Note: He puff system for dust detector upgrade

Local detection of surface dust is needed for the safe operation of next-step magnetic fusion devices such as ITER. An electrostatic dust detector, based on a grid of interlocking circuit traces biased to 50 V, has been developed to detect dust on remote surfaces and was successfully tested for the first time on the National Spherical Torus Experiment. In this note, we report a helium puff system that clears residual dust from this detector and any incident debris or fibers that might cause a permanent short circuit. Two consecutive helium puffs delivered by three 0.45 mm nozzles at an angle of 30° cleared the entire 5 cm × 5 cm surface of the detector.