Vanesa Tobon Valencia1, François Ménard2, Amélie Litman1, Hervé Tortel1, Jean-Michel Geffrin1, Julien Milli2
1 Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
2 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France
In 2019, initial financial support to our project was provided by PNPS, PNP and PCMI. The project was later strongly supported by PNPS, PNP and INSU and …
Vanesa Tobon Valencia1, François Ménard2, Amélie Litman1, Hervé Tortel1, Jean-Michel Geffrin1, Julien Milli2
1 Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
2 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France
In 2019, initial financial support to our project was provided by PNPS, PNP and PCMI. The project was later strongly supported by PNPS, PNP and INSU and was selected during the 2019 edition of the 80|PRIME initiative of CNRS, to celebrate CNRS's 80th anniversary. In this presentation, we will give a brief outline of the project and present some the mid-course results, obtained after 18 months of operations.
The microwave analogy is a well-known method relying on the Scale Invariance Rule (SIR) that has been used to measure the scattering properties of objects that would otherwise be difficult to manipulate individually [1]. The SIR states that the scattering properties of analog particles measured at a different wavelength are equivalent to those of the original particles of the same shape, as long as the refractive index and the size-to-wavelength ratio are conserved.
Our project uses the SIR and the micro-wave analogy experiment at Fresnel Institute to study the scattering properties of dust found in the Solar System and in planet-forming disks, the ultimate goal being to provide direct observational constraints on the first phases of planet assembly, when tiny solid particles start to grow to form larger bodies. We have, for now, considered two types of particles: fractal-like aggregates and compact particles with rough surfaces [2]. These particles were produced by additive manufacturing where the possibility to control their shape, structure, and refractive index is unique and a definite advantage over other measurement methods. In this talk, we will summarize our first results on these protoplanetary dust analogs. We will detail how they are produced, what are the measurement conditions and the scattering results. In particular, the phase function and degree of linear polarization of these analogs will be presented, i.e., the elements S11 and -S12/S11 of the Mueller matrix respectively. These measurements are compared to our numerical model [3] to validate the method and highlight their distinctive features, the ultimate goal being to retrieve the particles’ properties like the surface roughness, fractal dimension (Df), porosity and others. These results are the first laboratory measurements of protoplanetary dust disks analogs with controlled structures using the microwave analogy.
[1] J. M. Greenberg, et al. J Appl Phys, 1961, 32, pp. 233–242. https://doi.org/10.1063/1.1735984
[2] J. B. Renard, et al. Number of independent measurements required to obtain reliable mean scattering properties of irregular particles having a small size parameter, using microwave analogy measurements. J Quant Spectrosc Radiat Transf (Accepted)
[3] H. Saleh, et al. J Quant Spectrosc Radiat Transf, 2017, 196, pp.1–9. https://doi.org/10.1016/j.jqsrt.2017.03.024