A spiral freezer for continuous duty in continuous food process lines has a freezer compartment enclosing a double-helix arrangement, of which there is a helical run of a food-carrying conveyor in combination with a helical ramp or slideway for the food-carrying conveyor’s helical run to ascend or descend on. Multiple plate-like magnets are installed around a columnar rotating shaft, and the columnar rotating shaft is rotated, thereby forming a high-density erosion region on a target to increase film formation speed, and the erosion region is moved along with rotation of the columnar rotating shaft, thereby wearing the target uniformly. To handle the large current requirements of an ESD incident, the bipolar transistor has multiple base and emitter elements formed in an npn bipolar array. The lead 12 and the conductive lead 16 of an airtight terminal 10 constituted by the stem 11, the lead 12, the filling member 13, the conductive lead 16 are connected to a piezoelectric vibrating piece 20, further, the stem 11 is capped to a case 30 to thereby constitute a piezoelectric vibrator 1. The material can be, for example, magnesium oxide, a garnet, lithium barium fluoride andor a spinel.