In order to study the heating process of water by the microwaves of 2.5-20 GHz frequencies, the authors have performed molecular dynamics simulations by adopting a nonpolarizable water model that has fixed point charges on a rigid-body geometry. All runs are started from the equilibrated states derived from the I(c) ice with given density and temperature. In the presence of microwaves, the molecules of liquid water exhibit rotational motion whose average phase is delayed from the microwave electric field. Microwave energy is transferred to the kinetic and intermolecular energies of water, where one-third of the absorbed microwave energy is stored as the latter energy. The water in ice phase is scarcely heated by microwaves because of the tight hydrogen-bonded network of water molecules. Dilute salt water is significantly more heated than pure water because of the field-induced motion of salt ions, especially that of large-size ions, by the microwave electric field and energy transfer to water molecules by collisions.

A negative-ion-based neutral beam injection (NBI) system has been operated reliably in the Large Helical Device (LHD) since it was operational in 1998. The injection power achieved is 13.1 MW with three injectors. In one injector with modified ion sources with the multi-slotted grounded grid, the injection power reached 5.7 MW with an energy of 184 keV, both of which exceed the designed values of 180 keV-5 MW. The individual control of the arc-discharge with the divided arc and filament power supplies is effective to improve the beam uniformity. The injection duration is extended to 120 sec with a reduced power of 0.2-0.3 MW using one ion source with the cooled plasma grid. The performance of the negative-NBI in LHD is reviewed with regard to the progress of the negative ion sources.

Recent results of energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System (CHS) and Large Helical Device (LHD) are presented. Alfvén eigenmodes (AEs) and fishbone-like burst modes (FBs) destabilized by energetic ions were observed in NBI heated plasmas of CHS. The AEs are toroidicity induced Alfvén eigenmodes (TAEs) and global Alfvén eigenmodes (GAEs), where the identified toroidal mode numbers are n = 1 and 2 for TAEs and n = 0 for GAEs. The frequencies of the FBs are less than, at most, half of the minimum TAE gap frequency and do not exhibit the obvious density dependence related to Alfvén velocity. The modes have characteristic features of the energetic particle modes or the resonant TAEs excited by circulating energetic beam ions produced by NBI. Bursting amplitude modulation is observed in TAEs as well as in FBs. Rapid frequency chirping is observed in each burst, by a factor of 2-6 in FBs and about 25% in TAEs. In several shots, the power spectrum of the TAEs is split into multiple peaks having the same toroidal mode number through non-linear evolution of TAEs. A pulsed increase in energetic ion loss towards the wall is induced by m = 3/n = 2 FBs, but so far not by m = 2/n = 1 FBs, TAEs and GAEs, where m is the poloidal mode number. This research has been extended to LHD plasmas heated by neutral hydrogen beams with about 130 keV energy. Similar to CHS, TAEs and FBs were observed in relatively low density plasmas at low toroidal magnetic field (Bt = 1.5 T).

It is known that bulk metallic samples reflect microwaves while powdered samples can absorb such radiation and be heated efficiently. In the present work we studied heating mechanisms of metallic powders in a multimode 2.45 GHz microwave applicator. The present paper shows direct evidence of penetration of a layer of metallic powder by microwave radiation and provides theoretical explanation of such behavior.The most effectively heated powder is Fe because both eddy current loss (in alternating H-field) and magnetic reversal loss (in alternating E-field) mechanisms act in case of such metal. Diamagnetic metals Sn and Cu are heated better than paramagnetic Ti while Au is also only slightly heated. Cu- and Ni-based metallic glassy powders are also moderately heated. Weak heating of Au powder (which is a noble metal) can be explained by the absence on the particles of the oxide layer (shell), which allows eddy currents flowing through larger area compared to other metals, and reflection mechanism works much better in such case.