LN13325 - When the scriptwriters for Doctor Who imagined a futuristic device, they
came up with the Sonic Screwdriver. Now we have taken equipment
designed for MRI-guided focused ultrasound surgery and demonstrated a
real Sonic Screwdriver, used to lift and spin a free-floating
10 cm rubber puck. Energy from an ultrasound array forms a beam that
carries momentum and can push objects away objects in its path. If the
beam is designed as a vortex, then rotation is also possible.The helical, phased spiral wavefronts of vortex beams mean there is a rotating, angular component of momentum that can exert torque on an object. In this paper, we show how to generate vortex beams with many intertwined helices using a 1000-element ultrasound transducer array. These beams are strong enough to levitate and spin the 90 g puck made of ultrasonic absorber in water.
We use the screwdriving effect to test the theory that the ratio of angular momentum to energy in a vortex beam is equal to the ratio of the number of intertwined helices to the frequency of the beam. This theory is used in topics from quantum physics to biophotonics but it has not previously been proved in a single experiment. For the first time, our experimental results confirm directly the validity of this fundamental theory.
It may not be the Higgs Boson, but for those working on related topics, it's just as important!
