I’ve started gathering parts for building my first copper vapor laser. This first CVL I’m building is going to be similar to the Sci-Am design in relation to the bore setup. I am considering a thyratron driver instead of a rotary spark gap. The thyratrons are much quieter, but I may need an additional one to run the disassociation pulse and then the main lasing pulse. Though I have wondered if I could produce both pulses with one thyratron at an increased rate. That’s more math I have to work on later though.
I’ve ordered some quartz tubing in two different sizes: 10mm ID / 14mm OD and 20mm ID / 24mm OD. I also ordered some quartz rod to use as cylindrical focusing lenses: 2mm and 4mm diameter. The rod is for use as optics and other projects. All of their quartz products like this come as a minimum of 4 foot lengths. Overall the order was around 78 dollars + shipping. I ordered this quartz from QSI / Quartz Scientific Inc.
UPDATE: I received the quartz tube and rods, the tubes are in excellent condition and survived shipping. One of the rods had an end piece break off in transit, this is OK as I was planning on cutting it to much smaller pieces, it just saved me the trouble a little! QSI sent the stuff fairly quickly, it took less than a week to get here.
I received two 12kV / 30ma transformers I had purchased through eBay on Saturday. My understanding is that you need at least 200V/cm for copper vapor lasers. With a 12kV NST connected through a full wave bridge, the voltage would be around 16,920 VDC and at 200V/cm I would get around 84.6CM which is equivilant to around 33.3 inches. It makes sense to limit the bore length to 32 or even 30 inches between electrodes at this voltage.
Additionally I ordered a K type thermocouple off eBay for $30(for 2, including shipping, connectors and wire) . They’re rated up to 1800 degrees F. I also ordered a Watlow 96 process controller, also from eBay for $30 including shipping, that will help maintain a stable temperature inside the oven. Sometimes you can find process controls for kiln use, which I think would be a better option as they allow a slow preheat and a few other things more akin to a kiln. Since the CVL laser is basically a laser which needs to be run with the bore inside of a kiln I think it would reduce a lot of pre-heat stresses from the system.
The process controller allows you to set a target temperature you are trying to reach, and senses the current temperature in the oven using the thermocouple. If the temperature is below that set-point it will put out a low voltage high logic signal on one of it’s pins. This logic signal can be interfaced to a solid state relay (SSR) which powers the thermal tape, or Nichrome heating element to warm the bore inside the oven. Once it reaches the proper temeperature it will try to maintain a set temperature within limits you set. More aggressive temperature control can lead to many cycles of the heating element as the process controller turns it off and on many more times to maintain an exact temperature.
UPDATE: The Watlow 96 process controller arrived. This thing is great and extremely flexible. I spent some time messing with the programming guide last night. It’s quite amazing what this thing is capable. It supports a bursting mode which is supposed to help the heater elements or other devices attached survive a little longer than if it were to do long on, and long off periods. Basically the element will always be heated as the controller runs a preset duty cycle.
It also supports a soft start, it will use a low duty cycle until the thermocouple reports a preset temperature level and then it will crank up the power. This keeps the system from inducing any thermal shock into the system (if you set it up right) It’s going to take a few more hours of fiddling around to make sure everything is the way it should be. With the added serial output, I should be able to log the data from the Process Controller if I want to. It’s amazing the technology you can get for $30.
My next steps are to continuing ordering components as I can. I have been shopping for some refractory ceramic ‘fluff’ or sheets and have found a few different options. I was hoping to find a material that I could use for both a low temperature halide and a high temperature CVL, but most of the ceramic fluffs and refractory cements aren’t rated for much over 2400F it seems. I may need something more special/expensive when I go to build a non-halide type laser.
I’ve also been doing some shopping for refractory ceramic bores as I would like to build a CVL laser using actual copper, rather than a copper solution. I have no idea what the price will be, but I have some feelers out to a couple of manufacturers who do single quantity sales of items they have in stock. I’m hoping they may have some broken stock, or some odd sized stock that they might be willing to sell to a hobbyist at a reasonable price.
UPDATE: I received contact back from a company regarding refractory ceramic bores for building a pure Copper Vapor Laser. I spoke to Dick at www.earthwaterfire.com / Anderman Ceramics and he said that they have sold components for commercial Copper Vapor Lasers projects in the past and the material which was sold was a dense alumina product for temps just above 1600C. The closest he could get to my 25mm ID request (-/+ 4% tolerance) was a a 25mm ID with a 32mm OD, basically a 3.5mm wall thickness. For a 36 inch piece the price was US$165 and for 48″ US$225. This is not nearly as expensive as I thought it could have been and I will be ordering a 3 foot section soon. They also sell other ceramics and types which may be of interest, some I believe are rated over 5000F so if you need something that can take the heat it may be worth looking there.
I’ll post more updates as things move along and some photos as the components begin to show up.