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On Wednesday, October 29, 2003, at 05:54 PM, nano_tronics wrote:

about the no4 question what kind of vacuum are we taking about in

tubes with the getter are they in the high vacuum range or in the
ultra high vacuum range

NO4?? I didn't see that. I've no idea what you're talking about.

and if all precaution are take ex ( real good cleaning , glow
discharge, vacuum baking, ect ) can it be possible to go in the

range without degradation for a permanently seal vacuum tube made

low outgasing material or will it need to be pumped as long as

to stay in this range

Someone else who knows more should answer this, but I see no

why a good clean tube connected to a good HV system could not go UHV
once it's sealed and the getter fired properly. But my knowledge of
amateur-made permanently sealed UHV devices is sketchy at best!

the unit you are using is it torr, mbar or pas

Any time you see someone talking about vacuum in terms of 1 x 10

they are probably talking about torr. That's the only term I'm very
familiar with, although I know there are others, and it's what all

gauges I've seen are calibrated in. Even though Torr is a stupid

of measure. :)

- Gomez
.....................................................
Cryptographer Barbie says, "Gee, security is _hard_!"

about the no4 question what kind of vacuum are we taking about in CTR
tubes with the getter are they in the high vacuum range or in the
ultra high vacuum range

and if all precaution are take ex ( real good cleaning , glow
discharge, vacuum baking, ect ) can it be possible to go in the UHV
range without degradation for a permanently seal vacuum tube made of
low outgasing material or will it need to be pumped as long as need
to stay in this range

the unit you are using is it torr, mbar or pas

On Wednesday, October 29, 2003, at 12:35 PM, nano_tronics wrote:

here are my questions

1) how much ultimate vacuum i can achive with a diffusion pump

bellow

a) without a cold trap (and oil backstreaming problem that goes
with it )

Depending on the oil and how clean your rig is, probably 1x10^-

really don't want to run without a cold trap, in my opinion.

b) with a cold trap

Again "depending", perhaps 1x10^-8 with LN2.

c) a cheap an easy way to replace the LN2 coolant for the cold

Dry ice and acetone. You won't get as low an ultimate vacuum,

1x10^-6.

2) the pros and cons of air cooled VS liquid cooled diffusion

This should be self-evident.

liquid cooled
pro: better heat removal / condensation
con: complexity, source of cool water

air cooled
pro: simplicity, lower cost
con: not so good condensation of working fluid

3) on a liquid cooled VD pump can a radiator with a fan and a
circulator pump be used instead of running faucet water

I don't see why not. You might need a rather large radiator and

rig with a low ambient temperature to get the temperature down to

water temperature, which is often as cold as 50-60 degrees by the

the supply pipes run through. Or you might consider putting

chiller. Perhaps an old air conditioner, dehumidifier, or other AC

could be cannibalized and turned into a heat exchanger. But I've

told that air-cooled diffusion pumps work just fine, and virtually

leak detectors use them, and achieve very reasonable vacuums with

in the cold trap.

and at last

4) what is the ultimate vacuum that can be substained in a
permanently seal vessel with or without a getter
ex:( CRT tubes, magnetron tubes, radio tubes, ect, ect, ect )

There are too many possible variables to answer this. variables
include:

* how clean the vessel and contained materials are, including
fingerprints

* operating temperature

* what materials are used in your device - many materials out-gas

might have virtual leaks such as welds or tiny voids in a pinch-off

glass
to metal seal, especially in home-brew devices.

i hope i do not ask too much questions for my first time

Hah! Not possible- how else (other than reading certain hard to

books)
will you learn? Ask away!

I am only a beginner myself (and perhaps someone with more

may
disagree with some of my answers above - I bow to anyone's superior
wisdom.

Perhaps I shouldn't even give advice, my practical experience is
restricted
to working with really nice space simulation chambers (designed by
professionals), reading available literature, and listening to

more
knowledgeable than I.

I do have my own high vacuum system - a Veeco VE-300 that I

an
auction for the outrageously low sum of $20. It needed a _lot_ of
cleaning
though, and it didn't come with the bell jar or roughing pump. I
already had
a roughing pump though, and a friend gave me an even larger one. I

still
shopping around for a bell jar I can afford.

Fortunately, a generous friend with more experience than I, who

his own
home-brew high vacuum system, was willing to donate a lot of time

expensive materials (DC704, woohoo!) to the rebuild, so some time

winter
I should be able to finish the last details (it's waiting for me to
fabricate
a new mount for the new larger, roughing pump) and huff that sucker
down!

Best of luck with your system.

- Bill "Gomez" Lemieux

Was a 12 inch by 17 inch glass bell jar and screen on eBay a few
days ago... might still be there. Price was somewhere around $50
when I saw it last.

Was a 12 inch by 17 inch glass bell jar and screen on eBay a few
days ago... might still be there. Price was somewhere around $50
when I saw it last.

Ken Hunter

--- In VacuumX@..., Gomez <gomez@o...> wrote:

I am still shopping around for a bell jar I can afford.

- Bill "Gomez" Lemieux

Was a 12 inch by 17 inch glass bell jar and screen on eBay a few
days ago... might still be there. Price was somewhere around $50
when I saw it last.

Ken Hunter

--- In VacuumX@..., Gomez <gomez@o...> wrote:

I am still shopping around for a bell jar I can afford.

- Bill "Gomez" Lemieux

here are my questions

1) how much ultimate vacuum i can achive with a diffusion pump setup
bellow

a) without a cold trap (and oil backstreaming problem that goes
with it )

b) with a cold trap

c) a cheap an easy way to replace the LN2 coolant for the cold trap

2) the pros and cons of air cooled VS liquid cooled diffusion pump

3) on a liquid cooled VD pump can a radiator with a fan and a
circulator pump be used instead of running faucet water

and at last

4) what is the ultimate vacuum that can be substained in a
permanently seal vessel with or without a getter
ex:( CRT tubes, magnetron tubes, radio tubes, ect, ect, ect )

i hope i do not ask too much questions for my first time

Hi all, would anyone have any drawings (sketches) or plans that

vacuum system suitable for aluminising would be set up?
In other words how do all the bits and pieces join together?
The mechanicals and general wiring I would be ok with but valves,

route taken by the pipe work I am at a loss.
Failing any plans can a suitable book be recommended that is easily

Many thanks
Charles

I just got lost in thought. It was unfamiliar territory.

Hi James,
Can youy comment on the power requirements (volts, amps) of your
evaporation filament?

Thanks!

-Bill

--- In VacuumX@..., "James Lerch" <jlerch1@t...> wrote:

----- Original Message -----
From: "arcstarter" <arcstarter@y...>

Thanks Don, for your reply regarding the oxygen plasma.

This list sure has been quiet lately...

ON that note, let me recount my latest "WTF?" moment :)

I've just sealed the chamber on an 8" optic I'm coating, pump

went as
<snip>

----- Original Message -----
From: "arcstarter" <arcstarter@y...>

Thanks Don, for your reply regarding the oxygen plasma.

This list sure has been quiet lately...

ON that note, let me recount my latest "WTF?" moment :)

I've just sealed the chamber on an 8" optic I'm coating, pump down

James,

----- Original Message -----
From: "arcstarter" <arcstarter@...>

Thanks Don, for your reply regarding the oxygen plasma.

This list sure has been quiet lately...

ON that note, let me recount my latest "WTF?" moment :)

I've just sealed the chamber on an 8" optic I'm coating, pump down went as
usual. Did the glow discharge thing for 10 minutes or so (as usual). Opened
the diff pump valve, and the system dropped to 2e-5 torr on schedule (by the
time I manually spin the valve open, chamber is ready).

I do a quick cross check, everything is in order and its time to evaporate some
aluminum. I start slowly applying current to the filaments, I hear the step
down transformer starting to hum, I see the filaments start to glow dull red, I
wait for the magic moment when the aluminum goes from solid to liquid. In quick
succession each of the 6 filaments "blink to dark" for a moment as the aluminum
hits the transition temperature between solid and liquid. I now bring the
filament current up so each filament is glowing a bright orange/yellow color,
and watch as the "magic" happens.

Now the first off-nominal event rears its ugly head, as I'm watching the chamber
I hear two distinct "Clicks" from electrical relays changing position. My eyes
instinctively track to the position of the two clicks, and I see that the
Penning Ion Gauge is reading "Off Scale High", and the Thermocouple gauge is
indicating about a 1/2 torr chamber pressure! "UH OHHHH".

Now, in what feels like slow motion, I kill the filament power with one hand,
while the other starts spinning the diffusion pump to chamber valve handle as
fast as possible. I'm also thinking that perhaps this is why I see newer
diffusion pump valves are the 1/4 turn butterfly style, instead of the screw
type gate valve I have that takes "a gazillion" turns to close in an emergency!
:0

In what feels like an eternity, I have the diffusion pump valve about half
closed, and WOW look at that, the chamber pressure is back to normal
(2e-5torr)... I think to myself that's rather weird, and keep on spinning the
diffusion pump valve towards to the closed position...

Finally I've got the valve closed, and the chamber vented, lets have a look an
see what we see inside the chamber.

#1 Everything in "line of sight" of the filaments is the blackest black I've
ever seen!
#2 My first thought is "wow, this would be a great flat black for spider vanes /
focuser tubes"
#3 I drag my finger across some to see if it will wipe off, nope, seems pretty
well stuck in place.
#4 finally I think "what happened, what was different this time?"

Now, follow me on a mental flash back of early that day while I was clearing a
path to the alluminizer :)

I was moving some sheet metal out of the way when I slipped and cut my thumb.
Now, like most cuts, you stop what your doing and have a look, wondering "How
bad is it?" OK, its bad enough to need a bandage... (grumble)

So, as I scrounge around in the medicine cabinet for a band-aid, the Wifely
person comes along to see what I'm doing, and so it begins..

(Note WP = Wifely person)
WP: "What are you doing"
Me: "lookin for a band-aid"
WP: "Are you OK?"
ME: "Yea"
WP: "Let me see"
ME: "I'm OK, don't worry about it"
WP: "LET ME SEE IT!"
ME: Sigh, "OK"
WP: "You NEED stitches"
ME: Sigh, "No, I'm OK I need a band-aid"
WP: "You NEED a Tetanus shot"
ME: Sigh, "Nah, I had one a 'while' ago"
WP: "Well, at least let me put some Neosporin on it"
ME: "OK, sure, but I got to get back to work.."

After having my thumb properly treated and bandaged, I go back to work, where it
appears I promptly cover the tungsten filaments in an ever so thin coating of
Neosporin Ointment (Evil Stuff!). This petroleum product seems immune to plasma
cleaning, and is rather content to hang around in a rather good vacuum until
slightly heated.

Once this stuff is inside a vacuum chamber, forget about normal cleaning
methods! To get rid of the last traces (after six or eight failed coating
attempts!) I had to resort to Sandpaper, two cans of Automotive Brake Cleaner, A
heat gun, and evacuating the chamber empty while running naked tungsten
filaments at their highest current setting and repeating several tries.

Finally, at about 3am, I finally get that 8 inch mirror coated!

Have any of the amateur telescope metallizers ever attempted to
aluminize any mylar or similar plastics?

I coated some plastic flash light reflectors once, does that count? :)

Take Care,
James



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Bill,

Thanks Don, for your reply regarding the oxygen plasma.

This list sure has been quiet lately...

Have any of the amateur telescope metallizers ever attempted to
aluminize any mylar or similar plastics?

Don will you be at the Indy coating show?

-Bill

Bill,

The air plasma (N2 + O2) oxidizes the carbon to CO2. This is the
basis of a lot of plasma cleaning - the oxidation produces a

oxide.

Don

**

Guys,
This propane-tank vacuum metallization system of James Lerch at
is by far one of the coolest
hobby devices I have ever encountered!

Thanks for posting that and thanks for the good work! You are
indeed a bad influence on us susceptable types...

Now, I've been digging around over at the SVC site and have
encountered a few interesting documents. One is
, sort of a brief (66) page
history of vacuum coating. On page 41, reference E-27 the author
refers to John Strong coating the Palomar mirror with lanolin prior
to metallization. Looks like this is a possible alternate approach
to the meticulous cleaning phases some of the ATMers are doing?
Apparently the O2 glow plasma will burn it off well enough, but I
guess I would have thought that would leave carbon etc behind on

surface?

I've misplaced my own copy of Strong's Experimental Physics.
Might have to buy a replacement.

Other interesting historical accounts from the masters of the
vacuum costing field are at:


Comments? Let me qualify my own comments by the fact that I have
no idea what I am doing but I do it anyway. :)

-Bill



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--
____________________________________
Donald M. Mattox
Technical Director
Society of Vacuum Coaters
71 Pinon Hill Place NE
Albuquerque, NM 87122-1914

Telephone 505/856-7188
FAX 505/856-6716
E-mail donmattox@s...
WebSite

Bill,

Guys,
This propane-tank vacuum metallization system of James Lerch at
is by far one of the coolest
hobby devices I have ever encountered!

Thanks for posting that and thanks for the good work! You are
indeed a bad influence on us susceptable types...

Now, I've been digging around over at the SVC site and have
encountered a few interesting documents. One is
, sort of a brief (66) page
history of vacuum coating. On page 41, reference E-27 the author
refers to John Strong coating the Palomar mirror with lanolin prior
to metallization. Looks like this is a possible alternate approach
to the meticulous cleaning phases some of the ATMers are doing? Apparently the O2 glow plasma will burn it off well enough, but I
guess I would have thought that would leave carbon etc behind on the
surface?

I've misplaced my own copy of Strong's Experimental Physics. Might have to buy a replacement.

Other interesting historical accounts from the masters of the
vacuum costing field are at:


Comments? Let me qualify my own comments by the fact that I have
no idea what I am doing but I do it anyway. :)

-Bill



To unsubscribe from this group, send an email to:
VacuumX-unsubscribe@...



Your use of Yahoo! Groups is subject to