APPLICATION to Access the LULI Laser Facilities 2021 –2022
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APPLICATION to access the LULI laser facilities 2021 –2022 Title of the experiment: Study of metallization in dense Krypton and Argon Principal Investigator (PI): Dr. Valerio Cerantola [to whom all correspondence will be addressed] European X-ray Free Electron Laser facility GmbH Holzkoppel 4 22869 Schenefeld, Germany [Institution status 1]: RES e-mail: [email protected] phone: +4915771675077 PI status: PDOC 2 citizenship: IT 3 birth date: 23/09/1987 LULI co-PI: Dr. Alessandra Ravasio contacting your co-PI (if any) prior to submission is mandatory; she/he will have to assess the feasibility of your proposal in agreement with the technical staff Summary (less than 350 words - will be published on the LULI web site) This experiment will study the insulator-to-metal transition in pre-compressed Krypton and Argon using laser-driven shock compression. Pre-compressing the sample to high initial densities in a specially designed diamond anvil cell will allow us to reach ultra-high pressures and temperatures relevant to planetary interiors, and probe previously unexplored regions of the P-T phase diagram. Multiple-shock compression has been the widely used technique to study warm dense matter but has some shortcomings such as the difficulty in direct observation of temperature due to loss of transparency. Using laser-driven shock compression in a pre-compressed sample allows independent measurement of temperature, and more importantly, allows reaching significantly higher densities because shock-induced heating is reduced. Very few studies have used this technique so far and have been constrained to lower pre-compression pressures. Moreover, Krypton and Argon have not been studied using this technique, hence their metallization mechanism remains unexplored at higher densities and temperatures. This experiment will combine high static pre-compression and high energy laser-driven shock compression to give novel insights into the metallization mechanism of Krypton and Argon at extreme conditions. Number of access weeks requested: 1 on: nano2000 (choose the appropriate facility) Proposed access route: LASERLAB, STANDARD 4 Do you have received any support for this proposal? no (please select and - if yes - specify) Keywords (at least 3): pre-compression, shock-compression, metallization, noble gases Co-investigators (only for those who will physically participate to the experimental campaign at LULI, not including LULI researchers – one line per person) 1. Anand Dwivedi, PHD2, European-XFEL, [email protected], IN 3, 1995 2. Erik Brambrink, EXP2, European-XFEL, [email protected], DE3, 1975 3. Sylvain Petitgirard, EXP2, ETH-Zürich, [email protected],FR3, 1981 4. Thomas Preston, PDOC2, European-XFEL, [email protected], UK3, 1991 5. Karen Appel, EXP2, European-XFEL, [email protected], DE3, 1970 6. Cornelius Strohm, EXP2, DESY, [email protected], DE3, 1973 7. Marius Millot, EXP2, LLNL, [email protected], FR3, 1981 8. Zuzana Konôpková, PDOC2, European-XFEL, [email protected], SK3, 1983 9. Ulf Zastrau, EXP2, European-XFEL, [email protected], DE3, 1980 1 UNI (university), RES (public research organization), SME (small or medium enterprise), PRV (industrial and/or private organization) 2 UND (undergraduate), PHD (student), PDOC (post-doctoral researcher), EXP (experienced researcher), ENG (engineer), TEC (technical) 3 acronym only 4 standard (for all users), LASERLAB (for researchers working in EU member states other than France) or pluri-annual (for French users only) [please see instructions] Study of metallization in dense Krypton and Argon SCIENTIFIC CASE Noble gases are important tracers for a variety of planetary processes such as Earth’s accretion and the long-term degassing of the mantle. Recent detections of noble gases and their isotopes in comets [1] and white dwarfs [2] have opened the possibilities of determining the evolution, inner structure, and thermal behavior of extraterrestrial bodies and exoplanets, and the origin of the noble gases themselves. Understanding the behavior of noble gases at extreme conditions of temperature and pressure thus gives a deep insight into planetary and astrophysical evolution. Besides being excellent geochemical markers, noble gases also find use in many industrial applications. The 85Kr isotope of krypton is used in industries for leak testing, while 81Kr can be used to determine the age of ice and groundwater up to 2 million years old. Argon is widely used in the welding and casting industry, especially in manufacturing titanium. It is also used in the medical field for its narcotic abilities and is being researched for its neuroprotective behavior in models of brain injury. Having a filled-shell electronic configuration, noble gases are inert at ambient conditions and do not react with other elements. But at high pressure and temperature conditions, noble gases are predicted and shown to form stable compounds. For instance, a compound of argon and nickel, ArNi, is synthesized and shown to be stable at thermodynamic conditions representative of the Earth’s core [3], while DFT calculations predict that a monoxide compound of krypton, KrO, should form spontaneously and remain stable around 300 GPa [4]. Studying noble gases at extreme conditions is therefore of great relevance in the fields of chemistry, physics, Earth, and planetary sciences. The extreme densities relevant to most exoplanets are not reachable by static compression, i.e. in diamond anvil cell (DAC), or single shock compression techniques. Multiple shocks generated by stacked laser pulses could allow higher densities to be reached, but the thermodynamic state of the system is not easy to access and must be calculated from models. For instance, in the multi-shock compression of Ar [5], it becomes difficult to obtain multi-shock temperatures from the spectral radiance due to the partial transparency loss at the interface and is calculated using a model based on self-consistent fluid variational theory (SFVT). Instead of using the multi-shock compression technique, we can send a laser-induced shock wave through a sample that is pre-compressed at high static pressures inside a DAC. The equation-of-state of the system can then be directly measured through the Rankine-Hugoniot equations from the shock and particle velocities, and temperature can be measured independently with a pyrometric technique. This combination of static and dynamic compression is analogous to multiple-shock compression, allowing us to reach significantly higher densities because shock-induced heating is reduced. The initial onset pressure of the pre-compressed sample is extremely important because it not only allows the production of off-Hugoniot measurements for shocks incident on samples of various initial densities/pressures, but also because within the same sample, pressure-generated phase transitions could have a huge impact on the compression-density curve, as well as the ultimate pressure achievable, which has not been thoroughly investigated yet. At extreme conditions, noble gases also undergo an insulator-to-metal transition. The metallization pressures of rare-gas solids are expected to be high given the spherically-symmetric charge distribution due to their completely filled electronic shells. For example, the temperature dependence of the resistivity of Xenon becomes predominantly metallic between 121 and 138 GPa, and shows purely metallic behavior at 155 GPa [6]. While this metallization of Xe occurs near room temperature, Ar requires combined high pressures and temperatures to display conductivity [7][8]. Metallization of Ar is predicted to occur above ~160 GPa and the laser-heated diamond anvil cell data in [7] indicates an enhancement of conduction with temperature. Theoretical calculations of the equation-of-state of solid fcc Kr under high pressures have estimated the metallization pressure to be 316 GPa [10] at room temperature, but has not been verified experimentally. The equation-of-state of dense Kr has been determined up to 155 GPa and 45000 K [9] using multiple-shock reverberation compression experiments, but the conductivity values were obtained only using DFT calculations. Studying the metallization process in noble gases is also of importance because of the structural transitions associated with it [11]. Total-energy calculations in [11] suggest that the fcc phase of Ar observed at 1-atm should transform to a hcp structure prior to metallization, which in turn should transform to a bcc structure at pressures above metallization. McMahan [11] also suggests that all rare-gas solids may follow a generalized structural sequence of fcc→hcp→bcc, with metallization occurring near, if not within, the hcp interval. Most shock-compression studies of the insulator-to-metal transition of noble gases at extreme conditions have used the flyer-plate based multi-shock technique, which leaves out the region of the pressure-temperature-density phase diagram where these gases might show interesting metallization mechanisms. Very few studies have used the technique of laser-driven shock compression on pre-compressed samples to study metallization in noble gases [12]. The use of this method to study the metallization process in dense Kr and Ar remains largely unexplored so far. Our experiment aims to study the insulator-to-metal transition in dense Kr and Ar by Figure 1 : Phase diagram of Kr adapted from [9] showing our using high energy laser-driven shock compression simulated Hugoniots of Kr (red,