When tubing diameter is smaller than the transducer diameter, which device confines the sound beam to the proper range of angles?

• A. A scrubber
• B. A jet stream unit
• C. An angle plane angulator
• D. A collimator

Answer: (D)

When the transducer is larger than the tubing, you need a device that shapes and limits the beam so energy travels in a controlled, narrow set of rays. A collimator provides a fixed aperture and shielding that block rays outside a specified angular range, producing a nearly parallel beam. This confines the ultrasonic energy to the tube’s region and the intended angles, reducing off-axis reflections from the walls and improving flaw detection reliability. The other devices don’t constrain the beam in this way: a scrubber isn’t a beam-shaping component, a jet stream unit isn’t used for this purpose, and an angle plane angulator can change direction but doesn’t define a tight angular spread.