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With the development of high power magnetron, cathode is researched a lot to endure higher temperature and intense electron bombardment. In order to decrease the central part temperature of cathode in magnetron and extend magnetron's lifetime, a kind of variable pitch helical cathode is proposed in this paper. Computer simulations are adopted to verify whether cathode surface electric field distribution...
Magnetic field and temperature dependence of spin wave excitation and manipulation in RFeO3 (R=Nd) are studied with THz time-domain spectroscopy. Our studies reveal that the spin reorientation transition triggered by external magnetic field is strongly anisotropic: magnetic fields along a-axis is much easier to switch the spin alignment than that along c-axis in NdFeO3 crystal.
We have reported on terahertz magnonics, which is a signal transmission with high-energy spin waves (electromagnons) excited by THz wave. As source and medium for electromagnons, we choose Sm3Fe5O12 ultrathin films whose magnetic properties are modified by applying an epitaxial strain. Electromagnons are successfully detected in the strained Sm3Fe5O12 ultrathin film, using a transmittance THz time-domain...
THz ESR measurement has been a powerful means to study magnetic systems due to the advantages of high spectral resolution, ESR measurement beyond the zero field splitting or the magnetic phase transition. Using these advantages we have studied perfect kagome lattice antiferromagnet Cr-jarosite, which has attracted much attention in the field of magnetism recently, by our THz ESR.
In this paper, the simulation and design of a diode type magnetron injection gun (MIG) for a W-band CW gyrotron oscillator is presented. The simulation of the MIG, operating at the voltage of 55kV and the current of 4A, is finished with the help of a trajectory program EGUN. The simulation results indicate that the velocity ratio with velocity spread of less than 2.5% is 1.43.
Intense terahertz magnetic fields are used to control the magnetization state of ferromagnetic cobalt thin film. The dynamics visualized by magneto optic Kerr effect is non-resonant and take place over sub-picosecond time scale. The observed magnetic response is coherently locked to the THz carrier oscillations.
We analyze a novel, phase-sensitive contribution to the oscillating magnetoresistance induced by the combined driving of two radiation fields having commensurate frequencies ω1 and ω2. This commensurate oscillating photoresistance not only depends on the frequencies and polarizations of both electromagnetic waves, but varies drastically when changing the relative phase of two incident radiation fields...
An innovative compact normal room temperature magnet has been developed for use with millimeter-wave gyrotrons. An example of an electropermagnet has been made and tested to 2.0 T, has a 30 mm ID bore and a 25 mm flat field cavity region, suitable for efficient fundamental and 2nd harmonic mode high power pulse and CW gyrotrons to at least 110 GHz, and is only ∼22 kg. Gyrotron design with this magnet...
Terahertz metamaterial technique enables a sophisticated electromagnetic excitation of materials. Here, we demonstrate resonant excitation of spin precession motion of canted antiferromagnet ErFeO3 using the magnetic near-field produced by split ring resonator (SRR). When the resonance frequency of spin precession was near the magnetic resonance mode of SRR, we observed substantial increase of precession...
Classic analog of the electromagnetically induced transparency (EIT) in metamaterials has been demonstrated extensively by its attractive potential applications in light storage, slow light and sensing. However, the counterpart of EIT, electromagnetically induced absorption (EIA) has been studied rarely in coupled metamaterial systems. Here, we present the observation of the EIA effect in a vertically...
A short pulse gyrotron was designed, fabricated and tested for 300 GHz oscillation. The oscillation mode is TE32, 18 and its neighborhoods and the power is output from the top of the gyrotron. The superconducting magnet has 110 mm room temperature bore diameter, and the maximum magnetic field is 13 T. In the preliminary experiment, the 300 kW power was obtained at ∼300 GHz.
A terahertz magneto-spectrometer has been developed that utilizes the spectral up-conversion technique to measure broad-bandwidth terahertz radiation pulses in a single shot. Synchronizing the laser pulses to a pulsed mini-coil 30 T magnet is enabling cyclotron resonance measurements in a range of semiconductor structures.
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