Major objective is to develop a high pressure sodium (HPS) lamp using a clear sapphire arc-tube. Use of sapphire arc-tube will allow higher "wall loading" which, in turn, will result in a significant improvement in the light output as measured by lumens per watt or PAR (photosynthetically active radiation) per watt of power. Use of clear sapphire arc-tubes (as compared to translucent polycrystalline alumina currently used as arc-tube materialfor the HPS lamps) will not only allow higher "watt loading" in the design of the arc-tubes but will also allow more light output due to direct transmission from the clear sapphire tubes. It is expected that up to 20% increase in the light output may be possible using an optimized sapphire arc-tube.Second objective is to develop an optimized water-jacketed HPS lamp using the sapphire arc-tubes. Techniques will be developed to optimize the arc-tube so that the it works best within a lamp which has an outer water jacket to remove infrared radiation.
Potential Commercial Applications:Sapphire arc-tube HPS lamps will have very wide potential as a direct replacement of the currently marketed HPS lamps. With up to 20% increase in the light out put it will save a great deal of energy in the general lighting applications where ever the HPS lamps are used. Water-jacketed sapphire arc-tube HPS lamps will be very useful for applications needing "cool" high intensity light source. One such application is in the research plant growth chambers. Almost every plant growth facility in the world uses growth chambers. Optimized sapphire arc-tube HPS lamps with outer water jacket will allow the chambers to 1) use less energy (A/C) to remove heat, 2) require less refrigeration capacity to control temperature and 3) use higher radiation levels. The commercial greenhouse industry germinates billions of seedlings every year. Additional applications of sapphire arc-tube water jackets include public buildings like gymnasiums, auditoriums, ice rinks etc. The reduced long wave radiation from these lamps will allow people to be more comfortable and at the same time reduce the requirements for air conditioning.
