Hafnium activated metal halide arc discharge lamp

Claim 2

A HIGH INTENSITY METAL HALIDE ARE DISCHARGE LAMP COMPRISING: AN ACR TUBE HAVING SEALED ENDS AND CONTAINING A FILL INCLUDING MERCURY AND A METAL HALIDE, AND HAFNIUM ACTIVATED ELECTRODES DISPOSED WITHIN SAID ARC TUBE, THE SIZE OF SAID ELECTRODES BEING SUCH THAT DURING NORMAL OPERATION OF THE LAMP THE RATE OF EVAPORATION OF HAFNIUM FROM SAID ELECTRODES IS ABOUT EQUAL TO THE RATE OF DEPOSITION OF HAFNIUM FROM HAFNIUM HALDE THEREON, THEREBY ENSURING HAFNIUM ACTIVATION OF SAID ELECTRODES THROUGHOUT NORMAL LAMP LIFE, AND WHEREIN THE CONSTRUCTION OF SAID ELECTRODES IS SUCH THAT THEIR HOT SPOT TEMPERATURE DURING NORMAL LAMP OPERATION IS BETWEEN ABOUT 1825*C AND 2325*C.

Claim 3

A high intensity metal halide arc discharge lamp Comprising: a sealed arc tube containing hafnium activated electrodes and containing a fill including mercury, sodium halide and a metal halide, the total amount of halogen in said arc tube exceeding the stoichiometric equivalent thereof for all metals in said arc tube having a significantly more negative free energy of formation per iodine atom than hafnium iodide, and wherein said total amount of halogen is less than the sum of the stoichiometric equivalent thereof for the total amount of hafnium in said arc tube plus the stoichiometric equivalent thereof for all metals in the arc tube having a significantly more negative free energy of formation per iodine atom than hafnium iodide.

Claim 4

A high intensity metal halide arc discharge lamp Comprising: a sealed arc tube containing hafnium activated electrodes and containing a fill including mercury, sodium halide and a metal halide, the total amount of halogen in said arc tube exceeding the stoichiometric equivalent thereof for all metals in said arc tube having a significantly more negative free energy of formation per iodine atom than hafnium iodide, and wherein said total amount of halogen is less than the sum of the stoichiometric equivalent thereof for the total amount of hafnium in said arc tube plus the stoichiometric equivalent thereof for all metals in the arc tube having a significantly more negative free energy of formation per iodine atom than hafnium iodide.

Claim 5

A high intensity metal halide arc discharge lamp comprising an arc tube having sealed ends and electrodes disposed in said ends and containing a fill including mercury, an inert starting gas, sodium iodide, mercury iodide, scandium and hafnium wherein the quantity of hafnium is about 6.2 X 10 7 gram atoms per centimeter of arc length.

Claim 6

A high intensity metal halide arc discharge lamp comprising an arc tube having sealed ends and electrodes disposed in said ends and containing a fill including mercury, an inert starting gas, sodium iodide, mercury iodide, scandium and hafnium wherein the quantity of hafnium is about 6.2 X 10 7 gram atoms per centimeter of arc length.