Fundamental Physics Research on the ISS - Complex Plasmas and beyond

Fundamental Physics Research on the ISS - Complex Plasmas and beyond Gregor Morfill Max-Planck Institut für extraterrestrische Physik Fundamental Physics Workshop (RAL, 3. 5. 2006) Plasmas - the ´fourth state of matter´ - are also the most disordered state. However, so-called ´complex plasmas´ can exist as ordered liquids and crystals as well as gases. In addition they can be studied at the individual particle level. The talk focusses on some fundamental properties of these strongly coupled systems and on planned future developments on the ISS. Thanks go to: all my colleagues at MPE, who participate(d) in this research, my Russian partners V. Fortov, O. Petrov, V. Molotkov, A. Lipaev (all IHED) and the Cosmonauts, who performed some of the experiments. Special thanks also to: DLR/BMBF, Kayser-Threde GmbH, RSA, RKK-Energia, TSUP

What are ´Complex Plasmas´? • Consist of ions, electrons and charged • microparticles (plus neutral gas), • overall charge neutral • The (large) microparticles • can be visualised individually • The microparticles can be • dynamically dominant (mass • density ⋍ 100 times larger • than neutral gas density • and ⋍10 million times larger • than the ion density) • Time scales are ´stretched´- the • (complex) plasma frequency is ~ 100Hz

The name was chosen in • analogy to ´Complex Fluids´ • Complex Plasmas are • the 4th state of this • so-called ´soft matter´ • Complex Plasmas can exist • as essentially one-component • or two-component systems • Complex Plasmas can be • strongly coupled and can • exist in gaseous, liquid • and crystalline states Complex Plasmas – a new state of matter Thomas and Morfill, Nature (1995) The states of ´soft matter´ Complex plasmas Aerosol clouds Complex electrolytes Complex fluids Granular liquids Granular solids Liquid plasmas Crystalline plasmas

Discovery of liquid and crystalline plasmas gaseous liquid crystalline Thomas et al., PRL (1994), Chu and I, PRL (1994), Thomas and Morfill, Nature (1996)

Why can Complex Plasmas self-organise? The interaction between the microparticles is electrostatic (repulsivescreened Coulomb potential) … plus an attractive part… Charged microparticle Debye sphere - - + + 2λ~100a Complex plasmas are ´optically thin´ up to ~ 10 cm in depth PKE-Nefedov

CCD video camera grounded electrode macro lens particles laser sheet ‘shunt’ resistor 13.56 MHz RF-electrode generator ring cylindrical laser matching (copper) lens network Why can Complex Plasmas self-organise? The interaction between the microparticles is electrostatic (repulsivescreened Coulomb potential) … plus an attractive part… Charged microparticle Debye sphere - - + + The order parameters are: Γ = ES energy / Kinetic energy Κ = particle separation / shielding distance 2λ≥100a

Experiments in Space • The microparticles (a few µm diameter) have masses  1012 atomic masses. • Hence gravity is a major factor and high precision experiments require microgravity. • Since 2001 MPE and IHED (Moscow) have been conducting experiments on the ISS with complex plasma laboratories: PKE-Nefedov (2001-2005) PK-3Plus (since 2006) PK-4 (in phase A/B, co-financed ESA/DLR) • In addition there has been a great deal of laboratory research on Earth.

Location of PKE-Nefedov and PK-3Plus on the ISS ISS Service Module Both laboratories are located within the transfer compartment

~ 50 kg PKE-Nefedov Sergei K. Krikalev

PKE-Nefedov plasma laboratory (ISS 2001-2005) PK-3Plus plasma laboratory (ISS since 2006)

´Plasma-Lab´ a plan for a fundamental physics laboratory in space (on the ISS) and some major research aims… Proposal outline formulated by: Vladimir Fortov and Gregor Morfill (with the help of many partners and colleagues in Russia and Europe - and based in part on the ESA IAO 2004)

Plasma-Lab: a new ESA,DLR,Russia initiative BE condensation Based on the IMPACT facility The plans are to develop and build a modular science rack system for installation on the new Russian MLM module on the International Space Station. By utilising the same infrastructure for several experiment (laboratory) inserts, considerable cost savings are possible.

Plasma-Lab: a new ESA,DLR,Russia initiative BE condensation First science insert: RF plasma laboratory (equation of state, phase transitions) Second science insert: BEC gas (and quantum plasma) laboratory Third science insert: DC/RF plasma laboratory (kinetic study of liquids)

Plasma-Lab: a new ESA,DLR,Russia initiative BE condensation

Plasma-Lab: a new ESA,DLR,Russia initiative First science insert: RF plasma laboratory (adaptive electrodes) Main scientific aims: • explore the equation of state of this 4th state of soft matter (crystalline, liquid, gaseous) • investigate the physics at the ´critical point´ at the most basic (particle dynamics) level • investigate the onset of catastrophic transitions at the most elementary (kinetic) level • research the origin of (non-equilibrium, nonlinear) phase transitions etc.

the equation of state of ´complex plasmas´ 1. Are ´complex plasmas´ a new state of matter? 2. If so, what is the thermodynamics? 3. Is there any new physics, and what is it?

Equation of state of Complex Plasmas: Non-Hamiltonian physics Two effects are responsible for the non-Hamiltonian properties of Complex Plasmas: 1) Charge fluctuations, making the interaction potential time/space dependent 2) Charge ´cannibalism´, making the interaction potential density dependent Studying non-Hamiltonian physics with complex plasmas (an easily available experimental system) at the most elementary kinetic level opens a whole new field of research in fundamental physics. Sir William Rowan Hamilton: „On a general method in dynamics“ (1835) H(q,p) = ∑ pi2/2mi + U q = H/p p= - H/q Hamiltonian formalism is used to describe all physical systems (set of moving particles) that undergo changes by processes that maximise or minimise ´action´. Ivlev et al. (2004, 2005), Havnes et al. (1984)

Example: the ´classical tunnel effect´ Morfill et al., NJP (2006)

The ´classical tunnel effect´ Charge cannibalism: the available charge is redistributed from 3 to 4 particles, reducing the interstitial potential well and allowing particle penetration.

Counter-example: why doesn´t it work here? Ivlev et al., NJP (2005)

Example: Study of kinetic properties of liquids at the ´critical point´ • Near the critical point, systems attain a universal power law behaviour of thermodynamic and transport properties (as function of an order parameter – e.g. density)*. • This implies that the systems lose all memory of scales – why? • We wish to explore the kinetic origin of this phenomenon. • Experiments planned on the International Space Station. • *(K. Wilson, 1982)

Complex Plasmas at the ´critical point´ Numerical estimate (example) • Plasma parameters (PK-4 facility): Ne gas at p = 10 Pa, ni ~ 108 cm-3, Te ~ 8 eV, Ti ~ 0.03 eV   ~ 130 m, li ~ 400 m, Z ~4400a. • With decreasing pressure the range of attractive interaction increases andTc increases too. For example at p = 3 Pa we have maximal Tc = 2 eV at a ~ 5 m. PKE void closure experi-ment (2005) Khrapak et al. (PRL, 2005)

Universality and Scaling near the critical point: 1) Do Non-Hamiltonian systems have a Critical Point? 2) What is the Universality Class of liquid complex plasmas? 3) What are the Order Parameters? 4) What is the effect of finite particle size and inertia? 5) What is the origin of the scale-free behaviour, when viewed at the fundamental (kinetic) level? 6) What is the physics at the critical point in anisotropic systems? etc. PK-3Plus PK-4 IMPACT

Plasma-Lab: a new ESA,DLR,Russia initiative BE condensation Second science insert: BEC gas (and quantum plasma) laboratory Main scientific aims: • produce massive, long-lived BECs and investigate their properties • investigate the physics of interacting BEC gases at the most basic (particle dynamics) level • investigate the formation of BEC crystals and their properties • research the possibility of Bose-Fermi phase transitions (quantum plasmas) etc.

BE Gases and Quantum Plasmas: more topics • Interaction of ensembles of • neutral BEC´s • Dipolar quantum gases • Coherent multiple scattering • of matter waves • New phase transitions • Bose crystals • Massive BEC´s • Physics of ´charged´ • interacting BEC´s – do such ´quantum plasmas´ exist? • etc. Cornell, Ketterle and Wieman, 2001

Interacting quantum gases and ´quantum plasmas´… a possibility? What will such a system do? to ´dissolve´ – not enough energy… form Cooper pairs – reaction scale… evaporate partially – time scale... BE condensation e.g. a 1eV photoelectron imparts a (kinetic) energy of ~ 0.1nK to a BEC of 109 Rb atoms – i.e. we suddenly have a giant Fermion. Proposal to ESA: Ertmer, Morfill, Fortov, Rempe, Thoma, Thomas, Rasel, Dittus…(2004)

Plasma-Lab: a new ESA,DLR,Russia initiative Third science insert: DC/RF plasma laboratory (kinetic study of liquids) Main scientific aims: • explore the onset of cooperative phenomena in fluid systems at the kinetic level • investigate the origin of turbulence at the most elementary (particle interaction) level • investigate shear flows at the ´discrete´ limit of particle flows • research the physics of non-Hamiltonian fluids at the kinetic level etc.

exploring the onset of cooperative phenomena • When do interacting particle systems develop • cooperative behaviour? • 2. How do cooperative phenomena manifest • themselves at the kinetic level? • 3. How do macroscopic system properties, • e.g. surface tension, viscosity, develop? • 4. What is the relation to nanofluidics? • 5. What is the new physics?

Example 1. The hydrodynamic limit • When the system size, L, is too small compared to characteristic length scales of the fluid, the hydrodynamic description has to be replaced by e.g. molecular dynamics. This is expected to occur when the Knudsen Number Kn= λ/L ≥ 0.01. However, some results from nanofluidics suggest that hydrodynamics may apply even when Kn≈ 0.25 *. For liquid complex plasmas, λ ≈ λD , which is about 50μm. Such systems are easy to produce and study. • The onset of cooperative behaviour can only be investigated at the kinetic level – complex plasmas are ideal candidates. *Mugele and Persson, J. Phys. Cond. Matt. 16, R295 (2004), Becker and Mugele, PRL 91, 166104 (2003)

Limits of co-operative phenomena: converging and diverging laminar flows first observations at the kinetic limit v Fink et al. (2005)

2. Waves & turbulence in particle jet flow at the cooperative limit A ´Laval nozzle´ is produced by a glass tube constriction introduced in a dc. discharge complex plasma flow. collective single Fink et al. 2005 (PK-4, parabolic flight)

pathways to equilibrium in strongly coupled systems • What are the principal (kinetic) processes for the • free energy conversion? • 2. Are there different paths to equilibrium and • how are they selected? • 3. How do strongly coupled systems differ from • weakly coupled systems? • 4. Are instabilities started by single particles? • 5. What is the role of non-Hamiltonian • effects ?

1. Two stream instability - soliton production

2. Two-stream instability - a non-equilibrium phase transition Kretschmer et al. (2004) – parabolic flight measurements (PK-4)

etc.

Plasma-Lab: a new ESA,DLR,Russia initiative BE condensation current status and next steps

Plasma-Lab: a new ESA,DLR,Russia initiativecurrent status BE condensation Preparations for the proposed science inserts: Two RF Plasma laboratories have already been installed on the ISS. Adaptive electrode development is now in its third year (funded by DLR and MPG). A DC Plasma laboratory for the ISS has been studied in a DLR project, and phase B is currently funded by ESA. A BEC project under microgravity (drop tower) is under way, a Texus (rocket) experiment has been approved by DLR. The modular IMPACT rack strategy has been studied by industry at the system level (DLR and ESA funded).

Plasma-Lab: a new ESA,DLR,Russia initiativecurrent status BE condensation Esa support (in principle) exists, however, ELIPS 2 funding is too low. The decision to develop MLM science racks has been advocated within ESA. DLR is in favour of supporting this initiative. A budget of 10 Mio. Euros (nationally) has been earmarked for 2007 – 2010. The Russian Academy of Sciences has expressed its resolve that participation in Plasma-Lab has their highest priority in future space missions. A letter to M. Sacotte (ESA) to start negotiations has been sent. M. Sacotte supports the cooperation.

Plasma-Lab: a new ESA,DLR,Russia initiativethe next steps BE condensation 1. Detail the division of responsibilities and the resources: MLM rack including all infrastructure (ESA) Science inserts (DLR and Science Coordinators) ISS resources in MLM, transport, logistics, cosmonauts, training (Russia)

Plasma-Lab: a new ESA,DLR,Russia initiativethe next steps BE condensation 2. Select prospective project teams and the team coordinators 3. Constitution of an international science advisory board.

Plasma-Lab: a new ESA,DLR,Russia initiativethe next steps BE condensation 4. Contract negotiations (MOU) between ESA and RKK-Energia/RSA on the MLM activities. 5. Contract discussions (MOU) between DLR, RKK Energia and the Science PI´s (Russia, Europe) on the science inserts.

Plasma-Lab: a new ESA,DLR,Russia initiativethe next steps BE condensation 6. System study by Industry/Scientists for the Plasma-Lab requirements. 7. Pre-development (Phase A/B) could start immediately - once agreement has been obtained, both at ESA and DLR level as well as in Russia.

Plasma-Lab: a new ESA,DLR,Russia initiativethe next steps BE condensation Other scientific partners, international scientific consortia, with hardware and/or software responsibilities, laboratory support studies, etc.: are more than welcome!

thank you

Velocity profile through nozzle collective single

Example: Waves & turbulence in particle jet flow at the cooperative limit A ´Laval nozzle´ is produced by a glass tube constriction introduced in a dc. discharge complex plasma flow. collective single Fink et al. 2005 (PK-4, parabolic flight)

Limits of co-operative phenomena 2.Kinetics of ´jet´ formation PK-4 Fink, Thoma, Morfill, Fortov, Petrov, Usachev …(2005)

particle motion in front of a nozzle A ´Laval nozzle´ is produced by a glass tube constriction introduced in a dc. discharge complex plasma flow. PK-4 Fink et al. 2005 (PK-4, parabolic flight)

Kinetics of jet formation: preliminary conclusions • ´Nano-jets´, consisting of dimensions ~ 10 particle (atoms) interaction lengths, already exhibit hydrodynamic (cooperative) properties. • The ´jet effect´ - acceleration to supersonic speeds - (or in the case of complex plasmas to larger than the dust-acoustic speed) is observed. • The transition from single particle to collective behaviour still needs to be investigated in detail. • New effects have been seen (reverse shocks, rarefaction waves, reverse dust-acoustic waves, transverse flow oscillations). The possible generic role needs to be investigated.

Fundamental Physics Research on the ISS - Complex Plasmas and beyond