Cláudio C. Motta

Universidade de São Paulo

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Daniel T. Lopes

Hospital Universitário da Universidade de São Paulo

E.A. Périgo

ABB (Switzerland)

Ricardo Elgul Samad

National Nuclear Energy Commission

Rubens Nunes de Faria

National Nuclear Energy Commission

César Coelho Xavier

Universidade Federal do Espírito Santo

Hidetoshi Takiishi

National Nuclear Energy Commission

Elbis Santos Cardoso

Institute of Rural Management Anand

Robson K. B. e Silva

National Nuclear Energy Commission

Davi Pontes Nacaratti

Universidade de São Paulo

F.F. Sene

Instituto de Aeronáutica e Espaço

Cooperative Institutions

Universidade de São Paulo

Instituto de Pesquisas Energéticas e Nucleares

National Nuclear Energy Commission

Nuclear Engineering Institute

Instituto Tecnológico de Aeronáutica

Universidade do Vale do Paraíba

Universidade Brasil

University of Milano-Bicocca

Hospital Universitário da Universidade de São Paulo

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Theoretical Analysis of the Transmission Efficiency of a (6 + 1) × 1 Pump–Signal Combiner

Lucas Salustiano Mendes Ricardo Elgul Samad Cláudio C. Motta

An analytical formulation for the transmission efficiency of a(6+1)× 1 pump-signal combiner has been developed and is reported in this paper. The formulation is supported by the Coupled Mode Theory (CMT), and the Finite Difference Beam Propagation Method (FD-BPM). In this scope, the characteristics of commercial fibers FG200AEA, GDF20/200, P-20/400DC are considered to build a combiner computational model. Thus, the CMT was used to estimate the adiabatic length of the input bundle fibers and the combiner efficiency was analyzed based on FD-BPM.

Beam propagation method

SIGNAL (programming language)

Mode (computer interface)

10.1109/sbfotoniopc54450.2022.9992582

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Characterization of a surface wave argon discharge sustained by microwave

Cláudio C. Motta A.D. Fonseca G.H. Gomes Homero Santiago Maciel

Summary form only given. An experimental set-up for production of surface wave discharge in argon has been developed and is reported in this paper. A 600 W -2.45 GHz quasi-cw magnetron was used as microwave source which was coupled to the microwave circuit through an electric probe. A microwave resonator was built to operate as the electromagnetic launcher. The resonator, instead of the conventional coaxial type, consists basically of a WR-340 rectangular waveguide having at one end a precision microwave sliding short-circuit. A circular iris was used to couple the microwave source to the resonator. A glass discharge tube of 2.2 cm O.D., 1.8 mm thick and 1.5 m in length was placed in the resonator and by adjusting the sliding short-circuit position and the screw tuner it was possible to match the electromagnetic pattern in the resonator with the argon discharge tube. The microwave resonator was built to operate in a TE/sub 101/ mode in order to be able to excite a TM/sub 01/ mode in the plasma column. The discharge was operated in the 1-10/spl times/10/sup -2/ Torr pressure range in order to obtain a pressure versus column length characteristic curve.

Gas-filled tube

Coaxial

Cavity magnetron

Dielectric resonator antenna

Torr

10.1109/plasma.2000.854837

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Impregnated dispenser cathode auger spectroscopy

Cláudio C. Motta

In this paper an experimental apparatus for impregnated dispenser cathode Auger spectroscopy is described. The apparatus consists of three ultra-high vacuum chambers, all connected by 6 inches gate valves. In the first vacuum chamber the cathode under test was assembled and there are some vacuum windows with electric feedthrough to bias to the cathode heater and anode. The temperature cathode surface can be measured through a quartz window using a disappearing filament pyrometer. There is a translator to move the cathode from the first chamber to the second chamber where there are an Auger electron analyzer, an electron gun and an ion gun. The final chamber is a high vacuum reservoir responsible to maintain the vacuum pressure as low as 10 ^-10 torr.

Feedthrough

Auger electron spectroscopy

Torr

Vacuum chamber

Cold cathode

Electron gun

Hot cathode

Pyrometer

10.1109/ivec.2016.7561925

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Construction and characterization of an Ar-Fe hollow cathode tube with modeling of the argon plasma discharge

Cláudio C. Motta A. Mirage

Summary form only given. An argon-iron hollow cathode tube (HCT) was developed to be used in laser atomic spectroscopy experiments. This HCT has been employed in laser absorption and optogalvanic signal measurements. The light absorption and optogalvanic signal detection were accomplished using a tunable dye laser resonant with Ar 3p/sup 5/4p(/sup 3/S/sub 1/)→3p/sup 5/4d(3D/sub 1//sup 0/) transition, corresponding to wave length 591.2 nm. The cathode of HCT consists of an iron cylinder with 24 mm length and 8.0 mm radius with a 2.8 mm diameter hole. The cathode body was supported by two circular alumina disks and centrally attached by them. In one of the disks a number of holes were drilled in order to allow the insertion of the cathode feed wires. A thermalcouple was placed in contact with the cathode surface to measure the cathode temperature. The tube was made of glass type Schott 8250 with dimensions of 40 mm in diameter and 18 cm in length. The optical windows were made of fused-quartz and arranged in Brewster angle. The tube was sealed with 5 Torr argon pressure. A modeling of argon discharge based on a two-fluid theory of electron and argon ion transport was also developed in order to describe the electron-ion number densities, particle fluxes and electric potential profiles.

Torr

Gas-filled tube

Hollow-cathode lamp

10.1109/plasma.2000.854820

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Pressure field along the axis of a high-power klystron amplifier

Francisco Tadeu Degasperi S.L.L. Verardi Cláudio C. Motta

The pressure field in a high-power klystron amplifier is investigated to scale the ionic vacuum pump used to maintain the ultra high-vacuum in the device in order to increase its life-time. The investigation is conducted using an 1.3 GHz, 100 A - 240 keV high-power klystron with five reentrant coaxial cavities, assembled in a cylindrical drift tube 1.2 m long. The diffusion equation is solved to the regime molecular flow to obtain the pressure profile along the axis of the klystron drift tube. The model, solved by both analytical and numerical procedures, is able to determine the pressure values in steady-state case. This work considers the specific conductance and all important gas sources, as in the degassing of the drift tube and cavities walls, cathode, and collector. For the drift tube degassing rate equals to q/sub deg/= 2/spl times/10/sup -12//spl I.bar/mbar.L.s/sup -1/ cm/sup -2/ (degassing rate per unit area), to cavities q/sub cavity/=3/spl times/10/sup -13//spl I.bar/mbar.L.s/sup -1/cm/sup -2/, to the cathode q/sub cathode/= 6/spl times/10/sup -9//spl I.bar/mbar.L.s/sup -1/ and to the collector q/sub collector/=6/spl times/10/sup -9//spl I.bar/mbar.L.s/sup -1/, it was found that a 10 L.s/sup -1/ ionic vacuum pump connected in the output waveguide wall is suitable. In this case, the pressure obtained in the cathode is p/sub cathode/=6.3/spl times/10/sup -9/ mbar, in the collector p/sub collector/=2.7/spl times/10/sup -9/ mbar, and in the output waveguide p = 2.1/spl times/10/sup -9/ mbar. Although only the steady-state case is analyzed, some aspects that may be relevant in a transient situation, for instance, when the beam hits the drift tube walls, producing a gas burst, is also commented.

Klystron

Bar (unit)

10.1109/ppc.2003.1278017

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Citations (3)

Modelo auto-consistente para a cinética da descarga do laser a vapor de cobre

Cláudio C. Motta

ambipolar, e à Deus, pois apesar das inúmeras

Ambipolar diffusion

10.11606/t.43.1996.tde-24022014-104827

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A 3D-analysis of a slow-wave-structure using tangential vector finite elements

Cláudio C. Motta P.R. Pascholati

This paper presents the results from a numerical code based on a full-wave finite element analysis developed to solve the helix problem used as a slow-wave-structure in a typical TWT to operate in X-band. The three dimensional code has been used to produce accurate cold-test features including frequency dispersion, helix impedance and slab dielectric helix support effects.

Helix (gastropod)

Slab

Code (set theory)

10.1109/ivelec.2004.1316238

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Conductivity of organic molecules with graphene and metal leads

Cláudio C. Motta M. I. Trioni Guido Fratesi Gian Paolo Brivio

Organic molecules

Source

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Modeling of Fiber Bragg Gratings with Different Lengths for the Reflectivity Control for Fiber Lasers

Davi Pontes Nacaratti Ricardo Elgul Samad Cláudio C. Motta

An analytical formulation and modeling of an optical fiber Bragg gratings has been developed and is reported in this paper. Supported by the coupled-mode theory and considering that the mode fields of the unperturbed waveguide remain unchanged in the presence of weak perturbations, it is possible to obtain first-order differential equations that have solutions for some types of periodic perturbations. Finally, the model is applied to analyze the influence of structural parameters of fiber gratings, such as length, period and refractive index modulation on its reflectivity and bandwidth.

Fiber Bragg Grating

PHOSFOS

Long-period fiber grating

Coupled mode theory

Modulation (music)

10.1109/sbfotoniopc50774.2021.9461968

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A microwave window for high power TWTs

2021 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC) (2011)

Daniel T. Lopes Cláudio C. Motta

This paper describes the development of a microwave window for high power pulsed traveling-wave tubes for radar application. Given the operational frequency band, the window dielectric materials (beryllia or alumina), and the standard waveguide (WR-90), a tridimensional frequency domain solver was used to design the window geometry. We present here the effect of the window parameters and the experimental result of a preliminary built window. The agreement between simulated and experimental results was about 97% at the beginning of the band and 92% at the end.

Solver

Extremely high frequency

Frequency band

Window function

10.1109/imoc.2011.6169346

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