Adjustable-spring attenuator for radiated beams

Claim 1

A variable attenuator for use in a radiated beam path comprising at least one obturating element which element is capable of varying its physical form, whereby according to the degree of such variation the element may of itself, or in combination with other elements, attenuate a radiated beam path in which it is placed to a greater or lesser degree; and control means operatively connected to said obturating element for providing gradual variation in the physical form of the element, said obturating element comprising an elongated, cylindrical helical coil spring for location with the longitudinal axis of the coil spring normal to the beam path being attenuated, the coil density of the spring in the beam path being substantially infinitely controllable within the physical distortion limits of the cylindrical, helical coil spring, the spring defining a cylinder in elevation for disposition across the full height or width of the beam to be attenuated and variations of the spring coil density causing an alteration in the number of turns of the spring met by the beam and thus altering the degree of the obscuration, said coil spring being fixedly anchored at one end, and said control means comprising a cylinder element connected axially to the other end of the coil spring, said coil spring being continuously under stress, and means for adjustably rotating the cylinder to impose torque on the individual helical coils of the spring for altering the diameter of the cylindrical coil and the spacing between adjacent helical coils of the spring.