[Boatanchors] RE: 2X2 question

[B Riches]

Interesting - I guess we forget that glass is a "liquid". In 100+ year old 
homes that have the original window glass the panes are thicker at the 
bottom due to the flow of the glass by gravity.

Regards,

Bill Riches WA2DVU
Cape May, NJ
----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: "Mark Foltarz" <Foltarz at rocketmail.com>
Cc: <boatanchors at mailman.qth.net>
Sent: Sunday, April 09, 2006 3:56 PM
Subject: Re: [Boatanchors] RE: 2X2 question


> Mark Foltarz wrote:
>
>> Yes, my mistake on the mercury in the 2X2. It is a hard vacuum tube.
>>
>> For some reason I was fixated on the 866 and the thought that the 2X2 was 
>> an
>> 866 jr.  I had four of those in my Drake powers upply for my ART-13.
>>
>> But in regards to the early HeNe laser failures, I think that was most 
>> likely
>> bad seals where the optics are glued to the main tube body as opposed to
>> diffusion through glass.
>>
>> Thoughts?
>> de KA4JVY
>> Mark
>
> Lasers fail because of He diffusion through glass. Period. Consider the
> following:
>
> 1.  I have a number of HP 5501A lasers. (They are used in the HP 
> Interferometer
> systems) After a number of years (say 10) the laser power falls to 
> unusable
> levels. These are not $29 supermarket bar code scanning lasers, but $5000+ 
> Zeeman
> split, frequency stabilized units. HP agrees it's the He leaking through 
> the
> glass
>
> 2.  Liconix makes HeCd lasers. They have a He reservoir to replenish the 
> He lost
> to the tube by sputtering of the Cd. If the laser is NOT used for a couple 
> of
> years, it fails due to excess He leaking INTO the tube from the high 
> pressure
> reservoir.
>
> 3.  I was using an EMR photo multiplier in a He atmosphere. It failed in 
> about a
> month, due to He leakage into the tube.
>
> 4.  When I was doing cryogenic research, we has special glass dewers for 
> liquid
> He. Someone forgot to purge the He out of the dewer one night and ruined 
> it.
>
> Helium diffuses through glass. PERIOD.
>
> -John
>
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