Abstract: A booster charge is provided with an arcuate, semi-cylindrical surface dised in continuous contact with a length of explosive cord at a location medial of its length. A donor charge detonates the booster which, in turn, applies the detonation force to a side portion of the explosive cord to produce a cord detonation propagating axially in both directions. Reliability of the cord detonation is increased by the increased amount of the booster charge closely adjacent to the cord and by some focusing of the booster charge. The shock wave propagation in the cord is reliably augmented by the booster. The increased reliability factors permit miniaturization of the donor charge, the booster and the cord.