Direct-current current transformer for the measurement of an electric propulsion ion beam

Abstract

An important task in the development of electric propulsion devices is ground-based testing. In order to characterize electric thrusters, their generated ion beams are regarded as figures of merit and have to be well-known and understood. We present an approach to measure DC ion beam currents generated by electric thrusters by means of an inductive direct-current current transformer. In contrast to commonly used devices like Faraday cups, this device can measure the beam current non-intrusively by means of magnetic field coupling rather than charge collection. This paper shows the development of a prototype sensor which can measure currents in the typical range for electric thrusters with high resolution and satisfactory accuracy. A detailed SPICE model to assist during hardware development is also introduced and verified by test case measurements. The prototype has been tested and validated with a radio-frequency ion thruster. Its readout shows very good agreement with the output of an analytical model which computes a Gaussian-shaped ion beam in the far-field based on experimental input data.

Design of Integrated Micro-Fluxgate Magnetic Sensors: Advantages and Challenges of Numerical Analyses

“…Given the rather high saturation field above 0.6 T, these Jiles–Atherton parameters have not been adopted, except for some tests, as described later. The magnetic characteristics adopted in this research were instead extracted by a manual fitting of the hysteresis curve reported in [ 44 ], in [ 27 , 54 ], starting from the parameters of Table 1 . In particular, the curve reported in Figure 4 of [ 44 ], the curve in Figure 1 of [ 27 ] and the curve in Figure 6 of [ 54 ] have been fitted.…”

“…The magnetic characteristics adopted in this research were instead extracted by a manual fitting of the hysteresis curve reported in [ 44 ], in [ 27 , 54 ], starting from the parameters of Table 1 . In particular, the curve reported in Figure 4 of [ 44 ], the curve in Figure 1 of [ 27 ] and the curve in Figure 6 of [ 54 ] have been fitted. In the following, these will be referred to with the codes JA1, JA2, and JA3, respectively, for convenience.…”

“…In [ 27 ], it is stated that the JA2 curve was taken at 10 kHz, in the other cases instead the measurement frequency of the hysteresis loop is not specified. Presumably JA1 corresponds to the DC curve, since it constitutes data provided by the manufacturer VAC and because of the very narrow cycle, and JA3 corresponds to 5 kHz, since this is the driving frequency adopted in [ 54 ]. It is worth noting that these are only conjectures; however, they are reasonable as hysteresis loops generally become wider as frequency increases.…”

Sputtering of Mo and Ag with xenon ions from a radio-frequency ion thruster

“…The electric RF ion thruster (RIT-10, 37 extraction apertures), developed and built at Giessen University, Germany, was set up and operated following conventions and empirical data gained by the respective work group 2,14 . The radio-frequency generator (RFG) as well as the negative and positive high voltages (NHV and PHV) were operated as stated in Tab.…”

“…To estimate the radial current density (J in A/m 2 ) for a 2D Gaussian beam distribution over radius r at a given distance z from the thruster exit plane, the following expression approximated for an ion beam expanding from a point source was used 14 :…”