Design and Development of a Diagnostic System for a Non-Intercepting Direct Measure of the SPIDER Ion Source Beamlet Current

Abstract

Stable and uniform beams with low divergence are required in particle accelerators; therefore, beyond the accelerated current, measuring the beam current spatial uniformity and stability over time is necessary to assess the beam performance, since these parameters affect the perveance and thus the beam optics. For high-power beams operating with long pulses, it is convenient to directly measure these current parameters with a non-intercepting system due to the heat management requirement. Such a system needs to be capable of operating in a vacuum in the presence of strong electromagnetic fields and overvoltages, due to electrical breakdowns in the accelerator. Finally, the measure of the beam current needs to be efficiently integrated into a pulse file with the other relevant plant parameters to allow the data analyses required for beam optimization. This paper describes the development, design and commissioning of such a non-intercepting system, the so-called beamlet current monitor (BCM), aimed to directly measure the electric current of a particle beam. In particular, the layout of the system was adapted to the SPIDER experiment, the ion source (IS) prototype of the heating neutral beam injectors (HNB) for the ITER fusion reactor. The diagnostic is suitable to provide the electric current of five beamlets from DC up to 10 MHz.

A Versatile Board for Event-Driven Data Acquisition

“…The ions are extracted from the Ion Source (biased by the AGPS power supply with respect to ground) by the Extraction Grid, which Beamlet currents in different positions have been measured using two different configurations of the RP board. Continuous data acquisition provides information about the average current density and uniformity [18], whereas the event-driven acquisition provides information about the beam current fluctuations (MHz range) due to the plasma oscillations produced by the RF field generating the plasma [19,20]. Two different sensors have been used for continuous and event-driven data acquisition, respectively, as shown in Figure 5.…”