Traveling wave tube

A Ku-band 140 W space TWT of gain (>54 dB), electronic efficiency (>23%), collector efficiency (>74%), overall efficiency (>54%), I/M components (<-10dBc) for frequency 10.7-11.9 GHz has been created and fabricated for satellite communication arrangement. This paper proposes critical design issues and techniques associated with different assemblies like electron gun, PPM focusing, helix SWS, input & output couplers, and 3-stage depressed collector in order to meet the exacting prerequisite of space TWTs.

Kepler uzay aracı sayesinde 2600 adetten fazla öte gezegen onaylanmıştır. Onaylanan öte gezegenler ana yıldızlarına göre sınıflandırılmaktadır. Bu çalışmada ana yıldız özelliklerine göre sınıflandırılan öte gezegenlerin sınıflarına göre hangi özelliklerinin değiştiği ve hangi sınıflar için bu özelliklerin farklılık gösterdiğinin tespit edilmesi amaçlanmıştır. Ayrıca ana yıldız özelliklerine göre sınıflandırma yerine alternatif bir yöntemin kullanılması için ayrıcı faktörlerin bulunması da çalışmanın diğer bir amacıdır. Araştırmada NASA’nın oluşturmuş ve daha sonra bilim insanları tarafından düzenlemiş olan “The NASA Exoplanet Archive: Data and Tools for Exoplanet Research” adlı veri seti kullanılmıştır. Çalışmanda F, G, K, M sınıflarında bulunan 2275 öte gezegen ve bu öte gezegenlere ait yıldız sınıfı, yörünge dönemi, geçiş dönemi, etki parametresi, transit süresi (saat), transit derinlik (milyonda çap), gezegen yarıçapı (gezegen yarıçapı/dünya yarıçapı), denge sıcaklığı (kelvin), g...

As we begin to discover rocky planets in the habitable zone of nearby stars with missions like TESS and CHEOPS, we will need quick advancements on instrumentation and observational techniques that will enable us to answer key science questions, such as What are the atmospheric characteristics of habitable zone rocky planets? How common are Earth-like biosignatures in rocky planets?} How similar or dissimilar are those planets to Earth? Over the next decade we expect to have discovered several Earth-analog candidates, but we will not have the tools to study the atmospheres of all of them in detail. Ground-based ELTs can identify biosignatures in the spectra of these candidate exo-Earths and understand how the planets&#39; atmospheres compare to the Earth at different epochs. Transit spectroscopy, high-resolution spectroscopy, and reflected-light direct imaging on ELTs can identify multiple biosignatures for habitable zone, rocky planets around M stars at optical to near-infrared wave...

Next-generation wireless systems use the non-orthogonal modulation technique known as generalized frequency division multiplexing (GFDM). The nonlinearity of the high-power amplifier (HPA) greatly affects the performance of the wireless system. Without phase distortion and only amplitude distortion in the GFDM system using HPA Model Rapp. The effects of nonlinear distortion that occur involve distortion of the amplitude, signal constellation distribution, and spectral distribution. There are two contributions to this paper. First, the impact of HPA Model Rapp&#39;s nonlinear distortion on the GFDM system in the AWGN (additive white Gaussian noise) and Rayleigh channels was investigated. The simplicity of this model is the reason it was picked and has an AM/AM (amplitude modulation/amplitude modulation) curve. Second, the linearization of HPA with the use of a predistorter method in GFDM systems has been proposed. The nonlinear distortion impact of HPA can be mitigated by this predis...

A kinetic-theory based method of analysing the small-signal amplification of an axi-symmetric transverse magnetic(TM) mode of a circular cylindrical waveguide linearly interacting with an annular beam of gyrating electrons in a gyro travelling wave tube (TWT) configuration is presented. A gyro-TWT is designed at 94 GHz in the axi- symmetric second harmonic TM03 mode. The broad maximum of the growth-rate curve is slightly detuned from the design frequency which is capable of operating over a wide band of frequencies around the design frequency.

The guided ultrasonic waves have become interesting alternatives to classical pulse-echo nondestructive testing in industrial piping systems. These guided waves have the capability to travel for several meters along pipes, bringing back to the emitting transducer information about possible defects. For this reason, researches were conducted in many laboratories of the world for the last decades. In our country such preoccupation is relatively recent. Benefiting from a national research project, our team has also developed original software to solve the dispersion curves of tubes. These dispersion curves provide the travel velocity of the guided waves, which are functions of frequency. In most cases, for a given frequency, there are many propagating waves with specific stress-displacements patterns, which are called guides modes. Using these velocities, the experimentalist can adjust the receiver to detect the selected mode, which can be used to detect defects. The present paper presents the capabilities of the specialized software pack "Tubewave", developed by our team, for homogeneous, isotropic tubes, immersed in air or other light fluids.

A traveling-wave tube (TWT) with a sheet electron beam and staggered double-grating slow-wave structure (SWS) is a promising high-power, wideband terahertz amplifier. In such tubes, electron-optical systems (EOSs) with a converging sheet beam are mostly used, which allow a reduction of the cathode load, increase the lifetime, and enable operation in a continuous-wave (CW) mode. This paper presents the results of a 3D particle-in-cell (PIC) simulation of the 0.22 THz TWT driven with a converged sheet beam, which is compressed to less than 100 μm thickness in the EOS with a magnetically shielded cathode. The beam with high compression has a significant transversal velocity spread and essentially non-uniform current density distribution over the cross-section. These factors significantly affect the beam–wave interaction. We compare the performance of the TWT driven by the compressed sheet beam and by an idealized initially rectilinear beam without any velocity spread.