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Publications

Conferences

Effect of surface roughness of high current density nano-particle cathode for te...

2012 IEEE 13th International Vacuum Electronics Conference, IVEC 2012

Barik R.K., Tanwar A.K., Baek I.K., Eom K., Bera A., Sattorov M.A., Min S.H., Kwon O.J., Park G.S.

Abstract
High current density dispenser cathode is critical need for used in high power terahertz devices. Recently scandate cathode using nanoparticle offers very high current density more than 100 A/cm 2. Fabrication of this kind of cathode is challenging issue due to its nano dimension of the particle size. One of the critical parameter is surface roughness of the emission surface. We develop dispenser cathode using tungsten nano-particle of average particle diameter 50 nm, spherical morphology and uniform phase. In this paper we explain the effect of surface roughness on the emission current density of the dispenser cathode. © 2012 IEEE.
Experimental study on 0.1 THz clinotron

2012 IEEE 13th International Vacuum Electronics Conference, IVEC 2012

Sattorov M., Khutoryan E., Lukin K., Park G.-S., Bera A., Barik R., Kwon O., Min S.-H., Sharma A., Tanwar A.

Abstract
A multimode theory of resonant backward wave oscillator with inclined electron beam Clinotron is introduced. The mechanism of the efficiency enhancement due to mode interaction is unveiled through numerical simulation. The experimental setup for 0.1 THz Clinotron is being developed and the details of each part will be presented. © 2012 IEEE.
Irradiative damage characterization of a lysozyme during high-power THz ablation...

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

Eom K.H., Peltek S.E., Popik V.M., Jeong Y.U., Kwon O.S., Park W.Y., Lee W.S., So J.H., Park G.S.

Abstract
High-power pulsed THz waves which are generated by free electron laser near 2.2 THz are found to induce the nondestructive ablation of lysozyme. The peak electric field strength exposed on the sample is estimated over 10 kV/cm. The aerosol phase nanoparticles (ablated lysozyme) size is measured using real-time condensation particle counter, and the ablated lysozyme is analyzed using MALDI-TOF mass spectrometry to characterize irradiative damage during THz ablation process. The mass spectrum of ablated lysozyme shows no difference with control, but the sample remaining on the substrate shows thermal oxidation. These results confirm the nondestructive THz ablation of lysozyme; they suggest possible THz biological application such as mass spectrometry or electrospray using high-power pulsed THz waves. © 2012 IEEE.
Study of dispenser cathode development for terahertz vacuum devices application

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

Barik R.K., Tanwar A.K., Baek I.K., Eom K., Bera A., Sattorov M.A., Min S.H., Kwon O.J., Park G.-S.

Abstract
A Scandium oxide doped tungsten nano-powder for using in high current density thermionic cathode is believed to play a dominant role to improve emission capability. The nano-powder was prepared using sol-gel method by dissolving the blue tungsten and scandium nitrate into the solution. The result shows average particle diameter ∼50 nm, uniform grain size, spherical morphology, uniform phase and homogeneous mixing Sc2O3 doped W nano-powder. Dispenser cathodes will be prepared using this powder and expected excellent emission current density more than 100 A/cm2 which can be used for THz vacuum electron devices. © 2012 IEEE.
Non-bulk-like behavior of hydration water on fluid phase lipids revealed by tera...

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

Choi D.-H., Son H., Jung S., Park J., Park W.-Y., Kwon O.S., Park G.-S.

Abstract
Hydration state of lipid bilayer during the gel to fluid phase transition is measured with THz time domain spectroscopy (TDS). Hydration water showed bulk-water-like behavior at gel phase, but showed non-bulk-like behavior at fluid phase. © 2012 IEEE.
Automodulation processes in THz resonant backward wave oscillator with low focus...

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

Sattorov M.A., Khutoryan E., Lukin K., Park G.-S., Kwon O.

Abstract
The automodulation processes in THz resonant backward wave oscillator (BWO) operating at low focusing magnetic field have been studied. Automodulation behavior has been analyzed for different electron beam inclination angles. It has been shown that at low magnetic field the RF transverse electric field leads to steep change of beam-wave interaction power that causes automodulation. The theoretical results are compared with particle-in-cell simulations. © 2012 IEEE.
Determination of relaxation time of DNA hydration water by THz-TDS

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

Son H., Choi D.-H., Jung S., Park J., Park W.-Y., Kwon O.S., Park G.-S.

Abstract
Interaction of DNA and hydration water affects both structure and function of DNA. Here, we find out the relaxation time of DNA hydration water probed by THz-TDS under biological condition. Double Debye relaxation model is applied for figuring out relaxation time of hydration water. We observed 14.9ps for 50mM of DNA solution. This is much slower compared to bulk water, 8.15ps. The results indicate the existence of slow hydration water around DNA. © 2012 IEEE.
Bending transmission of human hair at terahertz frequency regime

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

Kim S., Kwon O., Baek I.-K., Eom K., Bera A., Min S.-H., Kwon O.S., Park W.-Y., Park G.-S.

Abstract
Frequency, geometry and dimensional dependences of the single-mode terahertz (THz) wave transmission along a dielectric bent fiber have been investigated. The human hair shaft, which resembles a dielectric rod and thus acts as a waveguide, is used for the transmission experiment. We here show the investigations based on a computational time-domain method in order to fully interpret the experimental results of hair-guided THz wave propagation. The frequency at which the difference between the wave vectors of the incident wave and the waveguide mode is comparable to the reciprocal of the length of the hair bundle gives low bending radiation loss under whole-body irradiation condition due to the maximized coupling coefficient. © 2012 IEEE.
Power estimation of electromagnetic coupling effectiveness by a X-band backward ...

14th IEEE International Vacuum Electronics Conference, IVEC 2013 - Proceedings

Min S.H., Kwon O., Sattorov M., Baek I.K., Kim S.T., Bera A., Barik R.K., Lee W.S., So J.H., Park G.S.

Abstract
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 relativistic backward wave oscillator (RBWO) of a HPM source with mode conversion. We used 500kA-5kA RBWO. The RF power is 0.5GW-30ns at 10GHz with mode conversion radiation from TM01 to TE11. © 2013 IEEE.
Sol-gel synthesis of Sc2O3 doped W nano-particle for cathode application

14th IEEE International Vacuum Electronics Conference, IVEC 2013 - Proceedings

Barik R.K., Bera A., Tanwar A.K., Baek I.K., Eom K., Sattorov M.A., Min S.H., Kwon O.J., Park G.-S.

Abstract
Sc2O3 doped W nano-powder is believed to play a dominant role for improving emission capabilities of the high current density thermionic cathodes. In this study a novel nano-particle synthesis approach was adopted in order to precisely control the particle parameters. The particle characteristics and sintering behavior has been analyzed using SEM, TEM, EDS, XRD and XPS. Uniform grain size with average particle diameter∼50 nm, spherical morphology, uniform phase and homogeneous mixing of Sc 2O3 doped W nano-powder was obtain which will enhance the emission current density, emission uniformity and life of the cathode. © 2013 IEEE.

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