The invention comprises a method and apparatus for reducing a kinetic energy of positively charged particles, comprising the steps of: (1) transporting the positively charged particles from an accelerator into an exit nozzle system along a beam line； (2) providing a first chamber of the exit nozzle system, the first chamber comprising: an incident side comprising an incident aperture, an exit side comprising an exit aperture, and a beam path of the positively charged particles from the incident aperture to the exit aperture； (3) filling the beam path in the chamber with a liquid； and (4) using the liquid to reduce the kinetic energy of the positively charged particles. The kinetic energy dissipater is optionally used in combination with a proton therapy cancer treatment system and/or a proton tomography imaging system.
