Budget CO2 lasers?

[Cyparagon]

There's a fundamental problem with your project. Any "burning" in a vacuum will raise the pressure significantly and severely compromise your vacuum. You can burn, or you can have a decent vacuum. You cannot have both.

 

[diachi]

There's a fundamental problem with your project. Any "burning" in a vacuum will raise the pressure significantly and severely compromise your vacuum. You can burn, or you can have a decent vacuum. You cannot have both.

You can't burn in a vacuum anyway, unless you have an oxidizer in there.

Cyparagon raises a good point though. OP, some clarification would be good! I had assumed you meant "vaporize" instead of "burn" but perhaps I shouldn't have assumed.

 

[Rivem]

There's a fundamental problem with your project. Any "burning" in a vacuum will raise the pressure significantly and severely compromise your vacuum. You can burn, or you can have a decent vacuum. You cannot have both.

That's what a vacuum pump is for. There will be a vacuum pump removing the gases produced by this reaction to maintain a set vacuum pressure. I've done this on a smaller scale at a higher pressure, so I'm sure the experiment will work out.

You can't burn in a vacuum anyway, unless you have an oxidizer in there.

Cyparagon raises a good point though. OP, some clarification would be good! I had assumed you meant "vaporize" instead of "burn" but perhaps I shouldn't have assumed.

Sorry, I wasn't very clear. I won't be burning anything in the chemical sense of combustion, but the energy required is about on par with burning most dry organic matter. The goal is nearly pure thermochemical decomposition: just getting molecules hot enough that they fall apart and become gases for analysis.

 

[Cyparagon]

That's what a vacuum pump is for... I've done this on a smaller scale at a higher pressure.

And vacuum pumps do not pull vacuums instantly. They take anywhere from several seconds to several days, depending on your pump and your desired pressure. No doubt you've seen this if you've played with the concept on small scale.

"combusion" gasses will be very corrosive, and will likely kill your vacuum system in short order, unfortunately.

The goal is nearly pure thermochemical decomposition: just getting molecules hot enough that they fall apart and become gases for analysis.

This is the sort of thing I wish people would START the thread with.

Your problem is closer to: "How can I analyse this sample?" Your problem is not necessarily: "How do I put a laser in a vacuum?" A problem well stated is a problem half-solved.

Either way, there are probably better ways to do this than using a laser in a vacuum. A heating element or IR source in an inert gas for example.

 

[Rivem]

And vacuum pumps do not pull vacuums instantly. They take anywhere from several seconds to several days, depending on your pump and your desired pressure. No doubt you've seen this if you've played with the concept on small scale.

"combusion" gasses will be very corrosive, and will likely kill your vacuum system in short order, unfortunately.



This is the sort of thing I wish people would START the thread with.

Your problem is closer to: "How can I analyse this sample?" Your problem is not necessarily: "How do I put a laser in a vacuum?" A problem well stated is a problem half-solved.

Either way, there are probably better ways to do this than using a laser in a vacuum. A heating element or IR source in an inert gas for example.

The vacuum pump is not going to be pulling the volatile gases through itself directly. The idea is to pull the vacuum first and then use an isolation chamber to maintain the vacuum and capture the gas. We're trying to decompose only milligrams of material, not make a constant stream of volatile gases. The goal is a very small amount of gas that I can run a few chemical tests on.

As I said earlier, the laser isn't going into the vacuum chamber either. In order for the experiment to work, a large amount of energy has to be imparted upon a small sample in a short amount of time to get it to a target temperature quickly. Hence the laser idea. The previous version used a small induction crucible which was a bit too slow. The other options are electronic dissociation (electrolysis) or an inert gas plasma torch which both seem like overkill and up the risk of contamination for the project. They're also not well-suited to the samples we'll be using.

The project has been worked out for a while with help from much more chemistry-inclined individuals than myself. I'm just looking for the cheapest method by which I can complete the next stage, and a laser seems like a good option right now.

My question, like many of the laser neophytes that come here, is focused on minimizing the laser cost and maximizing the power.

 

[Rivem]

Side note: Anybody have input on flashlamp-pumped lasers for this project? Costs?

 

[diachi]

Side note: Anybody have input on flashlamp-pumped lasers for this project? Costs?

About the only one I can think of that you'll be able to afford is the SSY-1. Meredith Instruments are probably the best place to go for that. These are pulsed, not CW like your average CO2 laser.

Meredith Instruments - Product Categories YAG & Solid State Lasers

Note: There is an export ban on these as far as I remember - they are difficult to get if you are outside of the US.

Every now and then a cheap Nd:YAG, Ho:YAG or Er:YAG pops up on eBay (Also typically pulsed) - I have a feeling a member here has one of those, can't remember who. That might be an option if you can find one.


See this page for more on the SSY-1: Sam's Laser FAQ - Commercial Solid State Lasers

 

[Rivem]

About the only one I can think of that you'll be able to afford is the SSY-1. Meredith Instruments are probably the best place to go for that. These are pulsed, not CW like your average CO2 laser.

Meredith Instruments - Product Categories YAG & Solid State Lasers

Note: There is an export ban on these as far as I remember - they are difficult to get if you are outside of the US.

Every now and then a cheap Nd:YAG, Ho:YAG or Er:YAG pops up on eBay (Also typically pulsed) - I have a feeling a member here has one of those, can't remember who. That might be an option if you can find one.


See this page for more on the SSY-1: Sam's Laser FAQ - Commercial Solid State Lasers

I'll look a bit more into these as well. Pulsed lasers aren't going to do any more or less for the project than CW, but I think the chances of a CW gas laser being useful for me in the future are higher.

 

[ultimatekaiser]

sorry I didn't read thoroughly enough on my last post. It sounds like you'd need something fairly expensive for what you're trying to do, and frankly I don't think a CO2 is the greatest choice. you can't really mount a ZnSe window in a vacuum chamber wall as it isn't good against pressure, it'll likely crack or deteriorate. if you're going for a high order vacuum, and you need lots of power in short order, a flashlamp laser is probably the way to go, but those don't come cheap. I've seen such analysis done, and a q-switched solid state laser is generally used, from inside the chamber using guided fiber delivery of the laser to the sample or similar. this both helps eliminate dirty optics mostly, as well as protect your vacuum/workspace. doing something freespace can work, but it makes setup much more complex. that and the gas laser would be huge, something solidstate is much smaller and gives you far more options. but the cost is probably very prohibitive. A FAP might work too, but a fairly long YAG rod with a lamp with a Q-switch can achieve far higher powers in extremely short pulses in the ns, or less. my ruby laser works in a similar fashion.

 

[Rivem]

sorry I didn't read thoroughly enough on my last post. It sounds like you'd need something fairly expensive for what you're trying to do, and frankly I don't think a CO2 is the greatest choice. you can't really mount a ZnSe window in a vacuum chamber wall as it isn't good against pressure, it'll likely crack or deteriorate. if you're going for a high order vacuum, and you need lots of power in short order, a flashlamp laser is probably the way to go, but those don't come cheap. I've seen such analysis done, and a q-switched solid state laser is generally used, from inside the chamber using guided fiber delivery of the laser to the sample or similar. this both helps eliminate dirty optics mostly, as well as protect your vacuum/workspace. doing something freespace can work, but it makes setup much more complex. that and the gas laser would be huge, something solidstate is much smaller and gives you far more options. but the cost is probably very prohibitive. A FAP might work too, but a fairly long YAG rod with a lamp with a Q-switch can achieve far higher powers in extremely short pulses in the ns, or less. my ruby laser works in a similar fashion.

Thanks for the input. I'm starting to lean towards the YAG pulsed laser. I may be able to go with a fairly low power laser, but it is the difference between something that should work and something that definitely will work. A bit of a premium in price for that will be worth it. The SSY-1 would do. I'll have to search around on eBay and see if anybody's got a complete used head before I start trying to buy parts though.

 

[ultimatekaiser]

Here to help The other thing to consider aside from the cost and size is the wavelength of the laser in question. The 1064nm is going to be a far more general absorbtion wavelength than 10.6um, which is going to excel more it at cutting steel or something. The Q switch can greatly boost your power. Far beyond what you'd get from a co2. Even a small rod can punch holes in razor blades and more. That's actually how they used to measure the power of Ruby rods back in the day...in 'Gillettes'. :tinfoil: even my little one can get me nearly a quarter of a joule, but over only 32ns. The equivelant CW would be around some 6MW or so! Enough power to blow tiny holes or at least mark/marr lots of things. It's a whole different type of ballgame. Just remember to be safe! Flashlamp lasers are definitely very dangerous, both in terms of eyesight (laser and flashlamp light, burns, etc) and electrical (lethal levels of high voltage).

 

[Rivem]

Here to help The other thing to consider aside from the cost and size is the wavelength of the laser in question. The 1064nm is going to be a far more general absorbtion wavelength than 10.6um, which is going to excel more it at cutting steel or something. The Q switch can greatly boost your power. Far beyond what you'd get from a co2. Even a small rod can punch holes in razor blades and more. That's actually how they used to measure the power of Ruby rods back in the day...in 'Gillettes'. :tinfoil: even my little one can get me nearly a quarter of a joule, but over only 32ns. The equivelant CW would be around some 6MW or so! Enough power to blow tiny holes or at least mark/marr lots of things. It's a whole different type of ballgame. Just remember to be safe! Flashlamp lasers are definitely very dangerous, both in terms of eyesight (laser and flashlamp light, burns, etc) and electrical (lethal levels of high voltage).

Wavelength isn't too big of an issue as long as it's above 450ish nm where molecular issues will occur. Ideal will probably generally be in the deep red- IR area. I'm well aware of the dangers though. I have worked with at least HV supplies and huge capacitors plenty before.

I'm going to go ahead and look for a pulsed YAG and primarily compare it to FAP and CO2 lasers. I still don't need very much power, but higher power does increase my chances of success.

 

[ultimatekaiser]

Yes you may have to do some experimentation. But if you're doing very small quantities, then the YAG is probably best, because have a much higher-power, but at the same time the laser will only be present for a very brief amount of time; rather than a CW option which has to (by comparison anyway) 'warm up'. Plus, you will likely only need single shots making you less likely to need water cooling, or need something additional as a control. Plus replacement and repair is easier, as a cheap CO2 won't last long, where as a YAG that is well made lasts pretty much forever if treated well- likely only requiring a new lamp once in a long while.

 

[Steelflight]

actually i can say you can "burn" somthing in a vacum per say but you won't have a flash point come do to no oxygen. i make charcloth in this fashion by eliminating the oxygen in a space but having severe heat inside. I.E. a can with pieces of cut cotton cloth. they start to burn but the small amount of oxygen is quickly usurped. with nothing to create a flash. they just smoke and blacken. (eventually ashen.) sorry but i can't offer much help with your gas build problem. best of luck.