Development of Low Cost Double Probe Plasma Measurement System for a Lean Satellite HORYU-IV

Abstract

A lean satellite is equivalent to a small/micro/nano/pico satellite that utilizes untraditional risk-taking development approaches to achieve low-cost and fast-delivery. Lean satellites have demonstrated great ability to be used for the study of space plasma and Earth's ionosphere which has helped in the prediction of many astrophysical phenomena and forecasting of geophysical changes on ground. Several methods have been employed in the measurement of space plasma parameters over the years using the Langmuir Probe. These methods employed different techniques using single probes or double probes. Single probe requires a well-defined reference which is difficult in small spacecraft. Moreover, high current flow in the saturation mode may destroy the probe and on-board circuitry. A low cost double Langmuir probe made of gold with its measurement circuit has been designed and tested inside RF generated Argon plasma in the pressure of 1.4x10-2 Pa that confirms the electron density from 10 10 to 10 12 m-3. Important design considerations such as operability of the designed system in low earth orbit grade plasma, mitigation of probe contamination and sputtering of the electrode surface were analysed in the paper to ensure that the developed system can provide high fidelity plasma measurement data throughout the life span of HORYU-IV (Arc Event Generator and Investigator Satellite) which is a 13 kg, 40 cm cubic lean satellite under development at the Kyushu Institute of Technology.

Investigation of Coatings for Langmuir Probes in an Oxygen‐Rich Space Environment

“…The I-V curves are therefore changed, resulting in errors in the derived plasma parameters . Currently, the most common coatings for Langmuir probes are DAG (a resin-based graphite dispersion; Lindqvist et al, 2016;Lundin et al, 1995;Wygant et al, 2013), Gold (Kai et al, 2012;Tejumola et al, 2016), and TiN (Titanium Nitride; Andersson et al, 2015;Eriksson et al, 2007;Wahlström et al, 1992). DAG and Gold have long history of use in oxygen-rich environments, but both have shortcomings.…”

Reliability of double probe measurements in nanodusty plasmas

“…Using the appropriate theory, ion densities and electron temperatures can be derived from the currentvoltage characteristic [21]. For measurements in dusty plasmas excited with radiofrequency (RF), double probes have many advantages over traditional Langmuir probes: (i) since only the current in-between the two probes is measured, RF compensation is not necessary [22] and the electron temperature measurement is only slightly affected by the plasma potential oscillations [23]; (ii) since only the small ion current is drawn by the probes, the influence on the plasma is minimized (iii) every component that is part of the measurement is floating, thus, issues arising from improper grounding are circumvented [24]; (iv) most importantly, negatively charged dust particles are repelled by the negatively biased probe tips, preventing contamination of the probe [25]. However, since the floating double probe only measures the ion current, interpretation of the probe current-voltage (I-V) characteristic can be more challenging than for a traditional Langmuir probe, where the plasma parameters are usually obtained from the electron current instead.…”

“…First, to obtain the ion density from the double probe measurement, many researchers simply assume the probe current to be equal to the charge density at the sheath edge times the Bohm speed [22,24,26,27]. This, however, neglects the fact that ions with sufficient angular momentum can actually miss the probe tip, which is often small compared to the sheath thickness.…”

“…Second, the electron temperature is typically obtained from the slope of the I-V characteristic at zero voltage difference between the two probe tips [22,24,27,37]. However, rather than measuring the whole electron energy distribution function (EEDF), double probes only collect high energy electrons, i.e.…”

“…However, rather than measuring the whole electron energy distribution function (EEDF), double probes only collect high energy electrons, i.e. the electrons whose energy is larger than the floating potential [24]. Thus, the shape of the EEDF has to be carefully considered when interpreting the results obtained from a double probe measurement [38].…”