Total Newbie on a budget

[R9000]

You do need diodes here, because otherwise, your linac will disconnect permanently when it gets to one end. Think of it this way: The diagram Bitternboy posted shows a circuit where there are two one-way paths for the current to follow, and a path for current to flow in either direction (if both switches are closed). Now if one switch opens (or disconnects), the current can only flow one way through the circuit now because the current is now forced across the diode that is connected over the switch. This means that, while the circuitry will stop your motor from trying to push the linac past its limits, it will still allow current to flow in the opposite direction so you can retract it.

Your diagram would stop the linac moving completely since it pulls both contacts of the motor to the same voltage, which then stops it (I think). You basically just need to make something like Bitternboy posted. The diodes you need can be fairly basic, you just need ones with a higher reverse voltage than you're running your motor at, and some that can handle the current through it (which you can measure while it's running). Also keep in mind that diodes introduce a small voltage drop when used (usually around 0.7-1V) but as long as your linac can move off the limit switch again, it'll be fine.
Something like this should do, but check your voltage and current as I said: https://www.arrow.com/en/products/1n...FQMM0wodY6MGTA

Oh, and don't get Zener diodes. They're not what you need here.