I assume the non reflective tube will only emit a narrow beam
No sorry that will not happen. That is not how optics works.
BUT the issue that I think every one has missed in a misguided attempt to display their electronics knowledge is that the OP has virtually no electronics knowledge and limited resources and is virtually incapable of following any direction provided here, as he has stated twice..
That never stopped us before in this forum, at least it gives the OP an idea of the magnitude of the problem. A lot of beginners can't distinguish between an easy project and a near impossible one. That is what we are here for.
To the OP you have probbly gathered by now you have your work cut out. You have two problems, the width of your beam and the sensitivity of your receiver. At these distances neither is a trivial problem.