Vacuum Seal (Glass to Metal) in Lamps

If the bubbles are around the leads i would check them for off gassing. Some thing could have contaminated them. Wires are drawn through die to reduce to size. Lubricants in the process could be still on the wire intermittently. If coated could be improper mix in the coating solvents causing the bubbles. Test the wire for impurities

Hi, Thanks for your reply. But still i've some questions, As u had pointed, the bubbles are around the leads only. Actually the Tungsten lead is supplied after beading (773 Glass), what i'd learned is the tungsten is oxidised before beading it so that the seal is perfect. So the tungsten lead has a oxide coating, if its impure.. are there any easy way

You mite look at some way to heat wire to burn off impurities. I don,t know what that would do to Oxide coating. Be aware that the heating may cause additional problems in the forms of impurities. The tungsten can draw the from the air as its cooled.

Hi, heating for outgassing is a good idea but may be this is oxidising the wire further.

So I would be careful to select the outgassing temperature starting at 250°C and rising from one experiment to the next in steps 300, 350, etc.

May be storage in vacuum (at or below 1 mbar) is doing the same with more safety.

Have success

RHABE

Hi,Indium foil is ideal for creating cryogenic vacuum seals. If there is any demand, please feel free to contact me for more details.