vacuum chamber

[torana68 (Roger)]

I'm wondering if these are for recoating if not what are they?

http://www.gumtree.com.au/s-ad/quean...rge/1084635726

[blink138 (Pat)]

wow they are bizarre!
being an optician i have only seen large commercial chambers for opthalmic multicoating like hoyas
very interesting
pat

[Stefan Buda]

The don't look like typical coating chambers but could be converted into that. Anyway that would be only a start as one needs pumps, gauges, power supplies, valves etc.

[AstralTraveller (David)]

How good a vacuum do you need for a coating chamber?

[OzEclipse (Joe Cali)]

I work in vacuum technology. Thin film deposition for optical surfaces is a highly skilled process. A telescope mirror needs to have a coating that is one atom thick distributed over the surface. If the coating is uneven then your 1/10 wave mirror quickly becomes 1/4, 1/2, or even 1 or 2 wave.

That item is just the vacuum chamber. Doesn't seem to have anything else. It has a couple of NW25 vacuum ports but these are only for attaching vacuum gauges and perhaps the roughing pump. (The mechanical vacuum pump that removes most of the air before the turbo pumps turn on.)

You don't need ultra high vacuum, high vacuum is ok. I've seen deposition units work at 1 billionth of an atmosphere. At that pressure there is plenty of mean free path. That means the aluminium atoms can travel 60 metres at that pressure without hitting any gas molecules.

The main thing is cleanliness. You'll need to operate the system in a clean environment. You also have to understand how to calculate the correct amount of metal to evaporate and deposit.

For this volume you would want 3-4 250 l/s turbomolecular pumps approx $20000 ea, 2 rotary pumps approx $2000 each, vacuum gauges for backing pumps and for high vac $6000.
Sub total : - $90000

You'll need high vacuum valves. A can't see any ports to attach the pumps though they might be underneath. However this chamber might be designed to be attached direct to the top of a giant oil diffusion pump (old tech). In that case, you'll need to get a 1 m flange with ISO flanges welded into it to take the turbo pumps.

Sub total $10000-$20000

I can't see any high current feedthroughs to supply the evaporation boats that will evaporate the aluminium nor any ports to connect the . You'll need to buy platinum evaporation boats, pure high grade aluminium

Sub total $10000


You are probably looking at an investment well north of $100000 for the unit alone plus the large clean space to house it.

I recommend you forget it or buy it and use it as an anchor.

cheers

Joe

[torana68 (Roger)]

I don't want it just interested to know its use, by the sound of it perhaps not telescope but something off Mount Stromlo/ANU that they were playing with?

[AstralTraveller (David)]

Originally Posted by torana68

I don't want it .....

No no - buy it. High vacuum is fun and games for the whole family. And if you still have hair you can get that chrome-dome look you've always wanted.

[blink138 (Pat)]

Originally Posted by OzEclipse

I work in vacuum technology. Thin film deposition for optical surfaces is a highly skilled process. A telescope mirror needs to have a coating that is one atom thick distributed over the surface. If the coating is uneven then your 1/10 wave mirror quickly becomes 1/4, 1/2, or even 1 or 2 wave.

That item is just the vacuum chamber. Doesn't seem to have anything else. It has a couple of NW25 vacuum ports but these are only for attaching vacuum gauges and perhaps the roughing pump. (The mechanical vacuum pump that removes most of the air before the turbo pumps turn on.)

You don't need ultra high vacuum, high vacuum is ok. I've seen deposition units work at 1 billionth of an atmosphere. At that pressure there is plenty of mean free path. That means the aluminium atoms can travel 60 metres at that pressure without hitting any gas molecules.

The main thing is cleanliness. You'll need to operate the system in a clean environment. You also have to understand how to calculate the correct amount of metal to evaporate and deposit.

For this volume you would want 3-4 250 l/s turbomolecular pumps approx $20000 ea, 2 rotary pumps approx $2000 each, vacuum gauges for backing pumps and for high vac $6000.
Sub total : - $90000

You'll need high vacuum valves. A can't see any ports to attach the pumps though they might be underneath. However this chamber might be designed to be attached direct to the top of a giant oil diffusion pump (old tech). In that case, you'll need to get a 1 m flange with ISO flanges welded into it to take the turbo pumps.

Sub total $10000-$20000

I can't see any high current feedthroughs to supply the evaporation boats that will evaporate the aluminium nor any ports to connect the . You'll need to buy platinum evaporation boats, pure high grade aluminium

Sub total $10000


You are probably looking at an investment well north of $100000 for the unit alone plus the large clean space to house it.

I recommend you forget it or buy it and use it as an anchor.

cheers

Joe

thank you very much for the lesson joe
do you work in an optical coating laboratory?
pat

[OzEclipse (Joe Cali)]

thank you very much for the lesson joe
do you work in an optical coating laboratory?
pat

I've specialized in stable isotope mass spectrometry past 30 years same as David (Astral Traveller). In addition, these days, I am laboratory manager of a large research school at the ANU. I know the basic theory of thin coatings.

We have small coating units for electron microscopy. These units put a conductive coating of gold or carbon on thin sections but use a different process to that used for mirrors. These coatings are not monatomic and therefore not suitable for optical coatings for telescope mirrors.

We don't have an optical coating units but I have seen optical coating units at other institutions in operation. The correct amount of metal needs to be evaporated to make sure that only a single layer of atoms is deposited otherwise you don't get a flat coating.

At the research school, I purchase the types of vacuum equipment I mentioned in my post for mass spectrometers and other supporting gear. That's why I can quote approximate prices off the top of my head.

It's a very expensive game. Sorry Torana. It sounded like you wanted to buy it. I was just trying to make sure you didn't make a very expensive mistake.

It's some sort of vacuum chamber but it could be anything.

Large vacuum chambers are used in a bewildering array of devices. Looking at the photo's, there was nothing identifying exactly what it came from but there were some clues.

It's probably a bit big for an electron microscopes or electron microprobe. The small ports you can see in the photo are NW style connectors - probably NW25, this indicated it is probably not part of an ultrahigh vacuum system. NW 25's usually have viton o-rings that are suitable for high but not ultrahigh vacuum. NW25's can be fitted with aluminium crush knife edge seals that will hold a higher vacuum than viton but usually, a deicated ultrahigh vac will use a different type of flange called a conflat that has two stainless steel knife edges that cut into a copper gasket made of a special type of annealed copper.

It could be for
electron beam welder chamber
part of a particle beam line from lucas heights
part of a large secondary ion mass spectrometer
outgassing test chamber for making payloads for space launch.
vacuum deposition (aluminizing ) chamber
many more

cheers
Joe

[torana68 (Roger)]

Originally Posted by OzEclipse

It's a very expensive game. Sorry Torana. It sounded like you wanted to buy it. I was just trying to make sure you didn't make a very expensive mistake. Joe

Joe, no worries, I'm more interested in learning than spending, bit of a shame they are not more usefull to anyone considering their initial cost

[AlexN]

Buy them and build a large nuclear fusor.