Why Osram low wattage daylight HQI-TS, have Dy-In-Tl-Na and not Dy-Tl-Cs, like the 250W and 400W?

Hello Dor,

Since all of these types are now obsolete I have looked up the Osram Berlin manufacturing specifications for HQI-TS 70/D and 150/D arc tubes.  They are both filled with the same chemistry, Osram type MHP15, which has the composition 21.6% DyI3, 21.6% HoI3, 21.6% TmI3, 17.6% TlI, 17.6% CsI  The 70D arc tube contains 1mg halide, the 150D has 1.6mg.

This is the same as the 250D which contains 5.4mg

The 400D has slightly modified chemistry with 8.5mg of 20% DyI3, 20% HoI3, 20% TmI3, 23.5% TlI, 16.5% CsI plus an extra 0.8mg pellet of HgJ2 to increase the free iodine content.

There is no sodium or indium dosing any of these daylight arc tubes, although you will of course see sodium and lithium lines in the spectrum of new lamps due to chemical impurities.  It takes about 100 hours for the sodium to be gettered and for the colour temperature to rise to its intended value, the feint lithium line remains much longer.

Probably only at the Excellence Osram moved to Dy-In-Tl-Na: https://www.lighting-gallery.net/gallery/displayimage.php?pos=-234216
Also: The original 70W/WDL, 150W/WDL, 70W/NDL and 150W/NDL, had Sn-In-Tl-Na, but the Excellence have Dy-Ho-Tm-Tl-Na.
And the /CD also have that Dy-In-Tl-Na.

James, can you please tell, how sodium gettering in metal halide lamps is performed?