Sorry, but you're not going to build an equivalent of a 50 million dollar device for $50. Maybe you were thinking of a cloud chamber or a cyclotron? Small versions of those might be doable on a small budget. I doubt you could make an interesting linear accelerator, and I don't know what you'd do with it anyway.
As for neutrino detectors, you're definitely not going to build one of those on your own. Neutrinos very rarely interact with anything, and are therefore extremely difficult to detect. There's really no way of scaling down neutrino detectors unless you're willing to wait a century or two before detecting anything
.