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High voltage terminals are enclosed with RTV560 silicone rubber. Space travelling wave tubes are exposed in irradiation environment. As one organic elastomer, silicone rubber is degraded by the radiation. In the paper, effect of electron irradiation on properties of RTV560 silicone rubber was investigation. The used electrons have an energy range 10~100 keV, and the irradiation fluence ranges from 1.0×106 rad to 1.0×107 rad. At last, roughness, hardness, DTA and TGA were measured and analyzed for all samples.

Vibration and Shock from the rocket launch bring high demands for the design of radiation cooled space travelling wave tube. In the paper, dynamic analysis of Ku band radiation cooled space travelling wave tube was carried on by means of finite element analysis method according to environmental conditions. And an optimized prototype was made and tested.

In the paper, Influence of interface status (ratio of brazing area and fit clearance) of brazed collector parts on contact heat resistance was theoretically analysised. And by ANSYS simulation, influence of ratio of brazing area and fit clearance on heat dissipation capability of collector for travelling wave tube was studied.

Amplification studies of a Ka-band harmonic-multiplying gyrotron traveling-wave tube (gyro-TWT) are reported. A coupled cavity with inner- and outer-intersecting couplings and precise control of the focusing magnetic field are used to improve the coupling between the fundamental and the harmonic and to adapt the sensitivity of the effect of focusing magnetic field on the beam-wave interaction in the gyro-TWT to high-order mode operation. Experimental results show that 75 kW of peak output power with a bandwidth of 1.06% and a gain of more than 25 dB can be reached at a pulse voltage of 67.2 kV and a pulse current of 15.8 A.

This paper proposes a new type of coupled-cavity interaction circuit for gyrotron traveling-wave amplifier applications with inner- and outer-intersecting coupling. For analysis, we use the equivalent-circuit method, as well as the Ansoft High Frequency Structure Simulator (HFSS) code. Calculated results for the frequency characteristics of the interaction circuit show that at the center frequency of 17.2 GHz a 3-dB bandwidth of more than 533 MHz (3.5% relative bandwidth) may be reached with the TE10 \square rectangular guide mode as input and the TE01 \bigcirc cylindrical guide mode as output.

The experiment on a Ku-band gyrotron backward- wave oscillator (gyro-BWO) with a single depressed collector and linear polarization mode output has been performed successfully. Stable magnetic tuning bandwidth of 5% and maximum power of 48 kW under a 40-kV 11.5-A electron beam were achieved. The overall efficiency of the gyro-BWO with a single stage depressed collector has been enhanced from 10.5% to 21%. The measured performance has demonstrated a strong potential of the gyro-BWO for new application requiring high-power tunable wave source.

Heat radiator performance of radiation cooled space traveling wave tube has been analyzed using ANSYS. Sunshine's effects on balance temperature of the heat radiator have been predicted.

Some experimental phenomena of a harmonic multiplying gyrotron traveling wave tube operating in 8mm band has been discussed in this extended abstract, it has been found that the output power of the tube decreased with the increase of the filament power and its bandwidth increased with the decrease of the output power for the same beam current.

The works related to harmonic multiplying gyrotron traveling wave amplifier were ever reported by us in IRMMW2006 and IVEC2007, which showed that there were some contradictions between output power and band-width.[1, 2] In [1], the output frequency bandwidth of more 500 MHz can be reached at output pulse power of only 10.07~12.88kW. In [2], output pulse power can be increased to 25kW with very narrow bandwidth. Because of using harmonic multiplying, the resonant circuit is usually used to increase the coupling between fundamental and harmonic. However, it will decrease operating bandwidth. In this article, a new method is utilized for enhacing output power and improving bandwidth.

In this article, a new method is utilized for enhacing output power and improving bandwidth. The works related to harmonic multiplying gyrotron traveling wave amplifier were ever reported by us in IRMMW2006 and IVEC2007, which showed that there were some contradictions between output power and band-width. The output frequency bandwidth of more 500 MHz can be reached at output pulse power of only 10.07~12.88kW. Output pulse power can be increased to 25 kW with very narrow bandwidth. Because of using harmonic multiplying, the resonant circuit is usually used to increase the coupling between fundamental and harmonic. However, it will decrease operating bandwidth.

In this paper, the design of a Ku-band 110-kW gyrotron traveling wave tube (gyro-TWT) amplifier with the operating mode TE11 is presented. The optimum interaction structure circuit of the gyro-TWT with distributed wall losses is derived from the self-consistent nonlinear code on the basis of the dispersion relationship and the linear theory. The effects of the parameters such as input power, driver frequency, pitch ratio and so on upon the performance of the gyro-TWT is discussed. The simulation results show that the gain and the bandwidth of the designed Ku-band gyro-TWT is about 37.7 dB and 1.2 GHz with 3 dB bandwidth respectively at the input power 19.0 W. The peak output power and the corresponding electron efficiency is about 110.7 kW and 23.1% respectively with the voltage 80.0 kV and the current 6.0 A at the pitch ratio 0.8.

For a gyro-amplifier, harmonic multiplying can lower the applied magnet field and more easily get RF driver. Theoretical studies and numerical simulation had been made in the references (G.S. Nusinovich et al., 2001), (K.R. Chu et al., 1997), (A.T. Lin et al., 2002) for the amplifier. Experimental results ever reported for a third-harmonic multiplying gyrotron travel wave amplifier (Chan-Wook Baik et al., 2005). In this paper, the simulations, designs and experimental results of a second-harmonic multiplying gyrotron traveling wave amplifier with the TE02 mode output was discussed.

A harmonic multiplying gyrotron traveling wave amplifier with the TE02 mode output has been designed in Institute of Electronics, Chinese Academy of Science (IECAS). First experimental results showed that the tube could stably amplify input signal, the output frequency bandwidth of more 500 MHz (33.0233.524GHz) had been reached at output pulse power of 10.0712.88kW, beam voltage of 60 kV, beam current of 11A. Harmonic multiplying makes the applied magnet field lower and the source for the input signal more readily available for a gyrotron travel wave amplifier. Theoretical studies and numerical simulation had been made in the references [1-3] for the amplifier. Experimental results ever reported for a third-harmonic multiplying gyrotron travel wave amplifier [4]. In this extended abstract, the experimental results and design of a second-harmonic multiplying gyrotron traveling wave amplifier with the TE02 mode output will be presented. Fig. 1 is the interaction circuit of the harmonic multiplying gyrotron travel wave amplifier, which consists of an input waveguide (TE01), a drift section, and an output waveguide (TE02). The lengths of the input waveguide L1, the drift section Ld and the output waveguide L2 are respectively 100mm, 80mm and 200mm. The corresponding waveguide radii are chosen respectively to be R1=11.17mm, Rd=9mm and R2=10.22mm, which makes that the cut-off frequency in the output waveguide (TE02) equal to two times of that in the input waveguide (TE01), i.e. ?c2=2?c1. In the drift section, the propagation of the TE01 and TE02 modes is prohibited.

Millimeter wave processing of materials is a method which has wide application prospect for improving material characteristics. In this paper, the investigated results of millimeter wave processing of materials in IECAS, such as millimeter wave sintering of Al/sub 2/O/sub 3/, ZnO, Nd/sub 2/Ti/sub 3/O/sub 9/, and chemical syntheses of spinels LiMn/sub 2/O/sub 4/ and LiCo/sub 0.1/Mn/sub 1.99/O/sub 3.92/S/sub 0.08/, as cathode materials of Li-ion batteries, with millimeter wave heating are presented.

In present paper a new niobate materials Ba5LixTixNb10-xO30 were synthesized by doping Li+ in the system BaO- TiO2- Nb2O5 in millimeter wave field. X-ray diffraction (XRD) quantitative and scanning transition spectroscopy (SEM) analysis were employed to study crystal structure and microstructure of reaction products. It was found that pure products could be obtained at temperature 900°, 8 min which is lower comparing with that by conventional method. The XRD data shown the crystal belongs to tetragonal tungsten bronze structure with space group P4bm. The grain size synthesized in millimeter wave field had smaller size, narrower distribution, better sinter-ability, and without hard agglomeration comparing whit that obtaining from conventional synthesis. At lower temperature Ba5LiTiNb9O30 is a tetragonal ferroelectric phase.

Laminated ceramic composite is a new type of material developed in recent years to improve the mechanical properties of structural ceramics. Gel casting and hot-pressure sintering technologies were used to obtain the laminated SiC/BN-Al2O3 composite. Mechanical properties of the laminated composite and monolithic SiC ceramic were compared, and the fracture toughness of the laminated composite is nearly one times higher than that of the monolithic ceramic. Dynamic process of crack propagation in laminated composite was observed in situ by SEM. The interfacial crack initiate first in interlayer near to the notch tip, and then the through layer crack formed in matrix layer at the notch tip. After the through layer crack grows across the first matrix layer, it can be deflected by the interlayer and becomes an interfacial crack again. The through layer crack and the interfacial crack are generated alternately until the failure of the composite. The load / displacement plot of laminated material possess several peaks, and each peak is caused by one propagation of the through layer crack. Toughening mechanisms of the laminated composite include crack deflection, interfacial crack, through layer branch crack and parallel main crack. Copyright © 2001 Society of Automotive Engineers, Inc.