There had been a small 4-port switch just upstream of the target that used to patch the primary ethernet cable through to the weldment. A second port on that switch served the bubbler cam. (I was worried that switch would die under the radiation load...)
I used a straight-through coupler to run the primary ethernet directly to the switch at the weldment (bypassing the little 4-port switch) and then ran a new cable back from the weldment to serve the bubbler cam.
The 4-port switch near the target was unplugged and put on the table behind the srcdaq computer.