A radial counter flow jet gas cooling system (120, 160, 200, 230, 290) for a rotor of a dynamoelectric machine, said rotor comprising: a plurality of conductor bars axially positioned about a centering pin; said radial counter flow jet gas cooling system (120, 160, 200, 230, 290) comprising: a plurality of axial inlet ducts; a plurality of radial outlet ducts in communication with the plurality of axial inlet ducts; the plurality of axial inlet ducts and the plurality of radial outlet ducts being respectively positioned about and made in a plurality of the conductor bars; an axial subslot positioned beneath the plurality of conductor bars; and a radial flow duct (150, 220, 250) in communication with the axial subslot, with the axial inlet ducts, and with a first radial outlet duct next to the centering pin, said radial flow duct extending along the centering pin; wherein the cooling system is configured for a cooling gas to pass through the axial inlet ducts and the radial outlet ducts to cool the plurality of the conductor bars, as well as in series through the axial subslot and the radial flow duct (150, 220, 250), in a counter flow direction into the plurality of axial inlet ducts, and to be exhausted via a first radial outlet duct next to the centering pin to cool the centering pin. a plurality of conductor bars axially positioned about a centering pin; said radial counter flow jet gas cooling system (120, 160, 200, 230, 290) comprising: a plurality of axial inlet ducts; a plurality of radial outlet ducts in communication with the plurality of axial inlet ducts; the plurality of axial inlet ducts and the plurality of radial outlet ducts being respectively positioned about and made in a plurality of the conductor bars; an axial subslot positioned beneath the plurality of conductor bars; and a radial flow duct (150, 220, 250) in communication with the axial subslot, with the axial inlet ducts, and with a first radial outlet duct next to the centering pin, said radial flow duct extending along the centering pin; wherein the cooling system is configured for a cooling gas to pass through the axial inlet ducts and the radial outlet ducts to cool the plurality of the conductor bars, as well as in series through the axial subslot and the radial flow duct (150, 220, 250), in a counter flow direction into the plurality of axial inlet ducts, and to be exhausted via a first radial outlet duct next to the centering pin to cool the centering pin. a plurality of axial inlet ducts; a plurality of radial outlet ducts in communication with the plurality of axial inlet ducts; the plurality of axial inlet ducts and the plurality of radial outlet ducts being respectively positioned about and made in a plurality of the conductor bars; an axial subslot positioned beneath the plurality of conductor bars; and a radial flow duct (150, 220, 250) in communication with the axial subslot, with the axial inlet ducts, and with a first radial outlet duct next to the centering pin, said radial flow duct extending along the centering pin; wherein the cooling system is configured for a cooling gas to pass through the axial inlet ducts and the radial outlet ducts to cool the plurality of the conductor bars, as well as in series through the axial subslot and the radial flow duct (150, 220, 250), in a counter flow direction into the plurality of axial inlet ducts, and to be exhausted via a first radial outlet duct next to the centering pin to cool the centering pin.