Non-intercepting continuous beam current measurement for a high-current ion implanter

Abstract For high accuracy dosage determination, a parametric current transformer (PCT) has been built into the target end-station of a Danfysik Model 1090 high-current implanter. The PCT is an instrument designed for continuous measurement of the intensity of a charged particle beam (a.c. or d.c.) without intercepting it. The PCT can be positioned outside the vacuum chamber. A special PCT has been designed for this application with an inner diameter of 340 mm. It is mounted around the beam scanning chamber, between the scanning magnets and the target position. Since the PCT is magnetically sensitive, it has been shielded. With the current transformer installed and with a well-known scanning area, it is possible to monitor the implanted dose with an accuracy better than 5%. The present article describes the current measurement system and its applications.