Fluidic laser calorimeter

Abstract

A laser calorimeter which operates by absorbing the energy of a laser beam directed through a lens at the front of the calorimeter. The calorimeter contains a absorbing medium with high absorbance characteristics at the laser wavelength in question. The absorbed laser energy is converted to heat. The device has a means for measuring the changes in temperature of the absorbing medium as well as a means for measuring the changes in pressure inside the calorimeter chamber. The absorbing medium is typically a liquid which also demonstrates preferable heat transfer characteristics. This in turn affords greater precision and a faster response time of the calorimeter when measuring the laser energy. A typical medium for such a device is a dimethylformamide solution which has extremely good absorbance characteristics for an optical path length of 0.015 inches at a laser wavelength of 1.064 microns.

What I now claim as the invention is: 
     
       1. A laser calorimeter for measuring laser energy comprising: a housing having a forward end defining an opening and an interior chamber, said chamber having an interior surface opposite said opening;   a lens disposed in said opening of said housing and attached peripherally thereto whereby said laser energy may enter said housing chamber;   a means disposed in said chamber for absorbing said laser energy in said housing chamber; and   a means extending sealably through said housing and into said chamber for measuring changes in temperature in said means for absorbing said laser energy.   
     
     
       2. The laser calorimeter for measuring laser energy of claim 1 further comprising a means extending sealably through said housing and into said chamber for measuring changes in pressure in said housing chamber. 
     
     
       3. The laser calorimeter of claim 2 wherein said interior surface opposite said lens comprises a mirror surface. 
     
     
       4. The laser calorimeter of claim 2 wherein said lens comprises a plano-convex lens. 
     
     
       5. The laser calorimeter of claim 2 wherein said means for measuring changes in temperature in said housing chamber comprises a thermistor. 
     
     
       6. The laser calorimeter of claim 2 wherein said means for absorbing said laser energy comprises a liquid dye solution disposed in said housing chamber. 
     
     
       7. The laser calorimeter of claim 6 wherein said liquid dye solution comprises a mixture having known specific absorbance characteristics of laser energy at specific wavelengths. 
     
     
       8. The laser calorimeter of claim 7 wherein said liquid dye solution comprises a mixture containing insert dye solution and dimethylformamide. 
     
     
       9. The laser calorimeter of claim 7 wherein said liquid dye solution comprises a mixture containing 55 mg of said dye solution per milliliter of dimethylformamide. 
     
     
       10. The laser calorimeter of claim 2 wherein said means for measuring changes in pressure comprises a pressure transducer attached to said housing and extending sealably into said chamber. 
     
     
       11. The laser calorimeter of claim 10 wherein said pressure transducer comprises: a bellows structure having an axis of linear motion and further having a cavity;   a linear variable differential transformer disposed on said bellows structure along said axis of linear motion; and   a means for attaching said pressure transducer to said housing so that said chamber extends sealably into said bellows cavity.   
     
     
       12. The laser calorimeter of claim 11 wherein said linear variable differential transformer comprises: a transformer core component having a first side and a second side opposite said first side;   a transformer coil element of an electrical circuit disposed near said first side of said transformer core;   a transformer coil element of an electrical circuit disposed near said second side of said transformer core; and   a means for attaching said transformer core to said extension bellows whereby said transformer core moves in the direction of the axis of linear motion with pressure changes inside said chamber.   
     
     
       13. A laser calorimeter for measuring laser energy of a laser beam comprising: a housing having a forward end defining a first opening, an interior chamber, and an aft end defining a second opening opposite said first opening;   a first lens disposed in said first opening of said housing whereby said laser beam may enter said housing chamber;   a means disposed in said chamber for absorbing said laser energy of said laser beam;   a means extending sealably through said housing and into said chamber for measuring changes in temperature in said chamber; and   a second lens disposed in said second opening of said housing whereby said laser beam may exit said housing chamber.   
     
     
       14. The laser calorimeter of claim 13 wherein said first lens and said second lens comprise a first plano-convex lens and a second plano-convex lens respectively. 
     
     
       15. The laser calorimeter of claim 13 wherein said means for measuring changes in temperature in said housing chamber comprises a thermistor. 
     
     
       16. The laser calorimeter of claim 13 wherein said means for absorbing said laser energy of said laser beam comprises a liquid dye solution disposed in said housing chamber. 
     
     
       17. A laser calorimeter for measuring laser energy comprising: a housing having an interior chamber;   an optical means for communicating said laser energy with said chamber, said means extending sealably through said housing so that said laser energy may pass through said optical means;   a means disposed in said chamber for absorbing said laser energy in said housing chamber; and   a means extending sealably through said housing and into said chamber for measuring changes in temperature in said means for absorbing said laser energy.