Applicability of laser ionisation for the test and calibration of in-situ dust instruments A. Mocker (1,2), Z. Sternovsky (3), E. Grün (2, 3), S. Kempf (3), and R. Srama (1, 2) (1) Institut für Raumfahrtsysteme, Universiät Stuttgart, Germany (2) Max-Planck-Institut für Kernphysik, Heidelberg, Germany (3) LASP, University of Colorado (mocker@irs.uni-stuttgart.de / Fax: +49 6221 516 660) Abstract In situ measurements, the direct interception and anal- ysis of dust particles by spacecraft-based instrumen- tation, allows us to gain insights into the dynamical, physical and chemical properties of solar system dust. The methods yielding the highest sensitivity for de- tection of dust particles in space, rely on impact ion- isation. To cover a sufficiently big energy range for the investigation of dust particle impacts and the cali- bration of impact ionisation instruments, we attempted to complement the particle impact experiments with laser ionisation. Therefore it was necessary to inves- tigate the properties of both processes with respect to their comparability. The findings of this study show that, in general, laser ionisation plasma is not compa- rable to that generated by hypervelocity particle im- pacts. However, particular aspects of the the laser ion- isation process can be used as a rough substitute for particle impacts, i.e. optimising and testing electronic components for impact ionisation instruments. 1. Introduction Soon after their introduction in 1962 [1], high- powered pulsed lasers were to be recognised as a flex- ible and powerful tool for the studying the interac- tion of intense electromagnetic field with solid bod- ies [2, 3]. The formation of a hot plasma from the irradiated surface was found to be depending sensi- tively on laser parameters, such as energy density, as well as the properties of the irradiated material. In general, the resulting ablation plasmas have high ion and electron temperatures and high degrees of ionisa- tion. Due to this, laser set ups were designed to cre- ate plasma plumes in order to test and optimise TOF mass spectrometer and other particle impact ionisation instruments or their components [4]. Being a simple method to emit ions from a surface with a higher rep- etition rate, much less effort and costs and in a wider polariser pyrolectric probe beam widening Laser Laser beam iris half−wave plate E 57° r t E entrance window target focusing lens vacuum chamber Figure 1: Optical set up of the laser ionisation experi- ments. energy range laser ionisation is regarded as an ideal supplement to a a micro-particle accelerator. Although there have been experimental and subsequent theoreti- cal investigations of the similarity of both ion emitting processes, these studies took place under very specific experimental conditions [5]. 2. Comparability of both processes Investigation of the comparability of the impact ioni- sation process and the formation of a plasma cloud due to the irradiance of a solid target follows three guiding themes: • How reproducible are mass spectra produced by hypervelocity impacts and by laser ablation under similar physical conditions? • Is laser ablation a useful analogue for the impact ionisation process? • How deep is our understanding of the impact ion- isation process itself? A program of hypervelocity impact and laser in- duced ionisation experiments was performed to inves- tigate these questions. These measurements were conducted with a time- of-flight mass spectrometer designed to provide as comparable as possible impact conditions and opti- mised to obtain direct information about the process, i.e. the velocity distribution of the generated ions. The EPSC Abstracts Vol. 6, EPSC-DPS2011-918, 2011 EPSC-DPS Joint Meeting 2011 c  Author(s) 2011