A fluid pressure pulse generator comprises a stator having a body with a cylindrical bore and a fluid flow chamber comprising a lateral opening and an uphole axial inlet, and a rotor having a cylindrical body rotatably seated within the bore, a rotor head connected to the rotor body, and a fluid diverter comprising a fluid passage through the rotor body and a nozzle in the rotor head. A fluid passage has an opening on an outside surface of the rotor body and an outlet at an end of the rotor body. The nozzle has an inlet end communicable with a drilling fluid and an outlet end in fluid communication with the fluid opening. The flow area of the nozzle increases from the inlet to outlet end such that the velocity of the drilling fluid slows while from inlet to outlet end.