Device for active control of the slot in a turbine.

Device (1) for active control of the slot in a turbine, especially a group 'aircraft powerplant comprising a rotor and a housing (4) surrounding the rotor forming a rotor gap; to this effect, the device comprises a cooling channel (3) is located on the outer circumference of the housing (4) and in the circumference direction) extends a distance from the outer face of the housing (4) and this channel is supplied cooling air from a plenum (2) and it has several outlet openings (5) 'to direct the cooling air onto the outside of the housing (4); this device being characterized in that the cross section of channel 10 'cooling (3) is reduced in the circumferential direction from the plenum (2):