Increased capacitance per unit of area with reduced series resistance and inductance is provided by a semiconductor-based capacitor with a spiral shape. -the larger lower surface of the compacting chamber is made up of a substantially flat surface provided with runoff means. It is configured that airflow resistance in the canister along a first route between the air communicating pipe and the exhaust pipe is smaller than airflow resistance along a second route between the introducing pipe and the exhaust pipe. The foam or elastomer material has the ability to be squeezed or collapsed into an extremely small delivery shape and then resiliently expand back to its original shape against the constraining forces of surrounding breast tissue.