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Homebuilt 3-5W Copper Vapour Laser System

Laserbuilder

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Hello to everybody, I am a laser hobbiist from Ukraine.

I don't know wether this laser project is unique or not (probably for the states of former USSR it IS unique, we have very few laser hobbiists here), but I didn't find any information on anything similar. Most of people who worked with lasers brought to life commercial CVL units or built small copper halid lasers from scrap and junk with quite low output power.

My project started, when I had a huge luck buying a russian NOS commercial self-heating sealed-off copper vapour laser tube in its factory crate and a set of mirrors for it. The name of the tube is UL-102

I didn't have any power supply and any information about it. After finding a datasheet for the tube I found out that it should give output of about 5W on both 510 nm and 578 nm lines and requires quite complicated power supply. Copper vapour lasers work in pulsed mode with a high pulse repetition rate. A very short (100-500 ns) high voltage (10-20 kV) pulse must be applied to the tube with repetition frequency of 8-15 kHz. Average power consumption of about 1.5-2 kW makes the bore of the tube heat up from the gas discharge in it, and in general it takes 30-40 minutes before lasing starts. Than I began to look for information about the power unit. I looked through a lot of articles in scientific magazines and books about lasers, found a manual from one very old russian commercial CVL.

So, the pulses for excitation of the tube can be formed by a conventional Blumlein generator, like in common TEA nitrogen lasers. But, because of very high pulse repetition frequency the spark gap must be replaced by a BIG hydrogen thyratron. The thyratron requires driver for its control grid. Both driver and main generator require power supplies with different voltages ranging from 300V DC for master oscillator to 6 kV DC for the Blumlein circuit. The laser tube needs a rigid metal base with optical resonator and a water jacket to stabilize the temperature of the tube on the outside -- glass-to-metal and metal-to-ceramic joints are vulnerable to overheating. So, everything except the laser tube itself and mirrors for it I had to build myself and make work properly.

There was a real problem of unstable work of the Blumlein generator, as the thyratron in it is not BIG enough. It works at its overload limit and loses its normal switching properties sometimes falling into continious arcing and short-circuiting the HVDC unit. Adding over-current defence and magnetic pulse compression cell to the output of the generator reduced this problem to the reasonable level, OCD switches off the unit 2-3 times per hour. Anyway, it works and I got very nice lasing! The beam is 20 mm in diameter and estimated output power is not less than 3 Watts, as the beam feels quite warm by skin and burns wood and cardboard very well when focused. I don't have a proper power meter to say wether it gives its full output or not. As the summary of this project I had filmed a small video about this laser system.
https://youtu.be/ozBpQRXav-k
Still, there is a lot of work to do on this unit as I want it to be safe and easy to use, there is a lot of exterior design work left.

Feel free to ask any questions and requests for additional pictures. Sorry, if I have some mistakes in my English.
 

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grainde

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Very impressive! A 3 - 5W 520 nm laser :drool:
How long did it take you to get it up and running? + rep
 
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Laserbuilder

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It actually gives a mix of two lines -- green (510 nm) and yellow (578 nm). I've separated them using a shard of a DVD as a diffraction grating. Normally both lines are equal in power, but in mine laser yellow is somewhat weaker.

I've been working for nearly a year on this project. Including the 6 months of time looking for a new laser tube, as the first leaked air in it.
 

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CDBEAM777

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WOW....just WOW...." Jump'in Jesus on a Pogo Stick ".....Now...that is dedication...and just huge amount of sheer will power to " Stay the Course "...meaning....Stay on course to completion !!!

I thought I had some semi-complicated builds...Not like This !!! Working with these High Voltages....just freak me out !!!....:eek::eek::eek: Be real careful.....No Sh$t !!!

That color is beautiful !!! Thank you for sharing !!!

CDBEAM
 

Seoul_lasers

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Nice work. Thank you for showing the construction details of such a laser.
Cu-vapour lasers are quite labour intensive but quite a sight to behold once lasing.

Very rare to see these days. We used to have one at the Planetarium in Vancouver, and I am not sure if the unit is still there?
Very nice. +rep
 

diachi

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Very well done! The power supply is easily the hardest part of Cu vapor laser construction. Any of the home-built PSUs I've seen have used rotary pulsers. Opting for a thryatron must have resulted in much better results.

It's great to see someone doing DIY with gas lasers.
 

Benm

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That's one heck of a laser system indeed :)

Is there any way to select either line to lase?
 

LSRFAQ

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As a former CVL owner, just one question?

Why not insulate the tube and just cool the end bells?

Or do you have high temperature insulation under the cooling cylinder that I cannot see?

Steve
 

Laserbuilder

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do you have high temperature insulation under the cooling cylinder that I cannot see?
Yes, I do. One of the electrodes is insulated from the cooling cylinder with the bushing (on the photo) made of fiberglass and epoxy. It smells a bit when heated, but works well. Also there should be a correct temperature mode of the tube, cooling it too intensly may reduce performance of the laser because copper won't evaporate good enough and severe temperature gradients can occur which can cause the tube to crack. So, this water cooled cylinder, which doesn't have any direct contact with the tube, is enough for its thermal stability at the point that is recommended by the manufacturer.

As for lasing lines -- I cannot choose any of them freely, but I can suppress the green line by an orange filter, so only yellow one is present.
 

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CurtisOliver

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Wow :drool:, I am very impressed LaserBuilder. :) The fact you managed to get the 578nm line going as well. Good job, +rep from me. :beer:
 
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