Measurement of magnetostatic mode excitation and relaxation in permalloy films using scanning Kerr imaging

For a self-controlling drill rod for rotary boring rods of machine rock drills, comprising an inner drilling shaft adapted to be connected with the boring rods and the boring tool and having a flush channel and a housing mounted on the drilling shaft so as to be rotatable thereabout, control bars capable of swinging out being disposed on the outside of the housing, and the parts of the hydrostatic drives acting on the control bars as well as the control electronics and control electrical system being provided within the housing, whereby the required energy is generated by the rotary motion during the boring operation, the inventive improvement is that an annular space exists between the drilling shaft and the housing having a radial connection with the flush channel of the drilling shaft and being closed off at each end by a rotary check valve keeping out the borehole fluid, and that the annular space serves as a tank for the working fluid of the hydraulic system, said fluid being formed by the drilling shaft fluid.