I didn't give up on my project... I've just been looking for the material.
I found what I am going to use for my dry ice tube this morning and the best part of the deal is that it was free. After calling a million places and having no luck for 12 inch sections (unless you want 10 or 20 feet at $15 per foot plus tax) I found this tube in my neighbors garage across the street!
The tube came out of a Schnucks supermarket in St. Louis during a remodel and was originally used as a suction tube for the air conditioning system. So It's a Cerro brand
name tube with a Type L rating. It's length is 11.5 inches with an internal diameter of 2 inches...
My project has finally started! Now I need to go buy a 2" Type L cap and/or find a think chunk of copper to make the base out of and then braze the two pieces together.... All the supply stores are closed today (Saturday) so I'm stuck for today.
Just in case someone else is trying to do this be sure to get at least Type L pipe as it's thicker. Copper pipe is available in three basic types: Type M is thin-walled, Type L is medium-walled and Type K is thick-walled.
I measured my 2" Type L pipe and using dial caplipers that the outside diameter is 2.125" while the inside appears to be 1.985". I wouldn't make a dry ice tube using Type M pipe as the thicker the pipe the better the results will be. Since it's free I'll be more than happy to use this medium wall 2" pipe, but if you are going to buy some for yourself try to get Type K if you can find it.
My goal is to make a cheap dry ice tube for under $50 and I'm well on my way