DIY Nitrogen TEA Laser (2020) | Hacker News Reader

DIY Nitrogen TEA Laser (2020)

physicsopenlab.org

109 pointsRicoElectrico26 comments

This page buries and understates vision-related laser safety:

> It is also recommended not to look directly at the laser beam, to protect the eyes from the UV radiation produced by the discharges, to use hearing protection and to pay attention to the handling of the permanent magnets.

Especially for a page targeted broadly at "science enthusiasts" (in the site's tagline), I'd expect instead to see a glaring red warning at the top, along with effective links to getting this safety.

I have a small hole in my vision[1] because of laser exposure. Be careful with lasers, folks.

[1] https://dmd.3e.org/a-hole-in-my-eye/

Curious how you feel about this product:

https://youtu.be/qaNHWf1MN3g

oh my god, that cannot be legal. It sure ain't safe.

These are such a fun way to go blind!

I remember messing around with a UV laser (pretty sure it was nitrogen, but it needed a pump and all), when I was a young'un.

Never did get it working properly, which is probably good, as I likely would have blinded myself.

I made lots of trouble, when I was a kid. It's a miracle that I'm still alive.

UV lasers are dangerous. Invisible beams, and all.

IR lasers, too. Your pupils won't contract because they don't see the light, and a lot of damage can be done very quickly. You might not notice it immediately either, because your brain can paper over small bits of retinal damage to maintain a complete image, like it does with your ocular nerve blind spots.

Lasers are super cool, but I wouldn't DIY one unless I could keep it in a goggles-only room with interlocks on the door to cut power.

Both good comments. I love the article, but the "Safety Remarks" probably shouldn't have been so far down in the text!

I have some retinal damage from an unknown source. All I remember is one morning on the way to school mentioning that there was a spot in my vision that was dark like after looking at the sun, but it hadn’t gone away for hours. over 15years later it never went away, but it is indeed papered over by my brain. Still not sure if it was something internal, or if I played with the wrong end of a laser pointer.

I got something like that not long ago, and it was diagnosed as acute macular neuroretinopathy. Luckily, in many cases it apparently resolves on its own, and mine did. Was the spot slightly off-center in your vision? That's where it tends to happen.

As I recall, it's fairly random and fairly rare, but apparently it's been seen a bit more during COVID.

Mine is a cone shape extending out from my natural blind spot with the point ending just before the center of vision. so It's easy to miss with both eyes open. If I close one eye and look at a word, the word a few words to the right is.. a strange blur of the colours around it.

The pulse duration is measured in nanoseconds. I don't see (no pun intended) how that's going to put enough energy into anything to damage it.

What is the energy deposited over what area and time period on the retina? That's what defines the damage done.

Personally I would never mess with a DIY laser, and especially not one with a wavelength outside of the visible range. Invisible lasers scare me, because the blink reflex isn't there to minimize damage.

Your last point is a good one -- the blink reflex can help avoid harm from visible lasers but it acts in ~100 milliseconds. This laser fires in, what, about 100 nanoseconds? It "blinks" for you, a million times faster than you can.

Say it emits 100 watts for 100 ns when it fires. That's only 10 microjoules of energy. Not a lot of damage potential there unless it's firing at a very fast rate.

Finally, if it's not collimated, it's not going to be concentrated enough to hurt you anyway. I wonder what the beam divergence is like...

Exactly. You'll notice there is no information here on anything related to the numbers essential for safety. I suppose you could derive the energy inputs at least, which sets an upper bound on the energy outputs.

A 2ns pulse at a 100 Hz is small and slow, but I would like some guarantees and I want someone who has at least glanced at ISO 11553.

Some garage bullshit made by someone who clearly hasn't even HEARD of laser safety is not what I want outside of a sealed box.

Some garage bullshit made by someone who clearly hasn't even HEARD of laser safety is not what I want outside of a sealed box

A valid perspective, certainly, but at some point you may need to ask yourself if a site called "Hacker News" is right for you.

Usually the hacks don't have the potential to irreversibly blind someone.

Loved your use of the magnets! I thought I knew everything about the design and construction of nitrogen lasers but this is a very good idea.

That said, for the non-experts out there, TEA N2 lasers are not very useful because of their low energy outputs and very short (but not ultrashort) pulsewidths. But this is a great example of a laser that could have been built by Volta himself around the time of George Washington.

Nitpicking: without a cavity/feedback mechanism, it's only an amplified spontaneous emission (ASE) source rather than a laser.

This reminds me of a similar laser detailed in one of Scientific American's The Amateur Scientist articles from the 1970s.

I grew up reading those articles, they used to be great. You just knew a project was going to be fun when it included a "Model T spark coil" :-)

That was a great article in The Amateur Scientist column of SciAm.

As a kid I was fascinated by these articles, wanted to build them. But alas I was too young, too poor.

There was also a great infrared laser if I recall that used gold coated mirrors. I even used allowance money to buy a gold mirror from Edmund’s Scientific. I also got my mom to take me somewhere to get acrylic tubing and flat stock for the laser.

Sadly, that’s as far as I got. :(

The early ones -- make your own cloud chamber for atom splitting, X-ray machine made from vacuum tubes, big metal rocket powered by explosive powdered zinc -- were collected into a volume that's amazing.

https://www.amazon.com/Scientific-American-projects-amateur-...

I was shown one of these built in minutes from found components at Noisebridge in SF a few years back, an old TV flyback transformer, a couple of resistors and caps and a pair of straight edges almost parallel for the spark gap (the lasing exits parallel to the edges) - you can detect it with a sheet of paper (because of the dyes embedded in it)

There's a couple of good videos on these (and other home laser fun) on the youtube channel Les' Lab. https://www.youtube.com/channel/UC0ptp5KuvAJmp8kRV8dqZDA

Spark gaps are an interesting way to switch when you get to a high enough voltage. Marx generators use a similar principle, using the spark to place parallel capacitors in series with one another.

https://en.wikipedia.org/wiki/Marx_generator

I've often wondered if gas discharge tubes could serve a similar function at lower voltages, but I haven't gotten around to trying it out.

The whole point of using them is that they work at very high voltages and are very, very cheap. For low voltages there are just many more controllable and consistent ways of switch.

Simple thyristor and cap bank for example. Or just transistor and controller.

Indeed -- or the highly related Cockroff Walton generator: https://en.wikipedia.org/wiki/Cockcroft%E2%80%93Walton_gener...

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