Prototype flying-wire beam-profile monitor

A prototype flying-wire beam-profile monitor has been designed, fabricated, and tested to measure profiles of high-current high-duty electron beams. The device measures the beam's horizontal and vertical profiles with a pair of thin carbon filaments mounted on a wheel. The beam that intercepts the filaments, or wires, produces electrons by secondary emission in proportion to the incident beam current. The secondary electron signal is detected either by measuring the charge depletion current on the wires or by measuring the current collected on a pair of positively biased charge collectors. A servo motor is used to accelerate the wheel from rest to a speed of 25 RPS in less than half a revolution passing the wires through the path of the beam at a speed of /spl sim/10 m/s. The wheel is then decelerated back to rest before completing one full revolution. The precise timing requirements of this application led to the development of an indexer capable of controlling the servo motor position with less than 20 /spl mu/s of timing jitter.<
>