The Energy Spread of Ions From Gold Liquid Metal Ion Sources as a Function of Source Parameters

The energy distribution of Ga2+, Au2+ and Pr2+ ions emitted from Ga, Au, and Pr liquid metal ion sources has been studied as a function of source current, I, and angle of emission, alpha , and the results are compared with those obtained for the singly charged atomic ions emitted from these sources. It was found that for all three doubly charged species the FWHM of their energy distribution is angle independent, whereas the FWHM of the energy distribution of the singly charged species is not. For Au2+ and Pr2+ ions the FWHM was found to vary as I0.29 and I0.39 respectively. It is concluded that in order to explain these experimental results interactions other than ion-ion ones have to be taken into account, both for the singly and doubly charged atomic ions. It is also suggested that the processes responsible for the energy spread of the singly and doubly charged ions are of the same nature but differ in magnitude.

Section: Discussion Of the Experimental Resultsmentioning

confidence: 99%

“…A E 1 0 . 3 5 [22], whereas for Pr+ the dependence of higher-energy peak (A) merge together into a broad…”

Section: Into a Lower-energy Shoulder With Increasing Currentmentioning

confidence: 97%

On the energy distribution of doubly charged atomic ions emitted from liquid metal ion sources

Papadopoulos

1988

“…The curves for Au + , Sn + and Bi + follow a 0.35-0.45 power law. The Au + curve is from a Au 90 -Si 10 source, but the Au + curves from a variety of pure gold sources, by Papadopoulos [30,31], similarly obey a 0.35-0.39 power law, above about 2 µA. However, it may be argued that the disagreement is due to the very mixed beam [32][33][34] produced by gold, tin and bismuth, because Knauer's model only considers charged particles of a given chargeto-mass ratio.…”

Section: The Onset Of Gross Instabilities Of the Emittermentioning

confidence: 99%

Electrohydrodynamic instabilities and the energy spread of ions drawn from liquid metals

Mair

1996

This paper aims at shedding some light on the beam energy spread versus current curves of liquid metal ion sources (LMISs). Although Knauer's collisionless space-charge broadening model originally gave almost perfect agreement with experiment, deviations were discovered later at low and high currents. To make matters worse, as more metals were investigated, complete disagreement was found in certain cases. Although the low-current deviation from Knauer's model is not well understood and only tentative explanations can be given, the high-current deviation has been explained in terms of a self-sustaining instability that sets in at a critical current, the value of which varies greatly from metal to metal. This instability violates a basic premise of Knauer's model, namely that the ions' paths do not cross after their emission. Calculations show that, for metals for which there is total disagreement with Knauer's model, the instability sets in almost from the onset. An important result of this work is the development of a stability criterion for LMISs. It is shown that a low evaporation field and a high surface tension are two principal factors that improve stability. The stability is also affected, to a lesser extent, by the liquid density and charge-to-mass ratio of the ions.

“…With increasing current, the production of droplets increases. Droplets are produced very close to the Taylor cone [29]. If a droplet decays due to ion bombardment close to the tip, the energy distribution is broadened and there are more ions with lower energy.…”

Section: Ion Energy Distributionmentioning

confidence: 99%

IFM Nano Thruster performance studied by experiments and numerical simulations

Mühlich

Seifert

Aumayr

2020

Field emission electric propulsion thrusters are characterised by their low thrust range, which makes them ideal for the precise control of spacecraft. Decisive for precise control are the properties of the thruster ion beam, which includes the beam divergence angle and the thrust vector. The analysis of these properties is also necessary in order to be able to estimate the interactions of the beam with components of the spacecraft. Due to such interactions, solar panels or electrical instruments on board the spacecraft could be damaged by sputtering effects. The spatial ion current density and energy distribution of a test crown emitter beam, with different specifications compared to the IFM Nano thruster, were examined experimentally with a diagnostic system, including Faraday cups and a retarding potential analyser. In addition to the analysis of the beam profile of an emitting crown, a single emitting needle was analysed. Based on these experimental analyses, an ion trajectory simulation model was developed to determine the theoretical ion current density distribution. This model includes the properties of a liquid metal ion source, where the ion trajectories start from their point of origin, the so-called Taylor cone jet cap. The benchmark of the model shows that the thrust vector and divergence angle correspond to the experimental results and shows the identical calculations for different thruster parameters, like emission current and electrode voltage. The simulation allows for the optimisation of existing and novel thruster geometries in terms of performance, reliability and longevity.