quote: Mitchell Dvoskin

---

The one thing they showed that I did not understand the reason, is that as part of the manufacturing process, Osram dunks the bulbs in liquid nitrogen, which liqified the Xenon Gas in the bulb.

---

Likely used as a purification step. Since xenon boils at -108.2 Celsius, which is higher than oxygen or nitrogen, liquifying the xenon and then removing any residual gas with a vacuum before sealing the lamp would remove some of the more common gaseous impurities. Maybe some of our other xenon lamp experts would be willing to share more about the manufacturing process.

Here is a link comparing physical properties of some gases:

http://www.uigi.com/physical_prop_m.html
 

---

Posted by Phil Hill (Member # 371) on 05-22-2006, 04:36 PM:
 
The reason for the liquid nitrogen, which liquefies/solidifies the Xenon Gas in the bulb, is to prevent a "blowout" of the filling seal during the bulb sealing.

Since the finished xenon lamp/bulb is under a positive atmospheric pressure even when not lit, sealing the fill tube by "heat torching" would cause the internal bulb pressure to not allow the bulb to be sealed and the xenon would escape.

By super-cooling the xenon gas to a liquid, the bulb can be sealed and when allowed to come up to room temperature, the xenon gas would be at the correct positive pressure for the lamp.
 

---

Posted by John Pytlak (Member # 331) on 05-23-2006, 07:42 AM:
 
Thanks Phil.
 

---

Posted by Mitchell Dvoskin (Member # 751) on 05-23-2006, 07:51 AM:
 
They did mention that liquifying was to reduce pressure, but they did not say why that was needed. Thanks Phil.
 

---

Posted by Tim Reed (Member # 137) on 05-26-2006, 08:57 AM:
 
Actually, they dunk it to lower the pressure to prevent a "blowout" of the filling seal during the bulb sealing. When the heat rises, so does the internal pressure. Also, at those sub-zero temperatures, xenon becomes a liquid.

The xenon envelope is quartz.

The electrodes are tungsten.

Plus means positive.

Minus means negative.

 

---