NON-INTERCEPTING CONTINUOUS BEAM CURRENT MEASUREMENT FOR A HIGH-CURRENT ION IMPLANTER

For high accuracy dosage determination, a parametric current transform er (PCT) has been built into the target end-station of a Danfysik Mode l 1090 high-current implanter. The PCT is an instrument designed for c ontinuous 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 applicati on with an inner diameter of 340 mm. It is mounted around the beam sca nning chamber, between the scanning magnets and the target position. S ince 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 tha n 5%. The present article describes the current measurement system and its applications.