Abstract: A tornado detector comprising a sensor (30) for sensing the presence of sound having a frequency of about one hertz and for providing a sound sense signal in response thereto, a filter (50) to attenuate said sound sense signal wave components having frequencies greater than those which correspond to sound having a frequency of about one hertz, and an alarm (101) for generating an alarm signal in response to said filtered sound sense signal.

Abstract: A beam of radiant energy 50, 64 intersects a beam of ions 26 proximate the target 30 of the ions to force entrained contaminants out of the ion beam. The radiant beam of photons 50, 64 thus act as a filter for contaminants in the beam of ions.

Abstract: In semiconductor processing, it is desirable to protectively cover the wafer (40) prior to sawing the wafer (40) into individual chips. The compressive nitride protective cover tends to bow the normally flat surface of the wafer (40). If the compressive stress is too great, the wafer (40) and the circuits thereon may be damaged. The laser stress measurement apparatus (10) provides a method for checking the wafer (40) for excess stress without destroying the wafer (40). A light source (12) emits a beam of light onto a reflector (22) which reflects the light onto wafer (40). The light is deflected by wafer (40) back to the reflector (22) and thence to a light detector (52). The light detector (52) is positioned to receive the light in an exact center such that subsequent readings may be taken to determine a change in deflection. The change in deflection is then used in a formula to determine the compressive stress on wafer (40).