Design Of Diamond Film Used In Helix Traveling Wave Tube Slow-Wave Structure And Deposition Equipment

Helix traveling wave tubes are widely used in radar, satellite communication andelectronic countermeasures system. For the development of military science andtechnology, it is important to improve output power of helix traveling wave tube forrelated system. The lower heat dissipation capability of the slow wave structure limitoutput power of helix traveling wave tube. The high quality CVD diamond film has agreat thermal and electrical performance. We propose to deposit high quality diamondfilm on ceramic support rod and metal helix to improve the heat dissipation capabilityof slow wave structures. The slow wave structure with excellent heat dissipationcapability can improve the output power of the helix traveling wave tube. Using finiteelement simulation software ANSYS to design the structure of diamond film/ceramiccomposite support rod and diamond film/tungsten composite helix. With the help ofANSYS, the heat dissipation capability of these composite components has beensimulated.The simulation result of thermal conductive capability of the diamondfilm/ceramic composite support rod have show that depositing diamond film on allareas of support rod that parallel to the central axis of slow-wave structure cansignificantly enhance the thermal conductive capability of the support rod. The resultalso indicates that the thermal conductive capability of the composite support rod isincreased with the increase of thickness of diamond film. Coating uniform50μm thickdiamond film on the BeO ceramic support rod can reduce about50℃of the maximumtemperature on the helix.The thermal conductive capability of three mode diamond film/tungsten helixwhich structure of diamond film is different has been researched. The maximumtemperature of helix is decreased with the increase of the thickness of the uniformcoated diamond film. Coating50μm thick uniform diamond film can reduce about58℃of the helix maximum temperature. When diamond film deposited as stud on thehelix, the helix temperature is decreased with the increase of width of diamond filmstud. The diamond film stud which width is700μm and thickness is about50μm canreduce about76℃of the helix temperature. Combine the advantages of the first twomode, a new mode that diamond film non-uniform coating the helix has been designed.This mode can reduce about110℃of the helix temperature. When using diamond film/ceramic composite support and diamond film/tungsten composite helix in theslow-wave structure, the temperature of the helix is decreased about150℃.A HFCVD system which substrates and filaments are vertical arranged has beendesigned. The length of support rod and helix often exceed10cm. The new system candeposit high quality diamond film on the support rod and helix. The system has twomode. Single substrate mode used in deposit diamond film on just one substrate. Multisubstrates mode used in deposit diamond film on multi substrate at the same time.Using ANSYS software to simulate the temperature of the vertical substrate after thefilament parameters varied. The rules of the substrate temperature changed withfilament parameters have been got. The optimal parameters of single substrate systemare: using4or5filaments which length is13cm and diameter is0.6mm, the filamenttemperature is about2200℃, the distance between filament and substrate is10or12mm. The optimal parameters of8substrate system are: using8filaments whichlength is15cm and diameter is0.6mm, the filament temperature is about2100~2200℃, the distance between filament and central axis is about20~25mm, thedistance between substrate and central axis is about10~17mm, the substrate and it’srecently filament should arranged in the same radius, during the deposition processthe substrate and filament could not be moved.