Remember to exercise those argons!

[swamidog]

Hey Swami, would a roof prism from a binocular work? Oh, do you have a link to your videos? It's been awhile since I've seen one of those bad boys.

it's worth a try!

here's a link you my youtube channel: https://www.youtube.com/user/swamidog

 

[n2stuff]

it's worth a try!

here's a link you my youtube channel: https://www.youtube.com/user/swamidog

Thanks for the link. I love your videos they are so cool.

 

[paul1598419]

Yeah, I have many prisms too. Don't see as many around as I used to. Have you gotten a dove prism yet?

 

[swamidog]

Yeah, I have many prisms too. Don't see as many around as I used to. Have you gotten a dove prism yet?

no, but it's on my list to use as an image rotator.

 

[paul1598419]

They are great for that, as I'm sure you are already aware. One rotation of the prism equals two rotations of the image. I have a fairly large one at 6 inches on the long axis.

 

[LtKernelPanic]

*looks at the date of the last maintenance burn* *looks at today's date* DOH!

I knew I was forgetting something the other day...

 

[n2stuff]

I knew I was forgetting something the other day...

I can't remember the last time I fired mine up:thinking: The tube only has about 50-60 hours on it and puts out 166mW at full tilt.

 

[paul1598419]

Yeah, I've been procrastinating too. I have to unpack it all and set it up then run the thing for a few hours on low. I need to test the output power next time I do get around to it. I know the tube in mine has been replaced as it came from a guy who worked at Uniphase. It has low hours as well.

 

[n2stuff]

Yeah, I've been procrastinating too. I have to unpack it all and set it up then run the thing for a few hours on low. I need to test the output power next time I do get around to it. I know the tube in mine has been replaced as it came from a guy who worked at Uniphase. It has low hours as well.

Mine came from a guy that bought a pallet load of Argon lasers. I think this one was only tested and never made into service. It's sitting on its own shelf in my office so I have no reason not to fire it up anytime. It does 6 lines just off idle.

 

[ultimatekaiser]

Ha, I can’t even remember the last time i ran my white light....probably been at least a year.... I should probably dig it out and fire it up.

Though, to be fair small air cooled sealed tubes don’t have to have maintenance all that much. It’s generally the bigger ones that have the spare gas reservoirs in them that have to have that done to maintain the pressure. If it doesn’t have a gas reservoir than running it doesn’t have much benefit, as the amount of gas in it is finite.

 

[paul1598419]

Thanks for that, Matt. I will tell myself this every time I continue to procrastinate about running mine.

 

[Cyparagon]

If it doesn’t have a gas reservoir than running it doesn’t have much benefit, as the amount of gas in it is finite.

Can you elaborate? Does the end-bell not serve as a small gas reserve? What do you mean 'finite' - as opposed to what? Does a standard reservoir have infinite gas?

 

[ultimatekaiser]

Can you elaborate? Does the end-bell not serve as a small gas reserve? What do you mean 'finite' - as opposed to what? Does a standard reservoir have infinite gas?

Sure. Though the answer is pretty long and could fill a huge essay paper-but i'll try to sum it up as best as I can in an easy to understand way, and try not to miss anything.

In a nutshell:
Small Ion lasers are filled once and at a higher pressure than larger Ion tubes since they are going to be sealed indefinitely as a one time thing (in theory). They are started and have a small burn in time to stabilize and equalize, then are put into service. This burn in period eases optical variations and noise and breaks in the tube components and checks for preliminary failure primarily. During service, the pressure declines and the tube ages until failure- be it filament or too low a pressure etc.

Larger Ions are often filled at a lower pressure than the smaller tubes by contrast for optical efficiency as well as to ease degredation on the tube components. Electromagnets and other things are in place to help keep the bore from being eaten away among other things as these tubes are far more expensive and intended to be reused in many cases due to the extreme cost of making them by comparison to their smaller counterparts. Particularly in the case of a whitelight the krypton gas is depleted faster than the argon gas is and must be replaced at a different rate or the laser would cease to operate, so many of these tubes (and some argon only tubes too) possess seperate reserves that are sealed off from the main tubing. As gas is depleted and buried in the tube walls and components, these reservoirs cycle their valving upon request of the user or automatically as time goes on, releasing gas into the main tube to keep the pressure consistant. This is all fine and dandy during operation, but if the laser is then turned off for a long period the gas that was buried seeps back into the main tubing and results in a higher pressure than was started with initially if left too long (normal leakage from these reservoirs aside which also contributes) This results in lower efficiency and in some cases making the tube unable to start at all if severe enough, and also is hard on the power supply. As a result, normal maintenance for these calls for them to be run periodically to keep the pressure from getting out of hand, especially as the operating constraints are tighter. Too much gas in these tubes results in excessive wear and strain, as well as other issues too. Smaller tubes lack these additional reserves of gas. if they're not run for a long time, the gas that is leeching out was there at some point or another and the pressure cannot exceed that of it's initial fill, unlike these larger models. It may get touchy or noisy due to age and wear of the components but it doesn't go 'overpressure' per se. (short of a leak or something from being broken by a clumsy human )

You might then ask: "Well, if the smaller Ions are filled at a higher pressure, are the less optically efficient then?" and you'd be right. This is actually why alot of mid-to-late life uniphase tubes are popular with hobbyists, as they tend to have more lines output, as due to the pressure declining the number of lines output and total power output change as the pressure declines, as the atoms behave differently at lower pressures and the gain of those lines and their ratios change substantially over time. This mechanism is actually responsible (other than special orders or tube goofs like a wrong bore size or mirror types) for the lasers that often put out 8-9 lines instead of the normal 6 for example in the Cyonics/Uniphase argon tubes most of us know and love.

Also, to also address your comment about the end bell - yes it acts as a reservoir, but it's still part of the total pressure. The reason for this is because as gas is pushed through the bore by the discharge at a pretty appreciable rate-much faster than it can return via the smaller gas return path, and so this is done to help gas want to flow back to the rear of the tube since gas tries to fill the entire space equally. It's actually a common problem in some tubes and why a 543 and 643 omni look the same, but if you try to repump a 543 as a 643 it wont work, as the gas return is smaller and causes some wonky things to happen as the krypton can't cycle fast enough back to the rear of the tube resulting in some pressure issues as the argon cycles faster making the tube krypton heavy at the anode end. There's other factors involved too like heat balance and lots of other things but that's the fairly easy short version based on what I know. :tinfoil:

 

[Cyparagon]

Does the reservoir not have a direct connection to the bore gas? The reservoirs I've seen are about the same volume, if not smaller than a small frame end-bell. I've been told the gas is partially driven into the bore during operation, which is the mechanism for lowering the pressure. Is that not the case? How would this differ from small and large frame lasers?

 

[ultimatekaiser]

correct. As the laser runs, the ionized atoms are buried in the bore and tube walls due to the high circulation speed over time. The bore is usually made (as most of you know) of Beryllium Oxide, tungsten, and in some older cases graphite. The reservoirs are separate from the main gas fill and at a higher pressure. they usually have a sieve/valve or something precise used to give gas back to the main tube at a slow rate over time at request of the power supply (either by user or a detection circuit). The principle is not so different from the principles that drive the helium reservoir in a HeCd laser. Gas is lost through operation, and thus to maintain the pressure these gas flasks are used to give tiny portions of gas back to the main tubing structure. however during periods of inactivity the gas stuck in the tubing walls/bore walls can eventually find its' way free and back into the main bore slowly over time. This means that if the laser is mid or late life for example, then (ignoring any leakage from the gas reserves as well) there is significant gas loss already, and the valving has cycled probably a few times to keep the bore pressure correct. So if the laser is left sitting with no run time for months on end, then the gas that was previously lost to the tube walls will eventually work free and rejoin the main gas fill resulting in too much pressure in the main tube structure. If left unchecked, then it can make the pressure go too high for the supply to be able to restart it, and even if it does manage to, the greater gas density can cause additional wear in the bore via multiple mechanisms, strain on the power supply, and other issues. Thus, to combat this they are run usually monthly at a modest power to keep the pressure reasonable.

Similar things have to be done with HeCd lasers ironically or the same fault happens, as Cd buries Helium atoms as it re-condenses, causing the pressure to drop. Helium can pass through most types of glass however at slow rates, particularly at heightened temperatures, so a glass sieve is used to separate a reservoir of spare gas from the main tube. once the pressure is low enough, a circuit will detect it and will drive a heater around this He reserve and will drive gas into the tube to replace it. However this happens also at low temperature too, but at a much slower rate. Over time the tube still goes over-pressure just sitting and that's why its so hard to find a good HeCd nowadays, as many of them, like some larger ion lasers, have been sitting forever so the main gas pressure is often much too high. Adding in re-melts further amplifies the issue. in fact, HeCds in general are an incredible work of design and engineering and a very delicate balance of alot of very tight tolerances....but that's off topic. :tinfoil:

However, unlike Ion lasers, they're not so simple to re-process. Initial creation of a HeCd is a very non-trivial task and involves a HUGE amount of work even for the smallest ones, especially safely, and requires about 5x as long to do for various reasons. one can regas an Ion in a couple days. A HeCd can take weeks to reclaim....if it is even possible at all. It's quite an unfortunate turn of events too, as these lasers are now a part of history, and will soon cease to operate regardless of maintenance someday no matter what is done. In order to maintain them, they must be run, which obviously induces wear. They unfortunately cannot be stored indefinitely and retain their working function unlike something like, say, a CRT or a HeNe. There will come a time when if they are not being manufactured they will be lost to future generations from a demonstration standpoint...but such is the nature of technology advancing I guess. Pretty much all gas lasers are pretty much obsolete now save for very specific applications.

 

[Cyparagon]

The reservoirs are separate from the main gas fill and at a higher pressure. they usually have a sieve/valve or something precise used to give gas back to the main tube at a slow rate over time at request of the power supply (either by user or a detection circuit).

Mine has no electronics associated with it. How does it fill the main tube?