The Development of the Intensified Retarding Potential Analyzer (IRPA) onboard Sounding Rockets

Abstract

The development and verification of the intensified retarding potential analyzer (IRPA) as one of the sensors in the space plasma instrument package ‶Mesosphere and Ionosphere Plasma Exploration complex (MIPEX)″ which is going to be installed onboard a university-based hybrid sounding rocket to investigate the electrodynamic processes in-situ in the D, E layers of the ionosphere above Taiwan is reported.
IRPA is innovated from the conventional retarding potential analyzer (RPA), a widely used in-situ plasma measurement instrument, to obtain ion drift velocity in ram direction, ion density and ion temperature by measuring the ion energy distribution. By replacing the conventional metal collector with a channelelectron multiplier (CEM), IRPA is capable of effectly increasing the dynamic range, signal-to-noise ratio and frequency response to satisfy the scientific needs of this hybrid rocket mission. In this work, the design concept, performance analysis by simulation, hardware development and in-lab experiment of IRPA is presented respectively.
In practical measurement, the trajectories of the incident ions are easily affected by the external potential distribution of the instrument. To investigate the effects and to estimate the error, the wall effect and the grid potential leakage effect caused by the IRPA structure are examined comprehensively by the SIMION software, and the maximum induced uncertainty is about 7%, which is mainly contributed by the shift of the I-V curve resulting from the grid potential leakage effect. As the result, the flight model of the IRPA is designed with a larger aperture to reduce the structure effect and a reduced error is expected.
The gain and dynamic range of CEM are verified in the space plasma operation chamber (SPOC) at NCKU. Metal electrodes are easily contaminated by a thin dielectric, which significantly affects the measurement result. To remove the effect caused by this contamination, a pulsed triangular waveform as a sweeping voltage was utilized for the ion energy selection. It is demonstrated that both the contamination impedance effect and the potential shift effect are removed by the waveform with a varying VH and a VL with 0V respectively. The performance of the IRPA under the environment with an extremely low plasma densities, ~50 cm-3, is also verified in SPOC.

Date of Award	2018
Original language	English
Supervisor	Bing-Chih Chen (Supervisor)