A geothermal probe , comprising a main probe , which at least comprises: - a main probe heat medium circuit and a feeder probe medium circuit , - an evaporation chamber (2.1), which comprises a refrigerant chamber (4.1) of a counterflow evaporator and a closed refrigerant circuit , whereby the closed refrigerant circuit is filled with ammonia, i.e. NH 3 , as the refrigerant, - a riser (2.2), which is connected to the lower end (2.21) of the evaporation chamber (2.1), - a supply pipe (2.5), which is connected to the evaporation chamber (2.1) and is arranged in the refrigerant circuit , - a heat exchanger chamber (2.3), which comprises at least one heat medium chamber (4.2) of the counterflow evaporator and is arranged in a maln probe heat medium circuit of a heating medium, whereby the geothermal probe additionally has a feeder probe , which comprises at least: - an outer jacket (3.1), which is enclosed on its outside by the soil when the geothermal probe is In operation, - a probe gap (3.2), which is at least partially bounded by the inside of the outer jacket (3.1) and a probe bottom (3.3), in which the main probe is arranged, and - at least one inlet (7.1), for the fluid heat medium, which is arranged In at least one open feeder probe heat medium circuit , whereby the counterflow evaporator has at least one refrigerant chamber (4.1) and at least one heat medium chamber (4.2) and the geothermal probe has a measurement and control device , which is integrated into the process control system to provide a continuous gaseous refrigerant flow, and whereby the counterflow evaporator is a three stage counterflow evaporator , which comprises three segments of similar design connected in series so that the evaporator chamber (2.1) comprises three sections arranged in series and whereby the feeder probe is a catch basin for the refrigerant escaping from the main probe . - a main probe heat medium circuit and a feeder probe medium circuit , - an evaporation chamber (2.1), which comprises a refrigerant chamber (4.1) of a counterflow evaporator and a closed refrigerant circuit , whereby the closed refrigerant circuit is filled with ammonia, i.e. NH 3 , as the refrigerant, - a riser (2.2), which is connected to the lower end (2.21) of the evaporation chamber (2.1), - a supply pipe (2.5), which is connected to the evaporation chamber (2.1) and is arranged in the refrigerant circuit , - a heat exchanger chamber (2.3), which comprises at least one heat medium chamber (4.2) of the counterflow evaporator and is arranged in a maln probe heat medium circuit of a heating medium, whereby the geothermal probe additionally has a feeder probe , which comprises at least: - an outer jacket (3.1), which is enclosed on its outside by the soil when the geothermal probe is In operation, - a probe gap (3.2), which is at least partially bounded by the inside of the outer jacket (3.1) and a probe bottom (3.3), in which the main probe is arranged, and - at least one inlet (7.1), for the fluid heat medium, which is arranged In at least one open feeder probe heat medium circuit , whereby the counterflow evaporator has at least one refrigerant chamber (4.1) and at least one heat medium chamber (4.2) and the geothermal probe has a measurement and control device , which is integrated into the process control system to provide a continuous gaseous refrigerant flow, and whereby the counterflow evaporator is a three stage counterflow evaporator , which comprises three segments of similar design connected in series so that the evaporator chamber (2.1) comprises three sections arranged in series and whereby the feeder probe is a catch basin for the refrigerant escaping from the main probe . <EOS>