Meditec MLR/W Specs

[JPC]

I'm hoping this is the right spot. I have an old Meditec MLR/W argon laser tube on the rail with optics. I'm sure it's probably dead, but I just can't let it go without at least firing it up first. I used to have a power supply for it but I sold it in a time of need quite a while ago.

The only Meditec supply I've found recently is $750, way more than I care to pay, and also 3 Phase. The one I had originally was a single phase 220/240 range. Probably one of the guys on this forum bought it from me

It's water cooled with brewster stems and external optics. I have the start board and blocking diodes for it, so I really plan on just doing a really simple resistance type supply for it first. I would like to get some idea on the specs first though. Tube voltage and current would be a good place to start if that's even info someone would have anything else would be a bonus.

I know the odds are pretty low on a tube of this age, but if I can get a plasma going and get it lasing I might be up for building a pass bank supply for it, or maybe try building something new and use IGBTs.

Thanks for any info someone might have.

JonC

[mixedgas]

Its actually a licensed clone of a ~ 3watt tube by Continental Laser, and derived from a US Air Force multiyear study for a 5 watt ion laser. I've had those in my collection before. Tube drop is ~170V and I max is ~25 amps for short periods of time. You really do not want to do a "Simple resistance supply" for that tube. If you over open it up, the bores have a nasty habit of dusting and they are BeO inside, so DON'T open it up. It ran Quasi CW, idling at a few amps and "popping up" to treatment current. On the two I have opened up, I found the dispenser cathodes to be very fragile, hence getting it on a current regulated supply is imperative at its age. The cathode has a minimum wattage of 75 watts and there is a getter inside the end bell. I long ago tossed all the data. It will, if it were remotely close to the proper pressure inside, run off a 68B or a Lexel 88 Supply. However I don't remember them having hard sealed windows, so all bets are off.

There is very little difference between a 3P Meditech Supply and a Single Phase one, basically just the how the diode bridge is arranged.

Steve

[JPC]

Its actually a licensed clone of a ~ 3watt tube by Continental Laser, and derived from a US Air Force multiyear study for a 5 watt ion laser. I've had those in my collection before. Tube drop is ~170V and I max is ~25 amps for short periods of time. You really do not want to do a "Simple resistance supply" for that tube.

Interesting origins. It couldn't be an easier one to test, right? Hmm I'll have to think about my options then, but thank you for the basic specs.

If you over open it up, the bores have a nasty habit of dusting and they are BeO inside, so DON'T open it up.

The BeO hazard has always kept me handling it very tenderly (just in case the gas tube, delicate brewster stems and alignment hadn't!), someone had mentioned it to me long ago and it stuck pretty good Thanks for the additional warning though. As much as I like fiddling with lasers from time to time they're not worth life or limb.

It ran Quasi CW, idling at a few amps and "popping up" to treatment current.

I'm good with that, I have no plans to do laser shows with it. I mostly want to see if it's alive, and if it is, I can figure out what to do with it at that point. I still have my holography handbook around somewhere so maybe I'd dust that off.

On the two I have opened up, I found the dispenser cathodes to be very fragile, hence getting it on a current regulated supply is imperative at its age. The cathode has a minimum wattage of 75 watts and there is a getter inside the end bell. I long ago tossed all the data. It will, if it were remotely close to the proper pressure inside, run off a 68B or a Lexel 88 Supply. However I don't remember them having hard sealed windows, so all bets are off.

I'll add those PSUs to my possible options list. At this point maybe I should be investing my time and money into a YAG,DPSS or diode project or re-hashing my CuCl project to feed my laser habit, but I'm having a hard time letting this argon go for some stupid reason, but I've not really owned a ton of laser equipment like some folks. Maybe I should just reuse the optics rail for another project. I've attached photos of the brewster stems.

There is very little difference between a 3P Meditech Supply and a Single Phase one, basically just the how the diode bridge is arranged.
Steve

Good to know, thanks for the information Steve!

[mixedgas]

One of the reasons Continental Laser went out of business is the relative ease of refurbing the tube. (So I'm told, by a former employee) You'll note the Brewster stem is on a Cajon connector and the Cathode end bell is huge. So its easy to cut open the tube and re=cathode it, if your doing a batch of them. Continental had all the overhead for manufacturing the stems, tubes, power supplies, etc. The rebuilder only needed a welder, tube oven, and pumping station. So..... No overhead for a rebuilder.

That is a optically contacted sealed window, so there is a slim chance....

What part of "neu orc" are you located in? I may know someone near you....

Steve

[JPC]

Well it sounds like I could use it as an excuse to build some custom equipment like a well filtered glove box, tube oven and buy a diffusion pump in the worst case scenario, I'm not sure, yet, if I'm that committed to it though. Is there any good documentation or papers on laser reprocessing or is it mostly through the skilled and experienced? I'm guessing the odds of finding a cathode to be slim to none anyways.

I'm located about 45 minutes south of Albany in the Kingston/Saugerties area.

Is this Steve R. (the one in the LaserFAQ)? If it is you helped me get to a running Co2 laser many years ago.

JonC

[mixedgas]

New Cathodes are 250$ each, but usually you have to buy 10 just to get them. The issue is the cathode is not directly welded to the feedthroughs, intermediate welds of nickel and molybdenum are needed between the Kovar and the Tungsten matrix. That fact you will not find on line just anywhere. If you do not have the right weld sequence, the cathode (it is not just tungsten there) gets brittle at the weld and will shear off in the first few runs.

Cathodes are not stocked. They start out as a chunk of plastic loaded with metal dust and other active materials. The block gets CNC machined to shape then fused in a furnace. Hence no one talks much about cathode materials.

A diff pump does not get you to a high enough vacuum to activate the cathode surface. I have to get to 10-8 or better just to get the process started. That means turbo and ion pumps. The residual oil vapor from the diff pump will quickly poison the tube. Another thing learned the hard way is you have to use cold welded seals on the fill stem, valves won't cut it, any trace of oxygen or any hydrocarbon quickly ruins the tube.

Activation is not something I'm going to disclose in public. I really can not for legal reasons. It involves very slowly raising the current over a day or more while maintaining certain conditions. The cathode manufacturer will ask you to sign a NDA for the process.

From publically available info: The first cleaning mix is 8:2:1 Helium, Krypton, Argon, once activated. (That patent expires in a few years, but the disclosed activation sequence is wrong for your laser) The second processing mix is mostly krypton, then you transition to argon. The Heavier gas cleans the bore better. But It does not always flow or start well, hence the Helium.

One would really, really, really, like to have a helium leak detector or a residual mass analyzer for checking the welds and seals before one tries this. The developers of these tubes all had high power microwave tube labs or similar experience at their disposal.

All this occurs after the tube has spent time in a wet hydrogen furnace and while in a oven on the bakeout station. The windows get their own ovens because the crud goes there first all during pumpdown and processing. The hydrogen reduces any oxide in the tube to clean metal.

Best to just leave it alone. There are certain tubes I'll mess with, and there are some I've learned to just leave alone. I don't have access to orbital TIG any more. So I stick to certain tubes.

I had to talk my friend into buying a ion tube lab at Auction to learn all this. Somehow he is still my friend, (crosses fingers, says prayer) and we did get a few tubes done and in service.

I'd rather do a Hene or CO2 from scratch, its easier.

The basic doc is ~150$ printed from Microfilm by the National Technical Information Service. It is the final report to the Air Force by Dr. Bridges. It fills a few three ring binders.

And yes, I am Steve R.

Steve

[JPC]

New Cathodes are 250$ each, but usually you have to buy 10 just to get them. The issue is the cathode is not directly welded to the feedthroughs... ...The hydrogen reduces any oxide in the tube to clean metal.

That sounds like a really technically amazing process and certainly is not as straight forward as 'regas the tube' makes it sound!

Best to just leave it alone. There are certain tubes I'll mess with, and there are some I've learned to just leave alone. I don't have access to orbital TIG any more. So I stick to certain tubes.

I'll just work on getting it fired up and if it doesn't work, then that's that. Worst case being that if I build or find a PSU and the tube doesn't work, I'll still have a nice high power constant current supply and optical set for future use.

I had to talk my friend into buying a ion tube lab at Auction to learn all this. Somehow he is still my friend, (crosses fingers, says prayer) and we did get a few tubes done and in service.

Now that's friendship!

I'd rather do a Hene or CO2 from scratch, its easier.

My latest was the CuCl I mentioned, the EMF from my rotary gap took out the video camera, but I did manage to capture some intermittent lasing from it before that happened. I wanted to try a straight up CVL. I hunted down some pricing on a dense alumina bore which didn't seem outrageous and last week I was reading some documentation on PRAMANA CVL IGBT supplies (PDF) and step profile thermal insulation density(PDF) and it got me all excited about that type again.

The basic doc is ~150$ printed from Microfilm by the National Technical Information Service. It fills a few three ring binders.

From your summary above I'm sure it's worth all of that and more just for the general process information in it.

And yes, I am Steve R.
Steve

Awesome and thank you, the Co2 laser was a good experience and a lot of fun. It was a really big deal to me when I finally got it running and sealed my fate to keep coming back to this as a hobby. You might remember the one in the attached picture, although it's quite fuzzy.

I'm glad to find some of the laserists I remember are still doing things, I lost track years ago and while Sam's Laser FAQ was still everywhere around I didn't see much from the pro/hobby laser crowd, I thought they had just dried up or went to secret communities.

[buffo]

I'm glad to find some of the laserists I remember are still doing things, I lost track years ago and while Sam's Laser FAQ was still everywhere around I didn't see much from the pro/hobby laser crowd, I thought they had just dried up or went to secret communities.

Come to SELEM this summer and you'll likely run into many of those old laserists, including Steve.

We didn't go to a secret community, we went to PL!

Adam