Creation of high energy density in matter with heavy ion beams for equation of state studies.
Technische Universität, Darmstadt
[Ph.D. Thesis], (2004)
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|Item Type:||Ph.D. Thesis|
|Title:||Creation of high energy density in matter with heavy ion beams for equation of state studies|
Precise equations of state (EOS) measurements of matter under extreme conditions driven by heavy ion beams require proper target configurations to create well defined states of the studied material. The aim of this work is to evaluate the potential of the SIS-18 heavy ion beam at GSI to produce samples of matter at high energy density suitable for accurate EOS measurements. First the basic principles of matter under extreme conditions driven by heavy ion beams are summarized. The influence of different cooling mechanisms is discussed resulting in an estimation of the effective heating time, which limits the maximum target temperature. This estimation is an improvement compared to previous works. The energy deposition of ion beams was studied experimentally to evaluate numerical tools which are needed for new target calculations. A time resolved two-dimensional schlieren technique was applied to provide a comprehensive test for hydrodynamic calculations. To interpret the experimental data and to link them to the results of a hydro simulation, a 3D ray-tracing modeling was developed. An overall agreement between computed and experimental schlieren images was found and it was shown that the schlieren diagnostics is capable to detect phase boundaries in the target. Discrepancies between experimental results and the hydro calculation could be connected to an insufficient equation of state that was used for the simulation. It was also demonstrated that for target materials with a high yield point a hydrodynamic description is not applicable for the current beam parameters. Under these circumstances the dominant energy diffusion mechanism is heat conduction. With the schlieren technique it was possible to follow a thermal wave propagating in a target and thus to determine the temperature in the heated zone. Irreversible changes in the target material provide a second, independent way to determine the temperature in the irradiated region. The obtained results show that the experimental conditions can be well controlled and that the numerical tools are sufficiently precise to develop advanced targets for EOS measurements. A common methods for EOS measurements are shock wave experiments, which demand planar shock wave geometry. That is usually not provided in an ion-beam driven shock. A novel target configuration is proposed to generate a planar shock front with a pressure exceeding the pressure in a bulk sample by several times. The beneficial property of heavy ions to heat extended volumes of matter with good uniformity can be fully utilized, when isochoric heating conditions are fulfilled. To suppress hydrodynamic motion during the ion beam irradiation, a dynamic confinement is proposed. This concept provides homogeneous target heating by a low-Z tamper, which allows to apply x-ray scattering diagnostics using the PHELIX laser at GSI. Isochoric heating of macroscopic samples of matter with heavy ion beams together with excellent diagnostics possibilities promises to become a fruitful approach to warm dense matter studies.
|Place of Publication:||Darmstadt|
|Divisions:||05 Department of Physics|
|Date Deposited:||17 Oct 2008 09:21|
|Last Modified:||07 Dec 2012 11:50|
|Referees:||Seelig, Prof. Dr. Wolfgang|
|Advisors:||Hoffmann, Prof. Dr. Dieter H. H.|
|Refereed:||17 December 2003|