argon laser tube of copper?

[photonaholic]

Lets just say a helium neon laser is tons simpler, and even with all the resources I had available to me at corning glass works at the Pyrex scientific apparatus division in Big Flats, NY my first attempts failed.

And that was with master glass craftsmen with million dollar plus glass working lathes at my disposal.

Good luck!

 

[scoobydoo6v92]

Other then the fact that quartz is a real witch to work with in a home lab (needs oxy-hydrogen flame) Whats wrong with the CR?

Pictures? I can quickly tell you a lot about CRs, but I need some images...

Whats broke on the SP?

I've helped one fellow repump a CR once, its a bit involved...

Steve

Yes I have to find the pictures I took of the tube. Basically it is broken where the metal hose from the ballast tank is welded to the glass port that connects to the ballast tank. I was told you can take out all the allen screws and take the ends of the tube off. Not sure if that is true. It is a super graphite CR-15. I know it is old but it is a neat looking laser and would love to have it run again. My dream anyway. Thanks

 

[scoobydoo6v92]

actually the tube isn't broken. The weld between the glass and metal is just seperated needs to be rewelded.

 

[LSRFAQ]

actually the tube isn't broken. The weld between the glass and metal is just seperated needs to be rewelded.

OK, I only wish it were that easy...

Thats a glass to metal seal, you buy one and replace it. A analogy, a basic glass is made of oxides dissolved in a flux, or binder. The goal in making a glass to metal seal is to find a metal that matches the expansion of the glass within 6-7 parts per million over the working temperature range or it will crack as it cools down from fusion. This metal is typically kovar for pyrex, pure molybdenum or for quartz, and either dumet or fernico for lead glass.

The first step is to machine the metal to shape. This has to have a very good surface finish or there will be small microscopic cracks that leak. The next step is to load it into a hydrogen furnace, with pure hydrogen and a touch of water vapor, and heat the metal red hot. The hydrogen removes any organic crud on the metal and then slowly reacts with the oxide layer on the metal to strip it.

That gets cooled down, and you have a brilliant, shiny, piece of metal.

Now here is the tricky part (known in the business as "mousey grey" , you need a very thin, but tough, uniform layer of oxide on the outside of the metal for the glass to dissolve into. So your going to oxidize the metal, but NOT the brown iron oxide rust of your car... You need the special "mousey grey" oxidation of different materials in the kovar alloy and its done in a furnace with a touch of oxygen... And its a shade of light grey that looks like a certain species of house mouse... Get it wrong and your seals are mickey-mouse. I've made quite a few that were bad, except its not funny when your tube starts leaking hours or days after you think its perfect..

I now buy them unless I'm just sealing a thin wire in the glass.

Odds are your quartz tube is sealed to pyrex via a couple of rings of of intermediate glasses, each with a slightly different expansion. Then the seal on the ballast tank is pyrex to kovar..

Quartz expands at 5.5x10 -7 cm/cm , pyrex expands at 88 x10-7cm/cm
So you need some intermediate glasses in there, each about 7 parts per million different from the last one..

Buying small amounts of kovar is fairly easy, buying the intermediate glasses is nearly impossible since the cold war is over.. So you buy a completed seal and fuse it in, them make a metal sleeve to slide over the metal tubing, which is brazed.

So the odds are you you have quartz fused to a graded seal followed by a pyrex to metal seal. A glassblower can spot the graded seal by holding it between to disks of polaroid polarizer and looking how the stress in the glass changes the polarization of the light.. The glassblower then cuts the broken glass to metal seal off but leaves the graded seal.. This is done using a metal blade impregnated with diamond dust, and not the ones at home depot.. Those don't work.. (ask me how I know..)

Now, those seals on your coherent usually pop during transport from stress, not during operation.. So the next step is to determine if your tube was running when when this happened (hopeless case) or if it was during transit.
If it was during transit, you have a small chance of recovering the tube, depending on how many hours it had on it...

You may some threaded fittings under plastic caps on your gas ballast. Those are valve actuators for pumping the tube and adjusting its pressure. They kinda work like a shrader valve on a tire, only a lot better as they need a leak rate so small, its unimaginable.. If there are two of them, one is for vacuum during pumpdown and the other is for backfilling the gas refill system..

At this point you find a nearby university with a glassblower and buy him a beer, lots of beer.. Glassblowers are known as " thirsty dragons" for a reason.. Besides they tend to like to make neat teaching demos for students, like Prinz Rupert's drops and simple neon plasma tubes.. He'll take one look at things and say yes or no...

Then you find a hot lab furnace or some massive heat tapes big enough to hold your tubes.

Need some pics of the cathode end of the tube.. I can tell a lot from the colors..

You realize this is a learning experience.. Not a way to make a long life, working laser..
Your far better off to cut down the coherent resonator, reuse the optics mounts, and make a pulsed oxygen or pulsed argon laser.. Or adapt the power supply to another head..

The glass to metal seal is about 60$. If , in a rare case, they did quartz to metal direct (moly seal, well bomco gets about 500$ for those)

There is always torrseal epoxy, but that would be a lot of work for a tube that only lasts a few weeks at best..

There would be a slim chance laser innovations or holospectra has a CR15 laying around, but very slim.. Much better to adapt to a modern ceramic tube.. Coherent designed their ceramic tubes around their graphite magnets, so in some cases... You have a easy shot, usually by lathing and milling some adapters...

I set you up with another option via PM, I suggest you follow it for a while.. If that doesn't work, I have a medical engineer friend who has a pile of small tubes.. About 65 or so.. Having a teenager of his own, he could probably be persuaded... But start with the other option I sent you..

Now dont every body go PMing me looking for 50-100$ tubes, it wont happen. Since this is for a educational situation, and I'm a former teacher, I'm bending the rules just once...

85SVG raw tubes are 550$ and shipping. 85SVG heads, and we have about 20 of them, are 1500 plus shipping. I90 MRAs, when I can get the tubes, are about 900$ eacg..

How about neon for your student demos??

Do you have a neon sign shop nearby? They almost never have the level of vacuum needed for a CW ion laser, but nor the right kind of glassblowing skills for pyrex, but watching the process is fascinating, it can be done with some minor changes in a school lab, the lead glass working is fairly easy for a beginner to work with, and you'd get a idea of what would need to be done on a big tube. Besides you'd just need a roughing pump and a small home made oven and some cheaper gasses. Air works just fine for a demo tube..
I learned much from a neon guy when I was 16. He would have hired me, but he wanted out of it because long term exposure to the toxic phosphors used in the older 1960s-1970s white tubes gave his glassblower a long nasty death.. If you just do the pure gasses with clear glasses, its a very safe process..

Old roughing pumps are cheap and nearly every hamfest I go to, I see a old welch duoseal laying around..

Steve

 

[LSRFAQ]

actually the tube isn't broken. The weld between the glass and metal is just seperated needs to be rewelded.

OK, I only wish it were that easy...

Thats a glass to metal seal, you buy one and replace it. A analogy, a basic glass is made of oxides dissolved in a flux, or binder. The goal in making a glass to metal seal is to find a metal that matches the expansion of the glass within 6-7 parts per million over the working temperature range or it will crack as it cools down from fusion. This metal is typically kovar for pyrex, pure molybdenum or for quartz, and either dumet or fernico for lead glass.

The first step is to machine the metal to shape. This has to have a very good surface finish or there will be small microscopic cracks that leak. The next step is to load it into a hydrogen furnace, with pure hydrogen and a touch of water vapor, and heat the metal red hot. The hydrogen removes any organic crud on the metal and then slowly reacts with the oxide layer on the metal to strip it.

That gets cooled down, and you have a brilliant, shiny, piece of metal.

Now here is the tricky part (known in the business as "mousey grey" , you need a very thin, but tough, uniform layer of oxide on the outside of the metal for the glass to dissolve into. So your going to oxidize the metal, but NOT the brown iron oxide rust of your car... You need the special "mousey grey" oxidation of different materials in the kovar alloy and its done in a furnace with a touch of oxygen... And its a shade of light grey that looks like a certain species of house mouse... Get it wrong and your seals are mickey-mouse. I've made quite a few that were bad, except its not funny when your tube starts leaking hours or days after you think its perfect..

I now buy them unless I'm just sealing a thin wire in the glass.

Odds are your quartz tube is sealed to pyrex via a couple of rings of of intermediate glasses, each with a slightly different expansion. Then the seal on the ballast tank is pyrex to kovar..

Quartz expands at 5.5x10 -7 cm/cm , pyrex expands at 88 x10-7cm/cm
So you need some intermediate glasses in there, each about 7 parts per million different from the last one..

Buying small amounts of kovar is fairly easy, buying the intermediate glasses is nearly impossible since the cold war is over.. So you buy a completed seal and fuse it in, them make a metal sleeve to slide over the metal tubing, which is brazed.

So the odds are you you have quartz fused to a graded seal followed by a pyrex to metal seal. A glassblower can spot the graded seal by holding it between to disks of polaroid polarizer and looking how the stress in the glass changes the polarization of the light.. The glassblower then cuts the broken glass to metal seal off but leaves the graded seal.. This is done using a metal blade impregnated with diamond dust, and not the ones at home depot.. Those don't work.. (ask me how I know..)

Now, those seals on your coherent usually pop during transport from stress, not during operation.. So the next step is to determine if your tube was running when when this happened (hopeless case) or if it was during transit.
If it was during transit, you have a small chance of recovering the tube, depending on how many hours it had on it...

You may some threaded fittings under plastic caps on your gas ballast. Those are valve actuators for pumping the tube and adjusting its pressure. They kinda work like a shrader valve on a tire, only a lot better as they need a leak rate so small, its unimaginable.. If there are two of them, one is for vacuum during pumpdown and the other is for backfilling the gas refill system..

At this point you find a nearby university with a glassblower and buy him a beer, lots of beer.. Glassblowers are known as " thirsty dragons" for a reason.. Besides they tend to like to make neat teaching demos for students, like Prinz Rupert's drops and simple neon plasma tubes.. He'll take one look at things and say yes or no...

Then you find a hot lab furnace or some massive heat tapes big enough to hold your tubes.

Need some pics of the cathode end of the tube.. I can tell a lot from the colors..

You realize this is a learning experience.. Not a way to make a long life, working laser..
Your far better off to cut down the coherent resonator, reuse the optics mounts, and make a pulsed oxygen or pulsed argon laser.. Or adapt the power supply to another head..

The glass to metal seal is about 60$. If , in a rare case, they did quartz to metal direct (moly seal, well bomco gets about 500$ for those)

There is always torrseal epoxy, but that would be a lot of work for a tube that only lasts a few weeks at best..

There would be a slim chance laser innovations or holospectra has a CR15 laying around, but very slim.. Much better to adapt to a modern ceramic tube.. Coherent designed their ceramic tubes around their graphite magnets, so in some cases... You have a easy shot, usually by lathing and milling some adapters...

Steve

 

[xXAxHillbillyXx]

OK, I only wish it were that easy...

Thats a glass to metal seal, you buy one and replace it. A analogy, a basic glass is made of oxides dissolved in a flux, or binder. The goal in making a glass to metal seal is to find a metal that matches the expansion of the glass within 6-7 parts per million over the working temperature range or it will crack as it cools down from fusion. This metal is typically kovar for pyrex, pure molybdenum or for quartz, and either dumet or fernico for lead glass.

The first step is to machine the metal to shape. This has to have a very good surface finish or there will be small microscopic cracks that leak. The next step is to load it into a hydrogen furnace, with pure hydrogen and a touch of water vapor, and heat the metal red hot. The hydrogen removes any organic crud on the metal and then slowly reacts with the oxide layer on the metal to strip it.

That gets cooled down, and you have a brilliant, shiny, piece of metal.

Now here is the tricky part (known in the business as "mousey grey" , you need a very thin, but tough, uniform layer of oxide on the outside of the metal for the glass to dissolve into. So your going to oxidize the metal, but NOT the brown iron oxide rust of your car... You need the special "mousey grey" oxidation of different materials in the kovar alloy and its done in a furnace with a touch of oxygen... And its a shade of light grey that looks like a certain species of house mouse... Get it wrong and your seals are mickey-mouse. I've made quite a few that were bad, except its not funny when your tube starts leaking hours or days after you think its perfect..

I now buy them unless I'm just sealing a thin wire in the glass.

Odds are your quartz tube is sealed to pyrex via a couple of rings of of intermediate glasses, each with a slightly different expansion. Then the seal on the ballast tank is pyrex to kovar..

Quartz expands at 5.5x10 -7 cm/cm , pyrex expands at 88 x10-7cm/cm
So you need some intermediate glasses in there, each about 7 parts per million different from the last one..

Buying small amounts of kovar is fairly easy, buying the intermediate glasses is nearly impossible since the cold war is over.. So you buy a completed seal and fuse it in, them make a metal sleeve to slide over the metal tubing, which is brazed.

So the odds are you you have quartz fused to a graded seal followed by a pyrex to metal seal. A glassblower can spot the graded seal by holding it between to disks of polaroid polarizer and looking how the stress in the glass changes the polarization of the light.. The glassblower then cuts the broken glass to metal seal off but leaves the graded seal.. This is done using a metal blade impregnated with diamond dust, and not the ones at home depot.. Those don't work.. (ask me how I know..)

Now, those seals on your coherent usually pop during transport from stress, not during operation.. So the next step is to determine if your tube was running when when this happened (hopeless case) or if it was during transit.
If it was during transit, you have a small chance of recovering the tube, depending on how many hours it had on it...

You may some threaded fittings under plastic caps on your gas ballast. Those are valve actuators for pumping the tube and adjusting its pressure. They kinda work like a shrader valve on a tire, only a lot better as they need a leak rate so small, its unimaginable.. If there are two of them, one is for vacuum during pumpdown and the other is for backfilling the gas refill system..

At this point you find a nearby university with a glassblower and buy him a beer, lots of beer.. Glassblowers are known as " thirsty dragons" for a reason.. Besides they tend to like to make neat teaching demos for students, like Prinz Rupert's drops and simple neon plasma tubes.. He'll take one look at things and say yes or no...

Then you find a hot lab furnace or some massive heat tapes big enough to hold your tubes.

Need some pics of the cathode end of the tube.. I can tell a lot from the colors..

You realize this is a learning experience.. Not a way to make a long life, working laser..
Your far better off to cut down the coherent resonator, reuse the optics mounts, and make a pulsed oxygen or pulsed argon laser.. Or adapt the power supply to another head..

The glass to metal seal is about 60$. If , in a rare case, they did quartz to metal direct (moly seal, well bomco gets about 500$ for those)

There is always torrseal epoxy, but that would be a lot of work for a tube that only lasts a few weeks at best..

There would be a slim chance laser innovations or holospectra has a CR15 laying around, but very slim.. Much better to adapt to a modern ceramic tube.. Coherent designed their ceramic tubes around their graphite magnets, so in some cases... You have a easy shot, usually by lathing and milling some adapters...

Steve

Yeah.. DUH everyone knows that! :thinking:
lol j/k

 

[Greenmechanic]

Yeah.. DUH everyone knows that! :thinking:
lol j/k

ROTFL
:crackup::crackup: My thought exactly.
There is no question that LSRFAQ is very well versed on this subject. :wave:

 

[photonaholic]

Having worked in the glass industry and lighting industry in the past, I can vouch for this.

It is a complex science / art.

 

[LSRFAQ]

Having worked in the glass industry and lighting industry in the past, I can vouch for this.

It is a complex science / art.

Because when I was 15-16 and wanting a laser, diodes were still 1-15 mW and IR only. I biked it 15 miles each way on weekends to the university library to learn about glass and ceramics, and read Laser Focus World and Photonics Spectra. The librarian finally figured out I was harmless and would let me stay without calling the university cops. And by bike I mean NO engine..

All in the hopes of building a HENE or a Argon. A local neon guy took me under his wing, but there was no way Corning 80 could become a argon, well, maybe for 5 seconds before it implodes.

My dad said he would buy me a HENE if I did a B or better average for the year. I had to bust my butt because my local school district sucked, and Dad put in massive overtime so I could go to a small religious school. I worked my summers painting the building and polishing floors and repairing the science lab and audio stuff, to help pay the tuition.. The physics teacher was a hard A$$ ex Navy Nuc, with a masters in EE, and the Chem teacher wrote out Schrodinger's equation on the board the first day of Class.. (Thank You SIRS!)

Thanks Dad, R.I.P...

The hene arrived as a kit from Heathkit with a tiny bar code reader tube,and the kit cost 300$. And YES, I had to solder the switching power supply by hand, took two days. It had a modulator in so it could vary the tube current about half a mA and you could get audio onto the beam. The Heathkit laser course was another 100$ and he got that too. A whopping .9 or so mW.


Back then a 1-5 mW hene from Metrologic was about 350-550$ depending on options.

Steve

 

[photonaholic]

I still have my old "merideth instruments" HeNe... Ah those were the days.

 

[jarrod694]

If you must use a metal for the bore, use stacked aluminum disks and and oxidize them. The AL oxide does not conduct, but you need a huge number of disks. The disks are then stacked in a water cooled alumina ceramic tube. That has been done, but they are hard to start.

A more modern tube is a set of copper disks mounted about 1/4" apart with a tungsten core brazed to the disk, the copper does the cooling, and the tungsten holds off the plasma. The copper disks have folds in them to spread the stress to the outer ceramic tube.

Your talking a excitation 350 to 1000 watts per centimeter of length for a modern CW argon. Pulsing makes use of duty cycle to allow the heat to escape.

The easiest home made argon that could run CW would be a quartz tube with graphite disks. The graphite heats to glowing hot and the cooling is by radiative heat into the cooling water around the tube. If you don't care about lifetime, the earliest argons were quartz bores, but the quartz dies very quickly and its hard to seal the cathode lead throughs direct to quartz.

A pulsed home made argon is possible. Pulsed Oxygen is a MUCH better candidate for a visible laser as is pulsed iodine vapor.


See:

:: Pulslaser ::


Sam's Laser FAQ - Home-Built Pulsed Multiple Gas (PMG) Laser

A Cold Cathode Pulsed Gas Laser" by R. K. Lomnes and J. C. W. Taylor in: Review of Scientific Instruments, vol 42, no. 6, June, 1971

The Scientific American Helium-Mercury design works, but your talking about 15 mW of average power.

I'd strongly suggest you read Lomnes and Taylor before starting any pulsed or cw gas laser construction.

This is lot of work. I've repumped and rebuilt existing tubes and its NOT easy, start with a N2 laser, then a N2 pumped dye laser, and work your way up. To really ARGON work CW you need a lathe, maybe a tig welder, and a turbo-pump roughing pump combination. I have a 270 litre per second ion pump, a turbo pump and two roughers and it can take me 24-48 hours to get to the level of vacuum needed for a cw ion laser, to process the cathodes. Pulsed lasers are far less stringent, you only need to get to .01 or .001 torr, I need to hit 10 to the minus 7 torr, minimum.

But a warning, a fingerprint or other crud in the wrong place inside the tube and your effort is wasted with argon.

Yes, welding grade argon works OK, sorta. . It works great for pulsed duty, but any oxygen or nitrogen or water vapor kills cw lasing. My rare gasses are about 700$ a bottle for CW grade gas. The difference is they bake out the tanks and purge them for scientific grade. Welding grade tanks are not flushed or baked, are often rusty on the inside, and who knows what was in them, before they repainted them for argon use. Helium, however, is reasonably pure from cheap tanks.

And yes, JDSU/uniphase makes their tube's main body from a copper alloy, with ceramic parts brazed in, but glass to metal and ceramic to metal seals are very tricky.

If you really want the details, a Air Force technical report by Bridges and Halstad gives the details of 4 early tube designs, but its 140$ for a hard copy and is NOT available as a free pdf. I have it. It would be hard for a non US citizen to get it.

One of these days I'll rewrite the PMG chapter and send it to Sam, but for now, its fairly correct.

Steve

Hi Steve,

You mention the use of copper disks with tungsten cores, in modern designs. Does the tungsten come in contact with the discharge? If so, how does the conductivity of the tungsten not interfere with the discharge?

You also said that pulsed oxygen is a much better candidate (and pulsed iodine) for a visible laser than is pulsed argon. Why? Does pulsed oxygen perform well?

 

[Cyparagon]

I think ionized argon has a much lower resistance than tungsten, especially when the tungsten is hot (seeing as it's encasing an arc)

 

[LSRFAQ]

I think ionized argon has a much lower resistance than tungsten, especially when the tungsten is hot (seeing as it's encasing an arc)

The tungsten disks are mounted in copper heat spreaders brazed to the wall of a alumina tube. The disks are spaced about 1-2 cm apart, and yes, the tungsten constrains the plasma. The copper heat spreaders have a diffuse array of smaller holes to act as a gas return, because in all ion lasers, cataphoresis pumps the gas towards the anode. The disks are floating, and thus charge up to the local potential of the discharge. I'll try to post a picture of a smashed tube in about two weeks.

Steve