CharPa - Charge state of the mesospheric smoke Particles

New instrument was developed in the frame of the REXUS (Rocket Experiment for University Students) project conducted by the German Space Agency, DLR (Deutsches Zentrum für Luft- und Raumfahrt). This experiment addresses scientific questions concerning Charge state of the mesospheric smoke Particles (CharPa).

The existence of the nanometer size particles of meteoric origin has been already proved by means of rocket soundings. The so-called Faraday cup is employed for the in situ measurements of these smoke particles. The Faraday cup is a cylinder (cup) with a collecting electrode placed behind two screening grids which are biased (one positively and other negatively) to reflect ambient plasma. The heavy meteoric smoke particles are not sensitive
to this bias and penetrate inside the cup producing small current on the electrode.

To correctly interpret the data measured by such an instrument one has to exclude an effect called triboelectric charging. This effect appears due to transfer of electrons between materials with different work functions (i.e. electrode and impacting dust particle).

The idea of the new experiment is to employ the Faraday cup with an electrode which is split into four parts each made of different material (Cu, Au, C, Cr) that is each part has different working function. The current from each part of the electrode has to be measured separately.
Comparison of these four measurement channels must yield information about charge state or working function of the material constituting the dust particles.

The rocket launch is planed for March 10-13, 2009 from Kiruna Esrange (Sweden).

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