Gammex Alignment HeNe

Hi LPF!

I recently asked what made HeNe interesting, and the answers convinced me to pick up my own HeNe and see for myself. I got a 1mW Gammex alignment laser (model 1A475), manufactured in February 2005. This laser was originally used to align radiotherapy machines. As I understand it, the operator would use the laser to pinpoint the location on the patient where the dose would be applied. I probably overpaid a fair bit at $83 shipped, but I'm excited to join the gas laser club!

As initially configured, this laser output a crosshair which could be manipulated by turning two knobs on a turret. The turret was easily removed by taking out two hex screws to expose a nice HeNe beam.

Here are some pictures of my new toy:
https://imgur.com/a/l7Ktw

Is there anything else I should know about this laser? Should I observe a duty cycle? I also assume at that 1mW, I don't need to be too careful about eye safety. If I avoid staring at the beam (or letting anyone else do so), everything should be fine, right? I do have some glasses that cover 580nm-760nm, but I'd rather not wear them if I don't need them.

For future Googlers, here are some text details, mostly transcribed from the pictures:
This laser was model 1A415, manufactured Feburary 2005, serial number 118537.
It claims to output no more than 1mW (class II).
The power supply is compatable with either 115VAC or 230VAC (with a small switch on the inside to swap between them). The PSU was made by Melles Griot and is labled 05-PSAA-959-045. Gammex then relabeled it as 67A0030. The PSU is labeled "Wmax: 12" which makes me think it draws at most 12W (presumably at 115VAC). The output is spec'd at 1200-1600VDC at 4.5mA.

The divergence seems pretty decent. The spot is 7mm in diameter at about 4m.

Oooh very nice, you got a nice self contained housing and the ability to see the bare tube, that's always good, gas tubes are pretty! Beam specs are always impressive. Welcome to the gas club, you may be sorry you joined, it's an addiction!

Wouldn't worry about duty cycle. Your eyes are safe, as long as you don't stare directly into the beam. Obviously don't touch the tube/head wiring while it's on, or for a little while after (Gas tubes can act as capacitors). The shock from a HeNe PSU isn't lethal but at a couple kV it still stings!

Nice of you to include that information for future searches.

Cool! Looks really nice, it's my GreeNe's twin brother. Glad you went with what I suggested. +rep!

bluestars said:

Is there anything else I should know about this laser? Should I observe a duty cycle?

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Just don't touch anything inside when the laser is on.

While 10 years for the laser is not a lot, though later you might notice that the laser does not switch on immediately. It needs some time to warm-up. Especially if it was not operated for a long time.

What do you plan to do with a nice beam?

Nice, nice, nice. Also, thank you for taking photo's and sharing. I didn't know a crossed line could be made with two cylinder lenses that way, I guess there is a beam splitter feeding them.

lazeristasUVISIR said:

While 10 years for the laser is not a lot, though later you might notice that the laser does not switch on immediately. It needs some time to warm-up. Especially if it was not operated for a long time.

What do you plan to do with a nice beam?

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When I first fired it up, it took about 10 seconds to start lasing. At first I thought this was some kind of safety feature, but when I started it a second time it came right on. It also does this "stutter" when it powers off, where the tube clicks a few times and the beam flashes on and off, I assume as the voltage drops.

I spent a fair bit of last night just looking at the beam and spot. I vape way more when I'm playing with lasers, just for the smoke. I want to try some of the Physics 101 experiments that I vaguely remember from college, and maybe eventually make a fake yellow laser with red/green (although that will probably end up using my LPC-826 lab laser for better color matching with available greens).

Alaskan said:

Nice, nice, nice. Also, thank you for taking photo's and sharing. I didn't know a crossed line could be made with two cylinder lenses that way, I guess there is a beam splitter feeding them.

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I'll post some more photos of the optics after work today, but IIRC there was a mirror at a 45° angle behind each lens, and the first was partially reflective. I'm trying to learn more about optics, so I might have to take it apart and stick each piece in the beam separately so I can see what they do.

Edit: here are some photos. Definitely looks like a beam splitter.
https://imgur.com/a/qFe3T

Sta said:

Cool! Looks really nice, it's my GreeNe's twin brother. Glad you went with what I suggested. +rep!

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Thanks for the suggestion. I just rep'd your post on my original thread.

If the first mirror is 50% reflective and the second 100%, that would explain it.

yeah I used to have 3 of these, two green and a red. They're fun small tubes. though I have some that are even smaller-only about the size of my finger...some of the smallest ever made. They're generally about a mW ish. The supply used on them is a bit mediocre so they tend to be a bit slow starting from a cold start, especially if they're fairly well used...but they're not bad after they warm up a bit usually. Has nothing to do with how long they sit. Hard seal HeNes don't really care how long they sit generally speaking if they were sealed properly. They shouldn't leak on any timescale that matters. I actually own an old one from the 60s. They're still a great laser even today.

Ultimate Kaiser might back me up on this (unless I'm wrong) but if they are hard start and don't lase for a few seconds - sometimes its better to power them on for 5-10 seconds then turn them off, wait a few seconds, then back on.

Sam said it puts less stress on it (not sure if he was talking PS or tube) but thats what I do with a couple of mine that are finicky.

Yeah generally as the tube starts to age they can get to be slow to start, especially as the gas pressure goes down. (Or if they're cold or very very old) Starting is stressful on the power supply, and a healthy tube should come right on immediately in most cases...but if you turn it on and it doesn't come on within maybe 10 or 20 secs, it's usually best to turn it off for a few to let it rest then try again. Leaving it on hoping it will start in vain will just destroy the starter.

After mine has warmed up, it will power on almost immediately. When it has not been used overnight, though, it will take a few seconds to lase. I just tried it and counted almost exactly 10 seconds from power up to beam. I'll keep that in mind if it ever goes beyond 10-15 seconds!

Yeah, all of the ones that I had were a little slow to start too. It's not that unusual. The red one is a cute little tube.