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ArcticMyst Security by Avery

Differences in gas lasers?

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Oct 5, 2013
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I assume my first gas laser will be a HeNe because they aren't too big and are reasonably priced. I am just wondering how does a HeNe differ from a HeCd. Also I hear about huge argon lasers that take up a huge amount of room and require tons of power. Are there such things and smallish argon? I'm taking making 20 pounds rather than 200 pounds. I'm just curious and I am thankful for any input.

Also I just checked my local Craigslist and someone posted a HeNe laser for sale. I text them and got the model which is a uniphase model1508-0. He says it seems to work fine. I'm assuming this person doesn't know much about this laser. What would a good price be? Before I say how much he is asking I want to see what people say it's worth about.

I am appreciative for any feedback.

Thanks,
 
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I assume my first gas laser will be a HeNe because they aren't too big and are reasonably priced. I am just wondering how does a HeNe differ from a HeCd. Also I hear about huge argon lasers that take up a huge amount of room and require tons of power. Are there such things and smallish argon? I'm taking making 20 pounds rather than 200 pounds. I'm just curious and I am thankful for any input.

Also I just checked my local Craigslist and someone posted a HeNe laser for sale. I text them and got the model which is a uniphase model1508-0. He says it seems to work fine. I'm assuming this person doesn't know much about this laser. What would a good price be? Before I say how much he is asking I want to see what people say it's worth about.

I am appreciative for any feedback.

Thanks,

The major difference between a HeNe and a HeCd is of course the lasing medium.

In a HeNe, there is an arc travelling through and ionizing the HeNe gas mixture, resulting in the atomic transition of the electrons. Resulting in the release of photons. These photons are then trapped by mirrors to allow them to resonate. Resonation occurs when a photon travels from it's place of creation, to a mirror, and then back.

When this light is allowed to a resonate, a "pool" of light forms. About 1% of this pool is allowed to exit, resulting in coherent light :)

The larger the cavity, the more gas, the more light. Or widening the bore, though this results in multimode output. That's a whole other story...

A HeCd is a tube using helium gas, and cadmium metal. The helium atoms are energized by the discharge (somewhere in the ballpark of 1500V) and then these atoms transfer this energy to the cadmium. This process takes a while to vaporize, and ionize the cadmium. This means that warm up for these tubes can be upwards of 10-15 minutes or more.

Though the helium is evenly dispersed, the cadmium is a chunk on the positive side more or less. The negatively charged ions however tend to travel towards the cathode. In a poorly made tube, this can degrade the cathode, and even damage the mirrors. In well designed tubes, there will be a cold trap to cool and trap these ions, and over time there will be a noticeable displacement of the cadmium from the cadmium well, to the cold trap.

Argon lasers!

Argon can be VERY large. I saw a 15W tube (maybe even more) at SELEM that took up the entire length of a pop up table, and half the width. The PSU took up about a yd^3 on the floor. These are run off of 3-phase power, and are water cooled. They are MONSTERS. I saw a running white-light also, equally large and beastly.

Though they can also be much smaller. The "small-framed" air cooled argons that most argon hobbyists own take up about 18"x5"x4". Their PSU has a similar profile. These are generally 110V air cooled, but some can be 220/240. Generally not though for the "small-frame" class.

Kryptons follow the same guidelines as above. However most are water cooled "large-frame".

Your Craigslist laser!

This is a "Novette" self contained tube. I personally wouldn't pay much for it. Though if you just wanted a tube and PSU all in one, and didn't want any more work beyond plugging it into the wall, then this is for you.

You won't see any plasma from it, just so you are aware.

I'd say about $50-65.

These run from DC wall adapters, so see what you need to power it, and get an adapter for it.
 
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A good way to learn about small-frame Argons is to google the forum for 'uniphase argon', and/or 'ALC60X'. (Also search repairfaq.org for the same.)

There are other brands/models, but these are some of the more popular ones, which can found on eBay, etc.

-Andy
 
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Got your message a bit ago and thought I'd answer here in case any of it is useful to others.

Bloom pretty much said what I was going to about the difference between HeNe and HeCd lasers. One thing I'd add though is that cadmium is *highly* toxic which is one reason NiCd (Nickel-Cadmium) batteries aren't really used anymore. Also as bloom found out some HeCd heads use asbestos insulation in them. They're not usually cheap either. I'd stick with an HeNe for a first gas laser since they're pretty idiot proof.

To answer your question about yellow tubes. 594nm is the only yellow HeNe color. They are fairly rare but they tend to pop up in spurts on eBay. There have been probably four or five that have popped up on eBay recently though. Expect to pay $250 or so for just a tube and a good $350+ for one with a power supply. I think I paid $350 and $400 respectively for my two yellows and PSUs.

Your best option for starting with gas lasers is to get a small red HeNe. You can get a tube in a head which makes hookup pretty much idiot proof. The down side is you won't see any plasma which is, IMO, part of the beauty and attraction of HeNe lasers. You can get a basic setup for ~100-125 and if you're willing to double that you can probably find a 543.5 green tube (like the big tube in my avatar) and PSU for $250ish.

Good luck in your quest for gas!
 

Roam

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Laser transitions in atomic lasers such as HeNe occur between levels of atoms. Whereas in ion lasers (Argon for instance), it occurs between excited levels of ions. That's the main difference.

In HeCd like HeNe you use helium buffer gas, but there are two ways at least, one like the HeNe is on the helium metastable (one He state that lives a long time before it decays):

He (meta)* + Cd -> Cd+* + He + e-

The other is by electron impact: Cd + e- -> Cd+* + 2e-

As it was pointed out these lasers have a reservoir containing metallic cadmium... its vapor would mix into the discharge in clean helium.

So there are both similarities and differences!
 
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The most obvious is different lasing medium but that was already covered. If I had a large enough garage seperate from my house I would love to get a HeCd but I'm too careful with dangerous material.
 




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