Re: Somewhat off topic. Neon gas tubes..

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Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 01:58 PM 10/2/2005, you wrote:
> Original poster: "Mercurus2000" <mercurus2000@xxxxxxx>
>
> I was just wondering, to make a neon light, all you really need is 
> to pump a chamber down to several torr and then backfill fully till 
> it's full with neon right?
> Adam

Gotta go lower than a few torr.  You want a "glow discharge" not an 
arc, so you need to be on the "vacuum" side of the "Paschen 
minimum".  Say, a few microns (0.001 torr)  1 torr = 1 mm of mercury. 
1 micron = 1e-6 meter Hg. 760 torr = 1.013 bar 1013 mbar = 1013 hPa = 
101.3 kPa.  (nobody uses SI units for vacuum, so if you start asking 
about pump ratings in Pa or mPa)

Also, unless you want to waste Ne (which is expensive), you want to 
pump out substantially lower, otherwise whatever is in there mixes with the Ne.

The usual scheme is to pump down substantially below, fire the 
getters, and run it really hot (with a "bombarder") to get the last 
gases out. Then, you backfill with the desired gas.