박경석 교수

The RAON is the name of the heavy ion accelerator facility under construction in Korea that includes the In-flight Fragment (IF) and Isotope Separation On-Line (ISOL) facilities to support cutting-edge research in various science fields. The superconducting linac is the driver for the IF facility that can accelerate beams from proton to uranium with 200 MeV/u, 400 kW (for uranium beam). A 70-MeV, 1-mA H− cyclotron is the driver for the ISOL facility and is followed by a post-accelerator consisti

The physical characteristics of an annular Pierce-type electron gun are investigated analytically. The electron gun is used in conjunction with a nonadiabatic magnetic reversal and adiabatic compression region to produce an axis-encircling beam. Typical magnetic field profiles that can generate zero velocity spreads are obtained from the analytical calculation, taking into account initial canonical angular momentum spreads at the cathode and the crossing of the beam trajectory and magnetic flux

Gigawatt-level circularly polarized radiation was transmitted using a coaxial beam rotating antenna in an X-band relativistic backward wave oscillator. The mode conversion from the TM01 mode to the circularly polarized TE11-like mode was experimentally and numerically shown. The simulated radiation pattern was in good agreement with the measured radiation pattern.

Noise reduction in a 2.45GHz strapped magnetron oscillator is experimentally demonstrated by electric priming using anode shape modification. The sideband noise is reduced by approximately 15dB at the nominal operating current and by 28dB at the start-oscillation current; this is due to electron prebunching into the π mode, resulting from the modulation of the drift velocity of the electrons by an azimuthally periodic electric field. In this experiment, a 4.3kV–330mA half-wave rectified input po

We have experimentally demonstrated a low-velocity spread, axis-encircling electron beam using a comparatively simple Pierce-type electron gun and single cusp magnetic field based on a recent theory [Jeon et al., Appl. Phys. Lett. 80, 3703 (2002)] developed with the assumption of small orbit gyration before the magnetic cusp, in which every physical property has been analyzed and the possibility of zero percent axial velocity spread was concluded. The velocity ratio and the axial velocity spread

This abstract describes the design, fabrication and testing of microfabricated 100 GHz coupled-cavity backward wave oscillator (CCBWO), which is operated in space harmonics -1 at 12 kV and 50 mA with round-beam radius 0.18 mm. The RF performance has studied using 3-D electromagnetic field simulator and particle-in-cell code. The cold-test assembly has been fabricated. The complete device assembly for hot-test is under fabrication. Experimental results will be presented.

A nonlinear theory is developed to predict the gain of a distributed vacuum amplifier employed with field-emitter arrays. Contrary to conventional expectation, it is shown that density modulation of the electrons in the emitting structure is limited by high resistive losses and electronic damping. Therefore, a modified schematic is suggested with the high-frequency modulator separated from the emitter that only dc bias voltage is applied to. Small-signal calculation shows that 15–25dB gain (with

an analysis of a two-section folded waveguide TWT for terahertz radiation is performed. The theory of high frequency characteristics including the dispersion properties and the beam-wave interaction impedance of this structure are analyzed for nonlinear interaction analysis. A THz-band folded waveguide TWT using 10.8kV, 50mA electron beam is designed and the nonlinear beam-wave interaction in the TWT is investigated by the use of MAGIC3D. The maximum radiation power of 34.7W corresponding to the

Desktop companion robots have attracted increasing attention, yet their application to support office workers requires further exploration. In envisioning the role of desktop companion robots as a helpful “peer” for office workers, we conducted a lab experiment (N=36) to examine how desktop companion robots’ behavior influenced office workers’ productivity, work experience, and robot perception. Participants performed a digitization task alongside robots under three conditions: (a) static robot,

To design high power oversized Relativistic Backward Wave Oscillator (RBWO) which can generate GW-level Power in THz frequency, numerical studies such as finite difference time domain (FDTD) and particle in cell (PIC) were performed. 0.1GW at 0.1THz was estimated. The Oversized BWO which means relatively wide cross-section space (oversized) to decrease power density comparing with fundamental BWO is made up of slow wave structure (SWS) of rectangular type wall radius designed to generate wave on

Enhancement of backward-wave interaction by additional feedback was experimentally demonstrated adopting an external energy recovery scheme. The experimental observation was confirmed by particle-in-cell simulation. Measured efficiency improved in accordance with the strength of external feedback at the optimal phase, which is attributed universally to the increase of the normalized current defined by the ratio of the beam current to the start-oscillation current, regardless of each assigned fee

The electron beam interaction with the radio-frequency field (RF) close to the surface of the slow-wave structure of W-band Clinotron is studied by numerical simulations with regard to the real RF field distribution, for the inclined electron beam to the periodical slow-wave structure under small angle α. It is demonstrated that the electron interaction with the transversal electrical field induces the selective settling of the electrons on the grating lamellas, and the power is then taken away

Effective electromagnetic coupling with electronic equipment at radiation is used by a high power microwave (HPM) weapons source which means a relativistic backward wave oscillator in here. In the process of researching, developing and using HPM source, we have been studying a real “effective coupling” source which is able to attack the overall target, suitable in all situation ns. The experimental results show the broken electronic equipment or circuit damages after the radiation by an X-band r