DEVELOPMENT OF SEALED SAPPHIRE RAMAN CELLS

RECENT DEVELOPMENTS IN HOT WINDOW RAMAN CELL TECHNOLOGY HAVE SHOWN THAT LONG LIVED DEVICES CAN BE MANUFACTURED. CELLS HAVE BEEN CONSTRUCTED UTILIZING ALUMINA TUBING AND SAPPHIRE WINDOW MATERIALS FUSED VIA CERAMIC BRAZING TECHNIQUES. SUCH DEVICES HAVE BEEN SHOWN TO HAVE LIFETIMES ON THE ORDER OF SEVERAL THOUSAND HOURS. CALCIUM ALUMINATE AND ALUMINA/YTTRIA EUTECTICS FORM USEABLE SEALS AT TEMPERATURES TO 1450 DEGREES C, BUT APPARENTLY ARE OF LIMITED LIFETIME AS THEY ARE CURRENTLY USED. LONG TERM CRYSTAL GROWTH AND POISONING VIA LEAD OXIDES FORMED OVER LONG PERIODS ALONG WITH THERMAL CYCLING TEND TO ACT AS MAJOR FAILURE MODES FOR THE LEAD VAPOR CELLS. WHAT WE PROPOSE IS TO DEVELOP THE SEAL TECHNOLOGY REQUIRED FOR THE MANUFACTURE OF AN ALL SAPPHIRE LEAD VAPOR RAMAN DEVICE. THE PROCESS TO TAKE PLACE VIA OPTICAL CONTACT BONDING AND SUBSEQUENT FIRING AT TEMPERATURES APPROACHING 1900 DEGREES C. THE RECRYSTALIZED JOINT TO HAVE NO BOUNDARY TO CHEMICALLY REACT WITH LEAD VAPOR NOR BUILT IN FAILURE MODE DUE TO DIFFERENCES IN CELL MATERIALS AND SEALANTS.