Thorium-free discharge lamp with reduced halides and increased relative amount of Sc
View Patent ↗A high-pressure gas discharge lamp has a sealed discharge vessel with an inner discharge space. Two electrodes project into the discharge space. The filling in the discharge space includes metal halides and a rare gas. The filling is free of Hg and Th and includes halides in an amount of 7.1-11.4 μg/mm 3 of the volume of the discharge space. The halides includes at least NaI and ScI 3 , provided in such amounts that a ratio of the masses of NaI to ScI 3 is 1.2-1.6.
1. A discharge lamp comprising:
a sealed discharge vessel defining a discharge space having a volume and comprising a filling including metal halides and a rare gas and being free of Hg and Th;
at least two electrodes projecting into said discharge space, said electrodes being free of Th,
wherein said metal halides are provided in an amount of 7.1-11.4 μg/mm 3 of the volume of said discharge space and comprise NaI and ScI 3 in such amounts that a ratio of masses of NaI to ScI 3 is 1.2-1.6.
2. The discharge lamp of claim 1 , wherein said metal halides further comprise at least InI.
3. The discharge lamp of claim 1 , where wherein said metal halides consist essentially of NaI, ScI 3 , ZnI 2 and InI.
4. The discharge lamp of claim 1 , wherein said metal halides are provided in an amount of 8.5-10.5 μg/mm 3 of the volume of said discharge space.
5. The discharge lamp of claim 1 , wherein the volume of said discharge space is 10-45 mm 3 .
6. The discharge lamp of claim 1 , wherein the volume is 19-25 mm 3 .
7. The discharge lamp of claim 1 , wherein the ratio of the masses of Nal to ScI 3 is 1.3-1.4.
8. The discharge lamp of claim 1 , further comprising an outer envelope disposed around said discharge vessel, wherein said outer envelope is sealed and filled with a gas.
9. The discharge lamp of claim 8 , wherein said outer envelope is filled with a gas having a thermal conductivity of 60-90 mW/m*K at 800° C.
10. The lamp of claim 1 , wherein said rare gas is xenon provided at a cold pressure of 11-17 bar.
11. The lamp of claim 1 , wherein said electrodes are made of tungsten.
12. The lamp of claim 1 , wherein said electrodes are rod-shaped with a rod diameter of 280-320 μm.
13. The lamp of claim 1 , wherein said metal halides further comprise at least ZnI 2 , and wherein an amount of the ZnI 2 is 4-6 wt-% of said metal halide.