Adaptation of the LIMM technique data treatment to perform measurements in vacuum

Abstract

Dielectric materials are used as thermal regulator on satellites, as they offer for the embarked electronic devices the required protection. Their behavior in space environment must be studied in order to prevent electrostatic discharges that can be harmful for satellites. An irradiation chamber called MATSPACE has been built to study these materials. It is equipped with various material characterization devices. We will focus this paper on the Laser Intensity Modulation Method (LIMM) and the Split Faraday Cup (SFC) arrangement in the chamber. In a first approach it was necessary to reconsider the thermal aspect of the LIMM data treatment as it was now used under vacuum. In a second step, a new deconvolution treatment has been developed in order to recover the charge profile near the surface and further in the bulk. The influence of frequency range in which the signal is recorded will be also presented.

Pulsed electro-acoustic (PEA) measurements of embedded charge distributions

“…The Laser Intensity Modulation Method (LIMM) method 12,46 uses a non-uniform thermal gradient in the bulk produced by irradiating the sample surface with an intensity modulated laser diode as the probe waveform. This creates a thermal wave that acts on the embedded charge, which creates a pyroelectric displacement current.…”

“…This minimizes the possibility of an electric discharge across the signal electrode or in the chamber for in vacuo measurements. 12 LIMM requires a thin electrode on the beam side of the sample (at least in present configurations), and so is not strictly an "open" method. 12 LIMM has potential for very high spatial resolution, on the order of ~1 m, but is much more surface sensitive due to the optical/thermal excitation method.…”

In situ space charge profile measurements on electronic irradiated material by LIMM

“…Before performing LIMM measurements under vacuum some preliminary studies have been made to identify the modification that should be made on the data treatment [3]. Then a new detection cell has been design taking into account the small amount of space available on the sample holder.…”

PEA System Modeling and Signal Processing for Measurement of Volume Charge Distributions in Thin Dielectric Films

“…It also gives insight into modifications to the PEA method that can be used to improve or better understand the method. Two models are presented: i) a ray-tracing model similar to many published models [1,[5][6][7][8][9][10][11][12][13][14][15], and ii) a full-wave model based on computing fields by satisfying boundary conditions at each interface [16,17].…”