The invention comprises a method and apparatus for slowing positively charged particles, comprising the steps of: (1) transporting the positively charged particles from an accelerator, along a beam transport line, and into a nozzle system； (2) placing a first liquid in a first chamber in a beam path of the positively charged particles； (3) placing a second liquid in a second chamber in the beam path of the positively charged particles； (4) moving the first and second chamber with the nozzle system； (5) slowing the positively charged particles using the first liquid and the second liquid； (6) moving the first chamber in a first direction to yield a longer first pathlength of the positively charged particles through the first chamber； and (7) moving the second chamber opposite the first direction to yield a longer second pathlength of the positively charged particles through the second chamber.
