Improving Accuracy of Noninterceptive Current Measurement for Use in IFMIF/EVEDA Accelerator

Current transformers (CTs) (ACCT/DCCT) are used as noninterceptive means of beam current measurement in the IFMIF/EVEDA accelerator. However, current measurement using CTs for long pulses with 100 ms or longer such problems as droops are apparent. This is due to the fact that this measurement is based on the current induction through transformers and is considered inevitable. We propose a method for retrieving the beam currents from the ACCT output waveforms using an experimentally obtained transfer function. This method has several advantages. The transfer function is easy to obtain from simple experiments with a function generator and an oscilloscope other than the ACCT and an amplifier, and the effects of stray capacitance, inductance, and magnetic materials nearby are inherently included in the transfer function. Square waveforms with different pulselengths are used to numerically obtain the forward and backward transfer functions, and this method for current waveform retrieval was validated. It was confirmed in experiments that square waveforms with lengths from 100 ms to 1.3 s could be retrieved without droops from the ACCT output.