Haibing Ding

Numerical Simulation and Experiment of Hardening Behaviors in Unsaturated Polyester Resin Artificial Marble Blocks Under Microwave Radiation

A high-power continuous microwave hardening system at the frequency of 915 MHz and the maximum output power of 60 kW is established to harden unsaturated polyester resin (UPR) artificial marble blocks of typical size 1600 x 900 x 600 mm3 in the industrial production. The microwave hardening system contains three major sections, including a 2000x1300x900 mm3 multimode cavity, microwave generators, and three groups of feeding-waveguide systems from microwave generators to the multimode cavity. An optimum hardening method by adjusting the value of incident power and processing time is found on the basis of study of UPR properties and can promote products qualities. A numerical coupled electromagnetic and heat transfer model has been built to simulate microwave hardening process and to predict temperature profiles of artificial marble blocks successfully. The result that there is no significant change in temperature profiles between fixed and temperaturedependent thermal parameters indicates thermal conductivity K and specific heat capacity CP, which are not sensitive to temperature. The effect of height between artificial marble block and cavity bottom on electromagnetic field, absorption power, and temperature distribution is also discussed in this paper. The contrast results between the two hardening methods prove that the microwave hardening can achieve better comprehensive characteristics than natural hardening. The establishment of the high-power microwave hardening system has improved the industrial production efficiency of UPR artificial marble 300 times.

The research on parasitic RF output of Multi-Beam Klystrons

The high order mode oscillation and parasitic RF output have serious influence on the normal operation and the purity of the output spectrum of MBKs. By putting a microwave absorbing block in the coupling slot of the double-gap coupling cavity, all the high order modes with π mode field structure can be suppressed effectively. The experiment indicated that the size and shape of the absorbing block have big influence on the stability of the MBK. The influence of the absorbing block on the properties of the modes in double gap coupling cavity (DGCC) is calculated and analyzed in this paper. By using PIC code, the beam-wave interaction in DGCC is also calculated. Based on above calculations, it is possible to determine the suitable size and shape of absorbing block while keeping the MBKs operate stable on the high power level.

Research and Development of S-Band High Power Multibeam Klystron

The design, manufacture, and test of an S-band high power multibeam klystron (MBK) are presented in this paper. The test results indicate that the performance of the MBK satisfies the design requirement. Several technical problems, such as the oscillation of high-order modes, a decrease of the beam current under no-driver (oscillating) conditions, and the high-voltage breakdown are also discussed. Some improvements have been taken to overcome these problems. The improved tube has a beam transmission rate over 98%, and operates very stably under DC and RF conditions.

Development of an S-Band High Average Power Multibeam Klystron With Bandwidth of 10%

An S-band high average power multibeam klystron (MBK) producing peak power of 500 kW and average power of 30 kW over 10% of relative simultaneous bandwidth has been designed and developed in Institute of Electronics, Chinese Academy of Sciences (IECAS). The biggest challenges were achieving over 10% relative simultaneous bandwidth performance with higher efficiency at the same time and focusing and transport of the intense electron beam because of the highest level average power in all types of MBKs in IECAS. Two prototypes were manufactured and both have been thoroughly tested. The fundamental mode was chosen for the RF interaction system, 24 beams are used to obtain a beam current of 50 A and the beam voltage is 29 kV. The efficiency is greater than 40% and the gain is greater than 37.5 dB over a relative simultaneous bandwidth of 10%. Both design considerations and experimental results have been addressed in this paper. The experimental results are close to design specifications.

Research progress on a high-power continuous wave multimode cavity used for microwave hardening

A microwave hardening system for giant artificial marble blocks has been designed and put into use for actual manufacturing. The high-power continuous wave multimode cavity as the main part of the system can totally process artificial marble blocks of typical size such as 1.6×0.9×0.6m3 which is the 1/5 of the maximum size. Microwave hardening takes less than 1 hour and it is shorter than natural hardening which needs at least 15 days. Mechanical characters of microwave hardened blocks basically conform to those under natural hardening.

The suppression of stray output of Multi-Beam broadband Klystron

The purity of output spectrum of high power microwave vacuum electronic devices is very important for the microwave electronic system. The stray outputs with frequency in or near the operating frequency band have been observed in some Multi-Beam Klystron (MBK). The exits of the stray outputs have serious influence on the normal operation of the microwave electronic systems. The variation of stray outputs with different operating frequency observed in an S band MBK was described, and the reasons for generating the stray outputs were analyzed by using 1D klystron code in this paper. The reflecting electrons and secondary electrons caused by the interception of electron beam on gap head of the cavity are responsible for the stray outputs. They will be accelerated by RF electric field on the cavity gap in reverse direction, and return back to previous cavity. The retuning electrons provide the feedback way between successive two cavities, and generate oscillation, which will be amplified by following cavities and form stray outputs. The stray outputs can be reduced or suppressed by decreasing the number of retuning electrons. It can be realized by making small slots on the surface of the gap head. The new MBK with slots on the gap head was made and tested, the power level of the stray outputs are less than -70dBc.

Design of X-band 80kW CW broadband klystron

The Institute of Electronics, Chinese Academy of Sciences (IECAS) is developing a new X-band 80kW CW broadband klystron with instantaneous bandwidth of 95MHz for using in communication system. The designs of the klystron are presented in the paper. And the results of design and calculation can reach the required specification.

Design of 100kW water load for P-band Continuous Wave Magnetron

Magnetron, as a kind of high-power high-efficiency and low-cost microwave generator, has been widely improved and used since 1930s. For industrial utility, magnetron with CW output power of 75 kW operating in 915 MHz is widely used. Therefore, one type of water load with tolerance of 100 kW is developed for the convenience of high power test. Three type of materials, ceramic, mica, Teflon are considered to be used as microwave window of water load. According to simulation result, its VSWR is optimized to be less than 1.08, 1.25 and 1.5 within a bandwidth of 100 MHz for ceramic, mica and Teflon respectively.

The research on RF output envelope of C-band Multi-Beam Klystron

The shoulder and the tilt of RF output envelope of the C-band broadband MBK are described and discussed in the paper. The RF envelope shoulder occurs mainly at low part of the operating frequency band, and is caused by the gassing of microwave attenuation material FeSiAl covering on the wall of the cavity. The RF envelope tilt is caused by the drop of the pulse voltage and the dependence of efficiency on the beam voltage. These physical phenomena are explained and analyzed in the paper. The methods for overcoming the RF envelope shoulder and reduce the RF envelope tilt are also discussed.

Design of a continuous wave Ka-band extended interaction klystron

A continuous wave Ka-band extended interaction klystron producing output power of 3 kW and bandwidth of 100MHz has been designed in Institute of Electronics, Chinese Academy of Sciences (IECAS). The electron beam voltage is 17kV, beam current is 0.9A, tube radius is 0.5mm and beam radius is 0.3mm. Electron optical system has been well optimized because of the continuous operating mode. The beam compression factor is 53:1 and the average emit current density in cathode is 6A/cm2. There are six cavities, single gap input cavity and five double gap coupled cavity. Double gap coupled cavities operate in 2pi mode and the efficiency exceeds 20% in required bandwidth. Design considerations and details are addressed in this paper.