R. K. Barik

Surface-coupling of Cerenkov radiation from a modified metallic metamaterial slab via Brillouin-band folding.

Metallic metamaterials with positive dielectric responses are promising as an alternative to dielectrics for the generation of Cerenkov radiation [J.-K. So et al., Appl. Phys. Lett. 97(15), 151107 (2010)]. We propose here by theoretical analysis a mechanism to couple out Cerenkov radiation from the slab surfaces in the transverse direction. The proposed method based on Brillouin-zone folding is to periodically modify the thickness of the metamaterial slab in the axial direction. Moreover, the intensity of the surface-coupled radiation by this mechanism shows an order-of-magnitude enhancement compared to that of ordinary Smith-Purcell radiation.

Experimental study on 0.1 THz Clinotron

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.

Study and Development of Alloy-film Dispenser Cathodes

In this paper, the developmental work on alloy-coated cathode and thermionic emission microscope (THEM) is presented. The cathode is incorporated with potted heater assembly. A contra-wound helix filament is used to minimize inductance. The heater is potted using non-shrinkable alumina powder at elevated temperature. To minimize thermal and mechanical stresses at the heater lead, a spring (micro-helix) is incorporated which slide fits into the lead wire that is partially buried into the potting region. The above alloy of 20s:2Re:1W is chosen on the basis of work carried out at Cambridge, using auger electron spectroscopy (AES) in conjunction with THEM.

Design and development of Thermionic Emission Microscope

Thermionic Emission Microscope (THEM) developed at CEERI has an electrostatic immersion lens to magnify the image. The geometry of lens and potentials are optimized to achieve a magnification of about 15 times with a clear image. The design of deflection plates and lens are carried out using OmniTRAK 3-D to ensure required deflection of beam without losing laminarity and beam interception with plates. Faraday cage, containing a narrow aperture, is designed to obtain elemental currents with low secondary emission. The emission picture of a B-Type cathode has been obtained. The results are satisfactory.

Power estimation of electromagnetic coupling effectiveness by a X-band backward wave oscillator with mode conversion

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.

Micro-fabricated millimeter wave vacuum electronic devices

0.1 THz Coupled Cavity Backward-wave Oscillator (CCBWO) is being developed utilizing two-step X-ray lithography. The characteristics of this 0.1 THz CCBWO are investigated through cold and hot tests.

Nanoparticle-based thermionic cathode for THz device application

A high-current-density, long life and uniform emission cathode is a key requirement for a THz-VED. Using a new synthesis approach Sc2O3 doped W-nanoparticles were made to fabricate cathode, which is believed to play a dominant role for above application. The fabrication details along with the emission results will be presented.

Efficient terahertz oscillation using a half-period staggered grating resonator

A highly efficient terahertz (THz) radiation mechanism is studied with the use of strong interaction between convection electrons and a half-period phase-shifted grating resonator. The large fraction of the fundamental TE mode is longitudinally polarized, and it excites the intense plasma–terahertz wave coupling at the shallow grating, which enables highly efficient RF generation at a relatively low operating voltage. A particle-in-cell (PIC) simulation predicts that the half-period phase-staggered grating resonator generates 0.22 THz wave with output power exceeding 100 W and interaction efficiency of more than 15% at a low beam acceleration voltage of 5.2 kV.

Cherenkov-like radiation from metallic metamaterials

The radiation of slit modes excited by convection electron inside a perfect metal film perforated with one dimensional array of cut-through slit is studied. The radiations of non radiating slit modes are achieved by grating coupler which provides the required momentum shift to them. Numerical simulation shows that the radiation intensity of these momentum shifted slit modes are more than that of Smith-Purcell radiation by more than one order magnitude.

Sol-gel synthesis of Sc 2 O 3 doped W nano-particle for cathode application

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 Sc2O3 doped W nano-powder was obtain which will enhance the emission current density, emission uniformity and life of the cathode.