Thanks for your answer. Is for making experiments with electricity, like CRT, tubes, etc...
A mechanical vacuum pump, at best, will get you down to a low enough pressure to experiment with gas discharge tubes, and things like the Crookes Radiometer. I think home-made plasma globes would be within your reach as well. But in that case you need to be be aware of the danger of implosion when messing around with large evacuated glass vessels.
If you want to experiment with stuff that uses electrons like CRT's, vacuum tubes, x-ray tubes and the like you need a much better vacuum, the kind that can only be obtained with things like diffusion pumps and turbopumps. I've found used & functional diffusion pumps on ebay for as little as $200 but that's a screaming deal that doesn't last long. But you have to be careful, many of the less-expensive ones are missing something, require high power to operate and/or something other (higher) than 110V to operate them. Used turbopumps can be had as well, but you _really_ have to be careful there, many need to be rebuilt or may be damaged. They also need a controller for additional $$. Turbopumps are like small turbine engines but operated in reverse. They spin at up to 100,000 RPMs so one mistake (like inadvertently venting your vacuum system to air while the turbo is running) will likely cause it to blow up. Literally.
Diffusion pumps work on a different principle, using a gas "jet" produced by boiling special organic liquids, to transfer momentum from the jet to gas molecules that wander into the pump, basically urging them on toward the exit side of the pump. The very hot working liquid will react with oxygen in the air so screwing up and dumping your vacuum chamber to air when the diffusion pump is running will cause big problems, too. As a grad student I had the "privilege" of rebuilding a diffusion pump where that had happened, and the parts in the interior of the pump were coated with baked-on varnish. As long as that varnish was in there, there was no hope of getting any kind of decent vacuum out of it. I resorted to using oven cleaner to get it all out, along with lots and lots of other solvents. I got it working again but it was a true PITA to get there. I earned my stipend on that one.
In addition to getting the vacuum pump(s) themselves you will need vacuum fittings and the right kind of tubing. The fittings are pretty special, and so is the tubing. Most plastic tubing outgasses too much to be usable for the high-vacuum side of your diffusion or turbopump. They also will collapse unless they are molded with a steel springlike insert. Stainless steel is the material of choice on the high vacuum side. If you can TIG weld SS you can save some money on fittings: but only if you can do it with ZERO pinholes in the welds.
If you go to the expense of building a high vacuum system for vacuum tubes etc. you also will want to have at least a couple of vacuum gauges. One for the (relatively) higher-pressure side of your diffusion/turbo pump, and another to monitor the low-pressure side of the system.
Sorry to come across as such a Negative Nellie, but experimenting with high vacuum systems can be a challenging and potentially expensive exercise. While there are deals to be had from places like ebay, it takes some experience to figure out what really is a good deal in that field of endeavor. As a high-schooler I had the opportunity to play around with making my own gas discharge tubes and that was fun, and not too challenging. Going past that, well, it gets more difficult in a hurry.
