Molybdenum foil
Short-arc ultra-high intensity discharge lamps are HID light sources with electrode spacing less than 10mm, which are widely used in directional lighting devices with high brightness and uniformity requirements, and usually need to be matched with specific optical systems to achieve specific lighting purposes. For example, ultra-high pressure xenon lamps for movie projectors and searchlights, ultra-high pressure xenon gold halide lamps for automobile headlights, ultra-high pressure gold halide lamps for stage and film lighting, xenon lamps and mercury lamps, laser pumps that need to be used in conjunction with optical systems, HID light sources for medical equipment, and non-illuminating HID light sources that use ultraviolet and infrared radiation through spectroscopic systems. The basic structural feature of this kind of light source is that the bubble tube made of quartz glass is used, and the molybdenum foil of welded metal electrode and lead is fused with quartz glass to form an airtight discharge cavity. The common technical feature is that the electrode spacing needs to be precisely controlled, and at the same time, the stability of the lamp's high temperature and high pressure working state requires a good thermal stress match between molybdenum foil and quartz glass to ensure.
Short-arc ultra-high pressure mercury lamp for micro-display projection is a typical representative of this kind of light source. The light source is made of quartz glass bubble tube with a wall load higher than 100W/cm2, sealed with an axially opposed tungsten electrode, and filled with mercury with a density higher than 0.2mg/mm3, about 104Pa of inert gas and trace halogen as working substances. The pole distance of this lamp can be as short as 1mm, and the bubble shell needs to withstand a high temperature of about 1000 ℃ and a pressure of more than 200atm when working.
In the prior art, the electrode assembly of the short arc ultra-high intensity discharge lamp is formed by tungsten electrode, molybdenum lead with basically the same diameter as the electrode and the thickness of about 20 ~ 30μm, and the edge of the molybdenum foil is formed by spot welding. In addition, in order to increase the spot welding strength and the current carrying property of the electrode assembly, the tantalum foil is generally used to transition between the electrode, lead and molybdenum foil.
In the prior art, the sealing of the short arc ultra-high intensity discharge lamp is to position the electrode assembly in the quartz bubble tube under the protection of vacuum or inert gas according to the set pole distance, and then control the flame to heat the quartz tube in the molybdenum foil part, so that it melts and contracts, and closely fits with the molybdenum foil to form the sealing part, and the electrode rod is fixed in the quartz on the side of the bubble shell. Then the electrode head is in the bubble shell cavity. In order to ensure the sealing quality and the normality of the electrode in the bubble shell as far as possible, the bubble shell and the flame are relatively rotated during sealing, and the melt sealing part is molded.
