NEC GLS-3030 Argon ion restoration questions

This is my first post, so hi everybody
I recently saved a NEC GLS-3030 (actually it is marked 3032) head from a gruesome fate, without the PSU. Never thought it would be of any use but after inspecting the tube I think there may be a chance to bring it back to life. Brief condition of the tube/head:

- no mechanical damage
- one mirror misaligned, somebody has played with the screws/mounting
- hours count: 00351 (makes no sense, I think it has way more)
- getters worn out, but some central areas still hold out (metallic patch)
- filament has sagged visibly in the middle (1-1.5mm), but still operational without any shorts, rough guess (hope that is still does not obstruct the bore
- when hooked to HeNe power supply the tube glows light-purple (like it should, I guess)

I set up a precisely regulated filament power supply (2.7V-3.3V) which works nicely, so next should be the main anode power. My questions are:

1. Is it safe to look unprotected at this tube while it works? (from the side of course Does the plasma discharge emit anything dangerous to the eyes? If I get to the point of mirror alignment, there's gonna be a lot of fiddling/staring around the working tube. I was unable to find any guidelines regarding this issue anywhere.

2. I do not have the cover for this laser head, can I run it for prolonged periods with the fan blowing only at the heatsink?

3. If I get it to start, any advice on the mirror alignment? I have a HeNe head to start with...

Thanks in advance!

tolstiakov said:

This is my first post, so hi everybody
I recently saved a NEC GLS-3030 (actually it is marked 3032) head from a gruesome fate, without the PSU. Never thought it would be of any use but after inspecting the tube I think there may be a chance to bring it back to life. Brief condition of the tube/head:

- no mechanical damage
- one mirror misaligned, somebody has played with the screws/mounting
- hours count: 00351 (makes no sense, I think it has way more)
- getters worn out, but some central areas still hold out (metallic patch)
- filament has sagged visibly in the middle (1-1.5mm), but still operational without any shorts, rough guess (hope that is still does not obstruct the bore
- when hooked to HeNe power supply the tube glows light-purple (like it should, I guess)

I set up a precisely regulated filament power supply (2.7V-3.3V) which works nicely, so next should be the main anode power. My questions are:

1. Is it safe to look unprotected at this tube while it works? (from the side of course Does the plasma discharge emit anything dangerous to the eyes? If I get to the point of mirror alignment, there's gonna be a lot of fiddling/staring around the working tube. I was unable to find any guidelines regarding this issue anywhere.

2. I do not have the cover for this laser head, can I run it for prolonged periods with the fan blowing only at the heatsink?

3. If I get it to start, any advice on the mirror alignment? I have a HeNe head to start with...

Thanks in advance!

Click to expand...

You can look at the plasma glow safely, no worries there. You'd be best making some sort of cover for it though, these tubes use a lot of power and as such require a lot of air moving through them to keep them cool. For example, a typical max current rating for a JDSU air cooled tube is 10A at ~100VDC, so 1kW, most of which is dissipated as heat. This head is probably ~90V at 8A.

Can you post more pictures of the discharge when you had the HeNe PSU hooked up? It looks like it is firing down the gas return path which IS NOT a good sign. No point even trying to align the mirrors if it isn't firing down the bore.

Hopefully you can get it working, looks like a nice tube!

Thanks for the answer, regarding the discharge path - it exhibits an interesting phenomenon - it seems to be sensitive to the voltage slew rate. If I hook the tube to the HeNe PSU and switch it on (slow slew), it always fires through the bore. And if I have the PSU on and touch the anode with the charged HV terminal (high slew), then most of the time it fires through the gas return pipe. I posted the pic of this later case just because it looked more cool

First I will try to power it up with 4-6A just to see if it starts and can work at all. I guess I should be able to cool it wide open like it is now. If it can hold the discharge, then I will make a proper cover.

I posted pics of the mirrors, I guess the one with inclination is the OC, right? Is this normal, at which angle should the beam be with respect to the bore axis, 45 degrees? Somebody has messed with this mirror and now it is way off. The last pic shows the distorted sight of the filament and the bore. Has anyone seen this kind of mounting arrangement, a picture of the proper setup is more than welcome.

Arcs are more effected by current, not voltage slew rate. The return capillary might be a stable arc path at your HeNe PSU's 5mA, but probably not with the main supply's 5000mA.

Ideally you want a >100cfm fan pulling air from the top of that heat sink.

ANY getter is intact getter.

Your filament supply needs to be AC with a center tap as the main PSU's cathode return. DC or AC not center-tapped will cause one part of the filament to be more negative than the other, and cause a few problems.

OC is on the end opposite the end-bell on these, if I recall.

HR should not be at 45 degrees unless there's a wavelength selection prism installed. I don't remember seeing a prism on these before, but it's certainly possible.

There are many tutorials/demonstrations on laser alignment online. HR alignment first is the preferred method. I'd recommend leaving the mirrors alone - they might be good enough to lase already. Get an arc first, then align.

Yeah its striking down the gas return (in your photo). if the filament is sagged significantly, then I'd shine a red HeNe through it (or a bright flashlight and look through it) and make sure the bore is clear. if its clear, then power it up somehow, and worry about alignment last. If the pressure is good it should start fairly easy. Sam's FAQ has alot of good temp power designs to start Ion lasers pretty well, but I'd not recommend them for continuous use. That and I think I saw a few on eBay recently, but who knows if they work. I'd reccommend a good >150 cfm blower with a good seal for the top at least for these, as they get quite hot. Ionized argon is fairly safe to look at, but it does put out fair bit of UV so don't stare too long or bad things may happen, but at low current its probably fine. max tube current is about 10A-ish as mentioned above, but best life is going to be around 6-7 for most air cooled tubes. I'll see if I can find specifics for your tube, or you can likely talk to someone else on here who has one. make sure everything you wire is well connected and insulated, they're well known for arcing as well as getting hot connectors if they have shoddy connections. Might try calling a surplus shop like Meredith Insturments or similar and see if they have parts you can use. might cost you a bit more, but would be safer and they may well have matched parts, which helps eliminate "?" from your testing and troubleshooting if you can afford it, as well as lots of time and patience.

I've made progress, I got the arc going This clear glass tube looks amazing when fired up.

Long story: Filament was at 3.0V (asymmetric power supply, but the tube didn't mind much). For anode power I set up my trusty old DC-AC inverter (which is actually a switch mode DC amplifier that can do +- 350VDC at up to 8A). I built a special feedback circuit that limits its output to 120VDC max and employs a precise current control. I set it to approx 5A and the tube started happily on the first igniter pulse The voltage was approx 80-90V, did not measure precisely. It won't start for currents less than 4A, but above 4A it starts easily every time. It is not lasing, however, but that's expected since somebody else messed up the alignment of one mirror.

Since I'm new to this type of laser, I have more questions:
1. Does anybody have a datasheet for this tube, what is the maximum heatsink temperature for this tube? The strongest fans I had were 50CFM, I put two of them and assumed they would be enough if I kept the current low, but this thing heats up massively IMO, I'd say the heatsink gets to anywhere between 150-200 degrees centigrade (under the fan which is blowing down directly trough it). Is this temperature normal? Does anybody know the rating of this thermostat switch that is on the heatsink?

1a. Since I do not have the original cover/fan, is the original fan pushing or pulling air from the top of the tube? Should the air circulate around the whole tube, or only around the heatsink? (according to the chassis is design the only path the air can get in/out is at the side of the heatsink, see the 1s pic of my first post)

2. I would love to set up this laser so the tube is visible while working, but I'm still concerned about this UV issue:
Tube glow from a 30mW Argon laser, is it safe to look at.
Here they say the UV amount emitted is dangerous with no protection. Can it be solved using a Plexiglas cover? Would it stand the heat of the tube, any better suggestion?

3. Which current is the lasing threshold for this tube, what is the lowest I can go? Wouldn't like to waste hours on alignment and later find out that I was below threshold. Which current is recommended for alignment?

Very well, so once I get a more powerful fan I shall attempt to align the mirrors. My old HeNe is succumbing to its age, it lases fine but the discharge is unstable and tends to flicker even with increased ballast resistor. Any trick that can fix this? Hope to use it to align these mirrors.

Looked up some specs on this. Max current is 9A and head fan is 100CFM using the original cover. I wouldn't recommend anything else. It's designed to have that type of airflow and as you've noticed, they get exceptionally hot. Healthy output is 5-30mW range. Most argons pull air the rough the sides and exhaust it directly off the sinks out the top, though some are axially cooled like newer uniphase tubes. Try contacting Sam Goldwasser, he may have parts for these. They were fairly common in imaging applications back in the day he may have a dead one sitting around you can nab parts from, or at least point you in the right direction. As for alignment, something with a narrow beam that diverges slowly in the red is likely your best bet. The mirrors are sealed to the tube so be careful not to adjust too far, fractions of a degree count. Plexiglass might work but I eould highly recommend aluminum over that any day of the week. Most of these use the fan to shed heat, but the case is also part of the heat-sinking. I'm sure you've noticed how thick and heavy the baseplate is. You should hear my mixed gas Ar/Kr ion fire up. It sounds like a jet taking off.

Edit: if you need a new HeNe I can probably send you one. Just let me know what model /specs and I'll see what Is available.

After hours of alignment attempts - no luck This prism on the cathode side complicates the procedure quite a bit, the apparent bore axis is offset from the center of the prism window (or mirror, hell if I know what it is), and it seems to be that way by design, so I have no idea about its intended position. And the prism itself is a headache since it obviously has to be tuned for a specific wavelength - certainly not the one HeNe emits. Tube current was at around 5.5A, afraid to go higher as I still don't have an adequate cover (got the 100CFM fan though, blowing downwards to the heatsink and around it)

The only way I was able to get reasonably useful surface reflections for alignment was when I set up HeNe on the prism side, at 45deg to the bore axis. After carefully aligning the beam to:
1. hit the center of the anode mirror and align reasonably along the bore
2. miss the sagged filament (which does not obstruct the bore too much, apparently)
3. pass the prism unobstructed roughly in the meridional plane of the window/mirror (as its design obviously requires, please see pics)
4. be reflected back precisely by adjusting the anode mirror tilt
5. be reflected back precisely by adjusting the prism
6. iterate steps 4 and 5 until all reflections converge
I was able to center all reflections and also have the beam exit on the other side without obstruction - so I guess this is the alignment for red color. One of the prism tilt adjustment screws (the upper one in the pics) aligns the sagittal plane, the one that was supposed to be aligned for wavelength selection. After powering the tube I tried to adjust this screw all the way, but did not get anything. I did not touch the other screws as I tried to set them previously using HeNe under 1/10 of a full turn. I have no feeling how sensitive this alignment is.

Any advice would be appericiated

@ultimatekaiser: Thanks for the info and the offer, I fixed my HeNe temporarily, I hope it holds out for some time now...

Hmm, might be easier to align if you had another Argon to align it with, or something near that wavelength at least. A 532nm Green might be close enough, or a 473nm blue. A green HeNe might even manage it. Direct injection diode lasers are no use as the reflections can fry them.

Ideally I'd imagine you'd center the prism and then use another single line 488nm argon to align this one. I've never aligned one with a prism so I can't say for sure.

I have read of a technique where you can align the HR by using the reflected light from the plasma as a guide, thus negating the need for an alignment laser. I haven't tried it - I imagine it'd be easier using an alignment laser. Again, I haven't aligned a tube with a prism before so I can't comment on what difference that'd make.

There are several users on here that may be able to offer advice on proper alignment procedures for cavities with a W/L select prism. Calling Steve Roberts! Or anyone else that might have experience here ...

Well ultimately if it was an external mirror tube, which it's not, you would align it with another argon, by removing one mirror a time. But, because this one is an internal mirror with a prism/redirect mirror you'd almost need to select a wavelength that will pass but will be close to the desired wavelength, problem is you can't really do that because the mirrors are highly reflective at the wavelength you're trying to use . Alignment is extremely sensitive with fractions of a degree making a difference. If it truly has a prism inside of it it will be nearly impossible to align...
Most prism set ups rely on the OC being aligned first, and then the prism is aligned horizontally, then if the mirror is on the prism substrate, it is rotated vertically into place. If not then it has to be aligned with the mirror, and then rotated to the 488 gain line. Different wavelengths refract differently through different materials, so usually using the same wavelength you're going to be using with the prism is desirable.

ultimatekaiser said:

Well ultimately if it was an external mirror tube, which it's not, you would align it with another argon, by removing one mirror a time. But, because this one is an internal mirror with a prism you'd almost need to select a wavelength that will pass but will be close to the desired wavelength, problem is you can't really do that because the mirrors are highly reflective at the wavelength you're trying to use . Alignment is extremely sensitive with fractions of a degree making a difference. If it truly has a prism inside of it it will be nearly impossible to align...
Most prism set ups rely on the OC being aligned first, and then the prism is aligned horizontally, then if the mirror is on the prism substrate, it is rotated vertically into place. If not then it has to be aligned with the mirror, and then rotated to the 488 gain line. Different wavelengths refract differently through different materials, so usually using the same wavelength you're going to be using with the prism is desirable.

Click to expand...

Ahh yes, I'm forgetting it's not an external mirror tube!

You were one of the people I had in mind when I suggested others may have more input!

Either using another 488 for alignment, or removing the prism first and re-mounting the HR without it would be two options.

diachi said:

Direct injection diode lasers are no use as the reflections can fry them.

Click to expand...

That's something of a myth. The mechanism is COD, and as such, it only happens when you're running the diode so close to failure, that any additional light on the output facet melts it. Therefore, there's really no chance of this happening with a diode being run at low power. And you'd want low power for this project anyway.

ultimatekaiser said:

Well ultimately if it was an external mirror tube, which it's not

Click to expand...

I'm pretty sure I see a mirror. On the end. On its own mount. In several different pictures.

Cyparagon said:

Either using another 488 for alignment, or removing the prism first and re-mounting the HR without it would be two options.



That's something of a myth. The mechanism is COD, and as such, it only happens when you're running the diode so close to failure, that any additional light on the output facet melts it. Therefore, there's really no chance of this happening with a diode being run at low power. And you'd want low power for this project anyway.


I'm pretty sure I see a mirror. On the end. On its own mount. In several different pictures.

Click to expand...

SAMs faq says they're internal mirror tubes, and all the ones I've ever seen are. Nothing is removable as far as I'm aware. The mounts are just braces, like on my small HeCd, the mirror is sealed to the bellows and it doesn't really mount the mirror, the screws just tilt the optic with gentle pressure.

Unfortunately I do not have another argon, just a 633nm HeNe and a 532nm DPSS. Could probably get a cheap Chinese 445nm pointer.

The mirrors are sealed in their own mounts, the bellows on the tube allow for small tilts required for alignment, nothing can be removed. One thing that is open to debate is whether the prism assembly is a transparent prism plus a HR mirror at 45 degrees (my first guess), or a prism with one side reflectively coated and a window opening which is left accessible for the alignment procedure.

There has to be a factory alignment procedure for this tube, and I'm sure the prism side mirror opening plays a role in it. On the second pic in my previous post a shiny blob can be seen, this is the bore axis (I illuminated the OC on the other side with white light). For some reason this opening is offset from the center of the window/mirror. I made a second attempt using a 532nm laser, but both mirrors are highly reflective at this wavelength. Maybe there is a trick how to use a very weak reflected/transmitted beam in this case, but I don't have any idea yet.

The feedback form on Sam's FAQ does not work (throws error 403), maybe somebody can tell me how to contact him?

They're probably aligned from the window, allowing the reflection to the output coupler and back. Allowing you to get a clean alignment with the bore. The hene would be your best bet, as I'm sure the bore is quite thin and small. You'll need a very thin low divergence beam to even attempt an alignment. Likely 1mm ish at least. What I'd probably do is aim the HeNe through the OC and bore, then direct the reflection back into the hene. Then search with the HR. The HR being at an angle makes this more complex. When they are aligned at the factory they usually are very close already and are likely just fine-tuned usually using a very expensive machine on a rail like an autocollimator. Yours is strange though as yours is the only one I've seen with the angled mirror setup.

Edit: are you sure the mirror on the angle is indeed a mirror, and that it is not the oc? I just was looking at the picture and noticed that that's on the cathode end. these tubes are backwards and output out the cathode not the anode from a picture I found.

Frankly speaking I cannot say for sure which mirror is the OC, and which is the HR. To both the naked eye and the camera, the cathode mirror (the angled one on the prism side) looks much more transparent than the anode mirror (please see pics in the previous posts). But this can be very deceptive because the cathode side has a large glass bulb so the BeO ceramics can be very well lit from the outside, so the observer can see it clearly through the mirror and the prism on the cathode side (with a yellowish-red hue). On the anode end the bore exit is very well shaded by the narrow and opaque anode tube, and everything is tucked below the ignition module where it's much darker. For this reason the anode mirror can look much more reflective when observed from the outer side. And what kind of design would want the beam at 45deg anyway?

When I shine a HeNe at the anode mirror I get a stronger central reflection and two side reflections (3 spots lined up). The annoying fact is that when I adjust the HeNe so that all of these 3 spots converge back to the HeNe, the beam is not hitting the mirror center. If I make the incoming beam hit the mirror center, I can align only the central reflection back to the HeNe. I was not able to get a reflection from the prism/mirror on the cathode end in that trial.

When I shine a HeNe at the cathode mirror (45deg to the bore axis), I can get both the anode mirror and cathode mirror/prism reflections, and both can be adjusted nicely for convergence. That's what I did the first time, but could not get it to lase by tuning the prism after powering the tube. What I did: The upper alignment screw sets the prism pitch for wavelength selection, and the right one adjusts the yaw. I decided to set the right one (yaw) at a number of fixed positions (1/10 of a full turn apart, symmetrically CW and CCW from the starting position), and then rotate the upper screw through its full range for each fixed position of the right screw. I did not touch the anode mirror.

What I might try next is to align once again from the prism side, and return to the anode side to see if I could get the prism reflection. It's obviously trial and error without that nice, big auto-collimator...