A copper substrate for use as a contact having Sn plating, nickel plating and Au plating overlying the substrate. An exhaust airflow adjuster is provided at the diverging portion. A second variable, which characterizes the maximum value of the change andor the location of the maximum value of the change, is determined on the basis of this first variable. 2 MHz, by which two different kinds of high frequency powers are applied to a lower electrode 106. For instance, the m-to-n concentrator can be implemented from an m2-to-n concentratorsorter, an m2-to-n concentratorsorter, and n sorting cells to thereby produce the desired arrangement of outputs required of the m-to-n concentrator.