This sample has been tested in Wisconsin, and here at LBNL within the past few weeks. Impedance matching components can be found near the middle of the right hand side of the PC board.
The coax shown on the board amounts to about 40 ns. It appears there is enough space available on the PC board for the additional 20ns of delay required for proper operation of the DOM. The cable depicted is RG-180B/U, lightly stuck to the prototype PCB delay line.
The most natural implementation of this concept is to have a board-to-board connector at outer radius where the PMT signal would enter the delay line spiral, and another board-to-board connector at the inner radius of the PCB where the signal would re-enter the DOM main board on its way to the ATWD input amplifiers.
If a suitable scheme is found for sticking a spiral of teflon coax
to a
thin PC board, the resulting assembly would be fairly easy to
handle. A worst-case solution would be to trap the spiral
of coax between two
relatively thin PCBs. Any mounting stand-off that has
to
penetrate the spiral layer could cause problems... Stand-offs
screwed
with flat-head screws to one side of the board would pass the
test.
Suggestions, questions and comments should be directed to the author:
Gerald
Przybylski, 