Krypton metal halide lamps
The present application discloses an arc tube for a metal halide lamp having a fill gas pressure sufficient for providing sufficient impedance for rapid warm-up of the light source after ignition. The fill gas consists essentially of krypton or comprises a mixture of krypton with xenon or argon, or both.
1 . An arc tube for a high intensity discharge lamp comprising:
an arc tube body having a chamber intermediate two end portions;
an electrode lead assembly sealed in each end portion;
a lamp fill contained within said chamber comprising mercury and one or more metal halides; and
krypton contained within said chamber at a pressure at substantially room temperature in the range of about 0.5 atmospheres to about 100 atmospheres.
2 . The arc tube of claim 1 wherein the pressure of the krypton is in the range of about 2.0 atmospheres to about 20 atmospheres.
3 . The arc tube of claim 2 wherein the pressure of the krypton is in the range of about 4.0 atmospheres to about 10 atmospheres.
4 . The arc tube of claim 3 further comprising xenon contained within said chamber at a pressure at substantially room temperature no greater than 2.0 atmospheres.
5 . The arc tube of claim 4 wherein the pressure of the xenon is in the range of about 0.5 atmospheres to about 1.5 atmospheres.
6 . The arc tube of claim 3 further comprising argon contained within said chamber at a pressure at substantially room temperature no greater than 2.0 atmospheres.
7 . The arc tube of claim 6 wherein the pressure of the argon is in the range of about 0.5 atmospheres to about 1.5 atmospheres.
8 . The arc tube of claim 1 wherein said arc tube body is formed from quartz.
9 . The arc tube of claim 1 wherein the metal halides comprise iodides of sodium, scandium and thorium or iodides of dysprosium, holmium, and thulium.
10 . An arc tube comprising a hermetically sealed chamber containing one or more metal halides and krypton at a pressure at substantially room temperature greater than about 1.0 atmospheres.
11 . The arc tube of claim 10 wherein the pressure of the krypton is greater than about 4.0 atmospheres.
12 . The arc tube of claim 11 wherein the pressure of the krypton is between about 4.0 atmospheres and about 10 atmospheres.
13 . The arc tube of claim 12 wherein the metal halides comprise iodides of sodium, scandium and thorium.
14 . The arc tube of claim 13 wherein the weight ratio of the iodides of sodium, scandium is 77:21:2.
15 . The arc tube of claim 11 wherein the metal halides comprise iodides of dysprosium, holmium, and thulium.
16 . The arc tube of claim 15 wherein the weight ratio of the iodides of dysprosium, holmium, and thulium is 40:50:10.