(1/2 0 1/2)and the ordered moment of 4.33±0.08μB/Mn^(2+)at 1.5 K,pointing along the c direction.The direction of the magnetic moment is chosen by single-ion anisotropy,which is relatively weak compared to the isostructural Ni^(2+)compound.Geometrical frustration has a strong impact on the thermodynamic properties of Ba_(2)Mn(PO_(4))_(2),but manifestations of the frustration are different from those in Ba_(2)Ni(PO_(4))_(2),where frustration by isotropic exchange couplings is minor,yet strong and competing single-ion anisotropies are present.A spin-flop transition is observed around 2.5 T.The evaluation of the magnetic structure from the ground state via the spin-flop state to the field-polarized ferromagnetic state has been revealed by a comprehensive neutron diffraction study as a function of magnetic field below TN.Finally,a magnetic phase diagram in the H-T plane is obtained.展开更多
基金supported in part by the Grant-in-Aid for Scientific Research from MEXT (No. 16082209)from JSPS (Nos. 21360457, 21340175,and 22-7912)+1 种基金the LHD project budget (NIFS09ULHH508)partially supported by the JSPS-CAS Core-University program in thefield of‘Plasma and Nuclear Fusion’
文摘Beam-ion losses induced by fast-ion-driven toroidal Alfven eigenmodes （TAE） were measured with a scintillator-based lost fast-ion probe （SLIP） in the large helical device （LHD）. The SLIP gave simultaneously the energy E and the pitch angle X=arccos（v///v） distribution of the lost fast ions. The loss fluxes were investigated for three typical magnetic configurations of Rax-vac=3.60 m, 3.75 m. and 3.90 m, where Rax-vac is the magnetic axis position of the vacuum field. Dominant losses induced by TAEs in these three configurations were observed in the E/X regions of 50-190 keV/40°, 40-170 keV/25°, and 30-190 keV/30°, respectively. Lost-ion fluxes induced by TAEs depend clearly on the amplitude of TAE magnetic fluctuations, Rax-vac and the toroidal field strength Bt. The increment of the loss fluxes has the dependence of （bTAE/Bt）s. The power s increases from s = 1 to 3 with the increase of the magnetic axis position in finite beta plasmas.
文摘Magnetic properties and magnetic structure of the Ba_(2)Mn(PO_(4))_(2) antiferromagnet featuring frustrated zigzag chains of S?52 Mn^(2+)ions are reported based on neutron diffraction,density-functional bandstructure calculations,as well as temperature-and field-dependent measurements of magnetization and specific heat.A magnetic transition at TN■5 K marks the onset of the antiferromagnetic order with the propagation vector k=(1/2 0 1/2)and the ordered moment of 4.33±0.08μB/Mn^(2+)at 1.5 K,pointing along the c direction.The direction of the magnetic moment is chosen by single-ion anisotropy,which is relatively weak compared to the isostructural Ni^(2+)compound.Geometrical frustration has a strong impact on the thermodynamic properties of Ba_(2)Mn(PO_(4))_(2),but manifestations of the frustration are different from those in Ba_(2)Ni(PO_(4))_(2),where frustration by isotropic exchange couplings is minor,yet strong and competing single-ion anisotropies are present.A spin-flop transition is observed around 2.5 T.The evaluation of the magnetic structure from the ground state via the spin-flop state to the field-polarized ferromagnetic state has been revealed by a comprehensive neutron diffraction study as a function of magnetic field below TN.Finally,a magnetic phase diagram in the H-T plane is obtained.
